U.S. patent number 3,696,813 [Application Number 05/189,469] was granted by the patent office on 1972-10-10 for cryosurgical instrument.
This patent grant is currently assigned to Cryomedics, Inc.. Invention is credited to Ronald M. Wallach.
United States Patent |
3,696,813 |
Wallach |
October 10, 1972 |
CRYOSURGICAL INSTRUMENT
Abstract
An improved method for cooling a probe tip of a cryosurgical
instrument is provided by supplying a two phase refrigerant
comprising a gaseous phase and a liquid phase to a restricted
orifice adjacent an expansion chamber of the instrument, conveying
the refrigerant through said orifice into said expansion chamber
for expanding the gaseous phase into the chamber thereby providing
a Joule-Thomson refrigeration effect and for providing additional
cooling of the chamber by the evaporation of the liquid phase
therein, and, conveying an effluent gas of the expansion chamber to
atmosphere. A cryosurgical instrument comprises an expansion
chamber formed of a high thermal conductivity material having an
outer surface thereof which is adapted for contacting body tissue
which is to be treated, a means for conveying a gaseous refrigerant
from a source thereof to said expansion chamber, said means
including a stationary body forming an orifice of fixed dimensions
through which said gas expands into said chamber for cooling said
chamber, and, a means for exhausting said gas to atmosphere, said
exhaust means including a flow channel communicating between said
chamber and a quick acting flow valve, said valve biased for
interrupting a flow path through the valve between said exhaust
conduit and atmosphere and selectively operable to establish the
flow path through the valve.
Inventors: |
Wallach; Ronald M. (Norwalk,
CT) |
Assignee: |
Cryomedics, Inc. (Bridgeport,
CT)
|
Family
ID: |
22697465 |
Appl.
No.: |
05/189,469 |
Filed: |
October 6, 1971 |
Current U.S.
Class: |
606/26; 62/51.2;
62/293 |
Current CPC
Class: |
F25B
9/02 (20130101); A61B 18/02 (20130101); F25B
2309/021 (20130101) |
Current International
Class: |
A61B
18/00 (20060101); A61B 18/02 (20060101); F25B
9/02 (20060101); A61b 017/36 () |
Field of
Search: |
;62/514,293
;128/303.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Perlin; Meyer
Claims
What is claimed is:
1. A cryosurgical instrument adapted for operation in a cooling
mode and in a rapid warming mode comprising:
means defining an expansion chamber; said means including a body
formed of a high thermal conductivity material and having a surface
thereof shaped for contacting body tissue and providing heat
transfer with the tissue;
refrigerant supply means for conveying a gaseous refrigerant from a
source to said expansion chamber, said means including a stationary
body defining a flow restriction through which said gas is
introduced into said chamber for effecting a Joule - Thomson
expansion of said gas thereby cooling said chamber; and,
means for conveying an effluent gas from said chamber to atmosphere
during said cooling mode, said means including a quick acting two
position flow valve having means for positioning said valve in an
open position to enable flow and means for positioning said valve
in a closed position to interrupt flow and an exhaust flow channel
communicating between said chamber, said quick acting flow valve
and atmosphere, said valve including means for selectively opening
said flow channel during said cooling mode and closing said flow
channel during said warming mode.
2. The cryosurgical instrument of claim 1 wherein said exhaust flow
channel is arranged for conveying the effluent gas from said
chamber about a portion of said refrigerant supply means for
pre-cooling said gaseous refrigerant prior to introducing said
refringerant through said flow restricting means into said chamber,
and said gaseous refrigerant comprises a saturated gas.
3. The cryosurgical instrument of claim 1 wherein said refrigerant
supply means includes an elongated supply conduit, said flow
restricting means is positioned near a distal end of said supply
conduit, means are provided for supplying a gaseous refrigerant to
an inlet end of said supply conduit, said exhaust channel means is
formed by an exhaust conduit which is positioned with relation to
said supply conduit for forming an annular space therebetween, and
said quick acting valve is coupled in a flow path between said
outlet conduit and atmosphere.
4. The cryosurgical instrument of claim 3 wherein said quick acting
valve includes a valve seat and a valve element, means for biasing
said valve for causing said valve element to seat and thereby
interrupt said valve flow path and an operating lever for unseating
said valve element.
5. The cryosurgical instrument of claim 4 wherein said quick acting
valve includes means for establishing the flow of a metered amount
of gas less than an amount of maximum flow through said valve.
6. The cryosurgical instrument of claim 4 wherein said valve
includes means for automatically unseating said valve element and
providing a flow path to atmosphere when the pressure within said
instrument exceeds a predetermined safe pressure.
7. The cryosurgical instrument of claim 6 wherein said valve
includes a channel formed therein which communicates with said
exhaust channel, said valve includes means exposed to the pressure
of said valve channel for establishing a force on said valve
element which counteracts the force established by said biasing
means and unseats said valve face thereby establishing a flow path
through said valve to atmosphere from said channel when the
pressure in said instrument exceeds a predetermined safe level.
8. The cryosurgical instrument of claim 7 wherein said lever arm
includes means for enabling said arm to be rotated in a first
direction for unseating said valve element and said lever arm
further includes means for enabling said arm to be rotated in a
second opposite direction for establishing a force on said valve
element which operates against the force of said biasing means
thereby locking said valve element in an unseated position.
9. The cryosurgical instrument of claim 3 wherein said supply and
exhaust conduits are concentrically orientated and said quick
acting valve means is positioned near an end of said exhaust
conduit and is spaced radially therefrom, a hand gripping support
member formed about said valve thereby providing a pistol shaped
hand grip for said instrument, said valve actuating lever
positioned for quick acting operation by drawing the lever arm
towards said hand grip.
10. An improved method for cooling and warming an applicator head
of a cryosurgical instrument in contact with body tissue comprising
the steps of:
conveying a saturated gaseous refrigerant at substantially ambient
temperature and relatively high pressure toward a stationary flow
restricting means communicating with an expansion chamber in the
head of the instrument;
cooling said refrigerant prior to introduction into said chamber by
effecting heat exchange with an effluent gas emanating from said
chamber thereby condensing a portion of said refrigerant forming a
two phase refrigerant comprising a major amount of a gaseous phase
and a minor amount of a liquid phase;
introducing the two phase refrigerant through said stationary flow
restricting means into the relatively low pressure expansion
chamber, said chamber being in contact with body tissue, effecting
a Joule-Thomson expansion of said gaseous phase and boiling of said
liquid phase, thereby cooling said expansion chamber; and,
conveying an effluent from said expansion chamber to atmosphere
during cooling of said chamber and then cutting off the flow of
said effluent gas trapping a sufficient body of gaseous refrigerant
at substantially ambient temperature within said expansion chamber
to effect rapid warming of said chamber.
11. An improved method as defined in claim 10 wherein the saturated
gaseous refrigerant is carbon dioxide.
12. An improved method as defined in claim 10 wherein the saturated
gaseous refrigerant is nitrous oxide.
Description
This invention relates to surgical apparatus utilizing cryosurgical
techniques. The invention relates more particularly to an improved
cryosurgical instrument.
Surgical techniques have been developed for treating defective or
diseased body tissue by reducing the temperature of the tissue to
relatively low values. Various cryosurgical instruments are known
for aiding the medical practitioner in this form of treatment.
Generally, these instruments include a probe tip which is initially
placed in contact with the tissue to be treated and which is then
cooled. The cooled probe tip is normally maintained in contact with
the treated tissue for a short interval of time. In practice the
cryosurgical instrument is required to provide a reduction in
temperature of the probe tip to temperatures of less than
-55.degree. C. in order to achieve a useful heat exchange and
lowering of tissue temperature. It is also necessary that these low
temperatures be attained rapidly after the probe tip contacts the
tissue so that the tissue freezing is localized and the patient is
not subjected to prolonged cold treatment. Additionally, it has
been found that body tissue undesirably adheres to a cooled
treatment probe at these low temperatures and it is therefore
necessary to provide means for rapidly warming the treatment probe
in order to facilitate removal of the probe from the body
tissue.
In a known form of cryosurgical instrument, a refrigerant fluid
under pressure is expanded into a chamber through a restricted
orifice thus producing a cooling effect commonly known as the
Joule-Thomson effect. The probe tip, which is formed by an outer
surface of the chamber, is thereby rapidly cooled. The instrument
also incorporates means for effecting the rapid warming of the
probe tip in order to facilitate removal of the probe from the body
tissue.
Various arrangements have been employed for cooling and for warming
the probe tip. In one arrangement, the flow of a refrigerant gas to
the expansion chamber is controlled by a valve located upstream
from the chamber. Effluent gas from the chamber is exhausted to
atmosphere. Cooling of the probe tip is accomplished by actuating
the valve for enabling the flow of refrigerant gas to the expansion
chamber and then to atmosphere. Warming of the probe tip is
accomplished by interrupting the flow of gas to the expansion
chamber and heating the probe tip by electrical means including a
coil heater positioned in the probe tip.
In another cryosurgical instrument, probe tip cooling is provided
by unseating a flow valve element located downstream of the
expansion chamber and simultaneously forming a restrictive orifice
at the chamber inlet by contacting an orifice seat with a moveable
conduit. A refrigerant fluid then flows from a source, through the
orifice and exhausts through the unseated downstream valve. Warming
of the probe tip is accomplished by seating the downstream valve
element and simultaneously separating the moveable conduit from the
orifice seat thus permitting refrigerant fluid at ambient
temperatures to flood the expansion chamber.
These arrangements as well as other various cryosurgical instrument
arrangements are relatively complex and costly. At times they are
relatively difficult for a medical practitioner to handle and do
not provide him with the degree of manipulative facility necessary
in a medical procedure where the practitioner must devote his close
attention to the progress of the procedure. In addition, these
known instruments do not attain the cooling and warming rates which
are desirable with this medical procedure.
Accordingly, it is an object of this invention to provide an
improved method and apparatus for cryosurgical treatment.
Another object of the invention is to provide an improved method
for cooling a probe tip of a cryosurgical instrument.
Another object of the invention is to provide a cryosurgical
instrument having a relatively non-complex refrigerant fluid flow
arrangement for both cooling and warming the probe tip of the
instrument.
Another object of the invention is to provide an improved
cryosurgical instrument employing a gaseous refrigerant for both
cooling and warming the probe.
Another object of this invention is to provide a cryosurgical
instrument which extends to the medical practitioner a relatively
greater degree of manipulative facility than has been permitted by
prior instruments.
Another object of the invention is to provide a cryosurgical
instrument of improved reliability.
Another object of the invention is to provide an improved
cryosurgical instrument employing a refrigerant maintained under
relatively high pressure.
A further object of the invention is to provide a relatively
non-complex and a relatively low cost cryosurgical instrument.
In accordance with the general features of this invention, an
improved method for cooling a probe tip of a cryosurgical
instrument is provided by supplying a two phase refrigerant
comprising a gaseous phase and a liquid phase to a restricted
orifice adjacent an expansion chamber of the instrument, conveying
the refrigerant through said orifice into said expansion chamber
for expanding the gaseous phase into the chamber and providing a
Joule-Thomson refrigeration effect and for providing additional
cooling of the chamber by the evaporation of the liquid phase
therein, and, conveying an effluent gas of the expansion chamber to
atmosphere. In accordance with a more particular feature of the
method of this invention, a two phase refrigerant is supplied for
introduction into the evaporation chamber by conveying a saturated
gas refrigerant toward the restrictive orifice and by precooling
the saturated gas prior to introduction into the chamber thereby
condensing a portion of the saturated gas. Precooling of the
saturated gas phase refrigerant is accomplished in one embodiment
by flowing the effluent gas of the chamber about the saturated gas
which is supplied to the orifice.
In accordance with the features of the apparatus of this invention,
a cryosurgical instrument comprises an expansion chamber formed of
a high thermal conductivity material having an outer surface
thereof which is adapted for contacting body tissue which is to be
treated, a means for conveying a gaseous refrigerant from a source
thereof to said expansion chamber, said means including a
stationary body forming an orifice of fixed dimensions through
which said gas expands into said chamber for cooling said chamber
and a means for exhausting said gas to atmosphere, said exhaust
means including a flow channel communicating between said chamber
and a quick acting flow valve for completing a flow channel between
said conduit to atmosphere. The flow valve is biased for normally
interrupting the flow of effluent gas from the chamber thereby
maintaining a refrigerant gas at ambient temperature within said
expansion chamber and maintaining said chamber in a relatively warm
state. The quick acting valve is selectively operable for
completing a flow path from said exhaust conduit to atmosphere
thereby effecting the continuous flow of refrigerant gas into said
chamber and causing a cooling thereof. In accordance with other
more particular features of the apparatus of this invention, the
refrigerant gas comprises a gas under relatively high pressure and
said quick acting valve means is adapted for automatically enabling
the flow of gas from said expansion chamber to atmosphere when the
pressure within said instrument exceeds a predetermined safe
level.
The cryosurgical apparatus of this invention is further
advantageously constructed in a generally pistol shaped
configuration having a hand grip thereof and a trigger mechanism
providing for the actuation of the quick acting valve, and a probe
tip supported at a distal segment of a flow conduit.
These and other objects and features of the invention will be
apparent with reference to the following specification and to the
drawings wherein:
FIG. 1 is a perspective view of an embodiment of a cryosurgical
instrument for practicing the present invention;
FIG. 2 is a side view, partly in section and partly cut away, of
the cryosurgical instrument of FIG. 1;
FIG. 3 is a view taken along lines 3--3 of FIG. 2; and
FIG. 4 is a sectional view of an alternative quick acting valve for
use in the instrument of FIGS. 1 and 2.
Referring now to the drawings and particularly to FIG. 1, a
cryosurgical instrument is shown arranged in a generally pistol
shaped configuration. The instrument includes a gripping stock
formed by stock members 9 and 10, a triggering lever arm 12 for
actuating a quick acting valve, and an elongated tubular shaped
body 13 which extends from the stock and supports a probe tip 14
near a distal segment thereof. A refrigerant is coupled to the
pistol shaped instrument by a flexible conduit 18. As indicated in
greater detail hereinafter, the tubing 18 is coupled to a rotary
shut off valve 20 which interrupts the flow of refrigerant from a
source 22 (FIG. 2) to the instrument. During operation of the
instrument, the lever arm 12 is squeezed toward the stock thereby
effecting the flow of refrigerant through the instrument and
cooling of the probe tip 14. Release of this lever arm interrupts
the flow of refrigerant and warming of the probe tip occurs. The
general pistol shaped configuration of this instrument and the
convenient trigger lever arm 12 for operating a quick acting valve
of the instrument as well as the elongated tubular body 13 which
supports the probe tip at a remote point from the stock provide a
cryosurgical instrument for the medical practitioner which is
easily handled and readily operated. The medical practitioner is
thereby free to direct almost his complete attention to the
progress of the surgical procedure.
Reference is now made to FIGS. 2 and 3 for a more detailed
description of the construction and operation of this instrument.
The probe 14 is formed into a generally conically shaped
configuration having an outer surface 23 thereof which converges to
a tip 24. The tip 24 is brought into physical contact with tissue
to be treated during the cryosurgical procedure. Although a
particular probe and probe shape are illustrated in the drawings,
it is noted that the probe can assume various other particular
configurations in order to satisfy the particular needs of the
specific cryosurgical procedure which is practiced with the
instrument. The probe 14 is fabricated of a high thermal
conductivity material such as silver or other suitable material. A
circular shoulder 26 is integrally formed in the probe 14 and a
circular adapter plate 28 is positioned at this shoulder and
secured thereto by silver soldering. The probe 14 and the adapter
plate 28 define an internal volume 30 comprising an expansion
chamber.
A refrigerant which is conveyed toward the chamber 30 for cooling
the chamber comprises in accordance with a feature of the invention
a saturated gas which is maintained at a relatively high pressure
at ambient temperature. A saturated gas exhibits a high thermal
conductivity relative to unsaturated gas and is therefore an
efficient heat transfer medium for removing heat from the chamber.
Exemplary gases for use in the instrument comprise carbon dioxide
and nitrous oxide. FIG. 2 illustrates the storage tank 22 which is
partially filled with carbon dioxide 32 in the liquid phase and
with saturated carbon dioxide gas. The gas is confined within the
tank 22 above the level of the liquid phase carbon dioxide. This
pressurized saturated gas is supplied to the instrument through a
supply tank shut off valve 34, through a fluid coupling yoke 36,
and through the flexible high pressure tabulation 18. A pressure
regulator (not illustrated) may be attached to the yoke 36 when the
cryosurgical instrument is utilized as an accessory which is
coupled directly to the supply 22. The regulator will avoid excess
pressure in relatively warm climates. The tubulation 18 extends
through an aperture 38 formed in a rear surface 40 of the pistol
grip.
The gripping stock members 9 and 10 are formed for example of a
plastic material. Each member has a pistol grip shape and a flange
formed along a periphery thereof. The pistol grip members are
butted together at these flanges and form an internal volume in an
upper portion of the stock which encloses the shut off valve 20, a
portion of the inlet and exhaust flow chamber and a quick acting
control valve 42 for the instrument. The members 9 and 10 define an
exhaust chamber 43 which extends between the valve and an outlet
aperture 44 in the stock. Screws 46 extend between the pistol grip
members and secure the members together.
The instrument includes a means for conveying a refrigerant from an
inlet thereof to the expansion chamber. This means comprises the
shut off valve 20, an inlet conduit 51 and a body 52 forming a
restricted orifice. The flexible refrigerant supply line 18 is
coupled to the shut off valve 20 which comprises a rotary operated
ball valve assembly, the details of which are known in the art. For
purposes of clarity in FIG. 2 of the drawing, the shut off valve
assembly 20 is shown in FIG. 2 to be rotated by 90.degree. from its
preferred position as illustrated generally in FIG. 1. The valve is
mounted to the stock member 9 by a threaded shoulder which extends
through an aperture in grip member 9 and a nut 50 which engages the
threaded shoulder. The tubulation 18 is coupled to an inlet
aperture 53 of the valve and is secured in place by a lock nut 54.
The inlet conduit 51 which comprises an elongated tubular body for
conveying refrigerant from an outlet of the shut off valve to the
expansion chamber 30 is seated at one end at an outlet aperture 55
of the valve 50 and extends to the expansion chamber 30 at a distal
segment thereof. This refrigeration inlet tubulation 51 is coupled
to the valve 20 by a conventional coupling for high pressure use
including a conically flared end segment and a ferrule positioned
about the body 51 near the flared segment (not illustrated). The
tube 51 is locked to the threaded body of the valve 20 by a locking
nut 56.
The inlet tubulation body 51 extends along its length successively
through an adapter coupling 58 and through a T fitting 60. The
outer diameter of the tubular body 51 and the inner diameter of the
adapter 58 are selected to provide for support of the body 51 by
the adapter 58. The tubular body 51 is therefore supported at its
seated position at the outlet aperture 55 of the valve 20 and by
the inner surfaces of the adapter member 58. The outer diameter of
the tubular body 51 and the inner diameter of the T fitting 60 are
selected for providing an annular space between these bodies within
the T fitting 60. Adapter 58 is locked to the T fitting 60 by a
locking nut 62 which engages the threaded body of the T fitting at
one end thereof and is engaged by a locking nut 64 which is rotably
coupled to the ball valve locking nut 56.
A restrictive orifice is provided for the instrument by the plug
body 52 which is supported at an outlet aperture of the tubular
body 51 adjacent the expansion chamber 30. The plug body 52 is
shown positioned within the tubular body and is secured therein by
silver soldering. The body 52 includes a centrally formed bore 66
extending axially therethrough for providing a restricted orifice
through which the two phase refrigerant which is supplied to the
orifice is conveyed to the expansion chamber 30. Orifice 66
establishes a pressure drop between the pressure of the refrigerant
upstream of the expansion volume and the pressure of the expansion
chamber. A relatively large bore may be utilized as the orifice
thereby greatly reducing plugging and interruption of refrigerant
flow.
A means for exhausting gases to the atmosphere from the expansion
chamber is provided and includes an annular flow channel 67 formed
between the tubular bodies 13 and 51, and, the quick acting flow
control valve means 42 adapted for establishing and interrupting
the flow of effluent gas from this conduit to atmosphere. The
tubular body 13 is seated at an outlet aperture 68 of the T fitting
60. A seated segment thereof is conically flared and the tube is
secured to the T fitting by a ferrule (not illustrated) and a
locking nut 70. The body 13 thus extends from and is supported by
the T fitting 60. An aperture 72 is provided in the pistol grip
from which the tube 13 extends. The tube 13 is concentrically
positioned with respect to the tubular body 51 and has an inner
diameter greater than the outer diameter of the tubular body 51
thereby establishing an annular shaped exhaust flow channel 67
between these bodies. The adapter plate 28 includes an integral
cylindrically shaped extension 73 having a bore 74 therein and into
which the tubular body 13 extends. The adapter plate 28 is secured
to the body 13 by silver soldering for example. Probe 14 is thereby
supported at a distal position from the pistol grip. Effluent gases
of the chamber 30 will flow through the exhaust channel 67 to an
outlet aperture 75 of the T fitting 60. The direction of
refrigerant flow in the instrument is indicated in FIG. 2 by the
arrows.
An inlet of the manually operable quick acting valve means 42 is
coupled to the outlet aperture 75 of the T fitting 60. This valve
includes a flow path extending therethrough and is adapted for
alternatively establishing and interrupting the flow of effluent
gas from the expansion chamber 30 and through the exhaust channel
67 to atmosphere. The quick acting valve 42 includes a core body 82
having a cyclindrically shaped inlet segment 84 which is internally
threaded and which engages a threaded segment on an outer surface
of the T fitting 60. The core body 82 includes a similar
cyclindrically shaped internally threaded outlet segment 86 which
engages a threaded muffler body 88 having a disc 90 positioned in
an aperture thereof and operating to muffle the sound of effluent
gas flowing from the valve 42. The disc 90 is formed of sintered
bronze or stainless steel or other suitable material. The core body
82 further includes a bore 92, a channel 94 and a channel 96. A
flow passage through the valve is provided by the channel 94 which
communicates between the inlet segment 84 by the volume of the bore
92, and by the channel 96 which communicates between the bore 92
and the outlet segment 84 and muffler element 88. The bore 92 is
concentrically aligned with a bore 98 of relatively larger diameter
which is formed in the core body 82. A valve element 100 extends
into the bores 98 and 92. A coil spring 102 is positioned about the
valve element 100 and is compressed between a nut 106 and a
shoulder segment of the valve element 100. A groove 110 is formed
in the shoulder segment for receiving an O ring 112. The O ring
provides a seal between the valve shoulder and the inner surface of
the bore 98.
The valve element 100 includes an inner segment 113 thereof having
a face 114 which seats against an inlet aperture of the channel 96
and interrupts the flow path through the valve. The valve actuating
lever 12 is pivotally coupled by a pin 116 to a segment of the
valve element 100 which extends through an aperture in the nut 106.
As the lever 12 is squeezed counterclockwise by finger pressure as
viewed in FIG. 2, the lever 12 pivots about an outer edge of the
nut 106 and forces the valve element 100 to travel to the left
against the biasing action of the coil spring 102. The face 114 is
thereby unseated from the entrance aperture of channel 96 and a
flow passage is provided through the valve. As the lever 12 is
released, the spring 102 immediately causes the face 114 to reseat
and interrupts the flow path.
An upper edge of the lever 112 is beveled and an aperture which is
formed in lever 12 for receiving the pin 116 is spaced from an edge
of the lever by a distance sufficient for providing that lever 12
is rotable about the pin in a clockwise direction as viewed in FIG.
2. Clockwise rotation will translate the location of the pin 16 to
the left thereby unseating the face 114. As the lever is rotated
90.degree. clockwise as viewed in FIG. 2, an end segment of the
lever will contact the nut 116 thereby biasing the valve in a
locked open position. Rotation of the lever 12 by applying finger
pressure thereto for causing counterclockwise motion of the lever
will release the valve from this locked open position.
In operation, the refrigerant is conveyed through the conduit 51 to
the body orifice 52 at relatively high pressure wherein it expands
to a lower pressure within the expansion chamber 30. This expansion
is accompanied by a refrigerant effect commonly known as the
Joule-Thomson effect which cools the probe 14 and rapidly lowers
the temperature of the tip 24. The gases which thus expand, flow
from the expansion chamber 30 through the annular exhaust channel
67, through the flow path of the quick acting valve 42, and through
the muffler 88 and channel 43 to atmosphere. Cooling of the probe
is accomplished by squeezing the triggering lever 12 thereby
causing the flow of refrigerant through the instrument. The
refrigerant will continuously flow from the reservoir 22, through
the inlet means, through the orifice 66, and from the expansion
chamber 30 to atmosphere. Release of the trigger lever 12
interrupts the flow path in the valve 42. As a result, a back
pressure immediately develops within the channel 67 and the
pressure in chamber 30 rapidly rises to the pressure maintained in
the source 22 thereby interrupting the further flow of refrigerant.
When the flow is thus interrupted, the gases which occupy the
tubular body 51, the chamber 30 and the annular exhaust conduit
space 67 is substantially at ambient temperature and operates to
rapidly raise the temperature of the probe 14 for safe removal of
the probe tip from the tissue being treated.
Control of the temperature of the probe tip 14 to desired
intermediate temperatures between ambient temperature and maximum
low temperature can be effected by a repetitive actuation and
release of the lever 12. However, this form of temperature control
requires continuous attention by the medical practitioner for
regulating the temperature. In accordance with another feature of
the invention, an adjustable temperature control is provided by a
flow valve means 42 which is adapted for establishing a metered
flow of refrigerant. FIG. 4 illustrates an alternative arrangement
of the valve of FIG. 1 which is adapted for metering the flow of
refrigerant. The valve includes a threaded body 134 having an
internally threaded segment thereof which engages the valve core
82. A valve element 152 is positioned within the body 134 and a
tapered seating segment 146 is positioned adjacent the channel 96
for interrupting the flow channel when fully seated and for
establishing an orifice with the valve seat when displaced from the
seat. A lever arm 130 is coupled to a segment of the element 152
which extends through a cap 142. The cap 142 is threaded internally
and engages an externally threaded outer segment of the body 134. A
biasing spring 150 is provided and establishes a force on the
element 152 which maintains the element in a normally seated
position for interrupting flow through the valve. Rotation of the
lever arm 130 in a clockwise direction will cause the element 152
to travel to the left as viewed in FIG. 4 against the compressive
force of the spring 150. The tapered face of the segment 146 will
thus unseat and establish a flow path through the valve. The
distance traveled by the valve element 152 toward the left will
establish the size of the flow orifice between the tapered segment
146 and its seat formed in the core body 82 at the inlet of channel
96. This distance is in turn established by the position of the cap
142 on the body 134. The cap 142 is rotable to different axial
positions along the length of the body 134 and an inner surface
thereof functions as a stop for the element. Thus by adjusting the
position of the cap 134, the amount of unseating of the valve
element 146 can be accurately controlled. After this position is
located, a locking nut 140 is rotated against the collar thereby
locking the collar in a fixed position. Thus by squeezing the lever
130 in a clockwise direction, the valve can be caused to unseat by
a predetermined amount corresponding to a refrigerant flow rate
which will establish a desired probe tip temperature. The medical
practitioner need only squeeze the lever 130 for unseating the
valve element and the need for repetitively unseating and seating
the valve is eliminated.
In accordance with another feature of this invention, a saturated
gas refrigerant is utilized and the effluent gas from the expansion
chamber 30 flows over a portion of the refrigerant inlet means. By
this technique, portions of the inflowing saturated refrigerant gas
condense within the tubular body 51 to supply a liquid phase which
is conveyed along with the vapor phase of the refrigerant into the
expansion chamber 30. The orifice diameter employed with the gas
herein is suitably larger than could be used with a wholly liquid
refrigerant. As a result, both the gas and liquid phases are
sprayed into the expansion chamber. This liquid phase refrigerant
remains within the expansion chamber for a short interval of time
during which time it absorbs latent heat of vaporization. Thus, a
double cooling action is provided. By pre-cooling the saturated
refrigerant gas which is flowing to the restrictive orifice, there
is provided both a vapor and liquid phase refrigerant. The vapor
phase expands through the orifice and in accordance with the
Joule-Thomson effect provides a refrigerating effect thereby
cooling the applicator head 14. In cooperation with this cooling
effect, the liquid phase which has been provided by pre-cooling is
sprayed into the expansion chamber 30 and absorbs a quantity of
heat over a period of time equivalent to its latent heat of
vaporization. It has been found that the combined cooling
established by this combination of Joule-Thomson effect and the
latent heat of vaporization rapidly lowers the temperature of the
probe 14 and provides very rapid cooling of the tip 24.
As indicated hereinbefore, a typical saturated gaseous refrigerant
for use with the described cryosurgical instrument comprises
saturated carbon dioxide gas. At ambient temperatures, the
saturated gaseous phase of this refrigerant is maintained at a
pressure generally on the order of 800 psi. If this pressure is
greatly exceeded as might occur due to a malfunction in the system,
a hazard to safety could then exist. In accordance with another
feature of this invention, the cryogenic instrument includes means
for automatically providing a flow path between the source 22 and
atmosphere at a predetermined pressure in excess of safe operating
pressures. Referring once again to FIG. 2, the shoulder 112 of the
valve element 100 includes a face 120 thereof which seats against a
shoulder surface of the bore 98. The valve face 114 has a diameter
which is less than the diameter of the bore 92 thereby defining an
annular space about the valve element within this bore. Pressure
within the instrument is continuously applied through the channel
94 to this annular space and this pressure will be exerted against
the face 120 on the shoulder of the valve element. When this
pressure becomes excessive, it exerts a force on the face 120 which
causes the valve element to move toward the left as viewed in FIG.
2 and unseat the valve face 114. A flow path is thereby
automatically established within the valve which relieves the
pressure within the instrument. The pressure at which the valve
element will automatically unseat is determined by the surface area
of the valve face 120 exposed to the pressure and the spring
constant of the spring 102. These factors can be selected to
provide a desired pressure release when the pressure within the
instrument exceeds a predetermined safe level. As a secondary
safety feature, the flexible inlet line 18, which is formed of
nylon for example, is selected to have a burst strength at a
predetermined value greater than the pressure at which the valve
element unseats automatically.
In one embodiment of the invention which is not deemed limiting in
any respect the following parameters were employed. A refrigerant
comprising saturated CO.sub.2 gas at 840 psi was applied to a
cryosurgical instrument of the type shown in FIG. 2 wherein the
tubular member 51 was formed of an 113/4 inches length of stainless
steel tubing having a 1/8 inch outside diameter and a 0.028 inch
wall thickness. The tubular body 13 was formed of a 9 inches length
of stainless steel having a 1/4 inch outside diameter and a 0.035
inch wall thickness. The body includes a 0.013 inch bore 66 forming
a restrictive orifice. The volume of the expansion chamber 30 was
selected to provide a 70 to 1 expansion in the volume of the gas
phase. Under these conditions, the probe tip 24 which was formed of
silver reduced from ambient temperature to -50.degree. C. in about
five seconds when the probe was suspended in air under ambient
conditions. Release of the lever 12 interrupted the flow of
refrigerant gas and resulted in a warming of the probe tip which
was effected for a safe removal of the probe tip from body
temperature within a period of about five seconds.
Thus an improved cryosurgical method and apparatus have been
described which enhance the practice of cryosurgery. The described
process and apparatus facilitate the handling and operation of a
cryosurgical instrument as well as provide enhanced cooling and
warming of the applicator tip.
While I have described a particular embodiment of my invention,
various modifications may be made thereto by practitioners in the
art without departing from the spirit of the invention and the
scope of the appended claims.
* * * * *