CA2306196A1 - Implantable acoustic biosensing system and method - Google Patents
Implantable acoustic biosensing system and method Download PDFInfo
- Publication number
- CA2306196A1 CA2306196A1 CA002306196A CA2306196A CA2306196A1 CA 2306196 A1 CA2306196 A1 CA 2306196A1 CA 002306196 A CA002306196 A CA 002306196A CA 2306196 A CA2306196 A CA 2306196A CA 2306196 A1 CA2306196 A1 CA 2306196A1
- Authority
- CA
- Canada
- Prior art keywords
- sensor
- acoustic
- patient
- transducer
- biosensor system
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims description 20
- 230000004962 physiological condition Effects 0.000 claims abstract description 62
- 238000012544 monitoring process Methods 0.000 claims abstract description 38
- 210000004027 cell Anatomy 0.000 claims description 26
- 230000007246 mechanism Effects 0.000 claims description 24
- 210000001175 cerebrospinal fluid Anatomy 0.000 claims description 23
- 210000004556 brain Anatomy 0.000 claims description 21
- 239000012530 fluid Substances 0.000 claims description 18
- 239000008280 blood Substances 0.000 claims description 10
- 210000004369 blood Anatomy 0.000 claims description 10
- 239000002033 PVDF binder Substances 0.000 claims description 7
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 7
- 230000005855 radiation Effects 0.000 claims description 7
- 230000003213 activating effect Effects 0.000 claims description 6
- 230000001133 acceleration Effects 0.000 claims description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 5
- 230000005672 electromagnetic field Effects 0.000 claims description 5
- 230000002255 enzymatic effect Effects 0.000 claims description 5
- 239000000463 material Substances 0.000 claims description 5
- 229910052760 oxygen Inorganic materials 0.000 claims description 5
- 239000001301 oxygen Substances 0.000 claims description 5
- 239000000126 substance Substances 0.000 claims description 5
- 230000008878 coupling Effects 0.000 claims description 4
- 238000010168 coupling process Methods 0.000 claims description 4
- 238000005859 coupling reaction Methods 0.000 claims description 4
- 230000004044 response Effects 0.000 description 19
- 239000000758 substrate Substances 0.000 description 15
- 238000012806 monitoring device Methods 0.000 description 14
- 238000006073 displacement reaction Methods 0.000 description 13
- 230000002463 transducing effect Effects 0.000 description 13
- 230000005540 biological transmission Effects 0.000 description 7
- 238000010276 construction Methods 0.000 description 6
- 238000012545 processing Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 230000008859 change Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 208000003906 hydrocephalus Diseases 0.000 description 4
- 238000007917 intracranial administration Methods 0.000 description 4
- 230000035945 sensitivity Effects 0.000 description 4
- 238000001356 surgical procedure Methods 0.000 description 4
- 230000002861 ventricular Effects 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000007943 implant Substances 0.000 description 3
- 230000010354 integration Effects 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 238000007789 sealing Methods 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- 210000003625 skull Anatomy 0.000 description 3
- 230000003068 static effect Effects 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000003321 amplification Effects 0.000 description 2
- 230000003750 conditioning effect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000002513 implantation Methods 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 210000001519 tissue Anatomy 0.000 description 2
- 238000002834 transmittance Methods 0.000 description 2
- 238000002604 ultrasonography Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 241000282326 Felis catus Species 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- 210000001015 abdomen Anatomy 0.000 description 1
- 210000000683 abdominal cavity Anatomy 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000002706 hydrostatic effect Effects 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 1
- 208000015181 infectious disease Diseases 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000004377 microelectronic Methods 0.000 description 1
- 238000005459 micromachining Methods 0.000 description 1
- 239000012811 non-conductive material Substances 0.000 description 1
- 210000000056 organ Anatomy 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 238000007920 subcutaneous administration Methods 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000036962 time dependent Effects 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
- 230000001960 triggered effect Effects 0.000 description 1
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/021—Measuring pressure in heart or blood vessels
- A61B5/0215—Measuring pressure in heart or blood vessels by means inserted into the body
- A61B5/02158—Measuring pressure in heart or blood vessels by means inserted into the body provided with two or more sensor elements
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0002—Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network
- A61B5/0031—Implanted circuitry
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/026—Measuring blood flow
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/03—Detecting, measuring or recording fluid pressure within the body other than blood pressure, e.g. cerebral pressure; Measuring pressure in body tissues or organs
- A61B5/031—Intracranial pressure
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/41—Detecting, measuring or recording for evaluating the immune or lymphatic systems
- A61B5/413—Monitoring transplanted tissue or organ, e.g. for possible rejection reactions after a transplant
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
- G01F1/34—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure
- G01F1/36—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure the pressure or differential pressure being created by the use of flow constriction
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/72—Devices for measuring pulsing fluid flows
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R17/00—Piezoelectric transducers; Electrostrictive transducers
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/30—Piezoelectric or electrostrictive devices with mechanical input and electrical output, e.g. functioning as generators or sensors
- H10N30/308—Membrane type
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
- A61B2562/02—Details of sensors specially adapted for in-vivo measurements
- A61B2562/028—Microscale sensors, e.g. electromechanical sensors [MEMS]
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M2205/00—General characteristics of the apparatus
- A61M2205/35—Communication
- A61M2205/3507—Communication with implanted devices, e.g. external control
- A61M2205/3523—Communication with implanted devices, e.g. external control using telemetric means
Abstract
An implantable biosensor system for monitoring and optionally alleviating a physiological condition in a patient is provided and includes (a) at least one sensor for sensing at least one parameter of a physiological condition and for generating electrical sensor signals representative of the physiological condition; and (b) a first acoustic activatable transducer being directly or indirectly coupled with the at least one sensor, the first acoustic activatable transducer being for converting a received acoustic interrogation signal from outside the patient's body into an electrical power for energizing the processor, the first acoustic activatable transducer further being for converting the electrical sensor signals of the at least one sensor into acoustic signals receivable out of the patient's body, such that information pertaining to the at least one parameter of the physiological condition can be relayed outside the patient's body upon generation of an acoustic interrogation signal.
Description
' , ~ 1 IMPLANTABLE ACOUSTIC BIO-SENSING SYSTEM
AND METHOD
1$
AND METHOD
1$
2$ The present invention relates to a biosensing system aad method for monitoring internal physiological conditions of a patient. More particularly, the present invention relates to a biosensor system implantable in a patient's body that includes at least one sensor, an active acoustic transducer and a miniature processor. The sensor is used to monitor a physiological condition of the patient and relay information pertaining to the physiological condition through the miniature processor to the active acoustic transducer. The active acoustic transducer transmits this information out of the patient's body as an acoustic signal.
Transmission of an acoustic signal from the transducer is triggered by an externally generated acoustic interrogation and energizing signal, which is produced by a second acoustic transducer positioned externally, yet in intimate contact with, the patient's body. The miniature electronic processor is utilized for the various required functions such as conditioning, digitization and amplification of the sensor signals. The biosensor of the present invention can also include a shunt and a monitoring device embedded in the walls of the shunt for permitting identification and non-invasive testing of the operation of the shunt via the acoustic transducer.
Many medical conditions require the monitoring and measurement of internal physiological conditions of a patient. For example, hydrocephalus, which is a brain condition where cerebrospinal fluid accumulates at abnormally high pressures in ventricles or chambers of a patient's brain, may require monitoring of the infra-cranial fluid pressure of the patient.
Implantable devices for monitoring internal physiological conditions of a patient are known in the art. One such prior art device ' 3 .. .
includes an implantable pressure sensor that transmits pressure signals out of the patient by mechanism of a wire or contact passing through the patient's skull (see, for example, U.S. Pat. No. 4,677,985). These types of devices are generally unsatisfactory due to increased risk of infection and patient discomfort caused by the externally extending wire.
Monitoring devices that are completely implantable within a patient are also known in the art. One such prior art devices is described in U.S.
Pat. No. 4,471,786 and includes a sensor for sensing a physiological condition of the patient and a transmitter and battery assembly for transmitting the sensor signals out of the patient's body. These types of devices are also unsatisfactory for many types of medical conditions since the batteries are bulky and must be periodically r~laced, thus necessitating additional surgery.
Implantable monitoring devices that do not require batteries have also been developed. Such devices (see, for example, U.S. Pat. Nos.
Transmission of an acoustic signal from the transducer is triggered by an externally generated acoustic interrogation and energizing signal, which is produced by a second acoustic transducer positioned externally, yet in intimate contact with, the patient's body. The miniature electronic processor is utilized for the various required functions such as conditioning, digitization and amplification of the sensor signals. The biosensor of the present invention can also include a shunt and a monitoring device embedded in the walls of the shunt for permitting identification and non-invasive testing of the operation of the shunt via the acoustic transducer.
Many medical conditions require the monitoring and measurement of internal physiological conditions of a patient. For example, hydrocephalus, which is a brain condition where cerebrospinal fluid accumulates at abnormally high pressures in ventricles or chambers of a patient's brain, may require monitoring of the infra-cranial fluid pressure of the patient.
Implantable devices for monitoring internal physiological conditions of a patient are known in the art. One such prior art device ' 3 .. .
includes an implantable pressure sensor that transmits pressure signals out of the patient by mechanism of a wire or contact passing through the patient's skull (see, for example, U.S. Pat. No. 4,677,985). These types of devices are generally unsatisfactory due to increased risk of infection and patient discomfort caused by the externally extending wire.
Monitoring devices that are completely implantable within a patient are also known in the art. One such prior art devices is described in U.S.
Pat. No. 4,471,786 and includes a sensor for sensing a physiological condition of the patient and a transmitter and battery assembly for transmitting the sensor signals out of the patient's body. These types of devices are also unsatisfactory for many types of medical conditions since the batteries are bulky and must be periodically r~laced, thus necessitating additional surgery.
Implantable monitoring devices that do not require batteries have also been developed. Such devices (see, for example, U.S. Pat. Nos.
3,943,91 S and 4,593,703) employ sensors coupled with frequency tuned Lumped-Constant (L-C) circuits. The sensors mechanically translate changes in sensed physiological condition to the inductor or capacitor of the tuned L-C circuit for changing the reactance of the L-C circuit. This ..
change in reactance alters the resonant frequency of the circuit, which is then detected by an external receiver and converted to a signal representative of the monitored physiological condition.
Although these L-C type implantable monitoring devices are S superior to battery operated devices in some respects, they also suffer from several limitations that limit their utility. For example, the L-C circuits are difficult to calibrate once implanted, are inherently single-channel, and are only sensitive in a particular range of measurements_ Thus, L~ type monitoring devices are not always accurate after they have been implanted for a long period of time and are not suitable for use with sensors that have a wide sensing range. In addition, no processing power is provided.
Another implantabie monitoring device that does not utilizes wire connection or a battery supply makes use of large electromagnetic antennae to provide the energy required for the data processing inside the 1 S body. These antennas are big and risky to implant. Also, due to the high absorption of electromagnetic energy by human tissue, only subcutaneous implants are used, and energy into the depth of the body is realized by wiring coupling. Only small amounts of electromagnetic energy can be transmitted from an external antenna directly to a monitoring device deep in the body.
A general limitation of all of the above-described prior art implantable monitoring devices is that they are operable for sensing or $ monitoring only one physiological condition. Thus, if a doctor wishes to monitor, e.g., both the pressure and the temperature of the fluid in the ventricles of a patient's brain, two such devices must be implanted.
Furthermore, these prior art implantable devices merely monitor a physiological condition of the patient and transmit a signal representative of the condition out of the patient's body, but do not perform any processing or conversion of the signals.
In addition, due to inherent design limitations, these devices cannot be utilized for alleviating the underlying cause of the physiological condition monitored. For example, infra-cranial pressure sensors designed 1$ for use with patients suffering from hydrocephalus merely detect when fluid pressure levels within the patient's brain are high, but are not operable for reducing the amount of cerebrospinal fluid accumulated in the patient's brain. Thus, once these prior infra-cranial pressure sensors determine that the pressure in the patient's brain is too high, surgery must be performed to alleviate the condition.
An improved implantable biosensor for monitoring and alleviating internal physiological condition such as intracranial pressure has been described in U.S. Pat. No. 5,704,352 which discloses a biosensor system which includes at least one sensor for monitoring a physiological condition of the patient and a passive radio frequency transducer that receives sensor signals from the sensor or sensors, digitizes the sensor signals, and transmits the digitized signals out of the patient's body when subjected to an externally generated electromagnetically interrogation and energizing signal. The biosensor system described also includes a shunt, and as such it can be used for alleviating intracranial pressure monitored by the sensors of the biosensor.
Although this biosensor system presents a major advance over the 1 S above mentioned prior art devices and systems, it suffers from limitations inherent to the radio frequency transducer utilized thereby. Since this transducer requires the use of an antenna to receive and transmit signals, it posses limited reception and transmission capabilities due to the directional nature of such antennas. In addition, due to the high absorption of electromagnetic energy by human tissue, deeply embedded implants cannot be realized by this system and as a result, the infra body positioning of such a biosensor is limited to regions close to the skin which are accessible to electromagnetic signals, thus greatly limiting the effectiveness of such a system.
There is thus a widely recognized need for, and it would be highly advantageous to have, a biosensor system for monitoring and alleviating internal physiological conditions, such as infra-cranial pressure, devoid of the above limitations.
15 It is therefore an object of the present invention to provide a biosensor which can be used for non-invasive monitoring of body parameters.
It is another object of the present invention to provide such a biosensor which does not require wiring or an integral power source.
g It is yet another object of the present invention to provide a biosensor which is less sensitive to extracorporeal positional effect when energized as compared to prior art devices.
It is still another object of the present invention to provide a biosensor which is effectively operable from any depth within the body.
To realize and reduce down to practice these objectives, the biosensor according to the present invention takes advantage of the reliable conductivity of acoustic radiation within water bodies, such as a human body and of an acoustic activatable piezoelectric transducer.
According to one aspect of the present invention there is provided According to one aspect of the present invention there is provided an implantabie biosensor system for monitoring and optionally alleviating a physiological condition in a patient, the biosensor system comprising (a) at least one sensor for sensing at least one parameter of a physiological 1 S condition and for generating electrical sensor signals representative of the physiological condition; and (b) a first acoustic activatable transducer being directly or indirectly coupled with the at least one sensor, the first acoustic activatable transducer being for converting a received acoustic interrogation signal from outside the patient's body into an electrical power for energizing the processor, the first acoustic activatable transducer further being for converting the electrical sensor signals of the at least one sensor into acoustic signals receivable out of the patient's body, such that information pertaining to the at least one parameter of the physiological condition can be relayed outside the patient's body upon generation of an acoustic interrogation signal.
According to further features in preferred embodiments of the invention described below, the biosensor system further comprising a processor coupling between the at least one sensor and the first acoustic activatable transducer, the processor being for converting the electrical sensor signals into converted electrical signals representative of the physiological condition, the processor being energized via the electrical power.
According to another aspect of the present invention there is provided an implantable biosensor system for monitoring and alleviating a physiological condition in a patient, the biosensor system comprising (a) a shunt having a fluid passageway and being operable for draining fluid through the fluid passageway from a portion of a patient's body; (b) a monitoring and operating mechanism coupled with the shunt for non-1~
invasively monitoring the physiological condition and operating the shunt, the monitoring and operating mechanism including at least one sensor for sensing at least one parameter of the physiological condition and for generating electrical sensor signals representative of the physiological condition; and (c) a first acoustic activatable transducer being directly or indirectly coupled with the at least one sensor, the first acoustic activatable transducer being for converting a received acoustic interrogation signal from outside the patient's body into an electrical power for energizing the at least one sensor and for operating the shunt upon command, the first acoustic activatable transducer further being for converting the electrical sensor signals into acoustic signals receivable out of the patienfs body, such that information pertaining to the at least one parameter of the physiological condition can be relayed outside the patient's body upon generation of an acoustic interrogation signal and the shunt is operable 1 S upon command.
According to still further features in the described preferred embodiments the monitoring and operating mechanism further includes a processor coupled with the at least one sensor, the processor serves for converting the electrical sensor signals to converted electrical signals representative of the physiological condition.
According to still further features in the described preferred embodiments the command is an acoustic operation signal provided from outside the body.
According to still further features in the described preferred embodiments the shunt is a cerebrospinal fluid shunt for draining cerebrospinal fluid from the patient's brain.
According to still further features in the described preferred embodiments the at least one sensor includes a first pressure sensor positioned within the fluid passageway for sensing the pressure of the cerebrospinal fluid in the patient's brain and for generating a first pressure signal representative of that pressure.
According to still further features in the described preferred embodiments the at least one pressure sensor includes a second pressure sensor positioned at a distance from the first pressure sensor and being for sensing the pressure of the cerebrospinal fluid when flowing through the shunt and for generating a second pressure signal representative of that pressure.
According to still further features in the described preferred embodiments the processor receives the first and second pressure signals from the first and second pressure sensors and calculates the flow rate of cerebrospinal fluid through the shunt.
According to still further features in the described preferred embodiments the first acoustic activatable transducer includes (i) a cell member having a cavity; (ii) a substantially flexible piezoelectric layer attached to the cell member, the piezoelectric layer having an external surface and an internal surface, the piezoelectric layer featuring such dimensions so as to enable fluctuations thereof at its resonance frequency upon impinging of the acoustic interrogation signal; and (iii) a first electrode attached to the external surface and a second electrode attached to the internal surface.
According to still further features in the described preferred embodiments the piezoelectric layer is of a material selected from the group consisting of PVDF and piezoceramic.
According to still further features in the described preferred embodiments the processor includes a conditioner and a digitizer for converting the electrical sensor signal to the converted electrical signal.
According to still further features in the described preferred embodiments the converted electrical signal is a digital signal.
According to still further features in the described preferred embodiments the processor, the first acoustic activatable transducer and the at least one sensor are co-integrated into a single biosensor device.
According to still further features in the described preferred embodiments the biosensor system further comprising (c) an extracorporeal station positionable against the patient's body the extracoiporeai station including an interrogation signal generator for generating the acoustic interrogation signal, the interrogation signal generator includingat least secondtransducerfor transmittingthe one interrogation to the acousticactivatabletransducer for signal first and 1 S receiving the receivable acoustic signals from the first acoustic activatable transducer.
According to still further features in the described preferred embodiments the processor includes a memory device for storing the electrical sensor signals and an analyzer for analyzing the electrical sensor signals.
According to still further features in the described preferred embodiments the processor includes a programmable microprocessor.
According to still further features in the described preferred embodiments the at least one sensor is selected from the group consisting of a pressure sensor, a temperature sensor, a pH sensor, a blood sugar sensor, a blood oxygen sensor, a motion sensor, a flow sensor, a velocity sensor, an acceleration sensor, a force sensor, a strain sensor, an acoustics sensor, a moisture sensor, an osmolarity sensor, a light sensor, a turbidity sensor, a radiation sensor, an electromagnetic field sensor, a chemical sensor, an ionic sensor, and an enzymatic sensor.
According to still further features in the described preferred embodiments the first acoustic activatable transducer is capable of 1 S transmitting an identification code identifying the transducer.
According to yet another aspect of the present invention there is provided a method for non-invasive monitoring of a physiological condition within a patient's body, the method comprising the steps of (a) sensing at least one parameter associated with the physiological condition via at least one sensor implanted within the patient's body to thereby obtain information pertaining to the physiological condition as an electrical output; (b) converting the electrical output into an acoustic signal via an acoustic transducer and thereby acoustically relaying the 5 information to outside the patient's body; and (c) relaying an acoustic interrogation signal from outside the patient's body for activating the at least one sensor.
According to still -another aspect of the present invention there is provided a method for non-invasive monitoring and alleviating of a 10 physiological condition within a patient's body, the method comprising the steps of (a) sensing at least one parameter associated with the physiological condition via at least one sensor implanted within the patient's body to thereby obtain information pertaining to the physiological condition as an electrical output; (b) converting the electrical 15 output into an acoustic signal via an acoustic transducer and thereby acoustically relaying the information to outside the patient's body; and (c) relaying an acoustic interrogation signal from outside the patient's body for activating the at least one sensor and further for activating a shunt for alleviating the physiological condition.
The present invention successfully addresses the shortcomings of the presently known configurations by providing a biosensor which can be used for non-invasive monitoring of body parameters, which does not require wiring, which does not require an integral power source, which can be effectively positioned at any location and depth within the body and which is much less subject to interrogation positional effect as compared with prior art devices.
The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:
FIG. 1 a is a longitudinal cross section of a transducer element according to the present invention taken along lines A-A in Figures 2a-2e;
FIG. lb is a longitudinal cross section of a transducer element according to the present invention taken along lines B-B in FIGS. 2a-2e;
FIG. 2a is a cross section of a transducer element according to the present invention taken along line C-C in FIG. 1 a;
FIG. 2b is a cross section of a transducer element according to the present invention taken along line D-D in FIG. 1 a;
FIG. 2c is a cross section of a transducer element according to the present invention taken along line E-E in FIG. 1 a;
FIG. 2d is a cross section of a transducer element according to the present invention taken along line F-F in FIG. 1 a;
FIG. 2e is a cross section of a transducer element according to the present invention taken along line G-G in FIG. 1 a;
FIG. 3 shows the distribution of charge density across a piezoelectric layer of a transducer element resulting from the application of a constant pressure over the entire surface of the layer;
FIG. 4 shows the results of optimization performed for the power 1 S response of a transducer according to the present invention;
FIG. S shows a preferred electrode shape for maximizing the power response of a transducer according to the present invention;
FIG. 6 is a longitudinal section of another embodiment of a transducer element according to the present invention capable of functioning as a transmitter;
FIG. 7a-7f are schematic views of possible configurations of transmitters according to the present invention including parallel and anti-parallel electrical connections for controllably changing the mechanical impedance of the piezoelectric layer;
FIG. 8 is a longitudinal section of a transmitter element according to the present invention including an anti-parallel electrical connection;
FIG. 9 is a longitudinal section of another embodiment of a transmitter element according to the present invention;
FIG. 10 is a block diagram depricting the intrabody and extracoiporeal components of the biosensor system according to the present invention;
FIG. 11 is a schematic depiction of components of the biosensor system according to one embodiment of the present invention;
FIG. 12 is a longitudinal section of a shunt system including an acoustic transducer and pressure sensors according to another embodiment of the present invention;
FIG. 13 is a schematic depiction of the transducer and pressure sensors of Figure 12 isolated from the shunt; and FIG. 14 is a block diagram of the extracorporeal station components according to the present invention implemented within a S helmet.
p~~ TPTION OF THF P FF R FD .MBODIMENT
The present invention is of an intrabody bio-sensing system and method which can be used for both monitoring and alleviating physiological conditions within a patient's body. Specifically, the biosensor system and method of the present invention incorporates an active acoustic transducer communicating with sensors and optionally with a shunt implanted within the patient's body for monitoring and alleviating, for example, infra-cranial pressure of a patient suffering from hydrocephalus.
The principles and operation of an implantable biosensor system according to the present invention may be better understood with reference to the drawings and accompanying descriptions.
Before explaining at least one embodiment of the invention in 5 detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that 10 the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. For purposes of better understanding the system and method according to the present invention, as illustrated in Figures i0-i4 of the drawings, reference is first made to the construction and operation of a transducer as described in U.S. Pat.
15 application No. 09/000,553.
Referring now to the drawings, Figures la, lb and 2a-2e illustrate a preferred embodiment of a transducer element according to the present invention which is referred to herein as transducer element 1. Transducer element 1 serves for converting received acoustic signals into electrical power and for converting electrical power to transmitted acoustic signals.
As shown in the figures, the transducer element 1 includes at least one cell member 3 including a cavity 4 etched into a substrate and covered by a substantially flexible piezoelectric layer 2. Attached to piezoelectric layer 2 are an upper electrode 8 and a lower electrode 6, the electrodes for connection to an electronic circuit.
The substrate is preferably made of an electrical conducting layer 11 disposed on an electrically insulating layer 12, such that cavity 4 is etched substantially through the thickness of electrically conducting layer 11.
Electrically conducting layer 11 is preferably made of copper and insulating layer 12 is preferably made of a polymer such as polyimide.
Conventional copper-plated polymer laminate such as KAPTONT"" sheets may be used for the production of transducer element 1. Commercially available laminates such as NOVACLADT"" may be used. Alternatively, the substrate may include a silicon layer, or any other suitable material.
Alternatively, layer 11 is made of a non-conductive material such as PYRALINT"" .
Preferably, cavity 4 is etched into the substrate by using conventional printed-circuit photolithography methods. Alternatively, cavity 4 may be etched into the substrate by using VLSI/micro-machining technology or any other suitable technology.
Piezoelectric layer 2 may be made of PVDF or a copolymer thereof.
Alternatively, piezoelectric layer 2 is made of a substantially flexible piezoceramic. Preferably, piezoelectric layer 2 is a poled PVDF sheet having a thickness of about 9-28 pm. Preferably, the thickness and radius of flexible layer 2, as well as the pressure within cavity 4, are specifically selected so as to provide a predetermined resonant frequency. When using the embodiment of Figures 1 a and 1 b, the radius of layer Z is defined by the radius of cavity 4.
By using a substantially flexible piezoelectric layer 2, the invention described in U.S. Pat. application No. 09/000,553 allows to provide a 1 S miniature transducer element whose resonant frequency is such that the acoustic wavelength is much larger than the extent of the transducer. This enables the transducer to be omnidirectional even at resonance, and further allows the use of relatively low frequency acoustic signals which do not suffer from significant attenuation in the surrounding medium.
Prior art designs of miniature transducers, however, rely on rigid piezoceramic usually operating in thickness mode. In such cases the resonant frequency relates to the size of the element and speed of sound in the piezoceramic, and is higher by several orders of magnitude.
The invention described in U.S. Pat. application No. 09/000,553 provides a transducer which is omnidirectional, i.e., insensitive to the direction of the impinging acoustic rays, thereby substantially simplifying the transducer's operation relative to other resonant devices: Such a transducer element is thus suitable for application in confined or hidden locations, where the orientation of the transducer element cannot be ascertained in advance.
According to a specific embodiment, cavity 4 features a circular or hexagonal shape with radius of about 200 pm. Electrically conducting layer 11 preferably has a thickness of about 15 Vim. Cell member 3 is preferably etched completely through the thickness of electrically conducting layer 11. Electrically insulating layer 12 preferably features a thickness of about 50 Vim: The precise dimensions of the various elements of a transducer element according to the invention described in U.S. Pat.
application No. 09/000,553 may be specifically tailored according to the requirements of the specific application.
Cavity 4 preferably includes a gas such as air. The pressure of gas within cavity 4 may be specifically selected so as to predetermine the sensitivity and ruggedness of the transducer as well as the resonant frequency of layer 2.
As shown in Figure 2b, an insulating chamber 18 is etched into the substrate, preferably through the thickness of conducting layer 11, so as to insulate the transducer element from other portions of the subshate which may include other electrical components such as other transducer elements etched into the substrate. According to a specific embodiment, the width of insulating chamber 18 is about 100 l,un. As shown, insulating chamber 18 is etched into the substrate so as to form a wail 10 of a predetermined thickness enclosing cavity 4, and a conducting line 17 integrally made with wall 10 for connecting the transducer element to another electronic component preferably etched into the same substrate, or to an external electronic circuit.
As shown in Figures la and lb, attached to piezoelectric layer 2 are upper electrode 8 and lower electrode 6. As shown in Figures 2c and 2e, upper electrode 8 and lower electrode 6 are preferably precisely shaped, so as to cover a predetermined area of piezoelectric layer 2. Electrodes 6 and 8 may be deposited on the upper and lower surfaces of piezoelectric membrane 2, respectively, by using various methods such as vacuum 5 deposition, mask etching, painting, and the like.
As shown in Figure 1 a, lower electrode 6 is preferably made as an integral part of a substantially thin electrically conducting layer 14 disposed on electrically conducting layer 11. Preferably, electrically conducting layer 14 is made of a NickeLCopper alloy and is attached to 10 electrically conducting layer 11 by mechanism of a sealing connection 16.
Sealing connection 16 may be made of indium. According to a preferred configuration, sealing connection 16 may feature a thiclrness of about 10 a m, such that the overall height of wall 10 of cavity 4 is about 20-25 pm.
As shown in Figure 2c, electrically conducting layer 14 covers the 15 various portions of conducting layer 11, including wall 10 and conducting line 17. The portion of conducting layer 14 covering conducting line 17 is for connection to an electronic component, as further detailed hereinunder.
According to a preferred embodiment, electrodes 6 and 8 are specifically shaped to include the most energy-productive region of piezoelectric layer Z, so as to provide maximal response of the transducer while optimizing the electrode area, and therefore the cell capacitance, thereby maximizing a selected parameter such as voltage sensitivity, current sensitivity, or power sensitivity of the transducer element.
The vertical displacement of piezoelectric layer 2,'Y, resulting from a monochromatic excitation at angular frequency w is modeled using the standard equation for thin plates:
(v2 -YZvv2 +y2)~- 3(1 3Z)p+ 3iZco(1 3vz)~-O
ll 2Qh 2Qh wherein Q is the Young's modulus representing the elasticity of layer 2; h the half thickness of layer 2; ~ is the Poisson ratio for layer 2; y is the effective wavenumber in the layer given by: Y ' = 3p(i - V 2 ~ 2 ~Qh 2 , wherein p is the density of layer 2 and cv is the angular frequency of the applied pressure (wherein the applied pressure may include the acoustic pressure, the static pressure differential across layer 2 and any other 1 S pressure the transducer comes across); Z is the mechanical impedance resulting from the coupling of layer 2 to both external and internal media of cavity 4, wherein the internal medium is preferably air and the external medium is preferably fluid; P is the acoustic pressure applied to layer 2, and '~' represents the average vertical displacement of layer 2.
When chamber 4 is circular, the solution (given for a single frequency component ~) representing the dynamic displacement of a circular layer 2 having a predetermined radius a, expressed in polar coordinates, is:
IUYa)~Jo(Tr')-Jo~Ya)~+J ,(Ya)~IotY~')-Io(Ya)~ P
'f(r~~P)= 2hp~'~zLo(Ta)+itaZLz(Ya) Lo ~Z) = Io(Z)JuZ) + JotZ)IOZ)~ Lz ~Z) = Jz ~Z)IOZ) - Iz ~Z) J~ CZ) _ P,, _4 _1 icaH +1[3~ + (~Pwa A
wherein 'h(r, gyp) is time-dependent and represents the displacement of a selected point located on circular layer 2, the specific location of which is given by radius r and angle ~O; J and I are the normal and modified Bessei functions of the first kind, respectively; P,, , H,, are the air pressure within cavity 4 and the height of chamber 4, respectively; and p~ is the density of the fluid external to cavity 4.
The first term of the impedance Z relates to the stiffness resulting from compression of air within cavity 4, and the second term of Z relates to the mass added by the fluid boundary layer. An additional term of the impedance Z relating to the radiated acoustic energy is substantially negligible in this example.
The charge collected between electrodes 6 and 8 per unit area is obtained by evaluating the strains in layer 2 resulting from the displacements, and multiplying by the pertinent off diagonal elements of the piezoelectric strain coefficient tensor, a", e32 , as follows:
a~~ 2 a~ 2 Q(r,cp,t)=e3~ 8x ay wherein Q(r,tp,t) represents the charge density at a selected point located on circular layer 2, the specific location of which is given by radius r and angle ~p; x is the stretch direction of piezoelectric layer 2; y is the transverse direction (the direction perpendicular to the stretch direction) of layer 2; e3,, e3Z are off diagonal elements of the piezoelectric strain coefficient tensor representing the charge accumulated at a selected point on layer 2 due to a given strain along the x and y directions, respectively, which coefficients being substantially dissimilar when using a PVDF
layer. 'Y is the displacement of layer 2, taken as the sum of the displacement for a given acoustic pressure P at frequency f, and the static displacement resulting from the pressure differential between the interior and exterior of cavity 4, which displacements being extractable from the equations given above.
. . 29 The total charge accumulated between electrodes 6 and 8 is obtained by integrating Q(r, cp, t) over the entire area S of the electrode:
Q = JQ(r, cp, t ) c~'x The capacitance C of piezoelectric layer 2 is given by: C = 2h jdx' s S wherein E is the dielectric constant of piezoelectric layer 2; and 2h is the thickness of piezoelectric layer 2.
Accordingly, the voltage, current and power responses of piezoelectric layer 2 are evaluated as follows:
Z
2h jQ(r, cp, t ) cf'.x 4ih jQ(r, cp, t) cf',x Y = S , I = 2ic~ jQ(r, cp, t) .~-x, W =
The DC components of Q are usually removed prior to the evaluation, since the DC currents are usually filtered out. The values of Q
given above represent peak values of the AC components of Q, and should be modified accordingly; so as to obtain other required values such as RMS values.
According to the above, the electrical output of the transducer expressed in terms of voltage, current and power responses depend on the AC components of Q, and on the shape S of the electrodes. Further, as can be seen from the above equations, the voltage response of the transducer may be substantially maximized by minimizing the area of the electrode.
The current response, however, may be substantially maximized by maximizing the area of the electrode.
Figure 3 shows the distribution of charge density on a circular 5 piezoelectric layer 2 obtained as a result of pressure (acoustic and hydrostatic) applied uniformly over the entire area of layer 2, wherein specific locations on layer 2 are herein defined by using Cartesian coordinates including the stretch direction (x direction) and tl~e transverse direction (y direction) of layer 2. It can be seen that distinct locations on 10 layer 2 contribute differently to the charge density. The charge density vanishes at the external periphery 70 and at the center 72 of layer 2 due to minimal deformation of these portions. The charge density is maximal at two cores 74a and 746 located symmetrically on each side of center 72 due to maximal strains (in the stretch direction) of these portions.
15 A preferred strategy for optimizing the electrical responses of the transducer is to shape the electrode by selecting the areas contributing at least a selected threshold percentage of the maximal charge density, wherein the threshold value is the parameter to be optimized. A threshold value of 0 % relates to an electrode covering the entire area of layer 2.
Figure 4 shows the results of an optimization performed for the power response of a transducer having a layer 2 of a predetermined area.
As shown in the Figure, the threshold value which provides an optimal power response is about 30 % (graph b). Accordingly, an electrode which covers only the portions of layer 2 contributing at least 30 % of the maximal charge density yields a maximal power response. The pertinent voltage response obtained by such an electrode is higher by a factor of 2 relative to an electrode completely covering layer 2 (graph a). The current response obtained by such electrode is slightly lower relative to an electrode completely covering layer 2 (graph c). Further as shown in the Figure, the deflection of layer 2 is maximal when applying an acoustic signal at the resonant frequency of layer 2 (graph d).
A preferred electrode shape for maximizing the power response of the transducer is shown in Figure S, wherein the electrode includes two electrode portions 80a and 80b substantially covering the maximal charge density portions of layer 2, the electrode portions being interconnected by mechanism of a connecting member 82 having a minimal area.
Preferably, portions 80a and 80b cover the portions of layer 2 which yield at least a selected threshold (e.g. 30 %) of the maximal charge density.
According to the present invention any other parameter may be optimized so as to determine the shape of electrodes 6 and 8. According to further features of the invention described in U.S. Pat. application No.
09/000,553, only one electrode (upper electrode 8 or lower electrode 6) may be shaped so as to provide maximal electrical response of the transducer, with the other electrode covering the entire area of layer 2.
Since the charge is collected only at the portions of layer 2 received between upper electrode 8 and lower electrode 6, such configuration is operatively equivalent to a configuration including two shaped electrodes having identical shapes.
Referring now to Figure 6, according to another embodiment chamber 4 of hansducer element 1 may contain gas of substantially low pressure, thereby conferring a substantially concave shape to piezoelectric membrane 2 at equilibrium. Such configuration enables to further increase the electrical response of the transducer by increasing the total charge obtained for a given displacement of layer 2. The total displacement in such an embodiment is given by: 'I' = Po'Y~ + P'I',,c cos cat , wherein Po is the static pressure differential between the exterior and the interior of cavity 4; '1'DC is the displacement resulting from Po; P is the amplitude of the acoustic pressure; and'1'AC is the displacement resulting from P.
Accordingly, the strain along the x direction includes three terms as follows:
z Z z = a~ __ o ~ a~o~ ~ 2 ~ ~AC ~ Z o a~YD~ a'#',,c S ax P ax + P ax cos wt + 2P P ax 8x cos wt wherein the DC component is usually filtered out.
Thus, by decreasing the pressure of the medium (preferably air) -within cavity 4 relative to the pressure of the external medium (preferably fluid), the value of Po is increased, thereby increasing the value of the 10' third term of the above equation.
Such embodiment makes it possible to increase the charge output of layer 2 for a given displacanent, thereby increasing the voltage, current and power responses of the transducer without having to increase the acoustic pressure P. Furthermore, such embodiment enables to further 1 S miniaturize the transducer since the same electrical response may be obtained for smaller acoustic deflections. Such embodiment is substantially more robust mechanically and therefore more durable than the embodiment shown in Figures la and lb. Such further miniaturization of the transducer enables to use higher resonance frequencies relative to the embodiment shown in Figures la and lb.
Preferably, a transducer element 1 according to the invention described in U.S. Pat. application No. 09/000,553 is fabricated by using technologies which are in wide use in the microelectronics industry, so as to allow integration thereof with other conventional electronic components as further detailed hereinunder. When the transducer element includes a substrate such as Copper-polymer laminate or silicon, a variety of conventional electronic components may be fabricated onto the same substrate.
According to a preferred embodiment, a plurality of cavi#ies 4 may be etched into a single substrate 12 and covered by a single piezoelectric layer 2, so as to provide a transducer element including a matrix of transducing cell members 3, thereby providing a larger energy collecting area of predetermined dimensions, while still retaining the advantage of miniature individual transducing cell members 3. When using such configuration, the transducing cell members 3 may be electrically interconnected in parallel or serial connections, or combinations thereof, so as to tailor the voltage and current response of the transducer. Parallel connections are preferably used so as to increase the current output while serial connections are preferably used so as to increase the voltage output of the transducer.
Furthermore, piezoelectric layer 2 may be completely depolarized 5 and then repolarized at specific regions thereof, so as to provide a predetermined polarity to each of the transducing cell members 3. Such configuration enables to reduce the complexity of interconnections between cell members 3.
A transducer element according to the invention described in U.S.
10 ~ Pat. application No. 09/000,553 may be further used as a transmitter for transmitting information to a remote receiver by modulating the reflection of an external impinging acoustic wave arrived frnm a remote transmitter.
Referring to Figure 6, the transducer element shown may function as a transmitter element due to the asymmetric fluctuations of piezoelectric 15 layer 2 with respect to positive and negative transient acoustic pressures obtained as a result of the pressure differential between the interior and exterior of cavity 4.
A transmitter element according to the present invention preferably modulates the reflection of an external impinging acoustic wave by mechanism of a switching element connected thereto. The switching element encodes the information that is to be transmitted, such as the output of a sensor, thereby frequency modulating a reflected acoustic wave.
Such configuration requires very little expenditure of energy from the transmitting module itself, since the acoustic wave that is received is externally generated, such that the only energy required for transmission is the energy of modulation.
Specifically, the reflected acoustic signal is modulated by switching the switching element according to the frequency of a message electric signal arriving from another electronic component such as a s~sor, so as to controllably change the mechanical impedance of layer 2 according to the frequency of the message signal.
Preferably, a specific array of electrodes connected to a single cell 1 S member or alternatively to a plurality of cell members are used, so as to control the mechanical impedance of layer 2.
Figures 7a-7g illustrate possible configurations for controllably change the impedance of layer 2 of a transmitter element. Referring to Figure 7a, a transmitter element according to the invention described in U.S. Pat. application No. 09/OOO,SS3 may include a first and second pairs of electrodes, the first pair including an upper electrode 40a and a lower electrode 38a, and the second pair including an upper electrode 40b and a lower electrode 38b. Electrodes 38a, 38b, 40a and 40b are electrically connected to an electrical circuit by mechanism of conducting lines 36a, 36b, 34a and 34b, respectively, the electrical circuit including a switching element (not shown), so as to alternately change the electrical connections of conducting lines 36a, 366, 34a and 34b. -Preferably, the switching element switches between a parallel connection and an anti-parallel connection of the electrodes. A parallel connection decreases the mechanical impedance of layer 2, wherein an anti-parallel connection increases the mechanical impedance of layer 2.
An anti-parallel connection may be obtained by interconnecting line 34a to 36b and line 34b to 36a. A parallel connection may be obtained by connecting line 34a to 34b and line 36a to 36b. Preferably, the switching frequency equals the frequency of a message signal arriving from an electrical component such as a sensor as further detailed hereinunder.
According to another embodiment shown in Figure 7b, upper electrode 40a is connected to lower electrode 38b by mechanism of a conducting line 28, and electrodes 38a and 40b are connected to an electrical circuit by mechanism of conducting lines 27 and 29, respectively, wherein the electrical circuit further includes a switching element. Such configuration provides an anti-parallel connection of the electrodes, wherein the switching element functions as an on/off switch, thereby alternately increasing the mechanical impedance of layer 2.
In order to reduce the complexity of the electrical connections, layer 2 may be depolarized and then repolarized at specific regions thereof. As shown in Figure 7c, the polarity of the portion of layer 2 received between electrodes 40a and 38a is opposite to the polarity of the portion of layer Z received between electrodes 406 and 38b. An anti-parallel connection is thus achieved by interconnecting electrodes 38a and 38b by mechanism of a conducting line 28, and providing conducting lines 27 and 29 connected to electrodes 40a and 40b, respectively, the conducting lines for connection to an electrical circuit including a switching element.
According to another embodiment, the transmitting element includes a plurality of transducing cell members, such that the mechanical impedance of layer 2 controllably changed by appropriately interconnecting the cell members.
As shown in Figure 7d, a first transducing cell member 3a including a layer 2a and a cavity 4a, and a second transducing cell member 3b including a layer 2b and a cavity 4b are preferably contained within the same substrate; and layers 2a and 2b are preferably integrally made. A first pair of electrodes including electrodes 6a and 8a is attached to layer 2, and a second pair of electrode including electrodes~6b and 8b is attached to layer 2b. Electrodes 6a, 8a, 6b and 8b are electrically connected to an electrical circuit by mechanism of conducting lines 37a, 35a, 37b and 35b, respectively, the electrical circuit including a switching element, so as to alternately switch the electrical connections of conducting lines 37a, 35a, 37b and 35b, so as to alternately provide parallel and anti-parallel connections, substantially as described for Figure 7a, thereby alternately decreasing and increasing the mechanical impedance of layers 2a and 2b.
Figure 7e illustrates another embodiment, wherein the first and second transducing cell members are interconnected by mechanism of an anti-parallel connection. As shown in the Figure, the polarity of layer 2a a0 is opposite to the polarity of layer 2b, so as to reduce the complexity of the electrical connections between cell members 3a and 3b. Thus, electrode 6a is connected to electrode 6b by mechanism of a conducting line 21, and electrodes 8a and 8b are provided with conducting lines 20 and 22, respectively, for connection to an electrical circuit which includes a switching element, wherein the switching element preferably functions as an on/off switch, so as to alternately increase the mechanical impedance of j~ layers 2a and 2b.
Figure 7f shows another embodiment, wherein the first and second transducing cell members are interconnected by mechanism of a parallel connection. As shown, electrodes 6a and 6b are interconnected by mechanism of conducting line 24, electrodes 8a and 8b are interconnected by mechanism of conducting line 23, and electrodes 6b and 8b are provided with conducting lines 26 and 25, respectively, the conducting lines for connection to an electrical circuit including a switching element.
The switching element preferably functions as an on/off switch for alternately decreasing and increasing the mechanical impedance of layers 2a and 2b.
Figure 8 shows a possible configuration of two transducing cell members etched onto the same substrate and interconnected by mechanism of an anti-parallel connection. As shown in the Figure, the transducing cell members are covered by a common piezoelectric layer 2, wherein the polarity of the portion of layer 2 received between electrodes 6a and 8a is opposite to the polarity of the portion of layer 2 received between electrodes 6b and 8b. Electrodes 8a and 8b are bonded by mechanism of a conducting line 9, and electrodes 6a and 66 are provided with conducting lines 16 for connection to an electrical circuit.
Another embodiment of a transmitter element according to the present invention is shown in Figure 9. The transmitter element includes a transducing cell member having a cavity 4 covered by a first and second piezoelectric layers, 50a and 50b, preferably having opposite polarities.
Preferably, layers 50a and 50b are interconnected by mechanism of an insulating layer 52. Attached to layer 50a are upper and lower electrodes 44a and 42a, and attached to layer 50b are upper and lower electrodes 44b and 42b. Electrodes 44a, 42a, 44b and 42b are provided with conducting lines 54, 55, 56 and 57, respectively, for connection to an electrical circuit.
It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the spirit and the scope of invention described in U.S. Pat.
application No. 09/000,553.
S As is detailed hereinunder, in preferred embodiments, the present invention exploits the advantages of the acoustic transducer described hereinabove and in U.S. Pat. application No. 09/000,553.
Thus, according to the present invention there is provided an implantable biosensor system, which is referred to hereinunder as biosensor 100.
Biosensor 100 is implantable within a patient's body for monitoring a physiological condition therein. In the course of its operation, biosensor 100 relays, on command, information in the form of acoustic signals pertaining to a parameter or parameters associated with the physiological condition as these are sensed by an implanted sensor or sensors.
Furthermore, biosensor 100 according to the present invention is designed to be energized via an external acoustic interrogation signal.
As such, biosensor 100 is wire and/or integral power source independent. In addition, since the human body is, in effect, a water body and further since acoustic radiation is readily propagatable, if so desired, within water bodies in all directions, biosensor 100 of the present invention provides advantages over the prior art in terms of effective implantable depth within the body and further in terms of interrogation signal positional effect.
As further detailed hereinunder, according to a preferred embodiment of the present invention biosensor system 100 incorporates a shunt for alleviating a monitored physiological condition.
As shown in Figure 10, and according to one embodiment of the present invention, when implanted in a monitoring or treatment infra body site, biosensor 100 of the present invention is employed for sensing or monitoring one or more parameters of a physiological condition within the patient and for transmitting acoustic signals representative of this physiological condition or these parameters out of the patient's body.
According to this embodiment of the present invention, biosensor 100 includes one or more sensors 112 for sensing, monitoring or measuring one or more parameters of the physiological conditions of the patient.
Biosensor 100 also includes an acoustic activatable transducer 114.
Transducer 114 serves for receiving electrical signals from sensors 112 and for converting such electrical signals into acoustic signals. Transducer 114 also serves for receiving externally generated acoustic interrogation signals and for converting such acoustic energy into electrical power which is used for energizing sensors 112 and for rendering biosensor 100 wire and integral power source independent.
As further shown in Figure 10, transducer 114 includes a receiving assembly 117 and a transmitting assembly 118, preferably both are integrated into a single transceiver assembly.
According to a preferred embodiment of the present invention receiving assembly 117 and transmitting assembly 118 are assembled of transducer element 1, the construction of which is further detailed hereinabove with regards to Figures la, lb and 2a-2e. Alternatively, a plurality of transducer elements 1 can also be utilized in various configurations (as shown in Figures 7b-f, 8 and 9 hereinabove) in the receiving assembly 117 and transmitting assembly 118 of biosensor 100 of the present invention The components of transducer 114 can be formed from separate transducer element 1 units, although the integration of one transducer element 1 into a transceiver is preferred, due to the high degree of miniaturization required in biosensing devices.
5 According to a preferred embodiment of the present invention signals received and/or transmitted by biosensor 100 are processed by a processor 113. Electrical signals generated by sensors 112 are processed through processor 113 and are forwarded in their processed or converted form to transducer 114. In addition, acoustic signals received by 10 transducer 114 and which are converted to electrical signals (and power) thereby, are preferably further processed by processor 113.
To this end, processor 113, preferably includes a conditioner 116 and, when necessary, a digitizer 119 for processing the electrical signals received thereby from sensors 112 and/or transducer 114.
15 The acoustic interrogation signal is generated by an extracorporeal station 130 which includes an interrogator 115 and which is also illustrated in Figure 10, the operation and construction of which is described in further detail below.
Sensors 112 are operable for monitoring or detecting one or more physiological conditions within the patient's body, such as the pressure and/or the temperature of the cerebrospinal fluid in the cavities or ventricles of the patient's brain. Sensors 112 then generate sensor signals representative of these measured physiological parameters. The sensor signals are typically electrical analog signals but may also be digital, depending on the type of sensor employed. It will be appreciated that sensors having a built-in analog-to-digital converter are well known in the art.
Sensors 112 are preferably conventional in construction and may include, for example, pressure sensors, temperature sensors, pH sensors, blood sugar sensors, blood oxygen sensors, or any other type of physiological sensing, monitoring or measuring devices responsive to, for example, motion, flow, velocity, acceleration, force, strain, acoustics, moisture, osmolarity, light, turbidity, radiation, electromagnetic fields, chemicals, ionic, or enzymatic quantities or changes, electrical and/or impedance.
Examples of these and other sensor devices useful in context of the present invention are described in detail in the AIP Handbook of Modern Sensors by Jacob Fraden, hereby incorporated by reference.
In a preferred embodiment, sensors 112 are pressure sensor transducers such as the PVDF sensors described in U.S. Pat. application 09/161,658, which is incorporated herein by reference, or the MPX2000 series pressure sensors distributed by Motorola.
As mentioned above according to a preferred embodiment of the present invention transducer 114 is electrically coupled to sensors 112 through processor 113. Processor 113 conditions the sensor signals via conditioner 1 i6, converts the sensor signals to a digital form (when so required) via digitizer 119, and provides the processed or converted signal to transducer 114. Upon a command, transducer 114 converts the processed electrical signals into corresponding acoustic signals which are concomitantly transmitted out of the patient's body, when subjected to an acoustic interrogation signal from station 130.
In more detail, processor 113 is electrically connected to sensors 112 and both share a common miniature substrate such as is customary in the VLSI (Very Large Scale Integration) industry. Processor 113 directly receives sensors' 112 signals by, e.g., the shortest possible wiring.
Processor 113 serves several functions. As already mentioned, processor 113 conditions via conditioner 116 the signals received from sensors 112. Such conditioning is necessary due to tl~e miniature size and small capacitance of sensors 112, and as such, conditioner 116 provides not only appropriate amplification and filtering, but also impedance reduction, so as to substantially reduce noise pickup and thereby improve the signal-to-noise ratio of biosensor 100.
In addition, digitizer 119 is employed in processor 113 to convert the analog signals to digital signals and format the digitized signals as a binary data stream for transmission out of the patient by transducer 114 acoustic signals, which are received and interpreted by extracorporeal station 130.
Processor 113 is also operable for coding and formatting a unique device identification number for transmission with the sensors' signals for use in identifying a specific transducer 114 and/or sensor 112.
Preferably, processor 113 can be programmed to analyze the monitored signals before transmitting the signals out of the patient's body.
To this end, processor 113 can be provided with a memory device and a programmable microprocessor. Many more tasks which are applicable to biosensor system 100 of the present invention can be provided by processor 113, such as, for example, calculating a reading by correlating information derived from a plurality of sensors 112.
For example, if biosensor 100 is provided with a pressure sensor and a temperature sensor for measuring both the pressure and temperature of the cerebrospinal fluid in the patient's brain, processor 113 can then be programmed to adjust the pressure signal transmitted out of the patient's body to compensate for higher or lower temperature readings as sensed by the temperature sensor and vice versa, thereby providing more accurate readings.
It will, however, be appreciated by one ordinarily skilled in the art that sole or additional/supplementary processing can be effected by processors present in extracorporeal station 130.
Preferably, transmitting assembly 118 of transducer 114 employs modulations or other methods in modifying the transmitted acoustic signal, such modulation methods are well known in the art and are described in ' $0 detail in, for example, U.S. Pat. No. 5,619,997 which is incorporated herein by reference.
Extracorporeal station 130 is located outside the patient's body and is designed for powering or energizing transducer 114 of biosensor 100 which is implanted within the patient's body, and for receiving the sensors' acoustic signals.
As illustrated in Figures 10-1 i, according to one embodiment of the present invention and as further detailed in the following sections, transducers 321 of station 130 are mounted within a helmet 310.
Transducers 321 ~ are coupled via wiring with a signal generator 12C, a power amplifier 128, a modulator 132, a demodulator 133, a signal conditioner 134 and a recording and analyzing device 138.
Signal generator 126 and power amplifier 128 provide energy to extracorporeal transducer 321 for generating acoustic signals which propagate from the surface into the patient's body and energize intrabody acoustic transducer 114 when impinging thereon. Signal generator 126 and power amplifier 128 may be of any known type, including devices constructed in accordance with "Data Transmission from an Implantable Biotelemeter by Load-Shift Keying Using Circuit Configuration ~ $1 Modulator" by Zhengnian Tang, Brian Smith, John H. Schild, and P.
Hunter Peckham, IEEE Transactions on Biomedical Engineering, vol. 42, No. 5, May, 1995, pp. 524-528, which is incorporated herein by reference.
As already mentioned, transducers 321 are preferably of a type functionally similar to transducer element 1, the construction of which is further described hereinabove in Figures la, lb, 2a-2e, 7b-f, 8 and 9, each of which can serve as a transmitter, receiver or a transceiver, and are preferably constructed to comply with NCRP 113: Exposure criteria for medical diagnostic ultrasound 1992, puts I and II, provided that transducers 321 when serve as a powering transmitter is capable of transmitting sufficient energy in the form of an acoustic signal for energizing biosensor 100. Preferred transducers 32 i include commercial piston type transducers.
Transducers 321 are electrically connected to power amplifier 128 1 S and acoustically communicable with transducer 114. Transducers 321 transform and deliver the energy generated by generator 126 and power amplifier 128 to transducer 114 via the body of the patient, which serves in this respect as a water body.
Demodulator 133 is operatively coupled to transducers 321 and is provided for extracting digital data received thereby from transducer 114.
An example of a demodulator 133 that can be used in interrogator 115 of extracorporeal station 130 is the MC 1496 or MC 1596 type demodulator distributed by Motorola.
Signal conditioner 134 is connected to demodulator 133 for converting the demodulated data to a format suitable for recording or storing in external devices. An example of a signal conditioner 134 that can be used in station 130 of the present invention is the ADM202 type conditioner distributed by Analog Devices. Signal conditioner 134 may be connected with conventional recording and/or analyzing devices such as computers, printers, and displays for recording, presenting andlor further analyzing the signals transmitted by biosensor 100.
Thus, and according to this embodiment of the present invention, biosensor 100 described hereinabove is implanted in a patient for sensing, monitoring or detecting one or more parameters associated with a physiological condition of the patient. When it is desired to collect information from the body of the patient, a control console 124 commands interrogator 115 to trigger an energizing signal output from signal generator 126. The energizing signal is then modulated with other commands originating from control console 124 that governs processor 113 of biosensor 100 and multiplexer-demultiplexer 381. The modulated signal is amplified by power amplifier 128 and sent to transducer 321 to S energize and render biosensor 100 operative via transducer 114 thereof.
The energy thus provided through the body of the patient is also used to provide transducer 114 with energy to produce an acoustic signal related to the information thus collected by sensors 112. To this end, h~ansducers 321 of station 130 are placed in intimate physical contact with a portion of the patient's body preferably in which biosensor 100 is implanted. Station 130 generates an acoustic interrogation signal via transducers 321 for powering biosensor 100 and for retrieving via transducers 114 sensors' 112 signals as an acoustic signal generated by transducer 114. Interrogator 115 then demodulates sensors' 112 signals and delivers the signals to recording and analyzing device 138.
It will be appreciated that in cases where each of sensors 112 provides information pertaining to a specific parameter, specific information from each of sensors 112 can be accessed by station 130 by providing a unique identifying code for each sensor with the acoustic . ~ 54 interrogation signal. Such a code would be interpreted by processor 113 to command the retrieval of information from any specific sensor of sensors 112.
Referring now to Figures 11-13. According to another preferred embodiment of the present invention and as best illustrated in Figure 12, biosensor 100 further includes a shunt 202 for draining fluid from a portion of a patient's body, and a monitoring device 204 which is further detailed hereinbelow with respect to Figure 13. According to a preferred embodiment, monitoring device 204 is embedded within the walls of shunt 202 for non-invasively rrionitoring the operation of shunt 202.
In more detail, shunt 242 according to this embodiment of the present invention is a cerebrospinal fluid shunt and is used for draining cerebrospinal fluid from a patient's brain, when so required. Cerebrospinal fluid shunt 202 is preferably formed of medical grade synthetic resin material and presents opposed ventricular 206 and distal 208 ends connected by a fluid passageway 205 which includes a valve 105. When shunt 202 is implanted in a patient, ventricular end 206 is positioned in a ventricular cavity of the patient's brain and distal end 208 is positioned in $S
an organ or body cavity remote from the ventricular cavity so as to drain fluids from the patient's brain thereto.
As shown in Figure 11, an appropriate site to drain the cerebrospinal fluid out of the brain may be the abdomen cavity. A further S appropriate site for drainage is immediately after valve 105, in order to make the shunt tubing as short as possible and largely simplify the implantation thereof in surgery. Such drainage is effected via a tube 214 leading from shunt 202 to the patients abdominal cavity. Another appropriate site for draining cerebrospinal fluid out of the patient's brain may be the patient's skull, close to the spine. In this case the drainage tube is much shorter, simplifying the implantation surgery and reducing the risk to the patient. In both case, valve 145 which forms a part of, and is operable by, biosensor 100 is preferably used for alleviating intracranial pressure via shunt 202.
1 S As best illustrated in Figure 12, monitoring device 204 is preferably formed or embedded within the sidewall of shunt 202.
Referring to Figure 13, monitoring device 204 preferably includes one or more pressure sensors 212 and a transducer 214 which is electrically coupled with sensors 212. Like sensors 112, sensors 212 can . , 56 include, for example, temperature sensors, pH sensors, blood sugar sensors, blood oxygen sensors, or any other type of physiological sensing, monitoring or measuring device responsive to, for example, motion, flow, velocity, acceleration, force, strain, acoustics, moisture, osmolarity, light, turbidity, radiation, electricity, electromagnetic fields, chemicals, ionic, or enzymatic quantities or changes.
According to a preferred embodiment of the present invention, sensors 212 are provided for sensing the pressure of the cerebrospinal fluid in shunt passageway 205 and are preferably spaced a distance apart from one another for sensing pressure at different points within passageway 205. Sensors 212 may be placed anywhere within shunt 202 and may include piezoelectric or piezo-resistive transducers, silicon capacitive pressure transducers, variable-resistance laminates of conductive ink, variable conductance elastomeric devices, strain gauges or similar types of pressure sensitive devices.
Transducer 214 is also preferably formed or embedded within the sidewall of the shunt 202 and is coupled with sensors 212 for directly or indirectly (via a processor) receiving electrical pressure signals therefrom.
According to this embodiment of the present invention biosensor 100 which includes monitoring device 204 is implanted in a patient as illustrated generally in Figure 11 for draining or removing cerebrospinal fluid from the patient's brain for treating hydrocephalus. Monitoring device 204 which is preferably formed within the sidewalls of shunt 202 senses or detects the pressure of the cerebrospinal fluid within shunt 202 and delivers pressure signals to transducer 214. Preferably such monitoring is performed by sensors 212 periodically. Such periodic readings can be stored and processed within a processor for later access.
When it is desired to collect information from sensors 212, station 130 {or at least transducers 321 thereof) is placed adjacent a portion of the patient's body in which biosensor 100 is implanted. As described before, station 130 generates an interrogation signal delivered through transducers 321 for concomitantly powering biosensor 100 and retrieving data therefrom via transducer 214 in a fashion similar to as described above with respect to transducer 114. Should the data collected indicate an abnormal intracranial pressure, valve 105 of shunt 202 is opened to drain cerebrospinal fluid therethrough. To this end station 130 can be commanded to provide power for the opening of valve 105. This $g operation can be controlled either manually or by a preprogrammed processor.
According to another preferred embodiment of the present invention and as shown in Figures 11 and 14 there is provided a transducing assembly 351 which forms a part of station 130. In one configuration, as best seen in Figure 11, assembly 351 is incorporated into a helmet 310. Helmet 310 includes a plurality of transducers 321, each may serve as a transmitter, receiver or transceiver, positioned at various locations so as to provide full transmittance/reception spatial coverage of the brain volume.
As shown in Figure 11, a cable bundle 350 physically connects assembly 351 to multiplexer/demultiplexer 381, which is computer controlled. Multiplexer/demultipiexer 381 serves several functions, including (i) providing a transmittance signal to transducers 321 from power amplifier 128; (ii) conveying sensors' 112 or 212 signals from the body to signal conditioner 134; (iii) providing a computer-controlled multiplexing for transducers 321 when used as transmitters; (iv) providing multiplexing for transducers 321 when used as receivers; and/or (v) providing decoupling between the high power transmission signals from amplifier 128 and the low amplitude signals received from transmitting assembly 118 which is located within the body, into signal conditioner 134. It will be appreciated that multiplexer/demultiplexer 381 both isolates and routes the transmitted and received signals.
According to a preferred embodiment of the present invention the operation of assembly 351 included within helmet 310 is effected following pre calibration of the required location of the transducers over the helmet by, preferably, applying a method which is based on a positioning model.
Such a positioning model allows for an accurate placement of the extracorporeal transducxrs such that acoustic insonifying of the brain volume is provided at an approximately uniform level throughout.
In addition, to achieve such uniformity a three dimensional acoustic propagation model of the skull and brain can also be applied.
Employment of wide beam low frequency ultrasonic transducers may be advantageous in providing an economical coverage.
In addition, focusing the acoustic beams of the extracorporeal transducers on the intrabody transducer is also advantageous because in such cases narrow beam transducers of low frequency ultrasound can be efficiently utilized.
Thus, for appropriately positioning such extracorporeal transducers, either a positioning model or a converging (in-fire) spheroidal acoustic 5 array model with scattering can be used to provide the positional information required. With each of the transducers configuration envisaged above, a first run calibration session is employed in which communication between the helmet (extracorporeal) transducers and the intrabody hansducer is tested for maximal accuracy.
10 The present invention is advantageous over the existing art because it employs acoustic signals which are more readily propagatable in water bodies, such as the human body, as compared to radio fi~equency signals.
Although the invention has been described in conjunction with 15 specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art.
Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.
change in reactance alters the resonant frequency of the circuit, which is then detected by an external receiver and converted to a signal representative of the monitored physiological condition.
Although these L-C type implantable monitoring devices are S superior to battery operated devices in some respects, they also suffer from several limitations that limit their utility. For example, the L-C circuits are difficult to calibrate once implanted, are inherently single-channel, and are only sensitive in a particular range of measurements_ Thus, L~ type monitoring devices are not always accurate after they have been implanted for a long period of time and are not suitable for use with sensors that have a wide sensing range. In addition, no processing power is provided.
Another implantabie monitoring device that does not utilizes wire connection or a battery supply makes use of large electromagnetic antennae to provide the energy required for the data processing inside the 1 S body. These antennas are big and risky to implant. Also, due to the high absorption of electromagnetic energy by human tissue, only subcutaneous implants are used, and energy into the depth of the body is realized by wiring coupling. Only small amounts of electromagnetic energy can be transmitted from an external antenna directly to a monitoring device deep in the body.
A general limitation of all of the above-described prior art implantable monitoring devices is that they are operable for sensing or $ monitoring only one physiological condition. Thus, if a doctor wishes to monitor, e.g., both the pressure and the temperature of the fluid in the ventricles of a patient's brain, two such devices must be implanted.
Furthermore, these prior art implantable devices merely monitor a physiological condition of the patient and transmit a signal representative of the condition out of the patient's body, but do not perform any processing or conversion of the signals.
In addition, due to inherent design limitations, these devices cannot be utilized for alleviating the underlying cause of the physiological condition monitored. For example, infra-cranial pressure sensors designed 1$ for use with patients suffering from hydrocephalus merely detect when fluid pressure levels within the patient's brain are high, but are not operable for reducing the amount of cerebrospinal fluid accumulated in the patient's brain. Thus, once these prior infra-cranial pressure sensors determine that the pressure in the patient's brain is too high, surgery must be performed to alleviate the condition.
An improved implantable biosensor for monitoring and alleviating internal physiological condition such as intracranial pressure has been described in U.S. Pat. No. 5,704,352 which discloses a biosensor system which includes at least one sensor for monitoring a physiological condition of the patient and a passive radio frequency transducer that receives sensor signals from the sensor or sensors, digitizes the sensor signals, and transmits the digitized signals out of the patient's body when subjected to an externally generated electromagnetically interrogation and energizing signal. The biosensor system described also includes a shunt, and as such it can be used for alleviating intracranial pressure monitored by the sensors of the biosensor.
Although this biosensor system presents a major advance over the 1 S above mentioned prior art devices and systems, it suffers from limitations inherent to the radio frequency transducer utilized thereby. Since this transducer requires the use of an antenna to receive and transmit signals, it posses limited reception and transmission capabilities due to the directional nature of such antennas. In addition, due to the high absorption of electromagnetic energy by human tissue, deeply embedded implants cannot be realized by this system and as a result, the infra body positioning of such a biosensor is limited to regions close to the skin which are accessible to electromagnetic signals, thus greatly limiting the effectiveness of such a system.
There is thus a widely recognized need for, and it would be highly advantageous to have, a biosensor system for monitoring and alleviating internal physiological conditions, such as infra-cranial pressure, devoid of the above limitations.
15 It is therefore an object of the present invention to provide a biosensor which can be used for non-invasive monitoring of body parameters.
It is another object of the present invention to provide such a biosensor which does not require wiring or an integral power source.
g It is yet another object of the present invention to provide a biosensor which is less sensitive to extracorporeal positional effect when energized as compared to prior art devices.
It is still another object of the present invention to provide a biosensor which is effectively operable from any depth within the body.
To realize and reduce down to practice these objectives, the biosensor according to the present invention takes advantage of the reliable conductivity of acoustic radiation within water bodies, such as a human body and of an acoustic activatable piezoelectric transducer.
According to one aspect of the present invention there is provided According to one aspect of the present invention there is provided an implantabie biosensor system for monitoring and optionally alleviating a physiological condition in a patient, the biosensor system comprising (a) at least one sensor for sensing at least one parameter of a physiological 1 S condition and for generating electrical sensor signals representative of the physiological condition; and (b) a first acoustic activatable transducer being directly or indirectly coupled with the at least one sensor, the first acoustic activatable transducer being for converting a received acoustic interrogation signal from outside the patient's body into an electrical power for energizing the processor, the first acoustic activatable transducer further being for converting the electrical sensor signals of the at least one sensor into acoustic signals receivable out of the patient's body, such that information pertaining to the at least one parameter of the physiological condition can be relayed outside the patient's body upon generation of an acoustic interrogation signal.
According to further features in preferred embodiments of the invention described below, the biosensor system further comprising a processor coupling between the at least one sensor and the first acoustic activatable transducer, the processor being for converting the electrical sensor signals into converted electrical signals representative of the physiological condition, the processor being energized via the electrical power.
According to another aspect of the present invention there is provided an implantable biosensor system for monitoring and alleviating a physiological condition in a patient, the biosensor system comprising (a) a shunt having a fluid passageway and being operable for draining fluid through the fluid passageway from a portion of a patient's body; (b) a monitoring and operating mechanism coupled with the shunt for non-1~
invasively monitoring the physiological condition and operating the shunt, the monitoring and operating mechanism including at least one sensor for sensing at least one parameter of the physiological condition and for generating electrical sensor signals representative of the physiological condition; and (c) a first acoustic activatable transducer being directly or indirectly coupled with the at least one sensor, the first acoustic activatable transducer being for converting a received acoustic interrogation signal from outside the patient's body into an electrical power for energizing the at least one sensor and for operating the shunt upon command, the first acoustic activatable transducer further being for converting the electrical sensor signals into acoustic signals receivable out of the patienfs body, such that information pertaining to the at least one parameter of the physiological condition can be relayed outside the patient's body upon generation of an acoustic interrogation signal and the shunt is operable 1 S upon command.
According to still further features in the described preferred embodiments the monitoring and operating mechanism further includes a processor coupled with the at least one sensor, the processor serves for converting the electrical sensor signals to converted electrical signals representative of the physiological condition.
According to still further features in the described preferred embodiments the command is an acoustic operation signal provided from outside the body.
According to still further features in the described preferred embodiments the shunt is a cerebrospinal fluid shunt for draining cerebrospinal fluid from the patient's brain.
According to still further features in the described preferred embodiments the at least one sensor includes a first pressure sensor positioned within the fluid passageway for sensing the pressure of the cerebrospinal fluid in the patient's brain and for generating a first pressure signal representative of that pressure.
According to still further features in the described preferred embodiments the at least one pressure sensor includes a second pressure sensor positioned at a distance from the first pressure sensor and being for sensing the pressure of the cerebrospinal fluid when flowing through the shunt and for generating a second pressure signal representative of that pressure.
According to still further features in the described preferred embodiments the processor receives the first and second pressure signals from the first and second pressure sensors and calculates the flow rate of cerebrospinal fluid through the shunt.
According to still further features in the described preferred embodiments the first acoustic activatable transducer includes (i) a cell member having a cavity; (ii) a substantially flexible piezoelectric layer attached to the cell member, the piezoelectric layer having an external surface and an internal surface, the piezoelectric layer featuring such dimensions so as to enable fluctuations thereof at its resonance frequency upon impinging of the acoustic interrogation signal; and (iii) a first electrode attached to the external surface and a second electrode attached to the internal surface.
According to still further features in the described preferred embodiments the piezoelectric layer is of a material selected from the group consisting of PVDF and piezoceramic.
According to still further features in the described preferred embodiments the processor includes a conditioner and a digitizer for converting the electrical sensor signal to the converted electrical signal.
According to still further features in the described preferred embodiments the converted electrical signal is a digital signal.
According to still further features in the described preferred embodiments the processor, the first acoustic activatable transducer and the at least one sensor are co-integrated into a single biosensor device.
According to still further features in the described preferred embodiments the biosensor system further comprising (c) an extracorporeal station positionable against the patient's body the extracoiporeai station including an interrogation signal generator for generating the acoustic interrogation signal, the interrogation signal generator includingat least secondtransducerfor transmittingthe one interrogation to the acousticactivatabletransducer for signal first and 1 S receiving the receivable acoustic signals from the first acoustic activatable transducer.
According to still further features in the described preferred embodiments the processor includes a memory device for storing the electrical sensor signals and an analyzer for analyzing the electrical sensor signals.
According to still further features in the described preferred embodiments the processor includes a programmable microprocessor.
According to still further features in the described preferred embodiments the at least one sensor is selected from the group consisting of a pressure sensor, a temperature sensor, a pH sensor, a blood sugar sensor, a blood oxygen sensor, a motion sensor, a flow sensor, a velocity sensor, an acceleration sensor, a force sensor, a strain sensor, an acoustics sensor, a moisture sensor, an osmolarity sensor, a light sensor, a turbidity sensor, a radiation sensor, an electromagnetic field sensor, a chemical sensor, an ionic sensor, and an enzymatic sensor.
According to still further features in the described preferred embodiments the first acoustic activatable transducer is capable of 1 S transmitting an identification code identifying the transducer.
According to yet another aspect of the present invention there is provided a method for non-invasive monitoring of a physiological condition within a patient's body, the method comprising the steps of (a) sensing at least one parameter associated with the physiological condition via at least one sensor implanted within the patient's body to thereby obtain information pertaining to the physiological condition as an electrical output; (b) converting the electrical output into an acoustic signal via an acoustic transducer and thereby acoustically relaying the 5 information to outside the patient's body; and (c) relaying an acoustic interrogation signal from outside the patient's body for activating the at least one sensor.
According to still -another aspect of the present invention there is provided a method for non-invasive monitoring and alleviating of a 10 physiological condition within a patient's body, the method comprising the steps of (a) sensing at least one parameter associated with the physiological condition via at least one sensor implanted within the patient's body to thereby obtain information pertaining to the physiological condition as an electrical output; (b) converting the electrical 15 output into an acoustic signal via an acoustic transducer and thereby acoustically relaying the information to outside the patient's body; and (c) relaying an acoustic interrogation signal from outside the patient's body for activating the at least one sensor and further for activating a shunt for alleviating the physiological condition.
The present invention successfully addresses the shortcomings of the presently known configurations by providing a biosensor which can be used for non-invasive monitoring of body parameters, which does not require wiring, which does not require an integral power source, which can be effectively positioned at any location and depth within the body and which is much less subject to interrogation positional effect as compared with prior art devices.
The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:
FIG. 1 a is a longitudinal cross section of a transducer element according to the present invention taken along lines A-A in Figures 2a-2e;
FIG. lb is a longitudinal cross section of a transducer element according to the present invention taken along lines B-B in FIGS. 2a-2e;
FIG. 2a is a cross section of a transducer element according to the present invention taken along line C-C in FIG. 1 a;
FIG. 2b is a cross section of a transducer element according to the present invention taken along line D-D in FIG. 1 a;
FIG. 2c is a cross section of a transducer element according to the present invention taken along line E-E in FIG. 1 a;
FIG. 2d is a cross section of a transducer element according to the present invention taken along line F-F in FIG. 1 a;
FIG. 2e is a cross section of a transducer element according to the present invention taken along line G-G in FIG. 1 a;
FIG. 3 shows the distribution of charge density across a piezoelectric layer of a transducer element resulting from the application of a constant pressure over the entire surface of the layer;
FIG. 4 shows the results of optimization performed for the power 1 S response of a transducer according to the present invention;
FIG. S shows a preferred electrode shape for maximizing the power response of a transducer according to the present invention;
FIG. 6 is a longitudinal section of another embodiment of a transducer element according to the present invention capable of functioning as a transmitter;
FIG. 7a-7f are schematic views of possible configurations of transmitters according to the present invention including parallel and anti-parallel electrical connections for controllably changing the mechanical impedance of the piezoelectric layer;
FIG. 8 is a longitudinal section of a transmitter element according to the present invention including an anti-parallel electrical connection;
FIG. 9 is a longitudinal section of another embodiment of a transmitter element according to the present invention;
FIG. 10 is a block diagram depricting the intrabody and extracoiporeal components of the biosensor system according to the present invention;
FIG. 11 is a schematic depiction of components of the biosensor system according to one embodiment of the present invention;
FIG. 12 is a longitudinal section of a shunt system including an acoustic transducer and pressure sensors according to another embodiment of the present invention;
FIG. 13 is a schematic depiction of the transducer and pressure sensors of Figure 12 isolated from the shunt; and FIG. 14 is a block diagram of the extracorporeal station components according to the present invention implemented within a S helmet.
p~~ TPTION OF THF P FF R FD .MBODIMENT
The present invention is of an intrabody bio-sensing system and method which can be used for both monitoring and alleviating physiological conditions within a patient's body. Specifically, the biosensor system and method of the present invention incorporates an active acoustic transducer communicating with sensors and optionally with a shunt implanted within the patient's body for monitoring and alleviating, for example, infra-cranial pressure of a patient suffering from hydrocephalus.
The principles and operation of an implantable biosensor system according to the present invention may be better understood with reference to the drawings and accompanying descriptions.
Before explaining at least one embodiment of the invention in 5 detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that 10 the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. For purposes of better understanding the system and method according to the present invention, as illustrated in Figures i0-i4 of the drawings, reference is first made to the construction and operation of a transducer as described in U.S. Pat.
15 application No. 09/000,553.
Referring now to the drawings, Figures la, lb and 2a-2e illustrate a preferred embodiment of a transducer element according to the present invention which is referred to herein as transducer element 1. Transducer element 1 serves for converting received acoustic signals into electrical power and for converting electrical power to transmitted acoustic signals.
As shown in the figures, the transducer element 1 includes at least one cell member 3 including a cavity 4 etched into a substrate and covered by a substantially flexible piezoelectric layer 2. Attached to piezoelectric layer 2 are an upper electrode 8 and a lower electrode 6, the electrodes for connection to an electronic circuit.
The substrate is preferably made of an electrical conducting layer 11 disposed on an electrically insulating layer 12, such that cavity 4 is etched substantially through the thickness of electrically conducting layer 11.
Electrically conducting layer 11 is preferably made of copper and insulating layer 12 is preferably made of a polymer such as polyimide.
Conventional copper-plated polymer laminate such as KAPTONT"" sheets may be used for the production of transducer element 1. Commercially available laminates such as NOVACLADT"" may be used. Alternatively, the substrate may include a silicon layer, or any other suitable material.
Alternatively, layer 11 is made of a non-conductive material such as PYRALINT"" .
Preferably, cavity 4 is etched into the substrate by using conventional printed-circuit photolithography methods. Alternatively, cavity 4 may be etched into the substrate by using VLSI/micro-machining technology or any other suitable technology.
Piezoelectric layer 2 may be made of PVDF or a copolymer thereof.
Alternatively, piezoelectric layer 2 is made of a substantially flexible piezoceramic. Preferably, piezoelectric layer 2 is a poled PVDF sheet having a thickness of about 9-28 pm. Preferably, the thickness and radius of flexible layer 2, as well as the pressure within cavity 4, are specifically selected so as to provide a predetermined resonant frequency. When using the embodiment of Figures 1 a and 1 b, the radius of layer Z is defined by the radius of cavity 4.
By using a substantially flexible piezoelectric layer 2, the invention described in U.S. Pat. application No. 09/000,553 allows to provide a 1 S miniature transducer element whose resonant frequency is such that the acoustic wavelength is much larger than the extent of the transducer. This enables the transducer to be omnidirectional even at resonance, and further allows the use of relatively low frequency acoustic signals which do not suffer from significant attenuation in the surrounding medium.
Prior art designs of miniature transducers, however, rely on rigid piezoceramic usually operating in thickness mode. In such cases the resonant frequency relates to the size of the element and speed of sound in the piezoceramic, and is higher by several orders of magnitude.
The invention described in U.S. Pat. application No. 09/000,553 provides a transducer which is omnidirectional, i.e., insensitive to the direction of the impinging acoustic rays, thereby substantially simplifying the transducer's operation relative to other resonant devices: Such a transducer element is thus suitable for application in confined or hidden locations, where the orientation of the transducer element cannot be ascertained in advance.
According to a specific embodiment, cavity 4 features a circular or hexagonal shape with radius of about 200 pm. Electrically conducting layer 11 preferably has a thickness of about 15 Vim. Cell member 3 is preferably etched completely through the thickness of electrically conducting layer 11. Electrically insulating layer 12 preferably features a thickness of about 50 Vim: The precise dimensions of the various elements of a transducer element according to the invention described in U.S. Pat.
application No. 09/000,553 may be specifically tailored according to the requirements of the specific application.
Cavity 4 preferably includes a gas such as air. The pressure of gas within cavity 4 may be specifically selected so as to predetermine the sensitivity and ruggedness of the transducer as well as the resonant frequency of layer 2.
As shown in Figure 2b, an insulating chamber 18 is etched into the substrate, preferably through the thickness of conducting layer 11, so as to insulate the transducer element from other portions of the subshate which may include other electrical components such as other transducer elements etched into the substrate. According to a specific embodiment, the width of insulating chamber 18 is about 100 l,un. As shown, insulating chamber 18 is etched into the substrate so as to form a wail 10 of a predetermined thickness enclosing cavity 4, and a conducting line 17 integrally made with wall 10 for connecting the transducer element to another electronic component preferably etched into the same substrate, or to an external electronic circuit.
As shown in Figures la and lb, attached to piezoelectric layer 2 are upper electrode 8 and lower electrode 6. As shown in Figures 2c and 2e, upper electrode 8 and lower electrode 6 are preferably precisely shaped, so as to cover a predetermined area of piezoelectric layer 2. Electrodes 6 and 8 may be deposited on the upper and lower surfaces of piezoelectric membrane 2, respectively, by using various methods such as vacuum 5 deposition, mask etching, painting, and the like.
As shown in Figure 1 a, lower electrode 6 is preferably made as an integral part of a substantially thin electrically conducting layer 14 disposed on electrically conducting layer 11. Preferably, electrically conducting layer 14 is made of a NickeLCopper alloy and is attached to 10 electrically conducting layer 11 by mechanism of a sealing connection 16.
Sealing connection 16 may be made of indium. According to a preferred configuration, sealing connection 16 may feature a thiclrness of about 10 a m, such that the overall height of wall 10 of cavity 4 is about 20-25 pm.
As shown in Figure 2c, electrically conducting layer 14 covers the 15 various portions of conducting layer 11, including wall 10 and conducting line 17. The portion of conducting layer 14 covering conducting line 17 is for connection to an electronic component, as further detailed hereinunder.
According to a preferred embodiment, electrodes 6 and 8 are specifically shaped to include the most energy-productive region of piezoelectric layer Z, so as to provide maximal response of the transducer while optimizing the electrode area, and therefore the cell capacitance, thereby maximizing a selected parameter such as voltage sensitivity, current sensitivity, or power sensitivity of the transducer element.
The vertical displacement of piezoelectric layer 2,'Y, resulting from a monochromatic excitation at angular frequency w is modeled using the standard equation for thin plates:
(v2 -YZvv2 +y2)~- 3(1 3Z)p+ 3iZco(1 3vz)~-O
ll 2Qh 2Qh wherein Q is the Young's modulus representing the elasticity of layer 2; h the half thickness of layer 2; ~ is the Poisson ratio for layer 2; y is the effective wavenumber in the layer given by: Y ' = 3p(i - V 2 ~ 2 ~Qh 2 , wherein p is the density of layer 2 and cv is the angular frequency of the applied pressure (wherein the applied pressure may include the acoustic pressure, the static pressure differential across layer 2 and any other 1 S pressure the transducer comes across); Z is the mechanical impedance resulting from the coupling of layer 2 to both external and internal media of cavity 4, wherein the internal medium is preferably air and the external medium is preferably fluid; P is the acoustic pressure applied to layer 2, and '~' represents the average vertical displacement of layer 2.
When chamber 4 is circular, the solution (given for a single frequency component ~) representing the dynamic displacement of a circular layer 2 having a predetermined radius a, expressed in polar coordinates, is:
IUYa)~Jo(Tr')-Jo~Ya)~+J ,(Ya)~IotY~')-Io(Ya)~ P
'f(r~~P)= 2hp~'~zLo(Ta)+itaZLz(Ya) Lo ~Z) = Io(Z)JuZ) + JotZ)IOZ)~ Lz ~Z) = Jz ~Z)IOZ) - Iz ~Z) J~ CZ) _ P,, _4 _1 icaH +1[3~ + (~Pwa A
wherein 'h(r, gyp) is time-dependent and represents the displacement of a selected point located on circular layer 2, the specific location of which is given by radius r and angle ~O; J and I are the normal and modified Bessei functions of the first kind, respectively; P,, , H,, are the air pressure within cavity 4 and the height of chamber 4, respectively; and p~ is the density of the fluid external to cavity 4.
The first term of the impedance Z relates to the stiffness resulting from compression of air within cavity 4, and the second term of Z relates to the mass added by the fluid boundary layer. An additional term of the impedance Z relating to the radiated acoustic energy is substantially negligible in this example.
The charge collected between electrodes 6 and 8 per unit area is obtained by evaluating the strains in layer 2 resulting from the displacements, and multiplying by the pertinent off diagonal elements of the piezoelectric strain coefficient tensor, a", e32 , as follows:
a~~ 2 a~ 2 Q(r,cp,t)=e3~ 8x ay wherein Q(r,tp,t) represents the charge density at a selected point located on circular layer 2, the specific location of which is given by radius r and angle ~p; x is the stretch direction of piezoelectric layer 2; y is the transverse direction (the direction perpendicular to the stretch direction) of layer 2; e3,, e3Z are off diagonal elements of the piezoelectric strain coefficient tensor representing the charge accumulated at a selected point on layer 2 due to a given strain along the x and y directions, respectively, which coefficients being substantially dissimilar when using a PVDF
layer. 'Y is the displacement of layer 2, taken as the sum of the displacement for a given acoustic pressure P at frequency f, and the static displacement resulting from the pressure differential between the interior and exterior of cavity 4, which displacements being extractable from the equations given above.
. . 29 The total charge accumulated between electrodes 6 and 8 is obtained by integrating Q(r, cp, t) over the entire area S of the electrode:
Q = JQ(r, cp, t ) c~'x The capacitance C of piezoelectric layer 2 is given by: C = 2h jdx' s S wherein E is the dielectric constant of piezoelectric layer 2; and 2h is the thickness of piezoelectric layer 2.
Accordingly, the voltage, current and power responses of piezoelectric layer 2 are evaluated as follows:
Z
2h jQ(r, cp, t ) cf'.x 4ih jQ(r, cp, t) cf',x Y = S , I = 2ic~ jQ(r, cp, t) .~-x, W =
The DC components of Q are usually removed prior to the evaluation, since the DC currents are usually filtered out. The values of Q
given above represent peak values of the AC components of Q, and should be modified accordingly; so as to obtain other required values such as RMS values.
According to the above, the electrical output of the transducer expressed in terms of voltage, current and power responses depend on the AC components of Q, and on the shape S of the electrodes. Further, as can be seen from the above equations, the voltage response of the transducer may be substantially maximized by minimizing the area of the electrode.
The current response, however, may be substantially maximized by maximizing the area of the electrode.
Figure 3 shows the distribution of charge density on a circular 5 piezoelectric layer 2 obtained as a result of pressure (acoustic and hydrostatic) applied uniformly over the entire area of layer 2, wherein specific locations on layer 2 are herein defined by using Cartesian coordinates including the stretch direction (x direction) and tl~e transverse direction (y direction) of layer 2. It can be seen that distinct locations on 10 layer 2 contribute differently to the charge density. The charge density vanishes at the external periphery 70 and at the center 72 of layer 2 due to minimal deformation of these portions. The charge density is maximal at two cores 74a and 746 located symmetrically on each side of center 72 due to maximal strains (in the stretch direction) of these portions.
15 A preferred strategy for optimizing the electrical responses of the transducer is to shape the electrode by selecting the areas contributing at least a selected threshold percentage of the maximal charge density, wherein the threshold value is the parameter to be optimized. A threshold value of 0 % relates to an electrode covering the entire area of layer 2.
Figure 4 shows the results of an optimization performed for the power response of a transducer having a layer 2 of a predetermined area.
As shown in the Figure, the threshold value which provides an optimal power response is about 30 % (graph b). Accordingly, an electrode which covers only the portions of layer 2 contributing at least 30 % of the maximal charge density yields a maximal power response. The pertinent voltage response obtained by such an electrode is higher by a factor of 2 relative to an electrode completely covering layer 2 (graph a). The current response obtained by such electrode is slightly lower relative to an electrode completely covering layer 2 (graph c). Further as shown in the Figure, the deflection of layer 2 is maximal when applying an acoustic signal at the resonant frequency of layer 2 (graph d).
A preferred electrode shape for maximizing the power response of the transducer is shown in Figure S, wherein the electrode includes two electrode portions 80a and 80b substantially covering the maximal charge density portions of layer 2, the electrode portions being interconnected by mechanism of a connecting member 82 having a minimal area.
Preferably, portions 80a and 80b cover the portions of layer 2 which yield at least a selected threshold (e.g. 30 %) of the maximal charge density.
According to the present invention any other parameter may be optimized so as to determine the shape of electrodes 6 and 8. According to further features of the invention described in U.S. Pat. application No.
09/000,553, only one electrode (upper electrode 8 or lower electrode 6) may be shaped so as to provide maximal electrical response of the transducer, with the other electrode covering the entire area of layer 2.
Since the charge is collected only at the portions of layer 2 received between upper electrode 8 and lower electrode 6, such configuration is operatively equivalent to a configuration including two shaped electrodes having identical shapes.
Referring now to Figure 6, according to another embodiment chamber 4 of hansducer element 1 may contain gas of substantially low pressure, thereby conferring a substantially concave shape to piezoelectric membrane 2 at equilibrium. Such configuration enables to further increase the electrical response of the transducer by increasing the total charge obtained for a given displacement of layer 2. The total displacement in such an embodiment is given by: 'I' = Po'Y~ + P'I',,c cos cat , wherein Po is the static pressure differential between the exterior and the interior of cavity 4; '1'DC is the displacement resulting from Po; P is the amplitude of the acoustic pressure; and'1'AC is the displacement resulting from P.
Accordingly, the strain along the x direction includes three terms as follows:
z Z z = a~ __ o ~ a~o~ ~ 2 ~ ~AC ~ Z o a~YD~ a'#',,c S ax P ax + P ax cos wt + 2P P ax 8x cos wt wherein the DC component is usually filtered out.
Thus, by decreasing the pressure of the medium (preferably air) -within cavity 4 relative to the pressure of the external medium (preferably fluid), the value of Po is increased, thereby increasing the value of the 10' third term of the above equation.
Such embodiment makes it possible to increase the charge output of layer 2 for a given displacanent, thereby increasing the voltage, current and power responses of the transducer without having to increase the acoustic pressure P. Furthermore, such embodiment enables to further 1 S miniaturize the transducer since the same electrical response may be obtained for smaller acoustic deflections. Such embodiment is substantially more robust mechanically and therefore more durable than the embodiment shown in Figures la and lb. Such further miniaturization of the transducer enables to use higher resonance frequencies relative to the embodiment shown in Figures la and lb.
Preferably, a transducer element 1 according to the invention described in U.S. Pat. application No. 09/000,553 is fabricated by using technologies which are in wide use in the microelectronics industry, so as to allow integration thereof with other conventional electronic components as further detailed hereinunder. When the transducer element includes a substrate such as Copper-polymer laminate or silicon, a variety of conventional electronic components may be fabricated onto the same substrate.
According to a preferred embodiment, a plurality of cavi#ies 4 may be etched into a single substrate 12 and covered by a single piezoelectric layer 2, so as to provide a transducer element including a matrix of transducing cell members 3, thereby providing a larger energy collecting area of predetermined dimensions, while still retaining the advantage of miniature individual transducing cell members 3. When using such configuration, the transducing cell members 3 may be electrically interconnected in parallel or serial connections, or combinations thereof, so as to tailor the voltage and current response of the transducer. Parallel connections are preferably used so as to increase the current output while serial connections are preferably used so as to increase the voltage output of the transducer.
Furthermore, piezoelectric layer 2 may be completely depolarized 5 and then repolarized at specific regions thereof, so as to provide a predetermined polarity to each of the transducing cell members 3. Such configuration enables to reduce the complexity of interconnections between cell members 3.
A transducer element according to the invention described in U.S.
10 ~ Pat. application No. 09/000,553 may be further used as a transmitter for transmitting information to a remote receiver by modulating the reflection of an external impinging acoustic wave arrived frnm a remote transmitter.
Referring to Figure 6, the transducer element shown may function as a transmitter element due to the asymmetric fluctuations of piezoelectric 15 layer 2 with respect to positive and negative transient acoustic pressures obtained as a result of the pressure differential between the interior and exterior of cavity 4.
A transmitter element according to the present invention preferably modulates the reflection of an external impinging acoustic wave by mechanism of a switching element connected thereto. The switching element encodes the information that is to be transmitted, such as the output of a sensor, thereby frequency modulating a reflected acoustic wave.
Such configuration requires very little expenditure of energy from the transmitting module itself, since the acoustic wave that is received is externally generated, such that the only energy required for transmission is the energy of modulation.
Specifically, the reflected acoustic signal is modulated by switching the switching element according to the frequency of a message electric signal arriving from another electronic component such as a s~sor, so as to controllably change the mechanical impedance of layer 2 according to the frequency of the message signal.
Preferably, a specific array of electrodes connected to a single cell 1 S member or alternatively to a plurality of cell members are used, so as to control the mechanical impedance of layer 2.
Figures 7a-7g illustrate possible configurations for controllably change the impedance of layer 2 of a transmitter element. Referring to Figure 7a, a transmitter element according to the invention described in U.S. Pat. application No. 09/OOO,SS3 may include a first and second pairs of electrodes, the first pair including an upper electrode 40a and a lower electrode 38a, and the second pair including an upper electrode 40b and a lower electrode 38b. Electrodes 38a, 38b, 40a and 40b are electrically connected to an electrical circuit by mechanism of conducting lines 36a, 36b, 34a and 34b, respectively, the electrical circuit including a switching element (not shown), so as to alternately change the electrical connections of conducting lines 36a, 366, 34a and 34b. -Preferably, the switching element switches between a parallel connection and an anti-parallel connection of the electrodes. A parallel connection decreases the mechanical impedance of layer 2, wherein an anti-parallel connection increases the mechanical impedance of layer 2.
An anti-parallel connection may be obtained by interconnecting line 34a to 36b and line 34b to 36a. A parallel connection may be obtained by connecting line 34a to 34b and line 36a to 36b. Preferably, the switching frequency equals the frequency of a message signal arriving from an electrical component such as a sensor as further detailed hereinunder.
According to another embodiment shown in Figure 7b, upper electrode 40a is connected to lower electrode 38b by mechanism of a conducting line 28, and electrodes 38a and 40b are connected to an electrical circuit by mechanism of conducting lines 27 and 29, respectively, wherein the electrical circuit further includes a switching element. Such configuration provides an anti-parallel connection of the electrodes, wherein the switching element functions as an on/off switch, thereby alternately increasing the mechanical impedance of layer 2.
In order to reduce the complexity of the electrical connections, layer 2 may be depolarized and then repolarized at specific regions thereof. As shown in Figure 7c, the polarity of the portion of layer 2 received between electrodes 40a and 38a is opposite to the polarity of the portion of layer Z received between electrodes 406 and 38b. An anti-parallel connection is thus achieved by interconnecting electrodes 38a and 38b by mechanism of a conducting line 28, and providing conducting lines 27 and 29 connected to electrodes 40a and 40b, respectively, the conducting lines for connection to an electrical circuit including a switching element.
According to another embodiment, the transmitting element includes a plurality of transducing cell members, such that the mechanical impedance of layer 2 controllably changed by appropriately interconnecting the cell members.
As shown in Figure 7d, a first transducing cell member 3a including a layer 2a and a cavity 4a, and a second transducing cell member 3b including a layer 2b and a cavity 4b are preferably contained within the same substrate; and layers 2a and 2b are preferably integrally made. A first pair of electrodes including electrodes 6a and 8a is attached to layer 2, and a second pair of electrode including electrodes~6b and 8b is attached to layer 2b. Electrodes 6a, 8a, 6b and 8b are electrically connected to an electrical circuit by mechanism of conducting lines 37a, 35a, 37b and 35b, respectively, the electrical circuit including a switching element, so as to alternately switch the electrical connections of conducting lines 37a, 35a, 37b and 35b, so as to alternately provide parallel and anti-parallel connections, substantially as described for Figure 7a, thereby alternately decreasing and increasing the mechanical impedance of layers 2a and 2b.
Figure 7e illustrates another embodiment, wherein the first and second transducing cell members are interconnected by mechanism of an anti-parallel connection. As shown in the Figure, the polarity of layer 2a a0 is opposite to the polarity of layer 2b, so as to reduce the complexity of the electrical connections between cell members 3a and 3b. Thus, electrode 6a is connected to electrode 6b by mechanism of a conducting line 21, and electrodes 8a and 8b are provided with conducting lines 20 and 22, respectively, for connection to an electrical circuit which includes a switching element, wherein the switching element preferably functions as an on/off switch, so as to alternately increase the mechanical impedance of j~ layers 2a and 2b.
Figure 7f shows another embodiment, wherein the first and second transducing cell members are interconnected by mechanism of a parallel connection. As shown, electrodes 6a and 6b are interconnected by mechanism of conducting line 24, electrodes 8a and 8b are interconnected by mechanism of conducting line 23, and electrodes 6b and 8b are provided with conducting lines 26 and 25, respectively, the conducting lines for connection to an electrical circuit including a switching element.
The switching element preferably functions as an on/off switch for alternately decreasing and increasing the mechanical impedance of layers 2a and 2b.
Figure 8 shows a possible configuration of two transducing cell members etched onto the same substrate and interconnected by mechanism of an anti-parallel connection. As shown in the Figure, the transducing cell members are covered by a common piezoelectric layer 2, wherein the polarity of the portion of layer 2 received between electrodes 6a and 8a is opposite to the polarity of the portion of layer 2 received between electrodes 6b and 8b. Electrodes 8a and 8b are bonded by mechanism of a conducting line 9, and electrodes 6a and 66 are provided with conducting lines 16 for connection to an electrical circuit.
Another embodiment of a transmitter element according to the present invention is shown in Figure 9. The transmitter element includes a transducing cell member having a cavity 4 covered by a first and second piezoelectric layers, 50a and 50b, preferably having opposite polarities.
Preferably, layers 50a and 50b are interconnected by mechanism of an insulating layer 52. Attached to layer 50a are upper and lower electrodes 44a and 42a, and attached to layer 50b are upper and lower electrodes 44b and 42b. Electrodes 44a, 42a, 44b and 42b are provided with conducting lines 54, 55, 56 and 57, respectively, for connection to an electrical circuit.
It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the spirit and the scope of invention described in U.S. Pat.
application No. 09/000,553.
S As is detailed hereinunder, in preferred embodiments, the present invention exploits the advantages of the acoustic transducer described hereinabove and in U.S. Pat. application No. 09/000,553.
Thus, according to the present invention there is provided an implantable biosensor system, which is referred to hereinunder as biosensor 100.
Biosensor 100 is implantable within a patient's body for monitoring a physiological condition therein. In the course of its operation, biosensor 100 relays, on command, information in the form of acoustic signals pertaining to a parameter or parameters associated with the physiological condition as these are sensed by an implanted sensor or sensors.
Furthermore, biosensor 100 according to the present invention is designed to be energized via an external acoustic interrogation signal.
As such, biosensor 100 is wire and/or integral power source independent. In addition, since the human body is, in effect, a water body and further since acoustic radiation is readily propagatable, if so desired, within water bodies in all directions, biosensor 100 of the present invention provides advantages over the prior art in terms of effective implantable depth within the body and further in terms of interrogation signal positional effect.
As further detailed hereinunder, according to a preferred embodiment of the present invention biosensor system 100 incorporates a shunt for alleviating a monitored physiological condition.
As shown in Figure 10, and according to one embodiment of the present invention, when implanted in a monitoring or treatment infra body site, biosensor 100 of the present invention is employed for sensing or monitoring one or more parameters of a physiological condition within the patient and for transmitting acoustic signals representative of this physiological condition or these parameters out of the patient's body.
According to this embodiment of the present invention, biosensor 100 includes one or more sensors 112 for sensing, monitoring or measuring one or more parameters of the physiological conditions of the patient.
Biosensor 100 also includes an acoustic activatable transducer 114.
Transducer 114 serves for receiving electrical signals from sensors 112 and for converting such electrical signals into acoustic signals. Transducer 114 also serves for receiving externally generated acoustic interrogation signals and for converting such acoustic energy into electrical power which is used for energizing sensors 112 and for rendering biosensor 100 wire and integral power source independent.
As further shown in Figure 10, transducer 114 includes a receiving assembly 117 and a transmitting assembly 118, preferably both are integrated into a single transceiver assembly.
According to a preferred embodiment of the present invention receiving assembly 117 and transmitting assembly 118 are assembled of transducer element 1, the construction of which is further detailed hereinabove with regards to Figures la, lb and 2a-2e. Alternatively, a plurality of transducer elements 1 can also be utilized in various configurations (as shown in Figures 7b-f, 8 and 9 hereinabove) in the receiving assembly 117 and transmitting assembly 118 of biosensor 100 of the present invention The components of transducer 114 can be formed from separate transducer element 1 units, although the integration of one transducer element 1 into a transceiver is preferred, due to the high degree of miniaturization required in biosensing devices.
5 According to a preferred embodiment of the present invention signals received and/or transmitted by biosensor 100 are processed by a processor 113. Electrical signals generated by sensors 112 are processed through processor 113 and are forwarded in their processed or converted form to transducer 114. In addition, acoustic signals received by 10 transducer 114 and which are converted to electrical signals (and power) thereby, are preferably further processed by processor 113.
To this end, processor 113, preferably includes a conditioner 116 and, when necessary, a digitizer 119 for processing the electrical signals received thereby from sensors 112 and/or transducer 114.
15 The acoustic interrogation signal is generated by an extracorporeal station 130 which includes an interrogator 115 and which is also illustrated in Figure 10, the operation and construction of which is described in further detail below.
Sensors 112 are operable for monitoring or detecting one or more physiological conditions within the patient's body, such as the pressure and/or the temperature of the cerebrospinal fluid in the cavities or ventricles of the patient's brain. Sensors 112 then generate sensor signals representative of these measured physiological parameters. The sensor signals are typically electrical analog signals but may also be digital, depending on the type of sensor employed. It will be appreciated that sensors having a built-in analog-to-digital converter are well known in the art.
Sensors 112 are preferably conventional in construction and may include, for example, pressure sensors, temperature sensors, pH sensors, blood sugar sensors, blood oxygen sensors, or any other type of physiological sensing, monitoring or measuring devices responsive to, for example, motion, flow, velocity, acceleration, force, strain, acoustics, moisture, osmolarity, light, turbidity, radiation, electromagnetic fields, chemicals, ionic, or enzymatic quantities or changes, electrical and/or impedance.
Examples of these and other sensor devices useful in context of the present invention are described in detail in the AIP Handbook of Modern Sensors by Jacob Fraden, hereby incorporated by reference.
In a preferred embodiment, sensors 112 are pressure sensor transducers such as the PVDF sensors described in U.S. Pat. application 09/161,658, which is incorporated herein by reference, or the MPX2000 series pressure sensors distributed by Motorola.
As mentioned above according to a preferred embodiment of the present invention transducer 114 is electrically coupled to sensors 112 through processor 113. Processor 113 conditions the sensor signals via conditioner 1 i6, converts the sensor signals to a digital form (when so required) via digitizer 119, and provides the processed or converted signal to transducer 114. Upon a command, transducer 114 converts the processed electrical signals into corresponding acoustic signals which are concomitantly transmitted out of the patient's body, when subjected to an acoustic interrogation signal from station 130.
In more detail, processor 113 is electrically connected to sensors 112 and both share a common miniature substrate such as is customary in the VLSI (Very Large Scale Integration) industry. Processor 113 directly receives sensors' 112 signals by, e.g., the shortest possible wiring.
Processor 113 serves several functions. As already mentioned, processor 113 conditions via conditioner 116 the signals received from sensors 112. Such conditioning is necessary due to tl~e miniature size and small capacitance of sensors 112, and as such, conditioner 116 provides not only appropriate amplification and filtering, but also impedance reduction, so as to substantially reduce noise pickup and thereby improve the signal-to-noise ratio of biosensor 100.
In addition, digitizer 119 is employed in processor 113 to convert the analog signals to digital signals and format the digitized signals as a binary data stream for transmission out of the patient by transducer 114 acoustic signals, which are received and interpreted by extracorporeal station 130.
Processor 113 is also operable for coding and formatting a unique device identification number for transmission with the sensors' signals for use in identifying a specific transducer 114 and/or sensor 112.
Preferably, processor 113 can be programmed to analyze the monitored signals before transmitting the signals out of the patient's body.
To this end, processor 113 can be provided with a memory device and a programmable microprocessor. Many more tasks which are applicable to biosensor system 100 of the present invention can be provided by processor 113, such as, for example, calculating a reading by correlating information derived from a plurality of sensors 112.
For example, if biosensor 100 is provided with a pressure sensor and a temperature sensor for measuring both the pressure and temperature of the cerebrospinal fluid in the patient's brain, processor 113 can then be programmed to adjust the pressure signal transmitted out of the patient's body to compensate for higher or lower temperature readings as sensed by the temperature sensor and vice versa, thereby providing more accurate readings.
It will, however, be appreciated by one ordinarily skilled in the art that sole or additional/supplementary processing can be effected by processors present in extracorporeal station 130.
Preferably, transmitting assembly 118 of transducer 114 employs modulations or other methods in modifying the transmitted acoustic signal, such modulation methods are well known in the art and are described in ' $0 detail in, for example, U.S. Pat. No. 5,619,997 which is incorporated herein by reference.
Extracorporeal station 130 is located outside the patient's body and is designed for powering or energizing transducer 114 of biosensor 100 which is implanted within the patient's body, and for receiving the sensors' acoustic signals.
As illustrated in Figures 10-1 i, according to one embodiment of the present invention and as further detailed in the following sections, transducers 321 of station 130 are mounted within a helmet 310.
Transducers 321 ~ are coupled via wiring with a signal generator 12C, a power amplifier 128, a modulator 132, a demodulator 133, a signal conditioner 134 and a recording and analyzing device 138.
Signal generator 126 and power amplifier 128 provide energy to extracorporeal transducer 321 for generating acoustic signals which propagate from the surface into the patient's body and energize intrabody acoustic transducer 114 when impinging thereon. Signal generator 126 and power amplifier 128 may be of any known type, including devices constructed in accordance with "Data Transmission from an Implantable Biotelemeter by Load-Shift Keying Using Circuit Configuration ~ $1 Modulator" by Zhengnian Tang, Brian Smith, John H. Schild, and P.
Hunter Peckham, IEEE Transactions on Biomedical Engineering, vol. 42, No. 5, May, 1995, pp. 524-528, which is incorporated herein by reference.
As already mentioned, transducers 321 are preferably of a type functionally similar to transducer element 1, the construction of which is further described hereinabove in Figures la, lb, 2a-2e, 7b-f, 8 and 9, each of which can serve as a transmitter, receiver or a transceiver, and are preferably constructed to comply with NCRP 113: Exposure criteria for medical diagnostic ultrasound 1992, puts I and II, provided that transducers 321 when serve as a powering transmitter is capable of transmitting sufficient energy in the form of an acoustic signal for energizing biosensor 100. Preferred transducers 32 i include commercial piston type transducers.
Transducers 321 are electrically connected to power amplifier 128 1 S and acoustically communicable with transducer 114. Transducers 321 transform and deliver the energy generated by generator 126 and power amplifier 128 to transducer 114 via the body of the patient, which serves in this respect as a water body.
Demodulator 133 is operatively coupled to transducers 321 and is provided for extracting digital data received thereby from transducer 114.
An example of a demodulator 133 that can be used in interrogator 115 of extracorporeal station 130 is the MC 1496 or MC 1596 type demodulator distributed by Motorola.
Signal conditioner 134 is connected to demodulator 133 for converting the demodulated data to a format suitable for recording or storing in external devices. An example of a signal conditioner 134 that can be used in station 130 of the present invention is the ADM202 type conditioner distributed by Analog Devices. Signal conditioner 134 may be connected with conventional recording and/or analyzing devices such as computers, printers, and displays for recording, presenting andlor further analyzing the signals transmitted by biosensor 100.
Thus, and according to this embodiment of the present invention, biosensor 100 described hereinabove is implanted in a patient for sensing, monitoring or detecting one or more parameters associated with a physiological condition of the patient. When it is desired to collect information from the body of the patient, a control console 124 commands interrogator 115 to trigger an energizing signal output from signal generator 126. The energizing signal is then modulated with other commands originating from control console 124 that governs processor 113 of biosensor 100 and multiplexer-demultiplexer 381. The modulated signal is amplified by power amplifier 128 and sent to transducer 321 to S energize and render biosensor 100 operative via transducer 114 thereof.
The energy thus provided through the body of the patient is also used to provide transducer 114 with energy to produce an acoustic signal related to the information thus collected by sensors 112. To this end, h~ansducers 321 of station 130 are placed in intimate physical contact with a portion of the patient's body preferably in which biosensor 100 is implanted. Station 130 generates an acoustic interrogation signal via transducers 321 for powering biosensor 100 and for retrieving via transducers 114 sensors' 112 signals as an acoustic signal generated by transducer 114. Interrogator 115 then demodulates sensors' 112 signals and delivers the signals to recording and analyzing device 138.
It will be appreciated that in cases where each of sensors 112 provides information pertaining to a specific parameter, specific information from each of sensors 112 can be accessed by station 130 by providing a unique identifying code for each sensor with the acoustic . ~ 54 interrogation signal. Such a code would be interpreted by processor 113 to command the retrieval of information from any specific sensor of sensors 112.
Referring now to Figures 11-13. According to another preferred embodiment of the present invention and as best illustrated in Figure 12, biosensor 100 further includes a shunt 202 for draining fluid from a portion of a patient's body, and a monitoring device 204 which is further detailed hereinbelow with respect to Figure 13. According to a preferred embodiment, monitoring device 204 is embedded within the walls of shunt 202 for non-invasively rrionitoring the operation of shunt 202.
In more detail, shunt 242 according to this embodiment of the present invention is a cerebrospinal fluid shunt and is used for draining cerebrospinal fluid from a patient's brain, when so required. Cerebrospinal fluid shunt 202 is preferably formed of medical grade synthetic resin material and presents opposed ventricular 206 and distal 208 ends connected by a fluid passageway 205 which includes a valve 105. When shunt 202 is implanted in a patient, ventricular end 206 is positioned in a ventricular cavity of the patient's brain and distal end 208 is positioned in $S
an organ or body cavity remote from the ventricular cavity so as to drain fluids from the patient's brain thereto.
As shown in Figure 11, an appropriate site to drain the cerebrospinal fluid out of the brain may be the abdomen cavity. A further S appropriate site for drainage is immediately after valve 105, in order to make the shunt tubing as short as possible and largely simplify the implantation thereof in surgery. Such drainage is effected via a tube 214 leading from shunt 202 to the patients abdominal cavity. Another appropriate site for draining cerebrospinal fluid out of the patient's brain may be the patient's skull, close to the spine. In this case the drainage tube is much shorter, simplifying the implantation surgery and reducing the risk to the patient. In both case, valve 145 which forms a part of, and is operable by, biosensor 100 is preferably used for alleviating intracranial pressure via shunt 202.
1 S As best illustrated in Figure 12, monitoring device 204 is preferably formed or embedded within the sidewall of shunt 202.
Referring to Figure 13, monitoring device 204 preferably includes one or more pressure sensors 212 and a transducer 214 which is electrically coupled with sensors 212. Like sensors 112, sensors 212 can . , 56 include, for example, temperature sensors, pH sensors, blood sugar sensors, blood oxygen sensors, or any other type of physiological sensing, monitoring or measuring device responsive to, for example, motion, flow, velocity, acceleration, force, strain, acoustics, moisture, osmolarity, light, turbidity, radiation, electricity, electromagnetic fields, chemicals, ionic, or enzymatic quantities or changes.
According to a preferred embodiment of the present invention, sensors 212 are provided for sensing the pressure of the cerebrospinal fluid in shunt passageway 205 and are preferably spaced a distance apart from one another for sensing pressure at different points within passageway 205. Sensors 212 may be placed anywhere within shunt 202 and may include piezoelectric or piezo-resistive transducers, silicon capacitive pressure transducers, variable-resistance laminates of conductive ink, variable conductance elastomeric devices, strain gauges or similar types of pressure sensitive devices.
Transducer 214 is also preferably formed or embedded within the sidewall of the shunt 202 and is coupled with sensors 212 for directly or indirectly (via a processor) receiving electrical pressure signals therefrom.
According to this embodiment of the present invention biosensor 100 which includes monitoring device 204 is implanted in a patient as illustrated generally in Figure 11 for draining or removing cerebrospinal fluid from the patient's brain for treating hydrocephalus. Monitoring device 204 which is preferably formed within the sidewalls of shunt 202 senses or detects the pressure of the cerebrospinal fluid within shunt 202 and delivers pressure signals to transducer 214. Preferably such monitoring is performed by sensors 212 periodically. Such periodic readings can be stored and processed within a processor for later access.
When it is desired to collect information from sensors 212, station 130 {or at least transducers 321 thereof) is placed adjacent a portion of the patient's body in which biosensor 100 is implanted. As described before, station 130 generates an interrogation signal delivered through transducers 321 for concomitantly powering biosensor 100 and retrieving data therefrom via transducer 214 in a fashion similar to as described above with respect to transducer 114. Should the data collected indicate an abnormal intracranial pressure, valve 105 of shunt 202 is opened to drain cerebrospinal fluid therethrough. To this end station 130 can be commanded to provide power for the opening of valve 105. This $g operation can be controlled either manually or by a preprogrammed processor.
According to another preferred embodiment of the present invention and as shown in Figures 11 and 14 there is provided a transducing assembly 351 which forms a part of station 130. In one configuration, as best seen in Figure 11, assembly 351 is incorporated into a helmet 310. Helmet 310 includes a plurality of transducers 321, each may serve as a transmitter, receiver or transceiver, positioned at various locations so as to provide full transmittance/reception spatial coverage of the brain volume.
As shown in Figure 11, a cable bundle 350 physically connects assembly 351 to multiplexer/demultiplexer 381, which is computer controlled. Multiplexer/demultipiexer 381 serves several functions, including (i) providing a transmittance signal to transducers 321 from power amplifier 128; (ii) conveying sensors' 112 or 212 signals from the body to signal conditioner 134; (iii) providing a computer-controlled multiplexing for transducers 321 when used as transmitters; (iv) providing multiplexing for transducers 321 when used as receivers; and/or (v) providing decoupling between the high power transmission signals from amplifier 128 and the low amplitude signals received from transmitting assembly 118 which is located within the body, into signal conditioner 134. It will be appreciated that multiplexer/demultiplexer 381 both isolates and routes the transmitted and received signals.
According to a preferred embodiment of the present invention the operation of assembly 351 included within helmet 310 is effected following pre calibration of the required location of the transducers over the helmet by, preferably, applying a method which is based on a positioning model.
Such a positioning model allows for an accurate placement of the extracorporeal transducxrs such that acoustic insonifying of the brain volume is provided at an approximately uniform level throughout.
In addition, to achieve such uniformity a three dimensional acoustic propagation model of the skull and brain can also be applied.
Employment of wide beam low frequency ultrasonic transducers may be advantageous in providing an economical coverage.
In addition, focusing the acoustic beams of the extracorporeal transducers on the intrabody transducer is also advantageous because in such cases narrow beam transducers of low frequency ultrasound can be efficiently utilized.
Thus, for appropriately positioning such extracorporeal transducers, either a positioning model or a converging (in-fire) spheroidal acoustic 5 array model with scattering can be used to provide the positional information required. With each of the transducers configuration envisaged above, a first run calibration session is employed in which communication between the helmet (extracorporeal) transducers and the intrabody hansducer is tested for maximal accuracy.
10 The present invention is advantageous over the existing art because it employs acoustic signals which are more readily propagatable in water bodies, such as the human body, as compared to radio fi~equency signals.
Although the invention has been described in conjunction with 15 specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art.
Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.
Claims (33)
1. An implantable biosensor system for monitoring a physiological condition in a patient, the biosensor system comprising:
(a) at least one sensor for sensing at least one parameter of a physiological condition and for generating electrical sensor signals representative of the physiological condition; and (b) a first acoustic activatable transducer being directly or indirectly coupled with said at least one sensor, said first acoustic activatable transducer being for converting a received acoustic interrogation signal from outside the patient's body into an electrical power for energizing said processor, said first acoustic activatable transducer further being for converting said electrical sensor signals of said at least one sensor into acoustic signals receivable out of the patient's body, such that information pertaining to said at least one parameter of the physiological condition can be relayed outside the patient's body upon generation of an acoustic interrogation signal.
(a) at least one sensor for sensing at least one parameter of a physiological condition and for generating electrical sensor signals representative of the physiological condition; and (b) a first acoustic activatable transducer being directly or indirectly coupled with said at least one sensor, said first acoustic activatable transducer being for converting a received acoustic interrogation signal from outside the patient's body into an electrical power for energizing said processor, said first acoustic activatable transducer further being for converting said electrical sensor signals of said at least one sensor into acoustic signals receivable out of the patient's body, such that information pertaining to said at least one parameter of the physiological condition can be relayed outside the patient's body upon generation of an acoustic interrogation signal.
2. The biosensor system of claim 1, further comprising:
(c) a processor coupling between said at least one sensor and said first acoustic activatable transducer, said processor being for converting said electrical sensor signals into converted electrical signals representative of the physiological condition, said processor being energized via said electrical power.
(c) a processor coupling between said at least one sensor and said first acoustic activatable transducer, said processor being for converting said electrical sensor signals into converted electrical signals representative of the physiological condition, said processor being energized via said electrical power.
3. The biosensor system of claim 1, wherein said first acoustic activatable transducer includes:
(i) a cell member having a cavity;
(ii) a substantially flexible piezoelectric layer attached to said cell member, said piezoelectric layer having an external surface and an internal surface, said piezoelectric layer featuring such dimensions so as to enable fluctuations thereof at its resonance frequency upon impinging of said acoustic interrogation signal;
and (iii) a first electrode attached to said external surface and a second electrode attached to said internal surface.
(i) a cell member having a cavity;
(ii) a substantially flexible piezoelectric layer attached to said cell member, said piezoelectric layer having an external surface and an internal surface, said piezoelectric layer featuring such dimensions so as to enable fluctuations thereof at its resonance frequency upon impinging of said acoustic interrogation signal;
and (iii) a first electrode attached to said external surface and a second electrode attached to said internal surface.
4. The biosensor system of claim 3, wherein said piezoelectric layer is of a material selected from the group consisting of PVDF and piezoceramic.
5. the biosensor system of claim 2, wherein said processor includes a conditioner and a digitizer for converting said electrical sensor signal to said converted electrical signal.
6. The biosensor system of claim 2, wherein said converted electrical signal is a digital signal.
7. The biosensor system of claim 2, wherein said processor, said first acoustic activatable transducer and said at least one sensor are co-integrated into a single biosensor device.
8. The biosensor system of claim 1, further comprising:
(c) an extracorporeal station positionable against the patient's body said extracorporeal station including an interrogation signal generator for generating said acoustic interrogation signal, said interrogation signal generator including at least one second transducer for transmitting said interrogation signal to said first acoustic activatable transducer and for receiving said receivable acoustic signals from said first acoustic activatable transducer.
(c) an extracorporeal station positionable against the patient's body said extracorporeal station including an interrogation signal generator for generating said acoustic interrogation signal, said interrogation signal generator including at least one second transducer for transmitting said interrogation signal to said first acoustic activatable transducer and for receiving said receivable acoustic signals from said first acoustic activatable transducer.
9. The biosensor system of claim 2, wherein said processor includes a memory device for storing said electrical sensor signals and an analyzer for analyzing said electrical sensor signals.
10. The biosensor system of claim 9, wherein said processor includes a programmable microprocessor.
11. The biosensor system of claim 1, further comprising a shunt operable by said electrical power generated by said first acoustic activatable transducer, said shunt having a tubular sidewall and opposed ends, wherein said at least one sensor and said first acoustic activatable transducer are embedded in said shunt sidewall.
12. The biosensor system of claim 1, wherein said at least one sensor is selected from the group consisting of a pressure sensor, a temperature sensor, a pH sensor, a blood sugar sensor, a blood oxygen sensor, a motion sensor, a flow sensor, a velocity sensor, an acceleration sensor, a force sensor, a strain sensor, an acoustics sensor, a moisture sensor, an osmolarity sensor, a light sensor, a turbidity sensor, a radiation sensor, an electromagnetic field sensor, a chemical sensor, an ionic sensor, and an enzymatic sensor.
13. The biosensor system of claim 1, wherein said first acoustic activatable transducer is capable of transmitting an identification code identifying said transducer.
14. An implantable biosensor system for monitoring and alleviating a physiological condition in a patient, said biosensor system comprising:
(a) a shunt having a fluid passageway and being operable for draining fluid through said fluid passageway from a portion of a patient's body;
(b) a monitoring and operating mechanism coupled with said shunt for non-invasively monitoring the physiological condition and operating said shunt, said monitoring and operating mechanism including at least one sensor for sensing at least one parameter of the physiological condition and for generating electrical sensor signals representative of the physiological condition; and (c) a first acoustic activatable transducer being directly or indirectly coupled with said at least one sensor, said first acoustic activatable transducer being for converting a received acoustic interrogation signal from outside the patient's body into an electrical power for energizing said at least one sensor and for operating said shunt upon command, said first acoustic activatable transducer further being for converting said electrical sensor signals into acoustic signals receivable out of the patient's body, such that information pertaining to said at least one parameter of the physiological condition can be relayed outside the patient's body upon generation of an acoustic interrogation signal and said shunt is operable upon command.
(a) a shunt having a fluid passageway and being operable for draining fluid through said fluid passageway from a portion of a patient's body;
(b) a monitoring and operating mechanism coupled with said shunt for non-invasively monitoring the physiological condition and operating said shunt, said monitoring and operating mechanism including at least one sensor for sensing at least one parameter of the physiological condition and for generating electrical sensor signals representative of the physiological condition; and (c) a first acoustic activatable transducer being directly or indirectly coupled with said at least one sensor, said first acoustic activatable transducer being for converting a received acoustic interrogation signal from outside the patient's body into an electrical power for energizing said at least one sensor and for operating said shunt upon command, said first acoustic activatable transducer further being for converting said electrical sensor signals into acoustic signals receivable out of the patient's body, such that information pertaining to said at least one parameter of the physiological condition can be relayed outside the patient's body upon generation of an acoustic interrogation signal and said shunt is operable upon command.
15. The biosensor system of claim 14, wherein said monitoring and operating mechanism further includes a processor coupled with said at least one sensor, said processor serves for converting said electrical sensor signals to converted electrical signals representative of the physiological condition.
16. The biosensor system of claim 14, wherein said command is an acoustic operation signal provided from outside the body.
17. The biosensor system of claim 15, wherein said shunt is a cerebrospinal fluid shunt for draining cerebrospinal fluid from the patient's brain.
18. The biosensor system of claim 17, wherein said at least one sensor includes a first pressure sensor positioned within said fluid passageway for sensing the pressure of the cerebrospinal fluid in the patient's brain and for generating a first pressure signal representative of that pressure.
19. The biosensor system of claim 18, wherein said at least one pressure sensor includes a second pressure sensor positioned at a distance from said first pressure sensor and being for sensing the pressure of the cerebrospinal fluid when flowing through said shunt and for generating a second pressure signal representative of that pressure.
20. The biosensor system of claim 19, wherein said processor receives said first and second pressure signals from said first and second pressure sensors and calculates the flow rate of cerebrospinal fluid through said shunt.
21. The biosensor system of claim 14, wherein said first acoustic activatable transducer includes:
(i) a cell member having a cavity;
(ii) a substantially flexible piezoelectric layer attached to said cell member, said piezoelectric layer having an external surface and an internal surface, said piezoelectric layer featuring such dimensions so as to enable fluctuations thereof at its resonance frequency upon impinging of an external acoustic wave; and (iii) a first electrode attached to said external surface and a second electrode attached to said internal surface.
(i) a cell member having a cavity;
(ii) a substantially flexible piezoelectric layer attached to said cell member, said piezoelectric layer having an external surface and an internal surface, said piezoelectric layer featuring such dimensions so as to enable fluctuations thereof at its resonance frequency upon impinging of an external acoustic wave; and (iii) a first electrode attached to said external surface and a second electrode attached to said internal surface.
22. The biosensor system of claim 21, wherein said piezoelectric layer is of a material selected from the group consisting of PVDF and piezoceramic.
23. the biosensor system of claim 15, wherein said processor includes a conditioner and a digitizer for converting said electrical sensor signal to said converted electrical signal.
24. The biosensor system of claim 15, wherein said converted electrical signal is a digital signal.
25. The biosensor system of claim 15, wherein said processor, said first acoustic activatable transducer and said at least one sensor are integrated into a single biosensor platform.
26. The biosensor system of claim 14, further comprising:
(d) an extracorporeal station positionable against the patient's body said extracorporeal station including an interrogation signal generator for generating said acoustic interrogation signal, said interrogation signal generator including at least one second transducer for transmitting said interrogation signal to said first acoustic activatable transducer and for receiving said receivable acoustic signals from said first acoustic activatable transducer.
(d) an extracorporeal station positionable against the patient's body said extracorporeal station including an interrogation signal generator for generating said acoustic interrogation signal, said interrogation signal generator including at least one second transducer for transmitting said interrogation signal to said first acoustic activatable transducer and for receiving said receivable acoustic signals from said first acoustic activatable transducer.
27. The biosensor system of claim 15, wherein said processor includes a memory device for storing said electrical sensor signals and an analyzing mechanism for analyzing said electrical sensor signals.
28. The biosensor system of claim 27, wherein said processor includes a programmable microprocessor.
29. The biosensor system of claim 14, wherein said at least one sensor is selected from the group consisting of a pressure sensor, a temperature sensor, a pH sensor, a blood sugar sensor, a blood oxygen sensor, a motion sensor, a flow sensor, a velocity sensor, an acceleration sensor, a force sensor, a strain sensor, an acoustics sensor, a moisture sensor, an osmolarity sensor, a light sensor, a turbidity sensor, a radiation sensor, an electromagnetic field sensor, a chemical sensor, an ionic sensor, and an enzymatic sensor.
30. The biosensor system of claim 14, wherein said first acoustic activatable transducer is capable of transmitting an identification code identifying said transducer.
31. A method for non-invasive monitoring of a physiological condition within a patient's body, the method comprising the steps of:
(a) sensing at least one parameter associated with the physiological condition via at least one sensor implanted within the patient's body to thereby obtain information pertaining to the physiological condition as an electrical output; and (b) converting said electrical output into an acoustic signal via an acoustic transducer and thereby acoustically relaying said information to outside the patient's body.
(a) sensing at least one parameter associated with the physiological condition via at least one sensor implanted within the patient's body to thereby obtain information pertaining to the physiological condition as an electrical output; and (b) converting said electrical output into an acoustic signal via an acoustic transducer and thereby acoustically relaying said information to outside the patient's body.
32. The method of claim 31, further comprising the step of:
(c) relaying an acoustic interrogation signal from outside the patient's body for activating said at least one sensor.
(c) relaying an acoustic interrogation signal from outside the patient's body for activating said at least one sensor.
33. A method for non-invasive monitoring and alleviating of a physiological condition within a patient's body, the method comprising the steps of:
(a) sensing at least one parameter associated with the physiological condition via at least one sensor implanted within the patient's body to thereby obtain information pertaining to the physiological condition as an electrical output;
(b) converting said electrical output into an acoustic signal via an acoustic transducer and thereby acoustically relaying said information to outside the patient's body; and (c) relaying an acoustic interrogation signal from outside the patient's body for activating said at least one sensor and further for activating a shunt for alleviating the physiological condition.
(a) sensing at least one parameter associated with the physiological condition via at least one sensor implanted within the patient's body to thereby obtain information pertaining to the physiological condition as an electrical output;
(b) converting said electrical output into an acoustic signal via an acoustic transducer and thereby acoustically relaying said information to outside the patient's body; and (c) relaying an acoustic interrogation signal from outside the patient's body for activating said at least one sensor and further for activating a shunt for alleviating the physiological condition.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/303,644 | 1999-05-03 | ||
US09/303,644 US6432050B1 (en) | 1997-12-30 | 1999-05-03 | Implantable acoustic bio-sensing system and method |
Publications (1)
Publication Number | Publication Date |
---|---|
CA2306196A1 true CA2306196A1 (en) | 2000-11-03 |
Family
ID=23173059
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002306196A Abandoned CA2306196A1 (en) | 1999-05-03 | 2000-04-19 | Implantable acoustic biosensing system and method |
Country Status (6)
Country | Link |
---|---|
US (1) | US6432050B1 (en) |
EP (1) | EP1050264B1 (en) |
JP (2) | JP4693957B2 (en) |
AT (1) | ATE388665T1 (en) |
CA (1) | CA2306196A1 (en) |
DE (1) | DE60038260T2 (en) |
Families Citing this family (125)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7885697B2 (en) | 2004-07-13 | 2011-02-08 | Dexcom, Inc. | Transcutaneous analyte sensor |
US20030036746A1 (en) | 2001-08-16 | 2003-02-20 | Avi Penner | Devices for intrabody delivery of molecules and systems and methods utilizing same |
US7283874B2 (en) | 2000-10-16 | 2007-10-16 | Remon Medical Technologies Ltd. | Acoustically powered implantable stimulating device |
US7024248B2 (en) * | 2000-10-16 | 2006-04-04 | Remon Medical Technologies Ltd | Systems and methods for communicating with implantable devices |
US6764446B2 (en) | 2000-10-16 | 2004-07-20 | Remon Medical Technologies Ltd | Implantable pressure sensors and methods for making and using them |
WO2002056761A2 (en) * | 2000-11-17 | 2002-07-25 | Noveon Ip Holdings Corp. | Acoustic-based remotely interrrogated diagnostic implant device and system |
US7547283B2 (en) * | 2000-11-28 | 2009-06-16 | Physiosonics, Inc. | Methods for determining intracranial pressure non-invasively |
US6694158B2 (en) * | 2001-04-11 | 2004-02-17 | Motorola, Inc. | System using a portable detection device for detection of an analyte through body tissue |
DE10142019A1 (en) * | 2001-08-28 | 2003-03-20 | Philips Corp Intellectual Pty | Circuit arrangement for demodulating signals |
US10022078B2 (en) | 2004-07-13 | 2018-07-17 | Dexcom, Inc. | Analyte sensor |
US9694166B2 (en) | 2002-03-26 | 2017-07-04 | Medtronics Ps Medical, Inc. | Method of draining cerebrospinal fluid |
US7061381B2 (en) * | 2002-04-05 | 2006-06-13 | Beezerbug Incorporated | Ultrasonic transmitter and receiver systems and products using the same |
IL164685A0 (en) * | 2002-04-22 | 2005-12-18 | Marcio Marc Aurelio Martins Ab | Apparatus and method for measuring biologic parameters |
US8328420B2 (en) | 2003-04-22 | 2012-12-11 | Marcio Marc Abreu | Apparatus and method for measuring biologic parameters |
US9848815B2 (en) | 2002-04-22 | 2017-12-26 | Geelux Holdings, Ltd. | Apparatus and method for measuring biologic parameters |
US6898461B2 (en) | 2002-04-23 | 2005-05-24 | Medtronic, Inc. | Implantable medical device stream processor |
US7086042B2 (en) * | 2002-04-23 | 2006-08-01 | International Business Machines Corporation | Generating and utilizing robust XPath expressions |
US6941332B2 (en) | 2002-04-23 | 2005-09-06 | Medtronic, Inc. | Implantable medical device fast median filter |
US7698909B2 (en) | 2002-10-01 | 2010-04-20 | Nellcor Puritan Bennett Llc | Headband with tension indicator |
EP1549165B8 (en) | 2002-10-01 | 2010-10-06 | Nellcor Puritan Bennett LLC | Use of a headband to indicate tension and system comprising an oximetry sensor and a headband |
US7686762B1 (en) | 2002-10-03 | 2010-03-30 | Integrated Sensing Systems, Inc. | Wireless device and system for monitoring physiologic parameters |
US7211048B1 (en) | 2002-10-07 | 2007-05-01 | Integrated Sensing Systems, Inc. | System for monitoring conduit obstruction |
US20050256549A1 (en) * | 2002-10-09 | 2005-11-17 | Sirius Implantable Systems Ltd. | Micro-generator implant |
US9740817B1 (en) | 2002-10-18 | 2017-08-22 | Dennis Sunga Fernandez | Apparatus for biological sensing and alerting of pharmaco-genomic mutation |
US6685638B1 (en) | 2002-12-23 | 2004-02-03 | Codman & Shurtleff, Inc. | Acoustic monitoring system |
US8353857B2 (en) * | 2003-06-23 | 2013-01-15 | Codman & Shurtleff, Inc. | Implantable medical device having pressure sensors for diagnosing the performance of an implanted medical device |
US7047056B2 (en) | 2003-06-25 | 2006-05-16 | Nellcor Puritan Bennett Incorporated | Hat-based oximeter sensor |
US7920906B2 (en) | 2005-03-10 | 2011-04-05 | Dexcom, Inc. | System and methods for processing analyte sensor data for sensor calibration |
US8346482B2 (en) * | 2003-08-22 | 2013-01-01 | Fernandez Dennis S | Integrated biosensor and simulation system for diagnosis and therapy |
AU2004273998A1 (en) * | 2003-09-18 | 2005-03-31 | Advanced Bio Prosthetic Surfaces, Ltd. | Medical device having mems functionality and methods of making same |
US20050065592A1 (en) * | 2003-09-23 | 2005-03-24 | Asher Holzer | System and method of aneurism monitoring and treatment |
US8412297B2 (en) * | 2003-10-01 | 2013-04-02 | Covidien Lp | Forehead sensor placement |
US9247900B2 (en) | 2004-07-13 | 2016-02-02 | Dexcom, Inc. | Analyte sensor |
WO2005067817A1 (en) | 2004-01-13 | 2005-07-28 | Remon Medical Technologies Ltd | Devices for fixing a sensor in a body lumen |
US8751003B2 (en) * | 2004-02-11 | 2014-06-10 | Ethicon, Inc. | Conductive mesh for neurostimulation |
US8165695B2 (en) | 2004-02-11 | 2012-04-24 | Ethicon, Inc. | System and method for selectively stimulating different body parts |
CN1942140A (en) * | 2004-02-11 | 2007-04-04 | 伊西康公司 | System and method for urodynamic evaluation utilizing micro-electronic mechanical system |
US7979137B2 (en) | 2004-02-11 | 2011-07-12 | Ethicon, Inc. | System and method for nerve stimulation |
US7647112B2 (en) * | 2004-02-11 | 2010-01-12 | Ethicon, Inc. | System and method for selectively stimulating different body parts |
US7471986B2 (en) * | 2004-02-20 | 2008-12-30 | Cardiac Pacemakers, Inc. | System and method for transmitting energy to and establishing a communications network with one or more implanted devices |
US10227063B2 (en) | 2004-02-26 | 2019-03-12 | Geelux Holdings, Ltd. | Method and apparatus for biological evaluation |
EP1773186A4 (en) | 2004-07-08 | 2009-08-12 | Deborah Schenberger | Strain monitoring system and apparatus |
US20060064134A1 (en) * | 2004-09-17 | 2006-03-23 | Cardiac Pacemakers, Inc. | Systems and methods for deriving relative physiologic measurements |
US20060064133A1 (en) * | 2004-09-17 | 2006-03-23 | Cardiac Pacemakers, Inc. | System and method for deriving relative physiologic measurements using an external computing device |
EP1811894A2 (en) * | 2004-11-04 | 2007-08-01 | L & P 100 Limited | Medical devices |
US7813808B1 (en) | 2004-11-24 | 2010-10-12 | Remon Medical Technologies Ltd | Implanted sensor system with optimized operational and sensing parameters |
US20060122513A1 (en) * | 2004-12-06 | 2006-06-08 | Taylor William G | Doppler helmet |
US20070232918A1 (en) * | 2004-12-06 | 2007-10-04 | William Taylor | Doppler helmet |
US7585280B2 (en) | 2004-12-29 | 2009-09-08 | Codman & Shurtleff, Inc. | System and method for measuring the pressure of a fluid system within a patient |
US10390714B2 (en) | 2005-01-12 | 2019-08-27 | Remon Medical Technologies, Ltd. | Devices for fixing a sensor in a lumen |
WO2006089246A2 (en) * | 2005-02-16 | 2006-08-24 | Transoma Medical, Inc. | Impedance based sensor for monitoring leakage in aaa stent graft |
WO2006091581A1 (en) * | 2005-02-22 | 2006-08-31 | Richard Saunders | Controllable shunt |
US8588930B2 (en) * | 2005-06-07 | 2013-11-19 | Ethicon, Inc. | Piezoelectric stimulation device |
US8309057B2 (en) * | 2005-06-10 | 2012-11-13 | The Invention Science Fund I, Llc | Methods for elevating neurotrophic agents |
US7742815B2 (en) | 2005-09-09 | 2010-06-22 | Cardiac Pacemakers, Inc. | Using implanted sensors for feedback control of implanted medical devices |
US8649875B2 (en) | 2005-09-10 | 2014-02-11 | Artann Laboratories Inc. | Systems for remote generation of electrical signal in tissue based on time-reversal acoustics |
EP2295999B1 (en) * | 2005-09-14 | 2013-09-04 | The Government of the United States of America, as represented by the Secretary, Department of Health and Human Services | System containing ultrasonic transducers for use with magnetic resonance imaging |
KR101370985B1 (en) | 2005-10-24 | 2014-03-10 | 마시오 마크 아우렐리오 마틴스 애브리우 | Apparatus and method for measuring biologic parameters |
US20070142727A1 (en) * | 2005-12-15 | 2007-06-21 | Cardiac Pacemakers, Inc. | System and method for analyzing cardiovascular pressure measurements made within a human body |
US8060214B2 (en) | 2006-01-05 | 2011-11-15 | Cardiac Pacemakers, Inc. | Implantable medical device with inductive coil configurable for mechanical fixation |
US8078278B2 (en) | 2006-01-10 | 2011-12-13 | Remon Medical Technologies Ltd. | Body attachable unit in wireless communication with implantable devices |
US20070208390A1 (en) * | 2006-03-01 | 2007-09-06 | Von Arx Jeffrey A | Implantable wireless sound sensor |
JP2009529975A (en) * | 2006-03-17 | 2009-08-27 | ザ ボード オブ トラスティーズ オブ ザ レランド スタンフォード ジュニア ユニバーシティー | Energy generation system for implantable medical devices |
US7744542B2 (en) * | 2006-04-20 | 2010-06-29 | Cardiac Pacemakers, Inc. | Implanted air passage sensors |
US7650185B2 (en) | 2006-04-25 | 2010-01-19 | Cardiac Pacemakers, Inc. | System and method for walking an implantable medical device from a sleep state |
US7955268B2 (en) | 2006-07-21 | 2011-06-07 | Cardiac Pacemakers, Inc. | Multiple sensor deployment |
JP5156749B2 (en) | 2006-09-15 | 2013-03-06 | カーディアック ペースメイカーズ, インコーポレイテッド | Implantable sensor anchor |
US8676349B2 (en) | 2006-09-15 | 2014-03-18 | Cardiac Pacemakers, Inc. | Mechanism for releasably engaging an implantable medical device for implantation |
US20080071248A1 (en) * | 2006-09-15 | 2008-03-20 | Cardiac Pacemakers, Inc. | Delivery stystem for an implantable physiologic sensor |
US20080132962A1 (en) * | 2006-12-01 | 2008-06-05 | Diubaldi Anthony | System and method for affecting gatric functions |
US8340776B2 (en) | 2007-03-26 | 2012-12-25 | Cardiac Pacemakers, Inc. | Biased acoustic switch for implantable medical device |
US8204599B2 (en) | 2007-05-02 | 2012-06-19 | Cardiac Pacemakers, Inc. | System for anchoring an implantable sensor in a vessel |
WO2008156981A2 (en) | 2007-06-14 | 2008-12-24 | Cardiac Pacemakers, Inc. | Multi-element acoustic recharging system |
US8082041B1 (en) | 2007-06-15 | 2011-12-20 | Piezo Energy Technologies, LLC | Bio-implantable ultrasound energy capture and storage assembly including transmitter and receiver cooling |
US8352026B2 (en) * | 2007-10-03 | 2013-01-08 | Ethicon, Inc. | Implantable pulse generators and methods for selective nerve stimulation |
US8915866B2 (en) * | 2008-01-18 | 2014-12-23 | Warsaw Orthopedic, Inc. | Implantable sensor and associated methods |
US8961448B2 (en) * | 2008-01-28 | 2015-02-24 | Peter Forsell | Implantable drainage device |
WO2009102613A2 (en) | 2008-02-11 | 2009-08-20 | Cardiac Pacemakers, Inc. | Methods of monitoring hemodynamic status for ryhthm discrimination within the heart |
WO2009102640A1 (en) | 2008-02-12 | 2009-08-20 | Cardiac Pacemakers, Inc. | Systems and methods for controlling wireless signal transfers between ultrasound-enabled medical devices |
US20090204019A1 (en) * | 2008-02-13 | 2009-08-13 | Alec Ginggen | Combined Pressure and Flow Sensor Integrated in a Shunt System |
CA2715628A1 (en) | 2008-02-21 | 2009-08-27 | Dexcom, Inc. | Systems and methods for processing, transmitting and displaying sensor data |
WO2009158062A1 (en) | 2008-06-27 | 2009-12-30 | Cardiac Pacemakers, Inc. | Systems and methods of monitoring the acoustic coupling of medical devices |
EP2339955B1 (en) * | 2008-07-14 | 2012-09-05 | École Polytechnique Fédérale de Lausanne (EPFL) | Viscosimetric biosensor for monitoring analyte levels |
JP5362828B2 (en) | 2008-07-15 | 2013-12-11 | カーディアック ペースメイカーズ, インコーポレイテッド | Implant assist for an acoustically enabled implantable medical device |
EP2330970A1 (en) * | 2008-07-18 | 2011-06-15 | Neckarate GmbH & Co. KG | System for regulating intracranial pressure |
US20100152608A1 (en) * | 2008-09-12 | 2010-06-17 | Hatlestad John D | Chronically implanted abdominal pressure sensor for continuous ambulatory assessment of renal functions |
US8257274B2 (en) | 2008-09-25 | 2012-09-04 | Nellcor Puritan Bennett Llc | Medical sensor and technique for using the same |
US8364220B2 (en) | 2008-09-25 | 2013-01-29 | Covidien Lp | Medical sensor and technique for using the same |
US8591423B2 (en) | 2008-10-10 | 2013-11-26 | Cardiac Pacemakers, Inc. | Systems and methods for determining cardiac output using pulmonary artery pressure measurements |
US8593107B2 (en) | 2008-10-27 | 2013-11-26 | Cardiac Pacemakers, Inc. | Methods and systems for recharging an implanted device by delivering a section of a charging device adjacent the implanted device within a body |
WO2010059291A1 (en) | 2008-11-19 | 2010-05-27 | Cardiac Pacemakers, Inc. | Assessment of pulmonary vascular resistance via pulmonary artery pressure |
US20100140958A1 (en) * | 2008-12-04 | 2010-06-10 | Searete Llc, A Limited Liability Corporation Of The State Of Delaware | Method for powering devices from intraluminal pressure changes |
US9631610B2 (en) | 2008-12-04 | 2017-04-25 | Deep Science, Llc | System for powering devices from intraluminal pressure changes |
US9759202B2 (en) * | 2008-12-04 | 2017-09-12 | Deep Science, Llc | Method for generation of power from intraluminal pressure changes |
US9526418B2 (en) | 2008-12-04 | 2016-12-27 | Deep Science, Llc | Device for storage of intraluminally generated power |
US9353733B2 (en) | 2008-12-04 | 2016-05-31 | Deep Science, Llc | Device and system for generation of power from intraluminal pressure changes |
US9567983B2 (en) * | 2008-12-04 | 2017-02-14 | Deep Science, Llc | Method for generation of power from intraluminal pressure changes |
US8126736B2 (en) | 2009-01-23 | 2012-02-28 | Warsaw Orthopedic, Inc. | Methods and systems for diagnosing, treating, or tracking spinal disorders |
US8685093B2 (en) | 2009-01-23 | 2014-04-01 | Warsaw Orthopedic, Inc. | Methods and systems for diagnosing, treating, or tracking spinal disorders |
WO2010093489A2 (en) | 2009-02-13 | 2010-08-19 | Cardiac Pacemakers, Inc. | Deployable sensor platform on the lead system of an implantable device |
DE102009009880A1 (en) * | 2009-02-20 | 2010-10-14 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Valve for use in a conduit for carrying a fluid |
US8088091B2 (en) * | 2009-03-09 | 2012-01-03 | New Jersey Institute Of Technology | No clog shunt using a compact fluid drag path |
US8515515B2 (en) | 2009-03-25 | 2013-08-20 | Covidien Lp | Medical sensor with compressible light barrier and technique for using the same |
US8781548B2 (en) | 2009-03-31 | 2014-07-15 | Covidien Lp | Medical sensor with flexible components and technique for using the same |
US9131885B2 (en) | 2009-07-02 | 2015-09-15 | Dexcom, Inc. | Analyte sensors and methods of manufacturing same |
US11169010B2 (en) * | 2009-07-27 | 2021-11-09 | Integra Lifesciences Switzerland Sàrl | Method for the calibration of an implantable sensor |
US8376937B2 (en) * | 2010-01-28 | 2013-02-19 | Warsaw Orhtopedic, Inc. | Tissue monitoring surgical retractor system |
EP2686062A4 (en) * | 2011-03-18 | 2014-09-10 | Salk Inst For Biological Studi | Method for identification of retinal cell types using intrinsic properties |
DE102011055284A1 (en) * | 2011-11-11 | 2013-05-16 | Aesculap Ag | Implantable pressure measuring device |
US8974366B1 (en) | 2012-01-10 | 2015-03-10 | Piezo Energy Technologies, LLC | High power ultrasound wireless transcutaneous energy transfer (US-TET) source |
US20140171751A1 (en) * | 2012-12-19 | 2014-06-19 | Robert L. Sankman | Electronic bio monitoring patch |
JP6126388B2 (en) * | 2013-01-25 | 2017-05-10 | 積水化学工業株式会社 | Biological signal sensor and biological signal sensor system using the same |
US9333368B2 (en) * | 2013-02-01 | 2016-05-10 | Old Dominion University Research Foundation | Treatment of biological tissues using subnanosecond electric pulses |
WO2014193990A1 (en) | 2013-05-28 | 2014-12-04 | Eduardo-Jose Chichilnisky | Smart prosthesis for facilitating artificial vision using scene abstraction |
CN105814419A (en) | 2013-10-11 | 2016-07-27 | 马尔西奥·马克·阿布雷乌 | Method and apparatus for biological evaluation |
CA2936235A1 (en) | 2014-01-10 | 2015-07-16 | Marcio Marc Abreu | Devices to monitor and provide treatment at an abreu brain tunnel |
WO2015106137A1 (en) | 2014-01-10 | 2015-07-16 | Marcio Marc Abreu | Device for measuring the infrared output of the abreu brain thermal tunnel |
CA2936247A1 (en) | 2014-01-22 | 2015-07-30 | Marcio Marc Abreu | Devices and methods for transdermal drug delivery |
US11872018B2 (en) | 2015-03-10 | 2024-01-16 | Brain Tunnelgenix Technologies Corp. | Devices, apparatuses, systems, and methods for measuring temperature of an ABTT terminus |
US10226193B2 (en) | 2015-03-31 | 2019-03-12 | Medtronic Ps Medical, Inc. | Wireless pressure measurement and monitoring for shunts |
US9757574B2 (en) | 2015-05-11 | 2017-09-12 | Rainbow Medical Ltd. | Dual chamber transvenous pacemaker |
US20170340223A1 (en) * | 2016-05-31 | 2017-11-30 | ChuangHui Medical Technology Inc. | Implantable Automatic Wireless Intracranial Pressure Monitoring System and Method |
BR102017023879A2 (en) * | 2017-11-06 | 2019-06-04 | Braincare Desenvolvimento E Inovação Tecnológica S.A. | SYSTEM AND METHOD OF MONITORING AND INTRACRANIAL PRESSURE MANAGEMENT WITHOUT INVASIVE WIRE |
US11043745B2 (en) | 2019-02-11 | 2021-06-22 | Old Dominion University Research Foundation | Resistively loaded dielectric biconical antennas for non-invasive treatment |
US20220378291A1 (en) * | 2021-06-01 | 2022-12-01 | Twenty Twenty Therapeutics Llc | Ultrasound Intraocular Pressure Sensor in Sclera or in Cornea |
Family Cites Families (28)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3943915A (en) | 1974-11-29 | 1976-03-16 | Motorola, Inc. | Intracranial pressure sensing device |
US4593703A (en) | 1976-06-21 | 1986-06-10 | Cosman Eric R | Telemetric differential pressure sensor with the improvement of a conductive shorted loop tuning element and a resonant circuit |
US4198987A (en) * | 1978-01-09 | 1980-04-22 | Cain Clarence P | Measuring system including elements implantable beneath the skin |
JPS57177735A (en) | 1981-04-27 | 1982-11-01 | Toyoda Chuo Kenkyusho Kk | Telemeter type brain nanometer |
US4494950A (en) * | 1982-01-19 | 1985-01-22 | The Johns Hopkins University | Plural module medication delivery system |
FR2531298B1 (en) * | 1982-07-30 | 1986-06-27 | Thomson Csf | HALF-WAVE TYPE TRANSDUCER WITH PIEZOELECTRIC POLYMER ELEMENT |
JPS59164035A (en) * | 1983-03-09 | 1984-09-17 | 三菱電機株式会社 | Internal pressure measuring apparatus of living body tissue |
US4677985A (en) | 1985-08-12 | 1987-07-07 | Bro William J | Apparatus and method for determining intracranial pressure and local cerebral blood flow |
JPS62102734A (en) * | 1985-10-31 | 1987-05-13 | 東洋通信機株式会社 | Card for receiving sensor for measuring temperature in living body |
JPH0523323A (en) * | 1991-07-22 | 1993-02-02 | Nippon Zeon Co Ltd | Intracorporeal information monitoring apparatus |
IL108470A (en) | 1994-01-28 | 1998-12-06 | Mizur Technology Ltd | Passive sensor system using ultrasonic energy |
SE9401402D0 (en) * | 1994-04-25 | 1994-04-25 | Siemens Elema Ab | Medical implant |
JP2720834B2 (en) * | 1995-05-30 | 1998-03-04 | 日本電気株式会社 | Acoustic communication device |
US5743267A (en) * | 1995-10-19 | 1998-04-28 | Telecom Medical, Inc. | System and method to monitor the heart of a patient |
JPH09147284A (en) * | 1995-11-07 | 1997-06-06 | Siemens Ag | Radio inquiry device operated by surface acoustic wave |
US5704352A (en) * | 1995-11-22 | 1998-01-06 | Tremblay; Gerald F. | Implantable passive bio-sensor |
IL125758A (en) * | 1996-02-15 | 2003-07-06 | Biosense Inc | Medical probes with field transducers |
JP3626269B2 (en) * | 1996-02-29 | 2005-03-02 | 横浜ゴム株式会社 | Transponder fitted tire |
US5833603A (en) * | 1996-03-13 | 1998-11-10 | Lipomatrix, Inc. | Implantable biosensing transponder |
EP0827105A3 (en) * | 1996-08-29 | 2000-10-25 | Siemens Aktiengesellschaft | Identification or sensing device operating with acoustic surface waves |
US5749909A (en) * | 1996-11-07 | 1998-05-12 | Sulzer Intermedics Inc. | Transcutaneous energy coupling using piezoelectric device |
US6015387A (en) * | 1997-03-20 | 2000-01-18 | Medivas, Llc | Implantation devices for monitoring and regulating blood flow |
CN1227843C (en) * | 1997-05-02 | 2005-11-16 | 精工爱普生株式会社 | Polarized light communication device, transmitter, laser, polarized light communication device for organism, reflected light detection and pulse wave detector |
ES2231634T3 (en) * | 1997-05-14 | 2005-05-16 | Btg International Limited | POTENTIFIED IDENTIFICATION SYSTEM. |
CA2296510C (en) * | 1997-07-16 | 2006-02-07 | Trustees Of The Stevens Institute Of Technology | Method and apparatus for acoustic detection of mines and other buried man-made objects |
US5807258A (en) * | 1997-10-14 | 1998-09-15 | Cimochowski; George E. | Ultrasonic sensors for monitoring the condition of a vascular graft |
US5891180A (en) * | 1998-04-29 | 1999-04-06 | Medtronic Inc. | Interrogation of an implantable medical device using audible sound communication |
US6170488B1 (en) * | 1999-03-24 | 2001-01-09 | The B. F. Goodrich Company | Acoustic-based remotely interrogated diagnostic implant device and system |
-
1999
- 1999-05-03 US US09/303,644 patent/US6432050B1/en not_active Expired - Lifetime
-
2000
- 2000-04-19 CA CA002306196A patent/CA2306196A1/en not_active Abandoned
- 2000-04-28 DE DE60038260T patent/DE60038260T2/en not_active Expired - Lifetime
- 2000-04-28 EP EP00109256A patent/EP1050264B1/en not_active Expired - Lifetime
- 2000-04-28 AT AT00109256T patent/ATE388665T1/en not_active IP Right Cessation
- 2000-05-08 JP JP2000135205A patent/JP4693957B2/en not_active Expired - Fee Related
-
2011
- 2011-01-28 JP JP2011017259A patent/JP5127939B2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
EP1050264A1 (en) | 2000-11-08 |
JP4693957B2 (en) | 2011-06-01 |
ATE388665T1 (en) | 2008-03-15 |
JP5127939B2 (en) | 2013-01-23 |
DE60038260T2 (en) | 2009-03-19 |
JP2000350708A (en) | 2000-12-19 |
DE60038260D1 (en) | 2008-04-24 |
EP1050264B1 (en) | 2008-03-12 |
JP2011101821A (en) | 2011-05-26 |
US6432050B1 (en) | 2002-08-13 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP1050264B1 (en) | Implantable acoustic bio-sensing system and method | |
US6198965B1 (en) | Acoustic telemetry system and method for monitoring a rejection reaction of a transplanted organ | |
US5704352A (en) | Implantable passive bio-sensor | |
US6277078B1 (en) | System and method for monitoring a parameter associated with the performance of a heart | |
US6431175B1 (en) | System and method for directing and monitoring radiation | |
US6486588B2 (en) | Acoustic biosensor for monitoring physiological conditions in a body implantation site | |
US6475170B1 (en) | Acoustic biosensor for monitoring physiological conditions in a body implantation site | |
US6239724B1 (en) | System and method for telemetrically providing intrabody spatial position | |
US6237398B1 (en) | System and method for monitoring pressure, flow and constriction parameters of plumbing and blood vessels | |
US6330885B1 (en) | Remotely interrogated implant device with sensor for detecting accretion of biological matter | |
US20090048518A1 (en) | Doppler motion sensor apparatus and method of using same | |
USRE42378E1 (en) | Implantable pressure sensors and methods for making and using them | |
US8070695B2 (en) | Strain monitoring system and apparatus | |
US8298148B2 (en) | Integrated heart monitoring device and method of using same | |
US8343068B2 (en) | Sensor unit and procedure for monitoring intracranial physiological properties | |
US9364362B2 (en) | Implantable device system | |
US20040133092A1 (en) | Wireless system for measuring distension in flexible tubes | |
US20080058652A1 (en) | Medical Devices | |
WO2009138882A2 (en) | Doppler motion sensor apparatus and method of using same | |
US20130247644A1 (en) | Implantable pressure sensor | |
US20110054333A1 (en) | Stent Flow Sensor | |
WO2002056761A2 (en) | Acoustic-based remotely interrrogated diagnostic implant device and system | |
WO2008066761A2 (en) | Transducer apparatus and method for intravascular blood flow measurement | |
CN115969416A (en) | Equipment and detection method for monitoring urine volume |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
FZDE | Discontinued |