WO1994009700A1 - Acoustic imaging - Google Patents
Acoustic imaging Download PDFInfo
- Publication number
- WO1994009700A1 WO1994009700A1 PCT/US1993/005819 US9305819W WO9409700A1 WO 1994009700 A1 WO1994009700 A1 WO 1994009700A1 US 9305819 W US9305819 W US 9305819W WO 9409700 A1 WO9409700 A1 WO 9409700A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- acoustic
- pipe
- signals
- housing
- head
- Prior art date
Links
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/12—Diagnosis using ultrasonic, sonic or infrasonic waves in body cavities or body tracts, e.g. by using catheters
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
- A61B5/085—Measuring impedance of respiratory organs or lung elasticity
Definitions
- This invention relates to acoustic imaging of mammalian airway morphology and more particularly concerns noninvasively obtaining a signal representative of the cross-sectional area of an airway (e.g., oral, nasal, or pulmonary) of a subject (e.g., a person or an animal) using electroacoustical transducers.
- an airway e.g., oral, nasal, or pulmonary
- a subject e.g., a person or an animal
- a one-dimensional image of the cross-sectional area of an airway as a function of axial position along the airway may be determined from acoustic reflections measured by a single electro-acoustic transducer placed in a position remote from the airway opening.
- This image is referred to as an area-distance function and is represented by A(x) where x is the axial position along the airway.
- A(x) is useful for example in the diagnosis of mammalian pathologies associated with oral airways, larynx, pulmonary airways, and nasal airways. These pathologies include but are not limited to obstructive sleep apnea, asthma, obstructive pulmonary disease, tracheal stenosis, and nasal septum deviation.
- the distance separating the loudspeaker from the receiving transducer must be greater than the maximum airway penetration depth of interest; this ensures that secondary reflections from the speaker arrive at the receiving transducer only after data acquisition has been completed.
- imaging instruments for airway imaging previously described in the literature are 1 to 2 meters or more in length (Brooks et al., Reproducibility and Accuracy of Airway Area by Acoustic Reflection, J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 57(3): 777-787, 1984; D'Urzo et al..
- the present invention is based upon a new two- transducer method and a new associated theory that permits practical application of airway recon ⁇ structions by acoustic reflections. Because this theory explicitly incorporates reverberation within the wave tube and does not demand non-overlapping time windows of incident and reflected waves, it removes the distance constraint described above, permitting placement of the loudspeaker or launching transducer close to the receiving transducers. As such, the new theory allows fabrication of a practical miniature apparatus whose overall length is only a few centimeters rather than meters. The apparatus can image the respiratory tract of mammalian subjects, including the nasal oral and pulmonary cavities. Summary Of The Invention
- the improvement which comprises a light-weight, easy to manipulate, hand-held acoustic imaging head which is rugged and entirely hand supportable and operable by an operator, throughout an imaging procedure, which head comprises;
- At least one acoustic pressure wave sensing transducer mounted on the acoustic pipe at a location between the first and second ends of the acoustic pipe, for sensing reflections of the incident wave, received back in the acoustic tube through the open second end and generating a signal;
- E. means at least partially within the chamber, connected to the acoustic wave sensing transducer, for transmission of signals transduced, to processor means for processing said signals into a processor output signal characteristic of the morphology of a site within the mammal's respiratory tract.
- the invention provides signals representative of airway morphology in apparatus that is relatively small and portable. The invention may be used for diagnostic and screening purposes in a confined area such as a laboratory, a doctor's office, a place of work, and at bedside.
- Figure 1 is a cross-sectional side elevation of a preferred embodiment head of the invention.
- Figure 2 is a combined block-pictorial diagram illustrating operation of the head shown in Figure 1.
- Figure 3 is a fragmentary view of the outside wall of the housing for the embodiment head of the invention of Figure 1, showing a representative control panel.
- Figure 4 is an electrical wiring diagram for the embodiment head shown in Figure 1.
- Figure 5 is a partially fragmented sideview of a disposable nasal coupling device of the invention used in conjunction with the head of Figure 1.
- Figure 6 is a view from above of the coupling device shown in Figure 5.
- Figure 7 is an alternative shape for the coupling opening in the device of Figure 5.
- FIG. 1 a cross-sectional side elevation, there is seen a preferred embodiment acoustic imaging head 10 of the invention for imaging the internal morphology of portions of the respiratory tract of a mammal, including a human.
- Head 10 comprises a hand- holdable housing 12 having an elongate body 14 defined by a top end 16 and a base end 18 which presents a planar surface 19 for standing the head 10 on a flat surface in an upright position.
- the housing 12 presents an outer wall 20 extending between ends 16, 18 and defining an internal, closed chamber 22.
- Wall 20 advantageously includes integrally molded finger holds 24 and a palm grasping indentation 26.
- the outside surface of wall 20 may be a frictional surface to facilitate holding and operating the head 10 by a single human hand.
- the overall weight of head 10 will be such that it is light and easy to operate and manipulate.
- the head 10 is fully supportable by hand-holding by the operator.
- An aperture 28 pierces end 16 of the housing 12.
- the aperture 28 has mounted therein end 34 of an acoustic pipe 30 having a closed first end 32 within chamber 22 and an open end 34 outside of the housing 12.
- the end 34 of acoustic pipe 30 includes a rib 36 encircling the circumference of end 34, which functions as a means for coupling to the acoustic pipe 30 an adaptor in the form of coupling device 80 for mating with an orifice of the mammal respiratory tract for imaging.
- the acoustic pipe 30 substantially traverses chamber 22 and its dimensions dictate the overall dimensions of the housing 12.
- the acoustic pipe 30 is advantageously about 2.0 to 4.0 cm, preferably about 1.2 cm in diameter and has a length of between about 5 to about 40 cm, most preferably 5 to 20 cm.
- the end 32 of pipe 30 is closed by mounting thereon a loudspeaker or launching transducer 38 which, upon energization, will launch acoustic energy into the interior of acoustic pipe 30, propagating an incident sonic wave towards open end 34 of pipe 30 and outside the end 34.
- a loudspeaker or launching transducer 38 which, upon energization, will launch acoustic energy into the interior of acoustic pipe 30, propagating an incident sonic wave towards open end 34 of pipe 30 and outside the end 34.
- the head 10 is coupled to an orifice in the respiratory tract for imaging through coupling device 80, the propagated sound wave will enter the respiratory tract, strike anatomical features in the tract and be reflected back through end 34 into the interior of acoustic pipe 30 to form a transient wave field within the pipe 30.
- This wave field is representative of the morphology of the respiratory tract.
- Two spaced apart pressure transducers 40, 42 are mounted on the acoustic pipe 30 with their pressure sensor flush with the inner walls of acoustic pipe 30 in order to reduce parasitic acoustic reflections.
- the transducers 40, 42 are advantageously separated from each other a distance of from about 1.0 to about 15 cm. and both are separated from the end 34 of acoustic pipe 30 by at least about 2.0 cm.
- relatively shallow cavities i.e.; interior respiratory tract cavities which are to be imaged and which are close to the transducer (at most about 2 to 3 cm.
- the launching transducer 38 is energized to transmit a one- dimensional, essentially lossless acoustic wave into the acoustic pipe 30 by an electrical signal transmitted via conductor 48 which may terminate externally in a plug-type connector 50 mounted on the housing 12 wall 14 and in an amplifier 52 which will be described more fully hereafter.
- the transducers 40, 42 are each electrically connected by separate electrical conductors 54, 56, respectively, which also can terminate in plug-type connectors 58, 59 mounted on the housing 12 wall 14.
- the connectors 58, 59 can be used for connection to signal processing means external of head 10, as will be discussed more fully hereinafter.
- the connectors 50, 58, 59 are connectable through a communications cable to a signal processor, including a host computer (not shown in Figure 1) which is remote from the head 10.
- a host computer not shown in Figure 1 which is remote from the head 10.
- Figure 2 is a combined block-pictorial diagram illustrating the operation of an imaging system using the head 10 of the invention.
- a simplified assembly includes as the launching transducer 38 a loudspeaker such as model MDR 434.
- Acoustic pipe 30 is of length L.
- the launched incident wave travels through pipe 30 and into the airway.
- a reflected wave, or echo, representative of gradients in the acoustic impedance in the airway then propagates back into pipe 30 towards launching transducer 38.
- Receiving transducers 40 and 42 individually and together sense the pressure waves associated with the echo and provide transduced electrical signals representative of the incident and reflected waves for processing by microcomputer 60.
- Microcomputer 60 generates a digital probe signal converted to an analog signal by D/A converter 62, and amplified by amplifier 52 to drive launching transducer 38 and launch the incident probe acoustic wave.
- the transduced outputs from receiving transducers 40 and 42 are band-pass filtered by preamplifier 66 and then converted by A/D convertor 68 into digital signals.
- Microcomputer 60 stores these digital signals in its RAM capability.
- Microcomputer 60 processes the stored digital signals to provide an output signal A(x) , i.e., a one-dimensional image of the cross-sectional area of the airway as a function of axial position, x, along the airway.
- Computer 60 preferably processes these signals in accordance with the Ware-Aki algorithm ("Continuous and Discrete Inverse Scattering Problems in a Stratified Elastic Medium. I. Plane Waves at Normal Incidence", J. Acoust. Soc. Am., 54, 4, 911-921, 1969) to provide the area distance function, A(x) , from the impulse response of the airway, h(t) .
- the relationship between the pressure field and h(t) may be derived as follows.
- Equation (7) indicates that both waves propagate with an equal, non-zero delay.
- the symbol ⁇ denotes the well-known impulse function which is sometimes called the delta function.
- Equation (6) identifies the relationship between the pressure field and h(t) . Equation (6) may be discretized by the
- ⁇ t is the sampling duration of the time discretization
- n is the set of integers 1,2,3, etc.
- k is the index of the summation
- microcomputer 60 processes the stored digital data signals representative of the transduced signals from the spaced-transducers 40,42 to provide a signal representative of the impulse response of the airway, h(t), according to equation (8).
- Microcomputer >60 then processes the signal h(t) in accordance with the Ware-Aki algorithm to provide a signal, A(x) , representative of the morphology of the airway.
- the signal A(X) can then be stored in the storage capability of microcomputer 60 for future call-up when comparisons are desired, to subsequent images.
- the wave propagation in pipe 30 may be assumed lossless.
- Microcomputer 60 may determine the propagation delay by minimizing mean square differences between the transduced signals in the early part of their respective transients. The relative gain of the transducers may be determined in a similar manner.
- the first non-zero pressure value p(o,o) is preferably larger than some minimal threshold value to maintain stability.
- the pressure values occurring before this first threshold pressure are initially neglected to obtain a first approximation of h(t) .
- Microcomputer 60 then preferably bandpasses the discrete values sequence h(n ⁇ t) that represents the impulse response of the airway h(t) with a digital, linear-phase, finite impulse response (FIR) filter having a passband from 0.01 kHz to 9 kHz to attenuate physiologic noise associated with airway wall non-rigidity, instability of the impulse response, h( ⁇ t) , and artifacts associated with acoustic cross-modes.
- FIR finite impulse response
- Microcomputer 60 then processes the corrected h( ⁇ t) signal in accordance with the Ware-Aki algorithm to provide an output signal representative of the area-distance function, A(x) , of the airway graphically represented.
- the microcomputer 60 (such as Compuadd model 320 with an Intel 80386 microprocessor operating at 20 MHz) is coupled to a converter module having a 12-bit analog-to-digital (A/D) converter 68 with a sampling period typically of 24.0 ⁇ s and a 12 bit digital-to-analog (D/A) converter 62 coupled to pre-amplifier 66 typically with a band-pass filter having a passband from 0.1 kHz to 10.0 kHz (such as Tektronix model AM 502) that is coupled to transducers 40 and 42.
- D/A converter 62 is coupled to transducer 38 through amplifier 52.
- the head 10 of the invention when the head 10 of the invention is to be used for imaging relatively shallow body cavities near the orifice for coupling to the head 10, for example, the nasal vestibule to a depth of about 1 to 3 cm. , one can use a head 10 where only one of the transducers 40, 42 is present or active.
- the relationship between the pressure field and h(t) may be derived as described in the U.S. Patent 4,326,416 which is incorporated herein by reference thereto.
- it is necessary to calibrate the instrument This calibration procedure is also described fully in the U.S. Patent 4,326,416.
- the microcomputer 60 may also be coupled electronically to the input terminals of a display module (not shown in Figurel or 2) for visual display of processed signals from the transducers 40, 42.
- the processed signals can be input to a conventional printer for a printed record of the imaging results.
- Simultaneous visual display of processed signals is advantageous to the operator and permits the operator to practice a preferred method of operation. It will be appreciated by those skilled in the art that a hand operated device for use in imaging, for example, the nasal passages of a mammal requires a steady operator's hand and patient-subject to obtain consistently good and reproducible signal data.
- Slight inopportune movement on the part of the operator or patient can generate faulty data.
- the operator with experience can see on a visual display, inconsistent signals and periods of time when a series of incident waves propagated by the head are reflected, sensed and processed as consistent signals representative of the desired image.
- the operator in fact may have to manipulate the head 10 into certain positions in order to obtain consistent and reproducible signals (for example when a good coupling seal is difficult to achieve between the orifice and head 10) .
- the head 10 is advantageously used in a "pre-trigger" mode to sort out good signals from faulty signals, i.e.; inconsistent signals.
- a "circular buffer” whereby the microprocessor 60 is programmed to only store in the RAM the last 10 of 10 plus X signals received from A/D converter 68 (first in, first out) . These last 10 signals can represent a collection time period of about 2 seconds.
- the operator views the signals processed and put out by the microprocessor 60, as consistent, the operator can stop acquisition of new signals to maintain the last 10 consistent signals in the microprocessor memory for storage and future call-up. In this way, the useful signals are stored for later recall.
- miniature signal processing means 100 is mounted in the chamber 22 and includes the pre-a plifier 66, converter D/A 62 and converter A/D 68 with microcomputer 60. Integration of the computer circuitry into from one to three chips enables this miniaturization.
- a rechargeable battery 102 such as an AAA size battery is advantageously mounted in chamber 22 proximal to the housing base end 18 and includes a socket 104 for electrical recharge by connection to AC wall outlet sources.
- the battery pack 102 is electrically connected to the processing means 100 and the launching transducer 38, as a power source, controlled by switch circuitry described below (wiring not shown in Figure 1; see Figure 4) .
- the connectors 101, 103 are for connection of means 100 to a visual display monitor for observation and/or to a printer for obtaining a printed record of the processed signals.
- a portion of the outside of housing 12 wall 14 is shown, with a control 108 for energization and operation of the head 10, located in one of the fingerholds 24 to facilitate one-handed operation of head 10.
- a switch 109 is located in an adjacent fingerhold 24, which may be used to control such functions as START ACQUISITION OF DATA; STOP ACQUISITION OF DATA; DISPLAY DATA; SELECT DATA FOR DISPLAY; STORE DATA; RECALL DATA FOR DISPLAY; COMPARE NEW DATA TO RECALLED DATA, etc. Any and all of these functions (and others) can be controlled by finger-operated switches.
- the electrical wiring necessary for these control functions are not shown in Figure 1, for clarity of the drawing, but will be conventional and realized by those skilled in the art of electrical wiring.
- Figure 4 is a wiring diagram for the preferred embodiment head 10 described above, which is completely self-contained.
- a sterilizible, disposable nasal coupling device 80 having an input end 82 that attaches to the output end of pipe 30 and an output end 84 for insertion into a nostril.
- Channel 85 on the inside wall of coupling device 80 mates with and receives the rib 36 on end 34 of tube 30, for secure, removable attachment.
- Channel 85 and rib 36 cooperate to provide a means for attaching the acoustic pipe 30 end 34 to the coupling device 80.
- Other means of attachment will be apparent to those skilled in the art, such as the so-called "bayonet mount", screws, frictional fits, male-female connectors and the like.
- Nasal coupling device 80 may have output ends 84 of different sizes for snug sealing engagement with the inside of nostrils of different sizes. Its internal area contour is such that impedance matching between subject and apparatus is maintained with maximum acoustic energy transmission.
- Figure 6 is a top view of the coupling device 80 shown in Figure 5 and shows that the rim or edge 94 of end 84 may be relatively thin, i.e.; on the order of about 0.5 to about 1.5 mm in uniform thickness for a distance of about 10 mm from the edge 94 toward end 82 to facilitate a comfortable fit within the nostril and to allow trimming circa 10 mm off the length of the device 80.
- the wall 87 thickness below the 10 mm distance from the edge 94 may be increased towards end 82, where more structural stability and less flexibility is desired.
- the wall 87 of the oval shaped device 80 tapers from end 82 inwardly to end 84, on an inward slope of about 10 to 15° from the perpendicular.
- the preferred coupling device 80 may be fabricated from a wide variety of materials, both flexible, and inflexible in character. Representative of such materials are a wide range of synthetic and natural polymeric resins, preferably having properties which do not inhibit passage of acoustic waves through the device 80 from and to the pipe 30.
- the device 80 is advantageously fabricated from polycarbonate resins, polyvinyl chloride, polyvinyl alcohol, ABS resins, polystyrene, polyurethane, polytetrafluoro- ethylene, natural rubber and like resins.
- a preferred material is a flexible polysilicone rubber, for sealing engagement with an orifice to be used.
- Indicia such as line 86 can be placed on the device 80 to indicate the depth of desired insertion into the nostril which is preferably 2 to 3 mm penetration at most. This is advantageous to insure accurate imaging.
- scribe marks 88 can be placed on the device 80, indicating where the device 80 can be cut to trim it for a larger sized nostril.
- a vertical rib or mark on the axial line of device 80 may be placed on the outside body of device 80 as a reference mark or indicia to facilitate placing the device 80 in position on a patient's nose, removing it and replacing it in the same position for subsequent imaging.
- the device 80 can also be fitted internally with a filter 90 which does not inhibit passage of sound waves, but will stop passage of fluids such as mucous.
- the opening of device 80 at end 84 as shown in Figure 6 is round (oval) as defined by the wall 87.
- the shape of the opening may be circular, of any shape including perfectly round, oblong or shaped like a race-track having a greater dimension in one direction.
- Figure 7 shows a preferred circular shape for the opening of a device 80 at end 84.
- the geometry of the end 84 of device 80 preferably matches the geometry of the orifice to be coupled without any substantial distortion of the nasal vestibule.
- the invention is not to be limited to the description of the preferred embodiment described above, but include within the spirit and scope of the invention other embodiments.
- pipe 30 ( Figure 1) could be 1.2 cm in diameter and 10 cm in length.
- the two transducers are preferably separated by 3.0 cm but transducer 18 is still located 2.0 cm from the airway opening.
- This value of the propogation delay corresponds to a spatial step increment of about 0.2 cm.
- Ware-Aki an algorithm other than the Ware-Aki algorithm could be used to uniquely determine the area-distance function A(x) , of the airway from h(t). Also, algorithms other than the equation (8) above can be used to determine h(t) from the pressure field.
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE69324569T DE69324569T2 (en) | 1992-10-27 | 1993-06-16 | IMAGE DISPLAY WITH ACOUSTIC MEANS |
EP93916599A EP0625023B1 (en) | 1992-10-27 | 1993-06-16 | Acoustic imaging |
US08/117,176 US5666960A (en) | 1991-12-17 | 1993-06-16 | Acoustic imaging |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/808,907 US5882314A (en) | 1991-12-17 | 1991-12-17 | Airway geometry imaging |
USPCT/US92/09236 | 1992-10-27 | ||
PCT/US1992/009236 WO1993011703A1 (en) | 1991-12-17 | 1992-10-27 | Airway geometry imaging |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1994009700A1 true WO1994009700A1 (en) | 1994-05-11 |
Family
ID=26785136
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1993/005819 WO1994009700A1 (en) | 1991-12-17 | 1993-06-16 | Acoustic imaging |
Country Status (1)
Country | Link |
---|---|
WO (1) | WO1994009700A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6709404B1 (en) | 2000-07-27 | 2004-03-23 | E Benson Hood Laboratories | Pharyngometer with detachable wavetube |
WO2005063322A2 (en) * | 2003-12-23 | 2005-07-14 | Glaxo Group Limited | Method for predicting deposition of inhaled medicament at the lung |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3857385A (en) * | 1970-04-03 | 1974-12-31 | Jaeger E | Direct indicating devices for measuring respiratory resistance |
US4558708A (en) * | 1984-10-24 | 1985-12-17 | Tri-Med, Inc. | Patient's airway adapter to withdraw a patient's gas samples for testing free of sputum mucus and/or condensed water, by utilizing a hollow cylindrical hydrophobic liquid baffle |
-
1993
- 1993-06-16 WO PCT/US1993/005819 patent/WO1994009700A1/en active IP Right Grant
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3857385A (en) * | 1970-04-03 | 1974-12-31 | Jaeger E | Direct indicating devices for measuring respiratory resistance |
US4558708A (en) * | 1984-10-24 | 1985-12-17 | Tri-Med, Inc. | Patient's airway adapter to withdraw a patient's gas samples for testing free of sputum mucus and/or condensed water, by utilizing a hollow cylindrical hydrophobic liquid baffle |
Non-Patent Citations (2)
Title |
---|
"Determination of the Geometry of the Human Vocal Tract by Acoustic Measurement", M.R. SCHROEDER; The Journal of the Acoustical Society of America, Volume 41, No. 4, pgs. 1002-1010 (1967). * |
See also references of EP0625023A4 * |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6709404B1 (en) | 2000-07-27 | 2004-03-23 | E Benson Hood Laboratories | Pharyngometer with detachable wavetube |
WO2005063322A2 (en) * | 2003-12-23 | 2005-07-14 | Glaxo Group Limited | Method for predicting deposition of inhaled medicament at the lung |
WO2005063322A3 (en) * | 2003-12-23 | 2005-09-01 | Glaxo Group Ltd | Method for predicting deposition of inhaled medicament at the lung |
JP2007515237A (en) * | 2003-12-23 | 2007-06-14 | グラクソ グループ リミテッド | How to predict the accumulation of inhaled medicine in the lung |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US5666960A (en) | Acoustic imaging | |
US5746699A (en) | Acoustic imaging | |
US4326416A (en) | Acoustic pulse response measuring | |
US20120238909A1 (en) | Method For Acquiring, Processing and Transmitting Acoustic Energy Data | |
US20050014999A1 (en) | Device for verifying and monitoring vital parameters of the body | |
US6139507A (en) | Method and apparatus for measuring acoustic power flow within an ear canal | |
CA2213523C (en) | Apparatus and method for acoustic analysis of bone using optimized functions of spectral and temporal signal components | |
EP1336379A3 (en) | Ultrasound imaging of the heart | |
US20080228095A1 (en) | Medical device | |
US6491641B1 (en) | Apparatus and methods for acoustic rhinometry | |
EP0103640B1 (en) | Ear pathology diagnosis apparatus and method | |
EP0625023B1 (en) | Acoustic imaging | |
CN1172632C (en) | Sound pickup sensor | |
WO1994009700A1 (en) | Acoustic imaging | |
US5848973A (en) | Filter for use in an acoustic imaging device | |
CN110141271A (en) | Digital physiologic sound collector | |
Stinson et al. | Spatial distribution of sound pressure and energy flow in the ear canals of cats | |
Schwartz et al. | Improved phonocardiogram system based on acoustic impedance matching | |
JPH0414007B2 (en) | ||
CN214259355U (en) | Single-hand clamping type color ultrasonic machine for animals | |
Tanabe et al. | Application of reflectionless acoustic tube for extraction of the glottal waveform | |
CN112168208A (en) | Single-hand clamping type color ultrasonic machine for animals | |
Jones et al. | Acoustic characterisation of thoracic body tissues in the audible frequency range | |
WO2004045404A1 (en) | Device and method for measuring in body cavities | |
Bhagat et al. | Development of limb volume measuring system |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
WWE | Wipo information: entry into national phase |
Ref document number: 1993916599 Country of ref document: EP |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2119872 Country of ref document: CA |
|
WWE | Wipo information: entry into national phase |
Ref document number: 08117176 Country of ref document: US |
|
AK | Designated states |
Kind code of ref document: A1 Designated state(s): CA US |
|
AL | Designated countries for regional patents |
Kind code of ref document: A1 Designated state(s): AT BE CH DE DK ES FR GB GR IE IT LU MC NL PT SE |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application | ||
WWP | Wipo information: published in national office |
Ref document number: 1993916599 Country of ref document: EP |
|
WWG | Wipo information: grant in national office |
Ref document number: 1993916599 Country of ref document: EP |