Cryosurgical Apparatus

Abstract

A cryosurgical apparatus primarily adapted for use with gases which cool when expanded from a high-pressure state to a low-pressure state. The apparatus includes an expansion chamber which receives gas through a supply tube. The gas is supplied from a selector valve at either a high pressure or a low pressure. The supply tube includes a self-acting valve which is normally biased open when gas is supplied at low pressure but is forced closed by gas under high pressure. With the valve open, the expansion chamber is filled with the low-pressure gas and is substantially at room temperature. When the valve closes, high-pressure gas bypasses the automatic valve and enters the cooling chamber through a small orifice, expanding to a low-temperature state and cooling the expansion chamber.

Description

BACKGROUND OF THE INVENTION

This invention relates to cryogenic apparatus and is disclosed herein primarily in connection with apparatus for cryosurgery. Its applications, however, are not so limited and it may be employed wherever its unique advantages are desirable.

In U.S. Pat. Nos. 3,393,679 of Crump et al. and 3,451,395 of Thyberg there are disclosed cryosurgical instruments primarily designed to employ low-boiling liquids as the cooling media. The most commonly used liquids are the halogenated hydrocarbons. The device disclosed in each of those patents comprises a hand-held housing from which extends a low-temperature probe. The tip of the probe may be selectively warmed or cooled by depression of a lever on the housing. In its warming position, the lever opens the fluid supply valve and closes an exhaust valve so that the instrument is completely filled with liquid at room temperature. In its freezing position, the lever closes the inlet valve and opens the exhaust valve. The fluid is then admitted to the probe through a small orifice which bypasses the inlet valve. The fluid boils in the probe tip, causing it to be cooled and the resulting vapor is withdrawn through the exhaust valve.

Devices of the foregoing type have achieved outstanding commercial success. In many parts of the world, however--particularly in underdeveloped regions--supplies of low-boiling liquids are not readily obtainable. However, high-pressure gases which exhibit cooling upon expansion, such as, for example, by Joule-Thomson effect, are quite readily available. One such gas, for example, is nitrous oxide, the well-known "laughing gas" which is extensively used throughout the world as an anesthetic. It would, accordingly, be desirable to provide a cryosurgical instrument which could utilize such gases as the cooling medium. It would also be desirable to provide a cryosurgical apparatus which could be actuated remotely, as from a foot-operated valve, to avoid hand fatigue which may result from use of a finger lever. Accordingly, it is the primary object of the present invention to provide improved cryosurgical apparatus which may be operated from a source of high-pressure gas. Other objects are to provide apparatus which may be selectively warmed or cooled by operation of a remote control; to provide such an apparatus which does not require a finger-operated lever; and to provide such apparatus which is adapted for use in a number of cryogenic applications.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a cryogenic apparatus comprising a tip member defining a low-temperature low-temperature expansion chamber. A supply tube and an exhaust tube communicate with the chamber. Means are provided for selectively injecting fluid into the supply tube at either a high pressure or a low pressure. Included in the supply tube between the injection means and the chamber is an inlet valve which is normally biased open when the fluid is at the low pressure but closes under the influence of fluid at the high pressure. Means are also provided which form a fluid passage between the supply tube and the chamber, bypassing the valve.

BRIEF DESCRIPTION OF THE DRAWINGS

The manner in which the objects of the invention are achieved may be best understood by reference to the following description taken in connection with the attached drawings wherein:

FIG. 1 is a schematic illustration of a cryogenic system in accordance with this invention;

FIG. 2 is a longitudinal cross section of a portion of a cryosurgical instrument incorporating this invention;

FIG. 3 is an enlarged illustration of the tip of the instrument of FIG. 2;

FIG. 4 is a cross-sectional view illustrating a modification of the invention;

FIG. 5 is a cross-sectional view of a further modification of the invention;

FIG. 6 is a cross-sectional view of a still further modification of this invention;

FIG. 7 is an enlarged partial cross-sectional view of a still further modification of the invention; and

FIG. 8 is a longitudinal cross section of a still further modification of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 there is illustrated a cryogenic system including a supply bottle 10 of a suitable pressurized gas. This may be, for example, nitrous oxide at a pressure of 800 p.s.i. Associated with the bottle is the usual shutoff valve 12. Gas is supplied by a delivery line 14 through an auxiliary shutoff valve 16 which may be mounted in a control cabinet which also carries a pressure gauge 18. The delivery line branches at a tee 20. A three-way valve 22 includes ports 24, 26, 28. Port 24 is connected to one of the delivery line branches. The other branch of the delivery line passes to metering needle valve 30. The outlet of needle valve 30 is connected to a heat exchanger coil 32 which exhausts into a further tee 34 connected to port 26 of valve 22 and to a supply line 36 extending into a cryosurgical instrument 38. Port 28 of the three-way valve 22, is connected through a relief valve 40 to an exhaust muffler 42. Relief valve 40 is set to open at a predetermined pressure, such as 50 p.s.i. The three-way valve 22 may be controlled by any suitable means, such as a foot lever, and is designed to selectively interconnect port 26 with either port 28, as shown, or port 24. In the illustrated position, the high-pressure gas supply is shut off at port 24. However, it passes through the needle valve 30 which reduces the output pressure to 25-50 p.s.i. This gas passes through the heat exchanger 32 where its temperature is raised to substantially that of the ambient air and this warm low-pressure gas passes through supply line 36 into the instrument 38. If, for any reason, the pressure should increase above the 50 p.s.i. level of relief valve 40, this valve will open permitting the gas to escape through the exhaust muffler 42.

When three-way valve 22 is actuated from the position illustrated in FIG. 1, it will interconnect ports 26 and 24. This will permit high-pressure gas to pass directly from the bottle 10 into the supply line 36 of instrument 38. As the pressure on both sides of needle valve 30 will then be substantially equal, there will be essentially no flow through the valve.

It will now be seen that the above-described apparatus permits either high-pressure or low-pressure gas to be selectively applied to the cryosurgical instrument 38. The construction of instrument 38 will now be explained with particular reference to FIG. 2. It comprises a hand-held tubular casing 44 closed at one end by a nosepiece 46 and having near its other end a wall 48. A plug 50 extends through the wall 48 and is connected rearwardly to the end of supply line 36. Supply passages 52 in plug 50 permit gas to flow from the supply line 36 to a tubular inner chamber 54 secured to the inner end of plug 50. Inner chamber 54 is shorter and of smaller diameter than casing 44 so as to define therewith an annular exhaust passage 56 which communicates with atmosphere, or other suitable exhaust, through exhaust ports 58 in wall 48.

Extending forwardly from nosepiece 46 is a tubular probe 60 which is offset at its end to form an expansion chamber 62. Concentrically positioned within the probe 60, and of smaller diameter, is a supply tube 64 connected at one end to inner chamber 54 and having its remote end adjacent the expansion chamber 62. Referring to the enlarged view of FIG. 3 it will be seen that this remote end 66 of supply tube 64 defines an inlet opening 68. Extending radially from the inlet opening 68 is a small bypass orifice 70. Mounted within the inner chamber 54 is a coil spring 72. One end 74 of the spring extends through the plug 50 where it is secured as by brazing or a suitable weld 76. The opposite end 78 extends into the supply tube 64 where it is terminated with a small loop 80. Secured to loop 80 by another loop 82 is a short wire 84 which carries at its end a ball 86. The ball 86 is positioned closely adjacent the inlet opening 68 but is normally displaced therefrom by the action of spring 72. Although the sizes of the various parts may be varied to suit the particular application, in one embodiment the diameter of the ball 86 was 0.046 inch and it was spaced from opening 68 by approximately 0.060 inch. Ball 86 is slightly smaller than the inner diameter of the supply tube 64.

To explain the operation of the apparatus of FIGS. 1-3 it will be assumed that the valve 22 is in the position illustrated in FIG. 1 so that, as previously explained, only low-pressure gas is applied through line 36. This gas enters the cryosurgical instrument 38 through supply passages 52, inner chamber 54, and supply tube 64. It passes around the ball 86 and through inlet opening 68 into chamber 62. From chamber 62 it flows rearwardly through probe 60, and exhaust passage 56, out exhaust ports 58. As the gas is essentially at room temperature, it will be seen that the probe and the expansion chamber 62 will be warm. To cause the instrument to freeze, the three-way valve 22 is actuated to supply high-pressure gas directly to the cryosurgical instrument 38. This high-pressure gas flows into the instrument through the same line and in the same manner as at low pressure. However, the additional pressure acting upon ball 86 forces it outwardly and against the inlet opening 68 against the force of spring 72. The ball then closes opening 68 as shown in FIG. 3. The only path for the high-pressure gas-filling supply tube 64 is now through the bypass orifice 70. Accordingly, it escapes through this orifice and expands into the much reduced pressure of expansion chamber 62, thus becoming cool and extracting heat from the walls of the chamber and from any tissue which the chamber may contact. The cool exhaust gas then passes rearwardly through the instrument and exhausts in the same fashion as previously described.

It will now be apparent that, by means of this invention including the self-acting valve, it is possible to utilize high-pressure gases as efficient cooling media for cryosurgical instruments. It will also be apparent that such instruments may be selectively warmed or cooled by a remotely located valve, such as a valve controlled by a foot pedal.

A number of variations of this invention are possible and several such are illustrated in FIGS. 4-8. FIG. 4, for example, illustrates an embodiment wherein a separate piston is used to control the position of ball 86. In this embodiment, the inner chamber 54 is shortened to form a cylinder housing a piston ball 88 to which is secured a wire 90 carrying ball 86. The piston 88 is forced rearwardly by coil spring 92 and it advances against the coil spring under the influence of high-pressure entering the rear of the chamber 54.

In FIG. 5 is illustrated a modification which may be of particular value for applications involving a relatively long probe, such as might be required for brain surgery or for brain implants in laboratory animals. In this embodiment, the supply tube 64 includes a right angle extending downwardly through the probe 94. The ball 96 is mounted on the end of a wire 98 which is normally biased upwardly by a leaf spring 100. FIG. 6 illustrates a curved probe 102 wherein the ball 104 is mounted on the end of a curved wire 106 having an integral spring 108. The opposite end of the wire is carried by a member 110 which threadedly engages a suitable bracket 112 to permit accurate and adjustable location of the ball.

In the FIG. 7 modification, the end 66 of supply tube 64 is substantially spherical. The ball 114 is loosely positioned within the end 66 and retained by means of dimples 116 formed in the tube 64. A coil spring 118 is positioned on the outer surface of tube 64 and has an end 120 which extends through inlet opening 68 and bears against ball 114, tending to keep it in the rearward position.

In the FIG. 8 modification the ball is replaced by wire 122 having at its end a valve needle 124 for engaging the inlet opening. At its other end wire 122 has an enlarged head 126 biased rearwardly by a spring 128. Head 126 is forced outwardly by increased pressure.

It will be apparent to those skilled in the art that, by means of this invention, all of the objectives set forth have been achieved. It will also be apparent that a number of variations and modifications may be made therein without departing from the spirit and scope of this invention. Accordingly, the foregoing description is to be construed as illustrative only, rather than limiting. This invention is limited only by the scope of the following claims.

Claims

What is claimed is:

1. Cryogenic apparatus which comprises: a tip member defining a low-temperature expansion chamber; a supply tube communicating with said chamber; an exhaust tube communicating with said chamber, means for selectively injecting a fluid into said supply tube at either of a high pressure or a low pressure; inlet valve means in said supply tube between said injection means and said chamber, said valve means being normally biased open when said fluid is at said low pressure but closed under the influence of fluid at said high pressure; and means forming a fluid orifice between said supply tube and said chamber and bypassing said valve means.

2. The apparatus of claim 1 wherein the end of said supply tube adjacent said chamber defines an inlet opening therethrough and said inlet valve means comprises a valve member operable to close said inlet opening.

3. The apparatus of claim 2 wherein said valve member comprises a ball.

4. The apparatus of claim 1 wherein said valve means includes a spring normally biasing said valve means to its open position.

5. The apparatus of claim 4 wherein the end of said supply tube adjacent said chamber defines an inlet opening therethrough and said inlet valve means comprises a valve member operable to close said inlet opening.

6. The apparatus of claim 5 wherein said valve member comprises a ball.

7. The apparatus of claim 5 wherein said valve member comprises a needle.

8. The apparatus of claim 1 wherein said injecting means comprises a selector valve.

9. The apparatus of claim 1 wherein said injecting means comprises a source of high-pressure gas; means for reducing said high pressure to a low-pressure range; and selector valve means for bypassing said reducing means and admitting high-pressure gas from said source to said supply tube.

10. Cryosurgical apparatus which comprises: a hand-held casing; a tubular tip member extending from said casing defining at its end a low-temperature expansion chamber; a supply tube within said tip member and forming an annular exhaust passage therewith, the end of said supply tube being adjacent said chamber and defining an inlet opening therethrough; a source of high-pressure gas; a source of low-pressure gas; selector valve means selectively admitting said high-pressure gas or said low-pressure gas to said supply tube; an inlet valve member positioned within said supply tube to close said inlet opening under the influence of said high-pressure gas; spring means normally biasing said inlet valve member away from said inlet opening under the influence of said low-pressure gas; and means forming a gas orifice between said chamber and said supply tube and bypassing said inlet opening when closed by said inlet valve member.