AU2001271208A1

AU2001271208A1 - Device for mini-invasive ultrasound treatment of disc disease

Info

Publication number: AU2001271208A1
Application number: AU2001271208A
Authority: AU
Inventors: Lars Ake Alvar Lidgren
Original assignee: Ultrazonix DNT AB
Current assignee: Ultrazonix DNT AB
Priority date: 2000-07-17
Filing date: 2001-07-16
Publication date: 2002-05-02
Anticipated expiration: 2021-07-16

Description

vertebral discs, which preferably should be painless, avoid the risk for infections and carried through ambulatory.

A method for ther otherapy and coagulation of tissue involves use of focused ultrasound with high intensity. The ultrasound pass well through soft tissue and can be focused on remote spots within a surface of a few millimeters . The energy absorption in the tissue increases the temperature with a sharp temperature gradient such that the boundaries of the treated volume are clearly limited without causing any damages on the surrounding tissue (US 5 291 890, US 5 501 655). Ultrasound treatment or therapy of prolapsed intervertebral discs is previously known (EP 0 872 262) . Heat treatment or thermotherapy of discs has proven successful in a method called IDET (US 6 073 051, US 6 007 570, US 5 980 504) . The method has as its aim to insert a catheter into the disc by means of a cannula. Farthest out on the catheter there is a spool which is heated by applying a radio frequency voltage thereon

(US 5 785 705) . The heat is increased to about 90°C in nucleus pulposus where the heating element of the catheter has been located and treatment or therapy is carried through for about 15 minutes. Surgery with focused ultrasound has several advantages compared with other thermal techniques . In the first place, it is non-invasive, secondly, focus can be made movable and thirdly, the energy can be supplied in a few seconds. The limitation of ultrasound is its absorption in bone and its poor penetration through gas- -filled passages. Clinical applications of ultrasound surgery are today mostly used in ophtalmic surgery, urology and oncology. The effect of ultrasound can be divided into thermal and non-thermal effects . The thermal effects of ultrasound are caused by absorption of ultrasound in the tissue. This leads to a temperature increase which is dependent on the parameters of the ultrasound (frequency and intensity) and the acoustic properties of the tissue. The absorption of ultrasound in musculoskeletal tissues increases with the apatite and protein content, which means high absorption in bone, car- tilage, tendons and ligaments. Water however, has a low ultrasound absorption capacity and can for this reason be used as an acoustic medium between the ultrasound transducer and the tissue. Higher absorption can be expected in anulus fibrosus (high collagen content) than in nu- cleus pulposus (high water content) . This will lead to higher temperatures in the outer part of the interverte- bral disc than in the central part . In order to avoid that the temperature in anulus fibrosus exceeds a detrimental level at the same time as the temperature in nu- cleus pulposus reaches a sufficient level, the ultrasound can be transmitted from several ultrasound sources . In this manner, the fields will overlap each other and increase the effect in nucleus pulposus at the same time as the intensity in the surrounding tissue including anu- lus fibrosus can be kept low.

The object of the present invention has been to facilitate, at the abovementioned devices, location of the temperature focus of the ultrasonic field of the ultrasound transducer on a desired point in the disc, prefer- ably in nucleus pulposus. This is arrived at according to the invention by means of a device having the characterizing features of subsequent claim 1.

By means of the device defined in the claims, it is achieved that the temperature focus of the ultrasonic field of the therapeutic ultrasound transducer can be located and maintained on the desired point in the disc, preferably in nucleus pulposus .

The invention will be further described below with reference to the accompanying drawings, in which fig. 1 schematically illustrates a structural embodiment of the device according to the invention; fig. 2 schematically illustrates a therapeutic ultrasound transducer forming part of the device according to fig. 1; and fig. 3 schematically illustrates a calibrating device which may form part of a device according to fig. 1.

The treatment device 1 schematically illustrated in fig. 1 is adapted to generate, by means of a therapeutic ultrasound transducer 2 (so called therapeutic transducer) , an ultrasonic field 3 , the temperature focus F of which is intended to be located in the intervertebral disc 5, preferably in nucleus pulposus 6, of the patient 4 for treatment thereof. The therapeutic ultrasound transducer 2 comprises a plurality of, preferably three or more position transmitters 7 for determining its position. The therapeutic ultrasound transducer 2 is adapted to be inserted through the patient's 4 skin and engage the disc 5, preferably anulus fibrosus 8, to provide a local temperature increase in nucleus pulposus 6 so that enzymes such as collagenase present in the disc are acti- vated and cause decomposition of collagen and proteogly- canes, which results in shrinking of nucleus pulposus 6 primarily because of less hygroscopicity. The therapeutic ultrasound transducer 2 can be placed against the disc 5 without perforating anulus fibrosus 8 and thereby transmit the ultrasonic field 3 focused in temperature focus F towards the treatment volume. The transmitter element 9 of the therapeutic ultrasound transducer 2, e.g. a piezoelectric element, may be cooled with water for cooling the crystal and the tissue closest to the therapeu- tic ultrasound transducer 2 in a similar way as one today does in microwave therapy of cancer in the prostate gland (US 5 964 791) .

In order to provide said cooling, the therapeutic ultrasound transducer 2 is provided at its distal end 10 with at least one cooling chamber 11 with cooling liquid 12. This cooling chamber 11 is located between the transmitter element 9 and a membrane-like wall 13 of such flexible material that said wall is able to adapt to the surface of anulus fibrosus 8 when it is brought in contact therewith.

The therapeutic ultrasound transducer 2 further comp- rises at least one temperature sensor 14 for measuring the temperature before and/or during treatment. In order to increase the volume of therapy or treatment, the direction or setting of the therapeutic ultrasound transducer 2 can be varied such that temperature focus F is scanned over a larger area. The temperature sensor 14 is provided to measure the temperature at the inner side of the flexible wall 13 and it is preferably connected to said wall 13 such that it follows the wall 13 when said wall is deformed when brought in contact with the surface of anulus fibrosus 8.

The cooling liquid 12 is preferably water which is distributed through an inlet passage 15 to the cooling chamber 11 and through an outlet passage 16 therefrom such that the water can circulate through the cooling chamber 11. A sealing means 17 is provided within the transmitter element 9 for preventing cooling liquid 12 from finding its way out of the cooling chamber 11.

In more detail, the therapeutic ultrasound transducer 2 is adapted to cause a local temperature increase in nucleus pulposus 6 so that enzymes such as collagenase present in the disc 5, are activated and cause decomposition of collagen and proteoglycanes , which results in shrinking of nucleus pulposus 6 primarily because of less hygroscopicity. The treatment device 1 may comprise a rigid tube 18 with associated inner portion and several position transmitters 19, preferably three such transmitters. The tube 18 may, by means of optical navigation technique, be inserted dorsolaterally towards the disc 5. The inner por- tion of the tube 18 is then replaced by the therapeutic ultrasound transducer 2 and said tube 18 is schematically illustrated in fig. 1 with broken lines.

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field 3 will lie in the disc 5, preferably nucleus pulposus 6. The temperature in the temperature focus F preferably exceeds 45°C.

The treatment can be automatically interrupted if the patient 4 moves to an incorrect position relative to the therapeutic ultrasound transducer 2 or vice versa.

The invention is not limited to the embodiment described above, but may vary within the scope of the following claims. Thus, the treated disc 5 may e.g. be any disc in the body.

The diagnostic camera 21 may be a computerized tomography (CT) scanner which is provided to produce images of said anatomic structure 23 and these images can be processed in a computer program or software for obtaining a 3D-image in the monitor 24.

The therapeutic ultrasound transducer 2 may be provided to be positioned manually or be located on a positioning device 40 for positioning thereof relative to the disc 5 to be treated.

Claims

Claims :

1. Device for mini-invasive ultrasound treatment of disc disease, wherein at least one therapeutic ultrasound transducer (2) is provided for treatment of the disc (5) , preferably nucleus pulposus (6), of a patient (4) by ge- nerating by means of said therapeutic ultrasound transducer (2) an ultrasonic field (3), the temperature focus (F) of which is located in the disc (5), preferably nucleus pulposus (6), for heating thereof, c h a r a c t e r i z e d i n that an optical navigating device (20) comprises at least one diagnostic camera (21) which is adapted to produce at least one picture or image of the anatomic structure (23) of the treatment area (22) within which the disc (5) , preferably nucleus pulposus, to be treated, is located, that the optical navigating device (20) further comprises at least one signal receiving or signal sending unit (32) which is adapted to send signals to and/or receive reflected or other signals from position transmitters (31, 7) on a) a reference device (28) which has a set position relative to the disc (5), preferably nucleus pulposus (6), and b) the therapeutic ultrasound transducer (2) such that the position thereof relative to said treatment area (22) can be determined, that the therapeutic ultrasound transducer (2) is provided for insertion through the skin of the patient (4) and engagement of the disc (5) , preferably anulus fibro- sus (8), that the therapeutic ultrasound transducer (2) at its distal end (10) has a flexible wall (13) with the ability to adapt to the surface of anulus fibrosus (8) , that at least one ultrasound transmitting element (G) is provided within the flexible wall (13), that between the flexible wall (13) and the ultrasound transmitting element (G) there is located at least one cooling chamber (11) with cooling liquid (12) for cooling the ultrasound transmitting element (G) and the tissue closest to the therapeutic ultrasound transducer (2), and that at least one temperature sensor (14) is provided to measure the temperature in the disc (5) , preferably anulus fibrosus (8) .

2. Device according to claim 1, c h a r a c t e r i z e d i n that cooling liquid (12) is circulated through the cooling chamber (11) .

3. Device according to claim 2, c h a r a c t e r i z e d i n that the cooling liquid (12) is water.

4. Device according to any preceding claim, c a r a c t e r i z e d i n that the temperature sensor (14) is provided to measure the temperature at the inner side of the flexible wall (13) .

5. Device according to claim 4, c h a r a c t e - r i z e d i n that the temperature sensor (14) is connected to the flexible wall (13) such that it follows said flexible wall (13) during the deformation thereof when said wall is brought in contact with the disc (5), preferably anulus fibrosus (8) .

6. Device according to any preceding claim, c h a r a c t e r i z e d i n that a tube (18) with an associated inner portion is dorsolaterally insertable towards the disc (5) and navigatable by means of the optical navigating device (20) and that said inner portion then is replaced by the therapeutic ultrasound transducer (2) .

7. Device according to any preceding claim, c h a r a c t e r i z e d i n that the diagnostic camera (21) is an X-ray camera (25) .

8. Device according to claim 7, c h a r a c t e r i - z e d i n that the X-ray camera (25) comprises a calibrating device (26) with markers (27) which are adapted to determine the position of the anatomic structure (23) displayed in a monitor (24) and present at the patient's (4) disc (5) .

9. Device according to claim 8, c h a r a c t e r i - z e d i n that the monitor (24) is provided to display two X-ray photographs of said anatomic structure (23) taken with the X-ray camera (25) from two different locations.

10. Device according to any of claims 1-5, c h a r a c t e r i z e d i n that the diagnostic camera (21) is a computerized tomography (CT) scanner which is provided to produce images of the anatomic structure (23) at the patient's (4) disc (5), said images being processed in a computer program (software) for obtaining a 3D-image in a monitor (24) .

11. Device according to any preceding claim, c h a r a c t e r i z e d i n that the signal receiving or signal sending unit (32) is provided to receive or send signals in the form of infrared light and that said position transmitters (7, 31) are provided to send or receive signals in the form of infrared light.

12. Device according to any preceding claim, c h a r a c t e r i z e d i n that the temperature in the temperature focus (F) of the therapeutic ultrasound transducer (2) exceeds 45°C.

13. Device according to any preceding claim, c h a r a c t e r i z e d i n that a calibrating device (26) is provided for calibrating the effect emitted by the therapeutic ultrasound transducer (2) in the temperature focus (F) of said therapeutic ultrasound trans- ducer (2) and/or the position of said temperature focus (F) relative to the ultrasound transmitting element (G) of the therapeutic ultrasound transducer (2).

14. Device according to any preceding claim, c h a r a c t e r i z e d i n that the reference device (28) is attached to a vertebra (29) in the patient's vertebral column, preferably to the spinal process (30) of said vertebra (29) .

15. Device according to any preceding claim, c h a r a c t e r i z e d i n that the reference device (28) comprises position transmitters (31) consisting of metallic balls, preferably tantalum balls.

16. Device according to claim 15, c h a r a c t e r i z e d i n that the signal receiving or signal sending unit (32) of the optical navigating device (20) consists of at least one X-ray device.