Abstract:
A cryosurgical instrument for obtaining a tissue sample with a probe, including the probe including a probe head onto which the tissue sample is frozen and a probe shank for guiding the probe head to the tissue sample, a supply means for supplying a fluid into an expansion chamber configured such that supplied fluid expands therein for cooling the probe head, and a removal means connected to the expansion chamber for removing the expanded fluid therefrom via at least one opening on a distal end of the probe to remove the expanded fluid to an outer region outside the probe. A method for cooling a probe head of a cryosurgical probe including supplying a fluid to an expansion chamber near the probe head, expanding the fluid so that heat energy is withdrawn from the probe head, and removing the expanded fluid in a distal region of the probe.

Description:
FIELD OF THE DISCLOSED EMBODIMENTS 
       [0001]    The disclosed embodiments relate to a cryosurgical instrument for obtaining a tissue sample and to a method for cooling a probe head of a cryosurgical probe. 
       BACKGROUND 
       [0002]    In cryosurgery, the taking of tissue samples (biopsy) is facilitated, inter alia, by the targeted use of cold. In this case, a cryoprobe is brought close to a specific tissue region via an endoscope. While the probe head contacts the tissue to be removed, the probe head is cooled in such a way that at least certain portions of the tissue freeze solid on the probe head. After the surrounding tissue has been severed, the sample (biopsate) can be retracted into the endoscope and made accessible for tests. 
         [0003]    The cooling power can be provided, for example, by way of targeted use of the Joule-Thomson effect. In this case, a fluid, in particular a gas, experiences a change in temperature as a result of restriction (change in pressure). In cryosurgery, gas is expanded under high pressure into an expansion chamber in such a way that the volume thereof increases in size. In this case, the average particle spacing of the fluid increases, causing its temperature to fall. 
         [0004]    A corresponding cryoprobe is known from U.S. Pat. No. 7,156,840 B2. Cryoprobes of this type may also be used in thin hollow organs, such as for example bile or pancreatic ducts, in order to carry out histology of the tissue. 
         [0005]    An important criterion for the biopsy is the quality of the sample taken. Removal of the sample should not lead to any mechanical deformation of the sample. 
         [0006]    Flexible micro-endoscopes are used to work in the bile and pancreatic duct under endoscopic view. The outer diameter of this flexible micro-endoscope is very small, for example ≦3 mm. Only instruments having a much smaller outer diameter can be introduced into the working channel of endoscopes of this type. Frequently, the outer diameter of the instruments used here may not exceed one millimeter. 
         [0007]    Furthermore, in this field of use, the distances between the inlet opening of the endoscope and the working region are very long. The working channel of the endoscope is also correspondingly long. The instrument introduced into the endoscope, for example the cryosurgical instrument with the cryoprobe, must therefore have corresponding dimensions. For example, a length of 180 cm may be required. 
         [0008]    A further requirement for the use of a cryoprobe in the above-described specialist field is the provision of sufficient cooling power, so that the biopsate can be fixed sufficiently securely to the tip of the probe. The cooling power is decisively determined by the pressure differential in the expansion chamber. That is to say, the higher the differential is between the pressure of the gas prior to issuing via a nozzle opening and the pressure within the expansion chamber, the higher the cooling power is too. The smaller the corresponding gas feed line is, the more difficult it is to provide a sufficiently high pressure before the nozzle opening. Furthermore, the outflowing gas must be removed from the expansion chamber in order to maintain the pressure gradient. Gas returns having a sufficiently large diameter are conventionally provided for this purpose. However, with the smaller diameter of the return lines, the flow resistance, and thus the pressure within the expansion chamber, rises. 
         [0009]    For these reasons, it has proven extremely difficult to provide cryoprobes which have the required dimensions and at the same time provide sufficient cooling power. Conventional biopsy methods are therefore frequently used. Such methods include, for example, the obtaining of samples by means of a brush, or needle biopsy. 
         [0010]    However, the quality of the samples thereby obtained is conventionally much lower than that obtainable by a cryobiopsy. 
       SUMMARY 
       [0011]    The disclosed embodiments provide an improved cryosurgical instrument. In particular, disclosed embodiments include a cryosurgical instrument for obtaining a tissue sample that is suitable for use in thin hollow organs. Furthermore, disclosed embodiments also include a corresponding method for cooling a probe head of a cryosurgical probe. 
         [0012]    In the cryosurgical instrument for obtaining a tissue sample with a probe of the disclosed embodiments, the probe includes a probe head for freezing-on tissue, a probe shank for guiding the probe head up to the tissue, a supply means for supplying a fluid, in particular a gas, into an expansion chamber, and a removal means which is connected to the expansion chamber for removing the fluid, the expansion chamber being embodied in such a way that the supplied fluid expands for cooling the probe head. 
         [0013]    The cryosurgical instrument according to the disclosed embodiment is distinguished from those previously known in that the removal means includes on the distal region of the probe at least one opening which removes the fluid into an outer region outside the probe. 
         [0014]    In other words, the fluid is returned only partially (or not at all) within the probe. The gas supplied via the supply means spreads out in the expansion chamber and is removed from there into an outer region outside the probe. Thus, the provision of a return line within the probe may be partly or wholly dispensed with. The supply means can be made accordingly larger in order to provide sufficient pressure in the expansion chamber. Frequently, the issuing amounts of fluid are so small that they do not cause any damage within the organs. Nor does the fluid used present any risk to the patient. If the fluid is nevertheless to be removed, a separate mechanism may be provided for this purpose. The working channel of the endoscope used may be used, for example, for removing the fluid. 
         [0015]    In the probe according to the disclosed embodiments, the probe body defines an outer region and an inner region. Obviously, the fluid is removed out of the inner region into the outer region in conventional probes too. However, the corresponding means are located not on the distal region of the probe, but in the proximal region thereof. 
         [0016]    The cryosurgical instrument can include at least one opening at the distal end of the probe shank and/or in the probe head. That is to say, the distal region is defined in such a way as to include the probe head and the distal end of the probe shank. 
         [0017]    The cryosurgical instrument can include an adapter for removing the fluid in the proximal direction. An adapter of this type can for example introduce the fluid issuing from the probe into the working channel of an endoscope. Furthermore, the adapter can be configured so as to provide a removal means for the fluid. This removal means guides, like conventional cryosurgical instruments, the fluid to the proximal end of the probe. 
         [0018]    The adapter can include a protective tube with a seal, the probe being movably mounted in the protective tube and the seal sealing from the probe an interior or inner region of the protective tube for receiving the fluid. The fluid is therefore introduced via the supply means into the expansion chamber, passes from there into the outer region of the probe via at least one opening, the probe being surrounded by the protective tube in such a way that an intermediate space is produced between the probe and protective tube. The fluid can be guided into this intermediate space in the proximal direction. The seal at the distal end of the protective tube ensures that the fluid cannot escape in the distal direction. 
         [0019]    The protective tube can include a region for receiving the tissue sample. According to the disclosed embodiments, the tissue sample, which is fastened to the probe head, can therefore be retracted in such a way that it comes to lie within the protective tube. This allows the tissue sample to be protected from external influences, in particular mechanical loads. 
         [0020]    Generally, the protective tube can serve to convert the probe according to the disclosed embodiments so as to allow it to be used also in regions in which it is undesirable for fluid to issue close to the region of the operation. 
         [0021]    As previously described, the adapter can be adapted for introducing the fluid into a working channel of an endoscope. 
         [0022]    The at least one opening on the distal region of the probe can be arranged laterally of the probe shank or form the probe head in the form of a particle filter. The particle filter can for example have openings having a diameter of approx. 4 μm. 
         [0023]    Disclosed embodiments also include a method for cooling a probe head on the cryosurgical probe. The method includes the steps of supplying a fluid, in particular a gas, expanding the fluid in such a way that heat energy is withdrawn from the probe head, and removing the expanded fluid. The step of removing the expanded fluid includes diverting the fluid from the interior of the probe in the distal region of the probe. 
         [0024]    In this case too, a basic idea of the disclosed embodiments is that, in the cooling method, the fluid is removed in the distal region and, as a result, separate returning of the fluid is not necessary. In the method, the fluid can be supplied over a period of time which is ≦5 seconds. As a result, only very small amounts of gas are released that enter the outer region of the probe. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The disclosed embodiments will be described in greater detail, pointing out further features and advantages, by reference to the example embodiments illustrated in the drawings. 
           [0026]      FIG. 1  is a schematic view of a cryosurgical instrument. 
           [0027]      FIG. 2  is a schematic view of the cryosurgical instrument from  FIG. 1  within an endoscope in clinical use. 
           [0028]      FIG. 3  is a schematic view of the distal end of a rigid cryoprobe according to the prior art. 
           [0029]      FIG. 4  is a schematic view of the distal end of a flexible cryoprobe according to the prior art. 
           [0030]      FIG. 5  is a schematic view of the distal end of a cryoprobe according to one disclosed embodiment. 
           [0031]      FIG. 6  is a schematic view of the distal end of a flexible cryoprobe according to the prior art. 
           [0032]      FIG. 7  is a schematic view of the distal end of a cryoprobe according to another disclosed embodiment. 
           [0033]      FIG. 8  is a schematic view of the distal end of a cryoprobe according to another disclosed embodiment, with a protective tube. 
           [0034]      FIG. 9  shows a cryoprobe according to disclosed embodiments in the working channel of a flexible endoscope. 
           [0035]      FIG. 10  shows a cryoprobe according to disclosed embodiments with a protective tube and biopsate. 
           [0036]      FIG. 11  shows the cryoprobe of  FIG. 10  with the biopsate retracted. 
           [0037]      FIG. 12  is a schematic view of the distal end of another disclosed embodiment of a cryoprobe. 
       
    
    
     DETAILED DESCRIPTION 
       [0038]    The same reference numerals will be used in the following description for identical and equivalent parts. 
         [0039]      FIG. 1  shows schematically the construction of a cryosurgical instrument  1 . The cryosurgical instrument includes a handle  60  for guiding the cryoprobe  10 , the cryoprobe  10  being composed of a shank  13  and a probe head  15 . The probe head  15  forms the distal end  11  of the cryoprobe  10 . The proximal end  12  of the cryoprobe  10  directly adjoins the handle  60 . A connection  70 , which can be used to connect the cryosurgical instrument  1  to a compressed air source, is located at the proximal end of the handle  60 . The compressed air source supplies the cryosurgical instrument  1  with compressed air. 
         [0040]      FIG. 2  shows the cryoprobe  10  from  FIG. 1  in clinical use. The shank  13  of the cryoprobe  10  is located within the working channel of an endoscope  80 , the endoscope  80  being introduced into a hollow organ, for example a portion of the gut. The shank  13  and also the probe head  15  protrude beyond the distal end of the endoscope  80  and contact a region of the tissue  3  of the gut. The probe head  15  can be cooled by means of the Joule-Thomson effect in such a way that the region freezes solid on the probe head  15 . A tissue sample  5  may be separated out from the tissue  3  by way of a mechanical pull. 
         [0041]      FIGS. 3 and 4  are cross-sections of the distal end  11  of a cryoprobe  10 , according to the prior art. A distinction is conventionally drawn between rigid cryoprobes  10  ( FIG. 3 ) and flexible cryoprobes  10  ( FIG. 4 ). The cryoprobes according to  FIGS. 3 and 4  each include a probe head  15  which forms the distal end  11  of the cryoprobe  10 . This probe head  15  is fastened to the probe shank  13 . The probe head  15  and probe shank  13  surround a region which will be referred to hereinafter as the inner region of the probe  10 . A gas supply means  20 , which comprises a gas supply line  21  and a distal end  22  of the gas supply line  21 , is located in this inner region. Gas is brought under high pressure into an expansion chamber  50  in the interior of the probe head  15  via the gas supply line. The gas issues into this expansion chamber  50  via an outlet opening and withdraws heat energy from the probe head  15  owing to the Joule-Thomson effect. The unfilled interior of the cryoprobe  10  forms a gas return means  40 . That is to say, the issuing gas is removed in the interior of the probe  10  in the proximal direction, i.e. in the direction of the connection  70 . 
         [0042]      FIG. 5  shows the distal end  11  of a first example embodiment of the cryoprobe  10 . This cryoprobe  10  is also composed of a shank  13  and a probe head  15  which are adhesively bonded to each other. The shank  13  and probe head  15  form an outer sheath of the cryoprobe  10 . The gas supply line  21 , which allows gas to flow under high pressure into the expansion chamber  50  via a nozzle opening  24  at the distal end  22  of the gas supply line  21 , is located within the cryoprobe  10 . The gas return means  40  includes openings  41  to  41 ″ produced by perforation of the outer sheath of the cryoprobe  10 . The expanded gas can escape via these openings  41  to  41 ″ from the inner region of the cryoprobe  10 , in particular from the expansion chamber  50 , into the outer region of the cryoprobe  10 . The openings  41  to  41 ″ are located close to the distal end  11  of the cryoprobe  10 . 
         [0043]      FIG. 6  shows a further cryoprobe  10 , according to the prior art. The gas supply line  21 , which is closed at its distal end  22  and forms a part of the probe head  15 , extends along the longitudinal axis, in the inner region of the cryoprobe  10 . A lateral nozzle opening  24 , via which the gas flows into the interior of the cryoprobe  10 , is located close to the distal end  22  of the gas supply line  21 . The intermediate space between the gas supply line  21  and shank  13  of the cryoprobe  10  forms the gas return means  40 . 
         [0044]      FIG. 7  shows a second example embodiment of the cryoprobe  10 . In its general construction, the cryoprobe  10  according to  FIG. 7  is similar to that of  FIG. 6 . However, apart from a short portion close to the distal end  22  of the gas supply line  21 , the gas supply line  21  takes up the entire inner region of the shank  13  of the cryoprobe  10 . Close to the distal end  22 , the gas supply line  21  tapers in such a way as to produce an intermediate space between the gas supply line  21  and shank  13  or probe head  15 . This intermediate space serves as an expansion chamber  50  into which gas from the gas supply line  21  flows via the lateral nozzle opening  24 . Furthermore, this intermediate space forms a part of the gas return means  40  which removes the expanded gas into the outer region of the probe via openings  41  to  41 ′″. Thus, a gas return means  40  in the proximal region of the shank  13  may be dispensed with. 
         [0045]      FIG. 8  shows a third example embodiment of the cryoprobe  10 . The construction of this cryoprobe  10  corresponds substantially to that of the cryoprobe  10  shown in  FIG. 5 . The gas return means  40  is formed partly by the interior of the cryoprobe  10  and also by the openings  41  to  41 ′″. The cryoprobe  10  is located within a protective tube  90  which can be used to remove the gas in a targeted manner in the proximal direction. A ring seal  91 , which rests against the shank  13  of the cryoprobe  10  and distally seals the inner region of the protective tube  90  from the outer region, is located at the distal end of the protective tube  90 . The protective tube  90  and the ring seal  91  are embodied so as to allow the cryoprobe  10  to be moved within the protective tube  90  in the distal and proximal directions. Depending on the position of the cryoprobe  10  within the protective tube  90  and depending on the position of the openings  41  to  41 ′″, the expanded gas is removed in its entirety or only in part via the inner region of the protective tube  90 . In the position according to  FIG. 8 , the gas escapes directly into the organ via the openings  41 ,  41 ″, while the gas escaping through the openings  41 ′ and  41 ′″ penetrates the inner region of the protective tube  90  and is removed there in the proximal direction. 
         [0046]    The probes according to the disclosed embodiments are able to have a much thinner diameter than those of the prior art, since all or a large percentage of the interior of the cryoprobes  10  can be filled by the gas supply line  21 . As a result of the use of the protective tube  90 , it is possible to use the probes according to the disclosed embodiments also in applications in which it is not desirable for the gas to escape directly into an organ or tissue. 
         [0047]    However, there are numerous fields of application in which it is harmless for small amounts of gas to escape. For example,  FIG. 9  shows a cryoprobe  10  according to an example embodiment in the working channel of an endoscope  80  which is introduced into an intestinal tract. The gas necessary for freezing a tissue sample  5  solid escapes in this case directly into the intestinal tract via the opening  41 . As a result, the patient is not placed in any danger. 
         [0048]      FIGS. 10 and 11  show a development of the protective tube  90  from  FIG. 8 . As previously, the protective tube  90  with the ring seal  91  still serves at least partly to remove the gas issuing via the openings  41  to  41 ′″. However, the protective tube  90  of  FIGS. 10 and 11  additionally includes a sample chamber  93  at the distal end of the protective tube  90 . 
         [0049]    The sample chamber  93  serves to receive a tissue sample  5 . The cryoprobe  10  may be withdrawn into the interior of the protective tube  90  in such a way that the tissue sample  5  also comes to lie within the protective tube  90 , namely in the sample chamber  93 . This prevents the sample  5  from becoming stripped off when the cryoprobe  10  is extracted from the working channel of the endoscope  80 . 
         [0050]    In the example embodiments of  FIGS. 10 and 11 , the sample chamber  93  is formed as a result of the fact that the ring seal  91  is not located directly at the distal end of the protective tube  90 , but is slightly offset in the proximal direction. As a result, a portion of the inner region of the protective tube  90  is open in the distal direction for receiving the tissue sample  5 .  FIG. 12  shows a further example embodiment of the cryoprobe  10 . The openings  41  to  41 ′″ are located directly at the distal end  11  of the cryoprobe  10 . They are formed by a particle filter having a small hole diameter on the probe head  15 . The openings  41  to  41 ′″ coincide with the region which receives the tissue sample  5 . The entire interior of the cryoprobe  10  is used as the gas supply means  20 . The exterior immediately before the probe head  15  serves in this example embodiment as the expansion chamber  50 . The openings  41  to  41 ′″ thus have a double function. They are on the one hand the nozzle for the expansion of the gas and on the other hand part of the gas return means  40 . 
         [0051]    It should be noted at this point that all the aforementioned parts are claimed as essential to the invention both alone and in any combination, particularly the details shown in the drawings. Amendments thereof are the common practice of persons skilled in the art.