Abstract:
The present invention relates to a cryosurgical instrument, comprising a cryoprobe, having a line system through which a compressed cooling fluid flows, particularly a cooling gas, for cooling at least part of the cryoprobe, wherein the line system has an expansion channel having a line cross-section that is successively enlarged in the flow direction across a predetermined length such that the compressed cooling gas successively relaxes on the flow path thereof through the expansion channel beyond a predetermined length while simultaneously cooling off, at least partially.

Description:
FIELD OF THE INVENTION 
       [0001]    Embodiments disclosed herein relate to a cryosurgical instrument comprising a cryoprobe having ducting through which a compressed cooling fluid, such as a cooling gas, flows for cooling a least part of the cryoprobe. 
       BACKGROUND 
       [0002]    Targeted, controlled use of cold material is used in cryosurgery to devitalize biological tissue. In addition, particularly using flexible probes, foreign bodies are extracted from body cavities by freezing them solid on the cryoprobe or on a probe head; these foreign bodies include for example, swallowed and at the same time accidentally inhaled foreign bodies that must be removed from the respiratory tract. Cryosurgery is, however, also suitable for obtaining tissue samples (biopsy). In this case, a specific area of tissue, the tissue sample, freezes onto the probe head and after separation from the surrounding tissue can be made accessible for examination. 
         [0003]    There are various possibilities for deep freezing in surgery. One is based on the Joule-Thomson effect: the atoms or molecules of an expanding fluid and in particular of a gas below the inversion temperature work against mutual attraction with the result that the gas loses internal energy. It cools down. Usually CO 2  or N 2 O are used as the expanding fluid or gas—referred to below as cooling fluid or cooling gas. 
         [0004]    Cryosurgical instruments of the type just described usually have a probe that can be transported to the tissue to be treated and also gas line devices which penetrate the probes and release the working gas into the inner volume of the probes where it expands and results cooling down the probe. Since these probes are preferably made of thermally conductive material, this ensures elimination of the tissue heat via the probe and therefore a cooling effect. 
         [0005]    In cryoprobes where the cooling effect is generated by decompressing compressed gases, there is frequently a requirement for cooling a larger surface evenly or in accordance with a specific temperature profile. For example, a cryoprobe with a 2 mm diameter is supposed to be cooled evenly over a length of 50 mm. 
         [0006]    In such cases, according to the prior art, a plurality of nozzles are distributed inside the cryoprobe to achieve reasonably even cooling. The larger the number of cooling nozzles used, the more evenly the resulting temperature is reached over the length selected. With this procedure, the amount of gas required is divided between a plurality of nozzles. Consequently, the individual nozzles are very small in diameter. At the same time, however, production is disproportionately time-consuming. With small nozzles, close tolerances are placed on the geometry to achieve a constant flow behavior. On principle, smaller nozzle cross-sections are also more susceptible to blockages. 
         [0007]    It has also turned out that with cryosurgical instruments according to the prior art it is difficult to implement an essentially constant temperature curve or a predetermined temperature curve. Moreover, the construction of the prior art cryoprobes is very time-consuming and cost-intensive. 
       SUMMARY 
       [0008]    Consequently, the object of the embodiments disclosed herein is to develop a cryosurgical instrument of the type referred to above in such a manner that it is possible to achieve more even cooling of the cryoprobe that is technically easier to implement. 
         [0009]    In particular, this object is achieved by a cryosurgical instrument comprising a cryoprobe having ducting through which a compressed cooling fluid such as a cooling gas flows for cooling a least part of the cryoprobe. The ducting has an expansion channel having a channel cross-section that enlarges progressively in the flow direction over a predetermined length such that the compressed cooling gas gradually decompresses, at least partially, beyond a predetermined length on its flow path through the expansion channel while simultaneously cooling down. 
         [0010]    An aspect of the embodiments is to design a channel running over a predetermined length such that its cross-section over this length increases in such a way that expansion of the gas is distributed over this length. As a result, at the beginning of the channel there is only partial expansion and therefore not a full temperature difference. However, due to progressive expansion over the entire length, cooling occurs over a large area wherein the temperature achieved on the outside of the probe or the distribution thereof depends, among other things, on the widening of the cross-section in each case and the heat transfer resistance between the expansion channel and the outside of the cryoprobe. 
         [0011]    Preferably, in this case, the expansion channel is in a thermally conductive relationship with the outside of the cryoprobe via a heat conductor. Either independent components with a reduced heat transfer resistance or appropriate auxiliary means, such as thermal compounds, etc. may be used as heat conductors. It should be appreciated that beyond this, it is also possible to design a housing component of the cryoprobe as a heat conductor and to construct it of a material that guarantees optimum heat transfer. The expansion channel is preferably disposed as close as possible to the outside of the cryoprobe or close to the areas that are supposed to be cooled. 
         [0012]    In at least one embodiment, the expansion channel has a channel cross-section designed as a function of a heat transfer resistance of the heat conductor such that on the outside of the cryoprobe a predetermined temperature distribution, and in particular a constant temperature, adjusts itself at least over a section defined by the predetermined length discusses above. This means that, for example, in very thick wall sections between the expansion channel and the outside or the region to be cooled, the expansion channel is correspondingly designed to be significantly widened to achieve particularly effective expansion and cooling at this point. It should be appreciated that it is also possible to make appropriate adaptations to the expansion channel in regions on the outside of the cryoprobe where extreme cooling is desired. With a specific adaptation of the expansion channel&#39;s cross-section, it is thus possible to achieve an even or any other desirable temperature distribution on the outside of the cryoprobe, considering, for example, the existing wall thicknesses to the outside, the flow velocity, etc. 
         [0013]    The expansion channel is preferably formed such that the cooling gas flows in a turbulent flow. Of course, significant here, among other things, are the flow resistance in the expansion channel, the expansion channel cross-section and also the cooling fluid pressure, which is provided by an external cooling fluid supply. The advantage of the turbulent flow in the expansion channel is that it results in very effective heat dissipation and improved cooling of the outside of the cryoprobe. 
         [0014]    Preferably, for the formation of the expansion channel, at least one modeling component that in particular tapers/widens in the flow direction is disposed in at least one section of the line system such that the resulting channel cross-section progressively enlarges in the flow direction. If the ducting is a channel limited by side walls, then the modeling component may be disposed on at least one of these side walls as a component such as e.g., a wedge-shaped component tapering in the flow direction, resulting in just such a widening expansion channel through which the cooling fluid can flow with simultaneous progressive decompression and cooling. In place of the tapering, i.e., the wedge-shaped component, it is also possible to use a modeling component in the form of a hollow body such as for example, a component with an essentially central hole, the wall of said hole widening progressively in the flow direction which likewise leads to a widening expansion channel. 
         [0015]    Preferably, the expansion channel is formed by a tube and a modeling component that is inserted into the tube as a frusto-conical or similarly rotationally symmetrical, tapering component. Depending on the desired temperature distribution on the outside of the cryoprobe, it is also possible to change the shape of the modeling component and thus have a direct influence on the cooling effect. In this context, it is also possible to insert into the tube a modeling component in the form of a hollow body, the hollow body walls are designed to progressively widen in the flow direction such that the result is also a widening expansion channel. This corresponds substantially to the geometry referred to above of the widening hollow body component disposed in the channel and in particular a rotationally symmetrical hollow body as a modeling component. 
         [0016]    The tube forms, at least in part, a cryoprobe housing wherein the tube preferably consists of a material that has good thermal conductivity. Such an embodiment of the cryoprobe enables very easy and cost-effective production of the cryoprobe in accordance with the configurations referred to above. 
         [0017]    It should be appreciated that it is possible to use other modeling components or modeling component assemblies instead of the tapering or widening modeling components referred to above to create a cross-section of the ducting that enlarges progressively in the flow direction and thus an expansion channel for cooling the outside of the cryoprobe. 
         [0018]    In an embodiment, the tube preferably has an internal thread and the modeling component has a complementary external thread on a tapering wall with which it can be screwed into the tube forming an expansion channel in the resulting thread pitch that enlarges progressively in the flow direction. Because the expansion channel runs substantially in the form of a helix around the modeling component, the expansion path enlarges and thus the maximum cooling capacity to be achieved increases. Moreover; such an embodiment enables much more comprehensive cooling of the cryoprobe. It should also be appreciated that with an appropriate choice of different thread types it is also possible to influence the resulting outer temperature and its distribution. 
         [0019]    In an embodiment, the tube has an internal thread and the modeling component has a complementary external thread with which it can be screwed into the tube forming the expansion channel in the resulting thread pitch, wherein the external thread is formed as a conical or similar thread running in the flow direction and/or the internal thread is formed as a conical or similar thread running in the opposite direction. A conical thread here is understood to be a thread or threads where the thread pitch depth increases progressively similar to the external geometry of a cone. On screwing into a complementary external or internal thread this produces an expansion channel with a cross-section that expands in the flow direction. 
         [0020]    It should be appreciated that it is also possible to form comparable channels, grooves, etc. in the tube or modeling component in place of any type of thread described above to create a corresponding expansion channel. In this case, all methods known in the art may be used for the creation of flow channels. 
         [0021]    The expansion channel is preferably formed between an outer tube and an inner tube running therein. The result of this is that the warmer cooling fluid can be fed in through the inner tube to expand in the expansion channel located further to the outside and to cool the outside of the outer tube effectively. In connection with this, the outer tube may be used as a cryoprobe housing or may be joined to such a housing by way of an appropriate heat conductor. 
         [0022]    All of the embodiments discussed above may be used to form the progressively widening expansion channel in the double-walled tube, whereby the modeling component is then insertable in the outer channel or integrated therein. It is also possible to use a hollow body component as the modeling component whereby its hollow body region functions as a centrally disposed intake. 
         [0023]    The cryoprobe preferably comprises a cryoprobe tip that is disposed at one tube end of the double-walled tube and that brings the inner tube into fluid communication with the expansion channel forming a deflecting channel. In this way, the inner tube and the outer tube or the external channel formed in the outer tube may be used to feed in and discharge the cooling fluid, i.e., the cooling gas. The resulting geometric outer shape of such a tube corresponds to a cannula and thus to a shape that is very user-friendly for cryosurgery. 
         [0024]    The cryoprobe tip is preferably disposed on the tube end and is capable of being screwed on and off by way of a threaded device such that the cross-section of the deflecting channel is variable and is adaptable to an inlet region of the expansion channel. One advantage is that by adapting the deflecting channel it is also possible to influence a possible expansion of the cooling fluid gas in the cryoprobe&#39;s tip region. 
         [0025]    Preferably disposed around the inner tube of a double-walled tube and running helically with increasing pitch in the flow direction, is a modeling component, such as a wire, which is in fluid-tight connection with the walls of both tubes respectively such that a helical expansion channel, increasing progressively in cross-section, is formed between adjacent turns and the walls. It is also possible to influence the geometry and the cross-section of the expansion channel by the choice of the circumferential modeling component used. Thus, it is possible for example, to produce a progressively widening expansion channel by using a progressively tapering modeling component that is applied to the inner tube with an even helical pitch. 
         [0026]    Basically, the modeling component has good thermal conductivity, particularly in the region facing outwards, to ensure effective cooling of the outside or the regions of the cryoprobe to be cooled. To achieve effective cooling of the outside, it is also possible to arrange appropriate insulating layers in the region facing inwards; that is, for example, the region adjoining the intake with the “warm” cooling fluid prior to its decompression. This can be achieved by the use of appropriate intermediate insulating layers or by an appropriate choice of material for the modeling component or for the inner tube, etc. 
         [0027]    Basically, it is possible to wind the helical modeling component onto the inner tube, or to introduce it in the shape of an independent helix into the intermediate space between inner tube and outer tube and in particular to screw it in. 
         [0028]    In an embodiment, the modeling component is formed integrally on the inner tube and/or on the outer tube and in particular by means of a helical groove in the relevant walls of the tube wherein the pitch of the helical groove and/or its width increases in the flow direction. Thus, an expansion channel, which runs helically around the inner tube and is widened in cross-section in such a manner that there is progressive decompression of the gas and thus cooling over the entire length of the expansion channel, can also be created in this way. It is also possible to create comparatively colder and less cold regions, if this is necessary, by appropriately altering the cross-section over the length of the expansion channel. It is also possible to create the modeling components formed integrally on the inner tube and/or on the outer tube by means of cutouts of the adjacent areas, which then fit precisely on the complementary tube wall. It is also possible to arrange corresponding guide grooves or devices on one or both tubes, which enable the insertion of a helical modeling component. It is also possible to provide a plurality of different grooves in order, for example, to insert different modeling components or to achieve different pitches, cross-section changes, etc. 
         [0029]    In connection with modeling components that are insertable in the ducting and in the outer channel of a double-walled tube, it is also conceivable to design the modeling component flexibly such that the expansion channel can be modified as required. Thus, for example, by inserting a resilient helix that fits accurately over the inner tube and has a thread rising in the flow direction, the thread also being present in a perfect fit on the wall of the outer tube, it is possible to influence the change in the expansion channel&#39;s cross-section by moving or turning the helix in the axial direction of the tube. 
         [0030]    It should be appreciated that an adaptation may also be carried out using multi-part modeling components that permit a change in the expansion channel&#39;s cross-section over its length. 
         [0031]    This adaptation is preferably possible by way of a handle on the cryoprobe device or via an external control device so that the cryoprobe&#39;s temperature can also be controlled during the operation. In this case, all methods for the control of a surgical instrument known in the art may be used. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    Embodiments of the invention will be described in greater detail with reference to the associated drawings, in which: 
           [0033]      FIG. 1  illustrates a schematic diagram of a cryosurgical device according to an embodiment disclosed herein; 
           [0034]      FIG. 2  illustrates a first embodiment of a cryoprobe of the cryosurgical device in  FIG. 1 ; 
           [0035]      FIG. 3  is a second embodiment of a cryoprobe of the cryosurgical device in  FIG. 1 ; 
           [0036]      FIG. 4  illustrates a third embodiment of a cryoprobe of the cryosurgical device in  FIG. 1 ; 
           [0037]      FIG. 5  illustrates a fourth embodiment of a cryoprobe of the cryosurgical device in  FIG. 1 ; 
           [0038]      FIG. 6  illustrates a fifth embodiment of a cryoprobe of the cryosurgical device in  FIG. 1 ; 
           [0039]      FIG. 7  illustrates a sixth embodiment of a cryoprobe of the cryosurgical device in  FIG. 1 ; 
           [0040]      FIG. 8  illustrates a seventh embodiment of a cryoprobe of the cryosurgical device in  FIG. 1 ; 
           [0041]      FIG. 9  illustrates an eighth embodiment of a cryoprobe of the cryosurgical device in  FIG. 1 ; and 
           [0042]      FIG. 10  illustrates a further embodiment of a cryoprobe disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0043]    Throughout the description, the same reference numerals are to refer to identical parts and parts acting in an identical manner. 
         [0044]      FIG. 1  shows an isometric drawing of an embodiment of a cryosurgical instrument  1  disclosed herein. Instrument  1  comprises a cryoprobe holder  46  and a cryoprobe  2  insertable therein, which is coolable according to the embodiments disclosed herein by ducting, the design of which is described in greater detail below, in such a manner that it can be used to perform cryosurgical operations. 
         [0045]    The cryosurgical instrument  1  is equipped with gas supply line fittings  44 , which enable connection to a gas reservoir (not illustrated) or a similar gas supply. 
         [0046]      FIG. 2  shows a schematic diagram of a first embodiment of cryoprobe  2 . The embodiment is designed substantially with a cryoprobe surface that has substantially two-dimensional, meandering ducting  8  through which a cooling gas flows in a flow direction R S . 
         [0047]    In this embodiment, ducting  8  is designed such that it has a cross-section that widens over the flow path along flow direction R S , forming an expansion channel  12 . Consequently, the cooling gas flowing through intake  3  decompresses progressively on its way through expansion channel  12  to a discharge  5  and thus cools down according to the Joule-Thomson effect. Thus, an outside  7  of cryoprobe  2  can effectively be cooled by the correspondingly thermally conductive design of channel walls  9  of ducting  8 . 
         [0048]      FIGS. 3-9  illustrate further embodiments of cryoprobe  2  according to the embodiments described herein wherein the probes are basically formed from a double-walled tube comprising an inner tube  19  and an outer tube  21 . In this case, inner tube  19  acts as intake  3  through which the cooling fluid can be routed through the cryoprobe  2 . Disposed on free end  36  is a cryoprobe tip  34 , which forms a deflecting channel  38  thus establishing a connection between inner channel  26  of inner tube  19  and outer channel  30 , said channel being formed by inner tube  19  and outer tube  21 . 
         [0049]    Disposed in this outer channel  30  is a modeling component  16 , which tapers in flow direction R S  such that an expansion channel  12  that tapers progressively over a length  1  is formed. Cooling fluid, which flows via intake  3  through channel  26  and then into expansion channel  12  (via deflecting channel  38 ), expands therein progressively over length  1  such that it cools down and cooling occurs on outside  7  of cooling probe  2  by way of the thermally conductive outer wall  32  of outer channel  30 . 
         [0050]    Since the illustrated cryoprobe  2  is formed to be rotationally symmetrical from a double-walled tube with a constantly thick outer wall  32  and from a correspondingly rotationally symmetrical, tapering hollow body as modeling component  16 , there is also even cooling over the circumference of cryoprobe  2 . It is also possible to achieve uneven cooling over the circumference of cryoprobe  2  by an appropriately modified version of modeling component  16  or the position of inner tube  19  in relation to outer tube  21 . 
         [0051]      FIG. 4  illustrates a third embodiment of cryoprobe  2 , again comprising an inner tube  19  and an outer tube  21 , of which channels  26  and  30 , respectively, are in fluid communication with each other by a cryoprobe tip  34  and a deflecting channel  38  resulting therefrom. In this embodiment, a modeling component  16  is also inserted in outer channel  30  to form an expansion channel  12 . Here, modeling component  16  is designed as a rotationally symmetrical hollow cylinder with progressively widening inner walls. In order to fix hollow cylinder  16  in its position within outer tube  21 , the tube has insertion grooves  29  that enable custom-fit insertion. 
         [0052]      FIG. 5  illustrates a fourth embodiment of cryoprobe tip  2 , which also comprises a double-walled tube  19 ,  21  in the outer channel  30  of which a modeling component  16  is inserted to form expansion channel  12 . 
         [0053]    Unlike the embodiments described above, the illustrated modeling component  16  comprises an external thread  22  on a tapering wall  23 . The thread is capable of being screwed into an internal thread  20  formed on inner wall  28  of outer tube  21 . 
         [0054]    Due to the design of external thread  22  on inclined or tapering wall  23 , when this component is screwed into internal thread  20  on outer tube  21  a progressively widening thread pitch  24  is produced, which acts as expansion channel  12 . This channel is in fluid communication at an inlet region  40  with a deflecting channel  38  being formed by a cryoprobe tip  34  such that cooling fluid, expanding in flow direction R S , can flow via inner tube  19  through expansion channel  12  extending circumferentially in the form of a helix to cool down outside  7  of cryoprobe  2 . 
         [0055]    It is also possible to additionally influence the cooling effect on outside  7  with an appropriate choice of thread pitch and the depth of relevant thread pitch  24 . 
         [0056]      FIG. 6  illustrates a fifth embodiment of cryoprobe  2 . Unlike previous embodiments, modeling component  16  is designed as a widening hollow cylinder having an internal thread  20  that is complementary to an external thread  22  of inner tube  18  in such a manner that modeling component  16  can be screwed onto tube  19  forming a circumferential expansion channel  12  in the form of a helix in thread pitch  24  of the two complementary threads  20 ,  22 . 
         [0057]    Moreover, in this embodiment, cryoprobe  2  comprises a cryoprobe tip  34  that can be screwed via a threaded region  35  onto a free end  36  of double-walled tube  19 ,  21  in such a manner that the size of deflecting channel  38  formed by cryoprobe tip  34  is adaptable by screwing cryoprobe tip  34  in or out. 
         [0058]      FIG. 7  shows a sixth embodiment of cryoprobe  2 , which also comprises a double-walled tube  19 ,  21 , wherein inner tube  19  acts as intake  3  and outer tube  21  or outer channel  30  formed between inner tube  19  and outer tube  21  acts as return  5 . 
         [0059]    A modeling component  16  that has an external thread  22  is inserted in outer channel  30  to form an expansion channel  12 . Tube  21  has a complementary internal thread  20  for this purpose, said thread being designed as a conical thread running contrary to flow direction R S . This means that the cross-section of thread pitch  24  and expansion channel  12  enlarges progressively in the flow direction due to this conical thread running contrary to the flow direction and thus, as in the embodiments described above, widens progressively. It should be appreciated that it would also be possible to design an increasing thread pitch instead of the even thread pitch or to taper modeling component  16  correspondingly to achieve e.g., cooling of outside  7  that becomes more intense towards free end  36  of cryoprobe  2 . 
         [0060]    Alternatively, or in addition to, it is also possible to arrange a conical thread  22  running in the flow direction in modeling component  16  instead of thread  20 , running contrary to flow direction R S , in outer tube  21 . 
         [0061]      FIG. 8  shows a seventh embodiment of cryoprobe  2 , in which a modeling component  16 , in this case a wire, running around inner tube  19  in the form of a helix is wound between an inner tube  19  acting as intake  3  and an outer tube  21  on both walls  28 ,  32  of tubes  19 ,  21  such that between individual turns  42 ,  42 ′ and respective walls  28 ,  32  an expansion channel  12  is formed that also runs around inner tube  19  in the form of a helix that widens progressively. A cooling fluid entering in direction of flow R S  via inner tube  19  or intake  3  flows back via a circulation channel  38  into this helical expansion channel  12  where it gradually expands and cools down due to the progressively enlarging cross-section. Modeling component  16  or the wire may in this case be both an independent component wound onto inner tube  19  and may also be a component integral therewith and/or with outer tube  21 . In addition, it is also possible to guide modeling component  16  in corresponding grooves or similar guidance devices (not illustrated) to make positioning it easier. 
         [0062]      FIG. 9  shows an eighth embodiment of cryoprobe  2 , which functions according to the same principle as the embodiment of  FIG. 8 . Instead of modeling component  16  being executed as a wire, in the illustrated embodiment, an appropriate groove  43  is disposed on outer wall  32  of outer tube  21  in such a manner that resulting protrusion  45  presses fluid-tight on inner tube  19 . As groove  43  is applied to outer tube  21  helically and with increasing pitch, a circumferential, progressively widening expansion channel  12  arises between the individual turns of groove  43  or protrusion  45 , which channel the gas flows along and decompresses as it gradually cools down. 
         [0063]      FIG. 10  shows a similar embodiment in which grooves  43  or protrusions  45  are disposed on inner tube  19  such that protrusions  45  are in fluid-tight contact with outer tube  21  or its wall  32  while forming a corresponding expansion channel  12 . 
         [0064]    It should be noted that in addition to the embodiments of the modeling component illustrated herein, all modeling components that enable the formation of an expansion channel that enlarges progressively in cross-section may be used. It is also conceivable to execute the tube or outer tube  21  as a conically widening tube, etc. 
         [0065]    In connection with circumferential thread pitches for forming the expansion channel, it is also possible to use double and multiple helixes or similarly several in particular concentrically winding pitches or channels, etc.