WO1999059484A1

WO1999059484A1 - Thermoablation probe

Info

Publication number: WO1999059484A1
Application number: PCT/IL1999/000264
Authority: WO
Inventors: Benny Gaber
Original assignee: Benny Gaber
Priority date: 1998-05-19
Filing date: 1999-05-18
Publication date: 1999-11-25
Also published as: IL124549A0; AU3845899A

Abstract

A thermoablation probe (10) including a cannula (12) having a bore (16) formed therein with an open proximal end (14) which is adapted for inserting therein a thermal element (18), a plurality of filaments (22) extending outwards from a portion of the cannula (12) and in thermal contact therewith, the portion being called a thermal conduction portion (24), wherein a portion of the cannula (12), called an insulating portion (26), has no said filaments (22) extending therefrom, and at least one guide element attached to the filaments (22) for manipulating portions of the filaments (22).

Description

THERMOABLATION PROBE FIELD OF THE INVENTION The present invention relates generally to thermoablation probes and particularly to an expandable thermoablation probe which selectively cools/heats only those tissues which need to be necrotized while insulating neighboring, healthy tissues.

BACKGROUND OF THE INVENTION

Thermoablation is a well known method for necrosis of a uterine endometrium or other related tissue by the application of extreme cold or heat. Ideally, the extreme cold/heat should be carefully applied only to those tissues which must be destroyed and not to neighboring, healthy tissues. Various problems pose a challenge to achieving this ideal goal.

For example, matching a thermoprobe to the geometry and topography of the inner structure of the cervix (or other body cavity), the complex mechanisms of heat transfer by phase changes, conduction through body tissues and convection by body fluids as well as mass transfer, the incidence of tissue preservation by freezing rather than necrosis by freezing (in the case of cryoablation), and the difficulties in safely reaching inner tissues with the cryoprobe are just some of the problems facing the surgeon performing cryoablation.

There are various methods and apparatus in the prior art for cryoablation. US Patent 5,147,355 describes a method for cryoablation comprising the steps of inserting a catheter having a tip portion into the lumen of a blood vessel, guiding the catheter to a predetermined portion of the patient's body and positioning the tip portion adjacent tissue in the lumen of the blood vessel to be ablated, and then directing a flow of cryogenic fluid to the tip portion so as to cryoablate the tissue.

US Patent 5,207,674 describes a thermoelectric cryosurgery tool for treating neoplasms. The tool has cascade or thermoelectric modules coupled to a distal treatment tip which generates a steep temperature gradient. A heat pipe is coupled to the thermoelectric cooling modules.

US Patent 5,501,681 to Neuwirth et al. describes an intrauterine cryoablation cauterizing apparatus including an applicator comprising a distendable bladder connected to a catheter which is introduced into the uterus. The bladder is distended by introducing therein a non-toxic fluid under pressure and cooling the fluid to below 0°C for about 4-12 minutes.

US Patent 5,654,279 to Rubinsky et al. describes enhancement of cell necrosis by cryoablation by perfusion of the cells with thermal-hysteresis proteins prior to cryogenic freezing. The proteins promote growth of spicular ice crystals in the intracellular fluid which destroy the cell by piercing the cell membrane.

Russian Patent 475,998 describes a cryosurgery probe tip. The tip has a working chamber bag filled with a granular material that takes up the shape of the contacted tissue.

Russian Patent 1,178,423 describes an abdominal cavity organ cryosurgical instrument. The instrument has tips which have removable resilient membranes and which are joined so that they can rotate around an organ. The cryoinstrument attempts to reduce the volume of necrotized tissue so pathological formations can be destroyed with minimal damage to the surrounding healthy tissues.

Russian Patent 1,683,704 describes a multi-purpose ultrasound tissue cryo- destructor. The working end of the cryoprobe includes a corrugated steel pipe with a changing angle of slant and a mobile pusher. The purpose of the cryo-destructor is supposedly to enable maneuvering in closed cavities, to reduce trauma to the surrounding tissues in inaccessible zones and canals of complex profile, and to reduce the time taken by the operation.

Russian Patent 2,014,803 describes a cryosurgery instrument tip which includes an applicator in the form of a metallic chamber open at its distal end, filled by a capillary- porous material forming a branching cavity with communicating pores. The contact part of the capillary-porous material is shaped in the form of a concave base jutting slightly into the chamber of the applicator, and is fitted with a gas evacuation pipe.

Russian Patents 2,018,273 and 2,018,274 both describe a deep localized tissue cooler comprising an applicator made with corrugated surfaces which has a radial recess to relieve pressure. The cooler includes a cylindrical housing with coolant feed and return channels and an expansion chamber, and an applicator surface with concentric corrugations. European Patent Document EP 624347 describes a cryoprobe that includes one or more non-linear elements adapted to receive a refrigerant medium and to conform to a body surface. Each refrigerant-receiving element is curved, kinked or bent whereby the probe may be Y-shaped, L-shaped or T-shaped in use.

SUMMARY OF THE INVENTION The present invention seeks to provide an improved thermoablation probe which is expandable to fit the shape of any body cavity such as the cervix or uterus, and which selectively cools/heats only those tissues which need to be necrotized while insulating neighboring, healthy tissues. It is noted that throughout the specification and claims the term "filament" encompasses any thread-like structure such as a filament, hair, thread, wire, strand, cilium, or the like.

There is thus provided in accordance with a preferred embodiment of the present invention a thermoablation probe including a cannula having a bore formed therein with an open proximal end which is adapted for inserting therein a thermal element, a plurality of filaments extending outwards from a portion of the cannula and in thermal contact therewith, this portion being called a thermal conduction portion, wherein a portion of the cannula, called an insulating portion, has no filaments extending therefrom, and at least one guide element attached to the filaments for manipulating portions of the filaments.

In accordance with a preferred embodiment of the present invention the filaments can be flexed in a direction towards a distal and/or proximal end of the cannula by the at least one guide element.

Further in accordance with a preferred embodiment of the present invention the filaments are attached to the probe by being braided about the cannula. Alternatively the cannula itself is constructed of the filaments, preferably braided. Preferably the filaments have a higher thermal conductivity than the insulating portion.

Still further in accordance with a preferred embodiment of the present invention the insulating portion includes an auxiliary thermal insulator attached to the cannula. Preferably the auxiliary thermal insulator also generally thermally insulates initial portions of the filaments which protrude from the cannula.

Additionally in accordance with a preferred embodiment of the present invention the filaments extend from generally diametrically opposite sides of the cannula.

In accordance with a preferred embodiment of the present invention the filaments extend from the cannula generally in the shape of a human body cavity, such as a human uterus.

Further in accordance with a preferred embodiment of the present invention a removable sheath is provided over the cannula for smoothing entry of the thermoablation probe into a body cavity. The sheath may or may not be lubricated. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: Fig. 1 is a simplified pictorial illustration of a thermoablation probe constructed and operative in accordance with a preferred embodiment of the present invention;

Fig. 2 is a simplified sectional illustration of the thermoablation probe of Fig. 1, taken along lines II-II in Fig. 1 ; Fig. 3 is a simplified pictorial illustration of the thermoablation probe of Fig. 1 wherein filaments are pulled proximally by guide elements;

Fig. 4 is a simplified pictorial illustration of the thermoablation probe of Fig. 1 wherein the filaments are pushed distally by the guide elements; and

Fig. 5 is a simplified pictorial illustration of a removable sheath useful with the thermoablation probe of Fig. 1 in accordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Reference is now made to Fig. 1 which illustrates a thermoablation probe 10 constructed and operative in accordance with a preferred embodiment of the present invention. Probe 10 preferably includes a hollow cannula 12 having an open proximal end

14 leading into a bore 16 adapted for inserting therein a thermal element 18. Thermal element 18 may typically be a hot or cryogenic probe used in prior art systems, depending on whether probe 10 necrotizes tissue by the application of heat or cold, respectively. Bore 16 and thermal element 18 are preferably sized such that there is good thermal contact between thermal element 18 and the inner surface of bore 16. Probe 10 is preferably closed at a distal end 20.

A plurality of filaments 22 extend outwards from a portion of cannula 12 and in thermal contact therewith, this portion being called a thermal conduction portion 24. Another portion of cannula 12, called an insulating portion 26, has no filaments 22 extending therefrom.

There is thus a thermal transfer path comprising thermal contact heat transfer between thermal element 16 and an inner wall of bore 16 of cannula 12, conduction through the thickness of the wall of cannula 12, conduction through thermal conduction portion 24 to filaments 22, conduction through filaments 22 and heat transfer by a combination of conduction and convection from filaments 22 to tissue and fluids in the region of body tissues to be necrotized.

Filaments 22 preferably extend from generally diametrically opposite sides of cannula 12. In addition, filaments 22 preferably extend from cannula 12 generally in the shape of a body cavity in which it is desired to insert probe 10, such as a human uterus. In one preferred embodiment, cannula 12 is constructed separately from filaments 22, and filaments 22 are wound around cannula 12, cannula 12 serving as a mandrel. In another preferred embodiment, cannula 12 itself is constructed from braided filaments 22.

Filaments 22 are constructed of a material which has a higher thermal conductivity than insulating portion 26. A preferred material for filaments 22 is copper, silver or gold because of their excellent thermal conductivity on the one hand and ductility on the other hand for being able to take on the shape of the particular body cavity into which probe

10 is inserted. Insulating portion 26 may be constructed as part of cannula 12, in which case insulating portion 26 is constructed of a thermal insulating material, such as a plastic or a poorly conducting metal such as stainless steel. Alternatively or additionally, insulating portion 26 may include an auxiliary thermal insulator 28 attached to cannula 12, such as a plastic covering. Preferably the auxiliary thermal insulator 28 also extends over and thermally insulates initial portions of filaments 22 which protrude from cannula 12. Auxiliary thermal insulator 28 may cover each filament 22 by itself, or instead, may collectively cover all filaments 22 together. Preferably, the thickness of auxiliary thermal insulator 28 gradually thins with increasing distance from cannula 12.

Heat transfer is generally constrained to flow along the length of each filament 22 and is generally minimal in a direction up and down (in the sense of Fig. 2) in the area of insulating portion 26 and in the initial protruding area of filaments 22. There is however heat transfer in the up and down direction (in the sense of Fig. 2) between the rest of the length of filaments 22 (which is not covered by insulator 28) and the particular body cavity into which probe 10 is inserted. Unlike the prior art, heat transfer is linear along the length of filaments 22 instead of cylindrically around cannula 12.

One or more guide elements 30 are preferably attached to filaments 22 for manipulating portions of filaments 22. Guide elements 30 are illustrated as having a shape similar to a cylinder split longitudinally down its middle, but it is of course appreciated that any other arbitrary shape may also be employed. Guide elements 30 may interface with filaments 22 in any suitable manner. For example, filaments 22 may pass through holes formed in guide elements 30. Alternatively, guide elements 30 may be attached to filaments 22, such as by soldering or bonding. Filaments 22 extend from thermal conduction portion 24 at bending points 32.

As mentioned above, filaments 22 are preferably attached to probe 10 by being braided about cannula 12 (auxiliary thermal insulator 28 not being illustrated in this area in order to illustrate the braided portion). The braided attachment is a preferred method of attachment to easily permit flexing of filaments 22 and still ensure good thermal contact between cannula 12 and filaments 22. Alternatively, as mentioned above, cannula 12 itself may be formed of the braided filaments 22.

Reference is now made to Figs. 3 and 4 which illustrate manipulation of filaments 22. As seen in Fig. 3, by pulling guide elements a distance -δ from a reference line A in a direction of an arrow 34 towards proximal end 14 of cannula 12, filaments 22 are flexed to generally lie over cannula 12 pointing towards proximal end 14. This configuration would generally be used for inserting probe 10 into a body cavity.

As seen in Fig. 4, by pushing guide elements a distance +δ from a reference line A in a direction of an arrow 36 towards distal end 20 of cannula 12, filaments 22 are flexed to generally lie over cannula 12 pointing towards distal end 20. This configuration could be used for removing probe 10 from a body cavity, for example. It is appreciated that guide elements 30 can be used to manipulate filaments 22 in any configuration.

Reference is now made to Fig. 5 which illustrates a removable sheath 40 useful with thermoablation probe 10 in accordance with a preferred embodiment of the present invention. Sheath 40 is preferably constructed with a generally cylindrical shape, although other shapes may be employed as well. Sheath 40 may or may not be lubricated. Sheath 40 is preferably initially slipped over probe 10 prior to insertion into a body cavity and is adapted for covering at least a distal portion of cannula 12. After insertion into the body cavity, sheath 40 may be pulled distally off probe 10, such as by grasping and pulling strings 42 attached to sheath 40.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of the features described hereinabove as well as modifications and variations thereof which would occur to a person of skill in the art upon reading the foregoing description and which are not in the prior art.

Claims

C L A I M SWhat is claimed is:

1. A thermoablation probe ( 10) comprising: a cannula (12) having a bore (16) formed therein with an open proximal end (14) which is adapted for inserting therein a thermal element (18); a plurality of filaments (22) extending outwards from a portion of said cannula (12) and in thermal contact therewith, said portion being called a thermal conduction portion (24), wherein a portion of said cannula (12), called an insulating portion (26), has no said filaments (22) extending therefrom; and at least one guide element attached to said filaments (22) for manipulating portions of said filaments (22).

2. The probe (10) according to claim 1 wherein said filaments (22) can be flexed in a direction towards a distal end (20) of said cannula (12) by said at least one guide element (30).

3. The probe (10) according to claim 1 wherein said filaments (22) can be flexed in a direction towards a proximal end (14) of said cannula (12) by said at least one guide element

(30).

4. The probe (10) according to claim 1 wherein said filaments (22) are attached to said probe (10) by being braided about said cannula (12).

5. The probe (10) according to claim 1 wherein said cannula (12) itself is constructed of said filaments (22).

6. The probe (10) according to claim 1 wherein said filaments (22) have a higher thermal conductivity than said insulating portion (26).

7. The probe (10) according to claim 1 wherein said insulating portion (26) comprises an auxiliary thermal insulator (28) attached to said cannula (12).

8. The probe (10) according to claim 7 wherein said auxiliary thermal insulator (28) also generally thermally insulates initial portions of said filaments (22) which protrude from said cannula (12).

9. The probe (10) according to claim 7 wherein a thickness of said auxiliary thermal insulator (28) gradually thins with increasing distance from said cannula (12).

10. The probe (10) according to claim 1 wherein said filaments (22) extend from generally diametrically opposite sides of said cannula (12).

11. The probe (10) according to claim 1 wherein said filaments (22) extend from said cannula (12) generally in the shape of a human body cavity.

12. The probe (10) according to claim 1 and further comprising a removable sheath (40) adapted for covering at least a distal portion of said cannula (12).

13. The probe (10) according to claim 1 wherein said filaments (22) extend from said cannula (12) generally in the shape of a human uterus.