GB2244922A - Cryogenic device - Google Patents

Abstract

The invention relates to a tool suitable for use in cryogenic surgery for example in the treatments of tumours and polyps. A simple form of tool suitable for use in situations varying from high-grade hospitals to low-technology, unsophisticated environments is described. The tool may be in the form of a probe having a hollow body portion 2 enclosing a cavity 4. Orifices 5, 6 allow liquid nitrogen or other cryogenic fluid to enter the cavity 4 so as to cool a tip portion 10 of the tool when it is immersed in the liquid. Absorbent material 20 may be used to retain the fluid and the metal of the tip portion may be porous. An adjustable probe may have a contoured handle (Figure 4). Alcohol-impregnated material may be interposed between the tool tip and the tissue to be treated, to prevent adhesion and to improve hygiene. <IMAGE>

Description

CRYOGENIC DEVICE The invention relates to a cryogenic device, suitable for use particularly but not exclusively, as a probe or tool for example in cryosurgery.

Although the general technique of cryosurgery has been known for a long time, the use of tools to which cryogens are supplied has been restricted by the difficulties encountered in handling the fluids. For example, conduit tubes from a reservoir to a tool head will readily become rigid and brittle so that ease of movement of the tool is greatly reduced and breakage of the tubes is likely. Moreover, the low temperature of the conduits encourages condensation of moisture from the air which freezes and then thaws to create further problems.

Attempts have been made to prevent these disadvantages by introducing heating means whereby to protect the conduits from the effect of deep cold, but these have only contributed to the complex and cumbersome nature of some devices which have been proposed.

Alternatively available devices which do not use cryogens make use of the phenomenon known as the Joule-Kelvin (or Joule-Thomson) effect by which for example nitrous oxide or carbon dioxide at high pressure is allowed to expand in an expansion chamber. The lowest temperatures that can be achieved in this way are in the region of -79 C, which is not generally found in surgical practice to be low enough to ensure swift freezing of the affected tissue and thus its use involves painful treatment for the patient.

It is an object of the invention to provide a device suitable for a number of uses including cryosurgery, which device will reduce or obviate the above mentioned disadvantages. It is a further object of the invention to provide a device which is simple in construction and virtually maintenance-free, offering advantages of low cost and ease of handling.

The invention provides, according to one of its aspects, a cryogenic device suitable for use as a tool for localised contact with a substrate, the device including a body portion comprising an inner region capable of taking up cryogenic fluid, said body portion having at an end portion thereof an operating means adapted in use to contact the substrate to extract heat therefrom, there being provided means communicating between said inner region and an outer surface of the body portion to permit entry of a cryogenic fluid from an ambient body thereof into the inner region.

Advantageously, said operating means may comprise an operating member formed from stainless steel or phosphor bronze, these being examples of efficient heat-conductive metals. In an example of a device according to the invention, the hollow body of the device may be of stainless steel and at least a portion of the operating member may be of a highly conductive noble metal such as gold or platinum.

Conveniently the device may be provided with a handle of non-conductive material such as wood or plastics material, for example nylon or the like.

Preferably, said inner region may comprise an enclosure capable of containing cryogenic fluid therein.

Alternatively, said inner region may comprise porous material through which cryogenic fluid may pass.

Conveniently, there may be provided a passage between the enclosure and the operating member of the device, said passage being plugged by porous material, such as sintered metal. If desired, the operating member itself may comprise porous metal, for example sintered phosphor bronze.

Advantageously, in the use of the device having an enclosure in the form of a cavity, said cavity may be at least partially filled with absorbent material, such as cellulose tissue, cotton wadding or an open-cell synthetic plastics foam material.

In examples of operating members in devices according to the invention, said members may be designed for point-contact with tissue to be treated, or with a broader contact, or the member may be in the form of a probe designed for entry into a body cavity for treatment of warts, tumours, haemorrhoids, polyps including dental polyps, and the like.

Suitable cryogenic fluids may be selected from a group including nitrogen or helium. The use of nitrogen may be preferred since the dissipation of nitrogen in gaseous form during use is not environmentally detrimental.

The invention further provides, according to another of its aspects, a method of achieving low temperature tool surfaces for localised contact with a substrate, comprising procuring a cryogenic device including a body portion and an operating member, at least partially immersing the device as as to submerge the operating member completely within a reservoir of cryogenic fluid, maintaining the member submerged for a predetermined minimum time and removing the device from the fluid ready for immediate use.

There will now be described examples of devices according to the invention. It will be understood that the description is given by way of example only and not by way of limitation.

In the drawings: Figure 1 shows a side elevational view of a first example of a device according to the invention; Figures 2 and 3 show similar views of second and third examples; Figure 3 shows a handle suitable for use with any of the examples; Figure 4 shows an alternative handle; and Figure 5 shows a range of operating tips from which a surgeon may choose.

The device shown in Figure 1 comprises a body portion 2 which is in the form of a hollow tubular member enclosing a cavity 4. Orifices 5 and 6 provide communication between the cavity 4 and an external surface of the portion 2, the orifices 6 providing inlets for cryogenic liquid, as will be described below, and the orifices 5 providing outlets for gas which may form as the liquid evaporates. The body portion is of stainless steel.

At the lower end portion of the body portion 2 there is an integrally formed operating means comprising a shaped operating portion 8, having a narrow tip 10.

Figure 2 shows a similar view in which like portions have been identified with like reference numerals, a tip 10' in this example being broader than the tip 10 of Figure 1.

Tips 10 or 10' may be integral with the operating portion 8 or may be separately formed and replaceably secured to the portion 8 as required. The replaceable tips may be of highly heat conductive metal such as gold or platinum, the body portion 2 acting as a heat sink. A handle 12 shows associated with the device of Figure 2 is made of smooth surfaced plastics material and is provided with a threaded boss 14 which is suitable for use with any of the three examples.

Figure 3 illustrates the third example of a device in which the end portion 8 thereof is formed with an aperture 16 into which is inserted an operating member 18 of porous metal, in the present example sintered phosphor bronze.

Figure 4 illustrates an alternative handle which allows adjustment of the distance between the selected operating tip and, in the present examples, the surgeon's hand (not shown). The handle comprises a shaft 20 having a threaded boss 22 similar to the boss 14 of Figure 2.

The shaft 20 which is conveniently of nylon is provided over the greater portion of its length with a coarse pitch thread 24 which allows rapid adjustment of the length of the shaft 20 protruding from a contoured grip portion 26 having an internally threaded bore 28 through which the shaft 20 passes. It will be apparent that the surgeon may readily adjust the overall length of the device during surgery, as required.

Use of the devices according to the invention will now be described. A reservoir of cryogenic fluid, in the examples liquid nitrogen, is provided in the form of an insulated flask (not shown) having an entry portion through which the devices may be inserted so that the end portions 8 may be completely submerged and the body portions 2 at least partially submerged in the liquid nitrogen. Because of the provision of the orifices 6, the liquid nitrogen will flow therethrough into the cavity 4, thus enhancing the cooling of the devices, which it will be found cool rapidly to temperatures approaching -1960C, since the body portion is being cooled from both the external and interior surfaces. When the device is at the required temperature, it is withdrawn from the flask and the tip 10, 10' or 18 placed on the substrate to be treated.In most surgical operations, the lesion to be treated will be a wart, polyp or tumour, the tissue of which will be frozen sufficiently for cell damage and destruction to result in the shedding of the unwanted tissue. This process may be repeated several times during the operation, reimmersing the device in the reservoir during the interval in which the tissue is allowed to thaw. Where the lesion is relatively shallow temperatures higher than -196 C may well be found adequate.

For exceptional cases, for example large, deep lesions, the cryogenic fluid may be liquid helium which permits cooling down towards -270#C. It will be understood that although the step of immersing the device is the same in principle, additional liquid containment procedures will be necessary over those required by nitrogen.

It will be appreciated that a small quantity of cryogenic fluid may be temporarily retained in the cavity 4. This will prolong the length of time that the device remains at a sufficiently low operating temperature, before all the liquid cryogen evaporates and escapes through the orifices 6. To retain the cryogen in the cavity 4 even when the device is moved out of a vertical orientation, a plug of porous material 20 (Figure 2) may be provided in the cavity. The plug may be of cellulose fibre or of suitable porous plastics material such as open-cell foam. Alternatively the plug 20 may be an insert of sintered metal.

In the third example, shown in Figure 3, the provision of the sintered phosphor-bronze tip 8 not only assists in retaining the cryogen within the device but also permits the fluid to seep through the tip 8 into direct contact with the lesion.

Should it be required rapidly to cease the freezing effect of the device while in use, a heating coil (not shown) containing heated air or other gas may be provided in the tip or operating member to transfer heat thereto, or alternatively, a current of heated air may be provided.

It will be understood that while the body portion of the devices may be cylindrical as shown in the Figures, the shape may be determined by the purpose for which it is intended; for example, the body portion may comprise a elongated, relatively slender configuration.

Because use of the invention dispenses with the need to provide pipes and tube assemblies for the supply of cryogenic fluid, the invention permits use of so-called cryoprobes in comparatively low-technology situations, such as local general practice surgeries, chiropodists, veterinary surgeries and also in unsophisticated locations as may be found in third world countries.

Because internal body surfaces are moist, problems are sometimes encountered when the operating device freezes and adheres to the tissue to be treated or to surrounding tissue. This problem may be alleviated by providing an anti-adhesion device for use as an interposed barrier member between a cryogenic tool and a substrate to be treated, comprising a layer of porous or absorbent material at least partially charged with a quantity of a fluid which is in liquid form at normal temperatures and remains liquid at low temperatures. A suitable fluid may be an alcohol or an alcohol derivative, conveniently isopropyl alcohol.

Another disadvantage of a closed tip being placed directly on to a lesion can be that the tip is no longer sterile and if it were to be used on another patient, there would be the possibility of transviral contamination between patients. In fact it is not unknown for doctors to be infected in this way. Work published in the British Journal of Dermatology by S. K. Jones & J. M. Darville in 1989 proved that a variety of viral material could be transferred during treatment and would survive liquid nitrogen temperatures.

It has been found that for example, by placing a layer of material, such as a tissue, saturated in isopropyl alcohol in the range 50-100% v/v on the lesion before placing the cold cryoprobe, prevents sticking and makes subsequent removal simple, therefore no "defrost" step is required. Preferably, the alcohol strength may be 70% v/v.

Because isopropyl alcohol is in common use as a sterilising/disinfectant medium already, for example, for swabbing skin prior to injection and for cleaning surfaces too large to be otherwise sterilised, then, by placing the layer between the lesion and the probe, the probe tip does not touch the lesion. It therefore does not become contaminated and does not require sterilisation between use or indeed at all. This technique overcomes the need for sterilisation prior to treatment and the use of sterile disposable tips, thus cutting costs and time. The technique may be used with all cryoprobes including those described and claimed herein.

It will be understood that the alcohol or alcohol derivative will be selected according to circumstances of availability and convenience. The layer of material may be a fabric or a textile, woven or non-woven, and may conveniently be sterilised cellulose fibre material.

Various modifications may be made within the scope of the invention as defined by the following claims.

Claims (15)

1. A cryogenic suitable for use as a tool for localised contact with a substrate, the device including a body portion comprising an inner region capable of taking up cryogenic fluid, said body portion having at an end portion thereof an operating means adapted in use to contact the substrate to extract heat therefrom, there being provided means communicating between said inner region and an outer surface of the body portion to permit entry of a cryogenic fluid from an ambient body thereof into the inner region.

2. A device as claimed in claim 1 wherein said inner region comprises an enclosure capable of containing cryogenic fluid therein.

3. A device as claimed in claim 1 wherein said inner region comprises porous cryogenic fluid may pass.

4. A device as claimed in claim 2 wherein a passage is provided between said enclosure and the operating means, said passage being plugged by porous material.

5. A device as claimed in either one of claims 3 and 4, wherein the porous material is porous metal.

6. A device as claimed in claim 2, wherein the enclosure is in the form of a cavity at least partially filled with absorbent material.

7. A device as claimed in claim 6 wherein the absorbent material is an open-cell foam or similar material.

8. A device as claimed in any one of the preceding claims wherein said operating means comprises a operating member having a tip portion designed for point contact with tissue to be operated upon.

9. A device as claimed in any one of claims 1 to 7, wherein said operating means comprises an operating member is in the form of a probe.

10. A device as claimed in claim 9, wherein the overall length of the probe is adjustable.

11. A method of achieving low temperature tool surfaces for localised contact with a substrate, comprising procuring a cryogenic device including a body portion and an operating member, at least partially immersing the device as as to submerge the operating member completely within a reservoir of cryogenic fluid, maintaining the member submerged for a predetermined minimum time and removing the device from the fluid ready for immediate use.

12. A method suitable for use with a device according to claim 1, wherein there is interposed between a cryogenic device and a substrate to be treated, a barrier member comprising a layer of porous or absorbent material at least partially charged with a quantity of fluid which is in liquid form at normal temperatures and remains liquid at low operation temperatures.

13. A method as claimed in claim 12, wherein the fluid is an alcohol or an alcohol derivative.

14. A cryogenic device constructed and arranged substantially as hereinbefore described with reference to and as shown in the drawings.

15. A method of achieving low temperature too surfaces substantially as hereinbefore described with reference to the drawings.