WO2007082495A1

WO2007082495A1 - Mri positioning system for ultrasound brain surgery

Info

Publication number: WO2007082495A1
Application number: PCT/CY2006/000001
Authority: WO
Inventors: Christakis Damianou
Original assignee: Medsonic Ltd
Priority date: 2006-01-19
Filing date: 2006-01-19
Publication date: 2007-07-26

Abstract

The current invention relates to a simple and cost effective MRI compatible positioning system which is capable of carrying a HIFU transducer in order to treat brain cancer. The positioning system employs piezoelectric motors sheets, rods, angles, pulleys and belts in order to move the transducer in 3 dimensional patterns. The system includes a plastic base (1), an X stage (16) made out of plastic and a Z stage (56) which is attached to the Y stage by means of a plastic angle. The transducer (64) is attached to the Z stage by means of an arm (61,62). The positioning device is placed on the table of the MRI scanner and access of ultrasound to the brain is achieved from the top of the head. Since the positioning device is placed on the table of the MRI scanner, this device can be used in all the available MRI scanners.

Description

MRI POSITIONING SYSTEM FOR ULTRASOUND BRAIN SURGERY TECHNICAL FIELD

The present invention relates to an MRI compatible positioning system that carries a high intensity focused ultrasound (HIFU) transducer that can be used for treating brain tumors. BACKGROUND ART

High intensity focused ultrasound (HIFU) is use to induce changes in tissue either in the thermal mode or mechanical mode (also known as cavitation). Because of its thermal properties, HIFU is recently used extensively for medical applications.

HIFU in this patent is utilized in order to selectively destroy tumor tissue in brain of a subject with minimal invasiveness by using MRI to provide, to the operator performing the procedure, images of a region within the subject being heated.

Because of the spherical geometry of the transducer, necrosis can be induced only in the targeted area without damage to the surrounding tissue. Thus HIFU offers noninvasive, localized and nonionizing thermal therapy for deep-seated targets. The focal spot of the applicator is relatively small (1-3 mm in diameter). To treat a large region within the subject, the ultrasonic applicator must be moved by a positioning system in a predetermined pattern. The positioning system has to be MRI compatible.

The main goal of HIFU is to maintain a temperature between 50-100 oC for a few seconds (typically <10 s), in order to cause tissue necrosis. Typically, focal peak intensity between 1000- 10000 W/cm² is used with pulse duration between 1-10 s and a frequency of 1-5 MHz. In HIFU ablation ultrasonic energy is applied from outside of the subject's body to heat the tissues. The applied energy can be focused to a small spot (few rams) within the body so as to heat the tissues at such spot to a temperature sufficient to create a desired therapeutic effect. This technique can be used to selectively destroy unwanted tissue within the brain. The transducer must be immersed in a fluid container so that the flexible fluid container can be engaged between the transducer and the brain of the subject's body.

The idea of using HQDFU was proposed in the middle of this century by Lynn et al. (1942). The first complete system for the use of HIFU was developed by Fry et. al. 1954. FHFU' s maximum potential for clinical use has been established recently due to the developments of sophisticated systems (for example,^~Chapelon et al. 1992, Birhle et al. 1994 and Hynynen et al. 2001).

HIFU was explored in almost every tissue that is accessible by ultrasound. The following literature represents some examples of some applications explored: eye (Lizzi et al. 1977), prostate (Chapelon et al. 1992), liver (ter Haar et al. 1989), brain (Fry et al 1954; LeIe 1962; Vydkotseva et al. 1994) and kidney (Linke et. al. 1973; Hynynen et al. 1995). Ultrasonic imaging is the simplest and most inexpensive method to guide HIFU, however, it has poor contrast between soft tissues. On the other hand, magnetic resonance (MR) imaging offers superior contrast, but it is more expensive. The combination of ultrasound and MRI was first cited by Jolesz and Jakab (1991) who demonstrated that an ultrasonic transducer can be used inside a MRI scanner. The concept of using MRJ to monitor the necrosis produced by HIFU was demonstrated in the early nineties by Hynynen et al. (1992) in canine muscle. In the following years additional studies have been conducted (for example Cline et al. 1992, and Hynynen et. al. 1994), showing that the contrast between necrotic tissue and normal tissue was excellent. This was a great enhancement for the HIFU systems because the therapeutic protocols can be accurately monitored. Therefore the interest of using MRI as the diagnostic modality of guiding HIFU was increased.

The use of HTFU to ablate brain tissues has been explored in the past by Fry et al. 1954 and LeIe 1962. However, at that time MRI did not exist and therefore the previous systems were not guided effectively. The proposed system will enhance the therapy of brain cancer by combining HIFU for therapy and MRI for monitoring and guiding.

The main component of an ultrasonic system guided by MRI, is the positioning device. The positioning devices and HIFU transducers cause problems when used inside an MRI scanner. Any interference with the RF field will reduce the quality of the image. The imaging will occur if the robotic system and transducer or any other therapeutic object do not interfere with the magnetic and RF fields needed by the MRI system. Therefore these devices must be made out of non-magnetic materials.

The earlier designs of positioning systems (U.S. Pat. Nos. 5,247,935 and 5,275,165) use hydraulic principles to move the transducer. These systems place the transducer directly beneath the target (e.g., a tumor). Additionally, the hydraulic positioning systems have serious repeatability and reliability problems, and have never reached the clinics. The motors used in the hydraulic positioning systems interfere with the MRI scanner, and therefore are placed far from the MRI scanner, thus requiring the use of long motor drive shafts, which results to a large and complicated positioning system. Furthermore, the motors used in these positioning systems must be left energized which produces interference to the MRI system. Therefore the motors are placed at a distance from the MRI scanner.

In another patent (U.S. 5,443,068) the positioning device uses threaded shafts and screw drives through universal joints. This patent also requires the ultrasonic transducer to be placed directly beneath the object to be treated.. The above patent has also accuracy problems. The motors of this positioning system are made out of magnetic material and therefore they are placed at a distance from the MRI scanner.

The US Patent 6,582,381 describes a manual positioning system, which can be used only in an open MKl system. Despite the fact that open MRI offers several advantages, it is not widely used because of its poor image quality. Moreover, the manual system will be user dependent, whereas the proposed system, which is automated, is not user- dependent.

Patent EP 0596513 describes a system for creating lesions in the brain through images taken previously either by CT or MRI, and therefore it does not take advantage of the dynamic imaging ofMRI.

The patent (WO0209812) uses piezoelectric motors to move the transducer inside an MRI scanner. This type of positioning device can access the target from the bottom. Therefore, it can not access the human head from its top. The positioning device of patent (WO0209812) uses large amount of water and therefore the preparation cost of each procedure is much higher that the cost of procedure of the proposed system.

Another positioning system (US 6,675,037) utilizes piezoelectric motors in order to guide a biopsy needle. However, this system can not be used in HIFU, because there is no means to provide coupling between the holder that could hold the transducer and the tissue.

DISCLOSURE OF THE INVENTION

The current invention relates to a simple and cost effective MRI compatible postioning system which is capable of carrying a high intensity focused ultrasound in order to treat diseases of the brain. The positioning system employs piezoelectric motors and various materials (sheets, rods, angles, pulleys and belts) in order to move the transducer in 3 dimensions. The rotational motion of the piezoelectric motors is coupled to a timing belt which is placed around 2 plastic pulleys (one pulley is fixed by 2 plastic angles). The belt is coupled to a plastic rectangular sheet and thus the rotation of the belt results to a linear motion of the involved sheet. The same principle is applied for every stage. Totally 3 linear axes are implemented for the case of brain tumors. The piezoelectric motors that operate inside the MRI scanner do not affect the quality of the MRI scanner.

The positioning device is placed on the table of the MRI scanner and access of ultrasound to the brain is achieved from the top of the head. Since the positioning device is placed on the table of the MRI scanner, this device can be used in all the available MRI scanners (ie it is a universal positioning device). The existing systems are placed inside the table of the MRI scanner, and therefore the system geometry has to altered depending on the type of MRI scanner. Also, the existing systems can access the patient from the bottom to the top whereas this positioning device can access patient from the side or the top.

Another advantage of this device is that it is much simpler and inexpensive than the existing system, while maintaining high standards of repeatability and readability.

Another advantage of this positioning device is that it can be easily reduced or increased in size. This can be adjusted easily by modifying the rod length, sheet length and belt length. All the other components remain fixed in size. Thus, easily any size of positioning device can be designed. There is limitation though based on the diameter of the MRl scanner. Another advantage of this positioning device is that it is lightweight and therefore it can be transported from one MRI scanner to another (ie it is portable).

Another advantage of this positioning device is that the movement of the device is confirmed by an MR compatible camera.

The high intensity focused ultrasound transducer is of spherical shape. The transducer can be couple to the brain by means of a container which is filled with degassed water. The transducer can be applied through the skull using low frequency or through open skull. An open MRI coil is attached to the brain in order to provide excellent MRI signal. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows the block diagram of the base of the positioning device which carries a sheet that establishes movement of the positioning device in the X-direction.

Fig. 2 shows the bottom side of the sheet that establishes movement in the X-direction. 5 Fig. 3 shows the sheet that establishes movement in the Y-direction.

Fig. 4 shows the bottom of the sheet that holds the Z-stage.

Fig. 5 shows the angle that holds the Z-stage.

Fig. 6 shows the sheet that establishes movement in the Z-direction..

Fig. 7 shows the back side of the sheet that holds the transducer holder. 10 Fig. 8 shows the holder that carries the HQDFU transducer and the water container.

Fig. 9 shows the complete 3-d positioning system for treating brain tumors.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 shows the rectangular base 1 made out of polyethylene. This plastic base holds the 3 stages that establishes motion in the X, Y and Z direction. Four polyethylene angles 2,3,4 and 5 are 15 placed on base 1. Two brass rods 6 and 7 are attached to angles 2 and 3 and 4 and 5 respectively. A fixed polycarbonate pulley 8 is supported on polyethylene angles 9 and 10 through a plastic rod 11. A piezoelectric motor 12 is fixed on polyethylene angle 13. A neoprene belt 14 is placed around fixed pulley 8 and motor pulley 15 which is coupled to the motor 12.

Fig. 2 shows the bottom side of the polyethylene sheet 16 that establishes motion in the X- 20 direction. If motor 12 is energized, belt 14 which is coupled to sheet 16 rotates, and eventually motion of sheet 16 is established. The polyethylene angles 17, 18 and 19, 20 are fixed in the sheet 16 by means of brass screws. The sheet 16 is coupled to rods 6 and 7 of the base (Fig. 1). The coupling between the angles and rods is achieved by drilling holes through the angles.

Fig. 3 shows the rectangular sheet 16 (top side) which is made out of polyethylene. Four ^"25 polyelhylene angles 21,22, 23, and^~24-^~are placed^~δn^~sheet 16^~(top side]TTwo brass rods 25 and 26 are attached to angles 21 and 22 and 23 and 24 respectively. A fixed polycarbonate pulley 27 is supported on polyethylene angles 28 and 29 through a plastic rod 30. A piezoelectric motor 31 is fixed on polyethylene angle 32. A neoprene belt 33 is placed around fixed pulley 27 and motor pulley 34, which is coupled to the motor 31. The functioning of this stage is very similar to that of 30 the first stage (Fig. 1).

Fig. 4 shows the bottom side of the polyethylene sheet 35 that establishes motion in the Y- direction. If motor 31 is energized, belt 33 which is coupled to sheet 35 rotates, and eventually motion of sheet 35 is established The polyethylene angles 36, 37 and 38, 39 are fixed in the sheet 35 by means of brass screws. The sheet 35 is coupled to rods 25 and 26 of the sheet of Fig. 3. The coupling between the angles and rods is achieved by drilling holes through the angles.

Fig. 5 shows the top side of sheet 35. A polyethylene angle 40 is fixed on sheet 35. A polyethylene sheet 41 that carries the Z stage is fixed on angle 40.

Fig. 6 shows the rectangular sheet 41 made out of polyethylene. Four polyethylene angles 42,43, 5 44, and 45 are placed on sheet 41. Two brass rods 46 and 47 are attached to angles 42 and 43 and 44 and 45 respectively. A fixed polycarbonate pulley 48 is supported on polyethylene angles 49 and 50 through a plastic rod 51. A piezoelectric motor 52 is fixed on polyethylene angle 53. A neoprene belt 54 is placed around fixed pulley 48 and motor pulley 55, which is coupled to the motor 52.

10 Fig. 7 shows the bottom side of the polyethylene sheet 56 that establishes motion in the Z- direction. If motor 52 is energized, belt 48 which is attached to sheet 56 rotates, and eventually motion of sheet 56 is established The polyethylene angles 57, 58 and 59, 60 are fixed in the sheet 56 by means of brass screws. The sheet 56 is coupled to brass rods 46 and 47 of sheet in Fig. 6. The coupling between the angles and rods is achieved by drilling holes through the angles.

15 Fig. 8 shows the water container and holder of the transducer. Plastic rod 61 is attached on sheet 56. Brass rod 62 is coupled to plastic rod 61. Transducer holder 63 is attached to brass rod 62. HIFU transducer 64 is coupled to holder 63. Transducer 64 is immersed in container 65 which is filled with degassed water. The water is poured in a milar bag 66 The milar bag 66 is made thin enough to conform to the contours of the brain. A window 67 is opened in container 65 in order

20 to allow ultrasound energy to be applied in the human brain. The head is placed inside an open coil.

Fig. 9 shows the complete positioning system with all the components described in Fig.l to 8. The movement of the positioning device is monitored by an MR compatible camera (not shown in the figure) which is placed on a non magnetic holder.

25 Moreover, the positioning system includes optoelectronic encoders (not shown in any of the figures) for providing signals indicating the relative positions of the movable elements in the positioning system.

PATENT DOCUMENTS

US 5247935 Sep., 1993 Cline et al.

^~3O TJS 5275155 Jan., 1994 Ettinger et al.

US5443068 Aug., 1995 Cline et al.

US 6, 675,037 Oct., 2002 Tsekos.

US 6,582,381 June, 2003 Yehezkeli et. al.

EP 596513 1994-05-11 F. Fry and N. Sanghvi

35 WO0209812 2002-02-07 Yehezkeli et. al.

OTHER REFERENCES

Bihrle R, Foster RS, Sanghvi NT, Fry FJ, Donohue JP. High-intensity focused ultrasound in the treatment of prostatic tissue. Urology. 1994 Feb;43(2 Suppl):21-6 Chapelon JY, Margonari J, Vernier F, Gorry F, Ecochard R, Gelet A. In vivo effects of high- intensity ultrasound on prostatic adenocarcinoma Dunning R3327. Cancer Res 1992 Nov

15;52(22):6353-7

Cline HE, Schenck JF, Hynynen K, Watkins RD, Souza SP, Jolesz FA. MR-guided focused ultrasound surgery. J Comput. Assist. Tomogr. 1992; 16:956-65

Fry W, Mosberg W, Barnard J, Fry F. Production of focal destructive lesions in the central nervous system with ultrasound. JNeurosurg 1954;11:471 -

Jolesz FA, Jakab PD. Acoustic pressure wave generation within a magnetic resonance imaging system: potential medical applications. Magn. Reson. Imag 1991;l:609-13. ter Haar G, Sinnett D, Rivens I. High intensity focused ultrasound - a surgical technique for the teatment of discrete liver tumors. Phy Med Biol 1989 Nov;34(l 1): 1743-50.

Hynynen K, Darkazanli A, Damianou DC, Unger E, Schenck JF, MRI-guided ultrasonic hyperthermia. 1992 RSNA meeting.

Hynynen K, Darkazanli A, Damianou CA, Unger E, Schenck JF. The usefulness of a contrast agent and gradient-recalled acquisition in a steady-state imaging sequence for magnetic resonance imaging-guided noninvasive ultrasound surgery. Invest Radiol. 1994 Oct;29(10):897- 903.

Hynynen K, Damianou CA, Colucci V, Unger E, Cline HH, Jolesz FA. MR monitoring of focused ultrasonic surgery of renal cortex: experimental and simulation studies. Journal of Magnetic Resonance Imaging. 1995 May- June;5(3):259-66.

Hynynen K. , O. Pomeroy, D.N. Smith, P.E. Huber, NJ. McDannold, J. Kettenbach, J. Baum, S. Singer, and FA. Jolesz. "MR imaging-guided focused ultrasound surgery of fibroadenomas in the breast: a feasibility study," Radiology. 2001; 219(l):176-85.

LeIe PP. A simple method for production of trackless focal lesions with focused ultrasound: J. Physiol. 1962;160:494-512.

Linke C, Carteensen E., Frizzell, Localized Tissue destruction by High Intensity Focused Ultrasound, ArchTSurg., 19737WΓΪU778¥7^~89Ϊ7

Lizzi F., Coleman J., Driller J., Franzen L., Jakobiec F., "Experimental, ultrasonically induced lesions in the retina, choroid, and sclera", Invest. Ophthalmol. Visual ScL, pp.350-360, 1977. Lynn JG, Zwemer RL, Chick AJ, Miller AE. A new method for the generation and use of focused ultrasound in experimental biology. J Gen Phyciology 1942;26:179-93.

Vykhodtseva NI, Hynynen K, Damianou C. Pulse duration and peak intensity during focused ultrasound surgery: theoretical and experimental effects in rabbit brain in vivo. Ultrasound Med Biol. 1994;20(9):987-1000.

Claims

CLAIMSWhat is claimed is:

1. Apparatus for positioning a high intensity focused ultrasound (HIFU) transducer operated under magnetic resonance imaging guidance for treating brain tumors, comprising: a base that carries the X, Y, and Z stage; a first stage dedicated to control the position of the energy source in the X axis; a second stage dedicated to control the position of the energy source in the Y axis; a third stage dedicated to control the position of the energy source in the Z axis; a transducer holder; a HIFU transducer; and a water container for coupling ultrasound to the brain.

2. The positioning system of claim 1, comprises a stage for moving the transducer in the X direction which comprises: a piezoelectric motor; a first polycarbonate pulley couple to the motor; an angle supporting the motor; a belt (neoprene); a second fixed pulley (polycarbonate) which is placed within two plastic angles; the first and second pulley are coupled with the belt; two brass rods that are placed on the plastic rectangular sheet (base) by means of plastic angles

(2 per rod); a rectangular sheet (X-axis) which is guided by the brass rods by means of 4 plastic angles (2 for each rod) which couple the X-axis sheet with the two rods; a rectangular sheet (base) that carries the above components; 3. the X stage of claim 2, further comprises a stage for moving the transducer in the Y direction which comprises: a piezoelectric motor; a first polycarbonate pulley couple to the motor; an angle supporting the motor; a belt (Neoprene); a second fixed pulley (polycarbonate) which is placed within two plastic angles; the first and second pulley are coupled with the belt; two brass rods that are placed on the plastic rectangular sheet (X-axis) by means of plastic angles (2 per rod);. a rectangular sheet (Z-axis holder) which is guided thought the brass rods by means of 4 plastic angles (2 for each rod) which couple the sheet (Z-axis holder) with the two rods, a rectangular sheet (X-axis) that carries all the above components;

4. the Y stage of claim 3, further comprises a stage for moving the transducer in the Z direction which comprises: an angle which is placed on the top of the sheet of the Y axis; a sheet that carries the Z axis; a piezoelectric motor; a first polycarbonate pulley couple to the motor; an angle supporting the motor; a second fixed pulley (polycarbonate) which is placed within two plastic angles; a belt (neoprene); the first and second pulley are coupled with the belt; two brass rods that carry a rectangular plastic sheet (Z-axis); the sheet is guided thought the brass rods by means of 4 plastic angles (2 for each rod) which couple the sheet (z-axis) with the two rods:

5. the Z stage of claim 4, further comprises a transducer holder arrangement which comprises: a plastic rod; a brass rod attached to the plastic rod; a transducer holder that host a compact spherically focused transducer, which is coupled to the brass rod; a single element spherically focused transducer of small diameter (2-4 cm);

6. The positioning system of claim 1 wherein the coupling system comprises a water container. The container is filled with degassed water so that ultrasound energy is acoustically coupled to the brain. The transducer is immersed in the water container.

7. The water container of claim 6 further comprises an ultrasound transparent membrane adapted for contact with the brain. The membrane is placed inside the water container and it is filled with degassed water.

8. The positioning system of claim 1, is placed on the table of an MRI scanner and therefore it can be used for any MRI scanner without modifying the MRI scanner table.

9. The positioning system of claim 1, can access targets either from the top or sideways.

10. The positioning system of claim 1, is lightweight and therefore portable (it can be transported from one MRI scanner to another MRI scanner).

11. The positioning device of claim 1 is guided by magnetic resonance imaging (MRI) comprising: a magnetic resonance (MR) imaging means for imaging brain sites and for creating temperature sensitive images of ablated sites during surgery; an open MRI brain coil which is placed around the patients head and allows an energy source to be couplaTtcTthe patient's headT

12). The positioning device of claim 1 further comprises an MRI compatible camera which is placed on n MR compatible holder, monitors the movement of the positioning device thus providing visual confirmation that the device moves properly.