METHOD AND APPARATS FOR USE INPROSTATE CRYOSURGERYThis invention relates to a method and apparatus for use in prostate cryosurgery.
Fig. 1 illustrates a conventional technique for placement of cryosurgical probes for prostate surgery. The patient 10 is laid on his back with his legs 12 in a raised position. In Fig. 1, the patient's rectum, bladder, urethra, penis and prostate are denoted by numerals 14,16,18,20 and 22, respectively. An ultrasound imaging device 24 is inserted into the rectum 14 to image the area of the prostate 22. The surgeon then inserts cryosurgical probes 26 through the patient's skin to reach the prostate 22, using the ultrasound image produced by the imaging device 24 for guidance. The probes 26 are cooled by passing a suitable cryogen, for example, liquid nitrogen, through the tip; this can achieve temperatures of around-196 C to ablate the prostate.
A problem which severely limits the effectiveness of the operation is the difficulty in placing the cryosurgical probes 26 at precisely the correct positions relative to the prostate 22. The ultrasound imaging device 24 can produce only a very simple 2-dimensional image"slice", and so does not provide the surgeon with complete 3-dimensional information needed to position the probes 26 accurately. The positioning is dependent entirely on the skill and experience of the surgeon, who has manually to position, angle, and determine the depth of insertion, for each probe.
Since the prostate is buried beneath the skin, even a small angular deviation of the probe can cause the probe tip to miss the desired target region, and result in freezing of only a part of the prostate. Not only does this reduce the effectiveness of the operation, it also endangers the surrounding tissue, such as the urethra and the rectum. A fistula (which is a combined hole in the urethra and the rectum through which body waste can leak from one to the other) can be created, which is very unpleasant for the patient. Fistulas can only be corrected by lengthy and expensive further surgery.
A urethral warmer, and a rectal warmer, can be inserted in the urethra and rectum, respectively, to try to prevent unwanted freezing in those areas. Such warmers are described, for example, in commonly owned published International patent application WO-A-95/29643. However, such warmers are intended to provide only secondary protection, and may not be fully effective against direct freezing if the probe is positioned incorrectly very close to the urethra or to the rectum.
The present invention has been devised bearing the above problems in mind.
Broadly speaking, a first aspect of the invention provides apparatus for use in a cryosurgical prostate operation, comprising:a member insertable into a patient's urethra; andmeans for guiding insertion of one or more cryosurgical devices based on the position of the member.
The invention makes use of the inventors'appreciation that, in the vast majority of all males, the distance between the prostate and the bladder is substantially the same.
To the nearest centimetre, this distance is about 21 millimetres. Moreover, the urethra passes through the prostate. Therefore, by positioning the member (also referred to herein as a"sound") in the urethra relative to the bladder, the member also becomes positioned relative to the prostate. This provides a simple, yet extremely effective, technique for establishing a good positional reference with respect to the patient's prostate.
Preferably, the member is connectable to the guide to establish a predetermined geometry between the guide and the member. Preferably, the guide is in the form of one or more wall portions through which extend guide bores. The cryosurgical devices can be inserted through selected bores, the bores constraining the device to be inserted at a certain angle with respect to the urethral member (sound).
Urethral sounds are currently used for inserting catheters into the urethra and bladder. For example, such a sound would be used to insert the urethral warmer catheter mentioned previously. However, once the catheter is in position, the sound is removed and plays no further role.
In a second aspect, the invention provides a urethral sound comprising a tubular member insertable into a patient's urethra, and a coupling arrangement at a proximal end of said tubular member for forming a rigid coupling to a guide frame to provide a positional reference for guiding insertion of cryosurgical probes for prostate cryosurgery.
In a third aspect, the invention provides a guide for guiding one or more cryosurgical probes for prostate surgery, the guide comprising:at least one wall portion having guide bores extending therethrough, through which the cryosurgical probes may be inserted, each guide bore having a respective diameter which is sufficiently small, and a length which is sufficiently long, to constrain the probe to a predetermined angled path as it is inserted through the bore.
In a further aspect, the invention provides apparatus for prostate cryosurgery, comprising:a member insertable into a patient's urethra;a plurality of cryosurgical probes; anda guide connectable to the member for guiding insertion of the cryosurgical probes to the prostate region, based on the position of the member in the patient's urethra.
In a yet further aspect, the invention provides a method of positioning a cryosurgical probes in a patient for prostate surgery; comprising:inserting a member into the patient's urethra;coupling a guide to the member such that the member provides a reference position for the guide; andusing the guide to control the location and angle at which the cryosurgical probe is inserted into the patient, whereby the probe is positioned with its tip adjacent to the prostate.
In a further aspect, the invention provides a method of performing prostate cryosurgery in a patient, comprising:inserting a member into the patient's urethra;coupling a guide to the member such that the member provides a reference position for the guide;inserting a first cryosurgical probe through a first selected guide bore of the guide and into the patient's skin, the guide bore controlling the location and angle of insertion into the patient such that the probe tip is positioned at a first position adjacent to the prostate;inserting a second cryosurgical probe through a second selected guide bore of the guide and into the patient's skin, the second guide bore controlling the location and angle of insertion into the patient such that the probe tip is positioned at a second position adjacent to the prostate; andpassing cryogen fluid through the cryosurgical probes to oblate the prostate.
Embodiments of the invention are now described, by way of example only, with reference to the accompanying further drawings, in which:Fig. 2 is a schematic view showing an embodiment of apparatus for positioning the cryosurgical probes;Fig. 3 is an enlarged schematic view of the guide wall of Fig. 2;Fig. 4 is a schematic side view of a first embodiment of urethral sound;Fig. 5 is a schematic side view of a second embodiment of urethral sound;Fig. 6 is a schematic side view of a third embodiment of urethral sound; andFig. 7 is a schematic side view of a fourth embodiment of a urethral sound.
Referring to Fig. 2, the same reference numerals as those used in Fig. l have been used again where appropriate. In this embodiment, positioning of the cryosurgical probes 26 is aided by the use of a guide frame 30 supported on the operating table 32 on which the patient is laid. In order that the frame 30 can be used for accurate guidance of the probes 26, it is necessary to align the frame 30 relative to the patient's prostate 22. This is achieved by means of a urethral sound 34 which is inserted into the patient's penis 20 and advanced along the urethra 18 to the bladder 16. (In Fig. 2, the urethral sound 34 is shown shaded for clarity. However, it is to be understood that the sound 34 is tubular rather than solid). This embodiment exploits the inventors' appreciation that, in the vast majority of all males, the distance between the bladder 16 and the prostate 22 appears to be the same (at least to about the nearest half centimetre or less). This distance is approximately 21 millimetres.
Therefore, by positioning the urethral sound 34 relative to the bladder 16, the sound 34 is positioned relative to the prostate 22 which surrounds the urethra 18 at a know distance from the bladder 16. The sound 34 can thus provide a known reference position for the prostate 22.
As described hereinbefore, urethral sounds are known per se, and have previously been used for inserting a catheter along the urethra to the bladder. Once the catheter is in position, the sound is then usually removed. In contrast, in this embodiment, the sound 34 is left in position to provide a known position reference for the prostate 22.
Once the urethral sound 34 has been manoeuvred into position, its proximal end is coupled mechanically to the guide frame 30. The coupling arrangement couples the sound 34 rigidly to the frame 30, at predetermined angle, such that the frame 30 has a predetermined fixed geometrical relationship with the sound 34. For example, the coupling arrangement may be a spigot and socket system (a spigot on the proximal end of the sound 34 being received in a socket in the frame 30), or it may be a bayonet type coupling.
Thereafter, the cryosurgical probes 26 may be inserted through guide bores 46 in the frame, to be guided at a predetermined angle, such that the tip of the probe will be positioned in the region of the prostate 22.
Referring to Fig. 3, the frame 30 may, for example, be angled, and consist of first and second walls 40 and 42 secured together by brackets 44. In this embodiment, the brackets 44 have a fixed angle but, in other embodiments, the brackets 44 might be adjustable to suit the patient. The brackets would then be locked at a predetermined angle to achieve a known geometrical relationship with the urethral sound 34.
In this embodiment, the walls 40 and 42 each have an arrangement of guide bores 46 through which a cryosurgical probe 26 may be inserted. (In. Fig. 3, only a selection of the bores are shown in full length, for the sake of clarity in the drawing).
Each bore 46 is dimensioned to be slightly larger than the diameter of the probe 26, so that the probe may be slid easily therethrough, but at an angle defined precisely by the bore 46. Typically, the bores 46 will be arranged in a grid pattern; the spacing between adjacent bores 46 defines the"resolution"to which an individual probe 26 may be positioned.
Within each wall 40 and 42, the guide bores 46 may be generally parallel to each other, or the bores may be inclined relative to each other to define a curve such that the probes will tend to converge towards the prostate 22.
One of the factors affecting the positioning accuracy of the frame 30, is the thickness of the walls 40 and 42. If the walls 40 and 42 are too thin, they might not be effective in controlling the angle of insertion sufficiently accurately. The cryosurgical probes 26 used for prostate surgery are generally of about 3-5 millimetres in diameter, and for such probes, it is suggested that the wall thickness be at least 10 millimetres.
In this embodiment, the walls 40 and 42 are transparent, so that the surgeon's view of the patient, especially in the regions in which the probes are inserted, is not hindered.
Preferably, the walls 40 and 42 are of a material on which a surgeon can mark graphically an outline corresponding to the prostate. As is usual in prostate cryosurgery, the prostate is mapped prior to the operation, for example, using ultrasound, so that its size can be determined. This pre-operation mapping may also be useful in further defining the distance between the prostate and the bladder in the patient. In this embodiment, the lower wall 42 has a socket aperture 48 for receiving the proximal end of the urethral sound.
Although the illustrated embodiment includes first and second discrete walls 40 and 42, each of which is generally planar. In other embodiments, the walls 40 and 42 may be curved, and may, for example, be integrally formed as single generally continuous wall. In particular, if the wall has a generally constant radius of curvature, then it may be regarded as corresponding to a magnified profile of the prostate, which might aid graphical mapping of the prostate area onto the wall surface, and positioning of the probes.
Figure 4 illustrates a first embodiment of urethral sound 34. The sound consists of a tubular member 50 having a smoothly rounded distal tip 52 to aid insertion along the urethra. The proximal end 54 has a spigot portion 55 for insertion in the socket aperture 48 of the frame 30.
The region 56 of the sound 34 between the dotted lines 58 corresponds to the position of the prostate when the tip 52 is advanced to the patient's bladder. This region 56 is spaced a distance d=21 mm from the tip 52. In this embodiment, thermocouples 60 are provided on the surface of the tubular member 50 for monitoring the temperature of the urethra wall within the prostate during the freezing operation.
The thermo couples 60 are coupled by wires (not shown) extending through the proximal end 54 to suitable temperature monitoring apparatus (known per se).
During the freezing operation, the urethra should not itself be frozen, as this would damage the urethra wall tissue. The thermocouples 60 enable the most vulnerable part of the urethra to be monitored during freezing and, if the urethra is in danger of being frozen, the cooling effect of the probes can be reduced accordingly (for example, by reducing the rate of cryogen flow). This enables the maximum amount of cooling to be used which does not itself threaten the vulnerable urethral wall tissue.
The thermocouples 60 are preferably positioned around substantially the entire circumference of the member 50, so that the temperature can be measured from all sides. Additionally, the thermocouples 60 are preferably arranged at a number of different axial positions, so that the temperature of the urethral wall can be measured at different points along its length.
Fig. 5 illustrates a modified second embodiment of urethral sound 34. This is very similar to that illustrated in Fig. 4, except that the distal end of the sound is curved at right angles to the main longitudinal axis. Such a shape can provide a positive locating effect when the tip reaches the bladder, and prevent accidental movement of the sound during the cryosurgical operation.
Fig. 6 illustrates a third embodiment of urethral sound 34, which is similar to that of Fig. 4 but functions also as a urethral warmer to provide secondary thermal protection for the urethra and bladder. In this embodiment, an inflatable membrane 62 is provided at the distal tip of the sound 34, and a second inflatable membrane 64 is provided in the region 56. In use, the membranes 62 and 64 are inflated by circulating a heated solution of, for example, sterile saline, through internal conduits (not shown) leading to the membranes 62 and 64. As well as providing the aforementioned warming effect, the membrane 62 at the tip of the sound 34 will expand into the bladder, and thus provide a positive locating effect to prevent accidental withdrawal of the sound.
The thermocouple sensors 60 are preferably located on the membrane material, so that inflation of the membrane will press the thermocouple sensors into contact with the wall of the urethra. The membrane 64 may extend on only one side of the sound 34 (as illustrated), or it may project through apertures on all sides of the sound 34. As a further alternative, the membrane may be formed as a sleeve surrounding the section 56 of the sound 34, and be inflated by fluid entering the membrane through one or more first apertures (not shown) and exiting by one or more second apertures (not shown).
Fig. 7 illustrates a fourth embodiment of urethral sound 34 which is, in effect, a combination of the embodiments of Figs. 5 and 6. The same reference numerals have been used to denote the features described above.
In use, different sizes (i. e. different lengths and different diameters) of urethral sound 34 will be available, and the surgeon will select the most appropriate size of sound for the patient. In general, the surgeon should use the largest diameter sound 34 which can be safely manoeuvred through the penis and urethra to the bladder. The large diameter will minimise the chances of unwanted movement while in position, and provide good thermal contact with the urethral wall.
The urethral sound 34 may be made of any suitable material, for example, of plastics or of stainless steel. The sound 34 may be intended to be disposa after only one use, or may be intended to be sterilised and used again for a limited number of operations.
It will be appreciated that the above embodiments are merely illustrative, and are not intended to limit the scope of the invention. In particular, many different mechanical coupling, mounting, and guiding arrangements may be used other than those described above.
It will be appreciated that the invention, particularly as described in the preferred embodiments, can provide a simple, yet very effective, technique for positioning one or more cryosurgical probes accurately with respect to a patient's prostate. The invention can eliminate common positioning errors, and significantly reduce the risks of accidental damage to the patient's urethra, rectum and bladder.
Moreover, the accurate positioning can enable the surgeon better to target specific regions of the prostate with individual cryosurgical probes, leading to more effective surgery. The preferred designs also enable the temperature of the urethra in the region of the prostate to be monitored accurately.