WO1993009846A1

WO1993009846A1 - Apparatus for thermal treatment of the prostate

Info

Publication number: WO1993009846A1
Application number: PCT/SE1992/000785
Authority: WO
Inventors: Hans Wiksell
Original assignee: Hans Wiksell
Priority date: 1991-11-22
Filing date: 1992-11-13
Publication date: 1993-05-27
Also published as: SE469318B; SE9103465L; SE9103465D0; AU2959892A

Abstract

An apparatus for thermal treatment of the prostate has a liquid cooled urethral catheter (2), within which a microwave emitter (4)is disposed for heating a region around the prostatic urethra and a rectal probe for sensing the temperature in rectum, the catheter and the probe each comprising at least one temperature sensor (12, 16). Each temperature sensor includes a glass fibre having at one end a luminiscent member. The temperature sensor comprised in the catheter is removably disposed at the outer surface of the catheter, said one end being positioned in the region to be treated by heat during the heat treatment of a patient. The luminiscent member is an aluminium-gallium-arsenide stack, which, when illuminated, emits light having a frequency, which is dependent on the temperature of said member.

Description

Apparatus for thermal treatment of the prostate

The present invention relates to an apparatus for thermal treatment of the prostate, having a liquid cooled urethral catheter, within which a microwave emitter is disposed for heating a region around the prostatic urethra, the catheter at least having one temperature sensor.

Preferably a rectal probe is provided, having at least one temperature sensor for sensing the temperature in rectum. In the past, sensing of the temperature has been carried out by means of members such as resistance members, thermis¬ tors and thermo-electric members, which have caused problems in that the radiation from the microwave emitter affects the temperature sensing and in that the characteristic of the radiation, especially the shape of the major lobe, of the microwave emitter is affected by such temperature sensors. In said prior art high-frequency energy also is transmitted to the sensor wires, which generate an uncontrolled radiation. It is also very difficult to prevent a high-frequency signal from reaching the temperature sensor wires to be further conducted by these so as to cause disturbances in sensitive c measuring systems. A prior art, which has been practiced in order to avoid these systems is the use of conductors having a considerable electric resistance, e.g. carbon fibres. How¬ ever, said prior art does not lead to a complete freedom from interaction with the microwave emitter and further it results in low precision in the sensing of the temperature because of a deteriorated signal-to-noise ratio, which is unacceptable.

By using non-conducting glass fibres interaction with the microwave field is avoided. When illuminated the luminiscent member will be excited to emit light of another wavelength through photo-luminiscence than that of the incident light, said wavelength being strongly and reproducably dependent on the temperature. The photo-luminiscent light is returned by the fibre without disturbing the incident light. Having no electrical conductivity the glass fibre will not affect the field of the microwave emitter at the same time as no micro¬ wave currents can be induced in the fibre. Due to the ext¬ remely small dimensions and the design of the sensor it is also prevented that the temperature sensor will be different- ly heated than the surrounding parts. Due to the small dimen¬ sions of the sensor, a very small time constant of about 1 second is achieved, allowing a rapid detection of temperature changes, thereby improving the reliability of the temperature control. By using non-conductive materials the risk of electric shocks is eliminated.

The EP, Al, 0 370 890 and WO, Al, 91/13650 each discloses a device of this kind. The temperature sensor in the prior devices may be disposed within the catheter. The prior apparatuses suffer from an important drawback in that the cost per unit is relatively high and in that, the optosensors can not be sterilized by heat without the sensor being damaged in the temperature range in question due to the fact that they are non removably integrated in the catheter or in the probe. In practice, this results in the device being used only once with a very high cost for each operation as a consequence.

The object of the present invention is to remedy the above discussed drawbacks of the prior art and provide a new apparatus for thermal treatment of the prostate, in which the temperature sensor is integrated in the catheter, while providing an accurate and reliable temperature sensing.

Said object is accomplished by an apparatus as defined in the preamble of claim 1 having all the features as defined in the characterizing part of claim 1.

Due to the fact that the temperature sensor is removably disposed in the catheter two main advantages are obtained. The first one is, which is the most essential from an econo¬ mical point of view, that the catheter can be sterilized by heat without any risk of the optical fibre temperature sensor being damaged and the second one is that the sensor could be removed for control and calibration independently of the catheter.

Attempts have shown that a catheter made of silicone rubber may be autoclaved about 25 times at about 135°C, resulting in an apparatus cost for each operation of about only 4% of the corresponding cost for an operation in accor¬ dance with the prior art.

Another important advantage of the apparatus of the invention resides in the fact that it uses the frequency of the light for the determination of the temperature, since frequency signals normally have a better quality than ampli¬ tude signals, thus providing a more reliable temperature indication.

In a preferred embodiment of the apparatus of the in¬ vention the catheter is made of silicone rubber, which allows the catheter to be autoclaved at 135°C so that the catheter could be used a plurality of times, which economically is very important since the production cost of the catheter is relatively high.

In accordance with an improvement of the apparatus of the invention, alarms are provided to interrupt energy supply to the microwave emitter, if the intraurethal temperature ^•fcnd/or the maximum temperature sensed in rectum trespass predeter¬ mined limit values. The limit value for the intraurethal temperature may be 45°C, the temperature some millimeters outside the catheter within the prostate being 50-55°C, and an appropriate limit value for rectum may be 42-45°C. The invention will now be described more in detail with reference to the annexed drawings, in which;

Fig. 1 is a schematic side view of an embodiment of the catheter of the apparatus of the invention.

Fig. 2 is an enlarged section of the catheter of Fig. 1, Fig. 3 is a side view of a practical embodiment of the catheter and.

Fig. 4 is an embodiment of the rectal probe.

Fig. 1 discloses an urethra1 catheter 2 to be inserted into the urethra of a patient to be treated. A microwave emitter 4 or an antenna, which is supplied from a microwave source through a cable 6, is disposed within the catheter 2.

The antenna or the emitter 4 is a dipole antenna. A problem in this connection is that the antenna can not be supplied in the usual way, i.e. through a perpendicular feeder, since such a T-configuration formed by the dipole antenna and the feeder could not be inserted into the cathe¬ ter. Thus, the feeder has to run in parallel with the dipole antenna, the cable then disturbing the antenna. In a practical embodiment one part of the dipole is a coaxial cable peeled off at the end, so that the inner wire protrudes, the feeder forming the other part of the dipole. In order to avoid the problem with ground currents, which are generated in this kind of antenna, a ferrite ring is positio¬ ned around the feeder, which generates an effective inductan¬ ce in the feeder screen, thus causing an interruption the¬ rein.

The insertion of the catheter 2 and thus the microwave emitter 4 in the urethra is achieved by means of an expan¬ dable cuff 8, which is expanded by pumping a sodium chloride solution therein through the conduit 10 after insertion into the urinary bladder, the cuff 8 thus forming a reference position for the catheter 2 and the microwave emitter 4 at its position against the bladder bottom. The microwave emitter 4 should then be positioned in the region of the prostatic urethra, in which the treatment is to be performed.

Fig. 3 illustrates the extension of the heat treatment area having a heat maximum some millimeters outside the catheter 2 at 9. The length of the heat treatment area along the catheter is typically 35 mm and it extends radially 15 mm from the catheter wall.

A temperature sensor device is provided in the form of a glass fibre 12 removably inserted in a channel 14 in the surface of the catheter 2 for sensing the intraurethral temperature. An aluminium-gallium-arsenide stack 16 is provided at the sensing end of the glass fibre, which upon illumination emits light of another wavelength by photo- luminiscence, the frequency of the wavelength being reprodu- cably and strongly dependent on the temperature. The photo- luminiscent light is conducted by the fibre 12 to a measure¬ ment unit 18, without being influenced by the incident light. The unit 18 comprises optical filters and semi-conductor detectors, which by means of algorithms in a computer deter- mine the intensity of the light for check of the proper operation of the fibre and also the wavelength or frequency of the light for determination of the temperature. The fibre is surrounded by a protective envelope having an outer diameter of 25 mm. The fibre 12 is connected to the measure- ent unit 18 through an optical contact 30. The measurement unit 18 emits semi-conductor generated red light by means of a light diode, which is fed through the fibre 12 to the sensor end, at which the aluminium-gallium-arsenide stack is positioned. The stack has extremely small dimensions and is enclosed in an acrylic envelope having the same outer diame¬ ter as that of the envelope of the glass fibre.

The catheter 2 is formed with channels for cooling liquid. The cooling liquid inlet 20 communicates with the channels 24 within the catheter and the cooling liquid is fed through the space 28 to the outlet 22. Between the outer wall of the catheter 2 and the partition between the spaces 24 and 26 transverse partitions 28 are provided, which serve as spacers, see Fig. 2. Ordinary tap water could be used as cooling liquid. In order to reduce the overpressure relative¬ ly to the patient in the cooling water channels 24, 26 the cooling water is pumped through the inlet 28 under pressure and is at the same time drawn out through the outlet 22. A relatively small volume of cooling liquid in the range of 1-2 dl flows in the system having a velocity of 4-7 ml/s. The use of a relatively small volume of cooling liquid is a precau¬ tion. If, in case of a defect, the cooling liquid would be pumped into the urinary bladder, then there is no risk of the latter being ruptured, when such small volumes of cooling water are used.

The temperature sensor fibre 12 is inserted into a channel in the surface of the catheter 2, which is made of silicone rubber. The fibre is insertable against an abutment (not shown) , at which position the sensor stack 16 is dis- posed substantially in front of the microwave emitter 4.

The sensor fibre 12 is removable from the channel 14, the entire catheter then being sterilizable by means of auto- clavation at a temperature of 135°C. The temperature sensor with its fibre is preferably calibrated after each treatment and the apparatus of the invention is advantageously equipped with a calibrating oven, in which the calibration is auto¬ matically performed with a high degree of precision.

The temperature sensor may be influenced by the vicinity to the low temperature cooling water flow in the catheter, i.e. there is a risk of the intraurethral catheter indicating a lower temperature than the real one, the erroneous indica¬ tion being dependent on the temperature of the coolant. Every second a compensatory calibration calculation is made by a computer included in the apparatus of the invention, so that said erroneous indication is eliminated independently of the temperature of the coolant.

Said compensation is carried out so that the temperature is measured in a thermostats-controlled water bath, in which the temperature of the water flow can be controlled very accurately. With an intraurethral probe of the apparatus of the invention the temperature response from the fibre sensor is read in such a testing equipment with different cooling flows having different temperatures. In this way it could be determined in which way the compensatory value is affected by different coolant temperatures within the temperature range in question 20-5^βC.

Practical tests have further shown that the disturbances from the coolant is slightly reduced with the probe against wet tissue in comparison with dry tissue.

Also when no energy is supplied a certain cooling of the probe and the surrounding tissue takes place through the cooling liquid. A certain small amount of minimum energy is therefore preferably supplied during the heating in "zero position".

The temperature and the temperature profile, which are obtained at the rectal mucosa during the heat treatment are supervised by three sensors 32, 34, 36 disposed on the probe 38 to be inserted in rectum, see Fig. 4. The temperature sensor devices of the rectal probe 38 is constructed similar¬ ly to the urethral temperature sensor devices having glass fibres 40, 42 positioned along the outer surface of the probe body. The temperatures sensored by the rectal temperature sensors is read once a second and it is verified in the measurement unit that the highest sensored temperature is below a predetermined alarm limit. If said limit is trespas¬ sed then the energy supplied to the microwave emitter will be interrupted. The glass fibres are, as well as the urethral glass fibre disposed in external channels or tubes of silico- ne rubber into which they have been inserted against calibra¬ ted abutments. The channels or the tubes are disposed in longitudinal grooves in the outer and frontal, relatively to the patient, surface of the probe body. Also, the rectal probe is entirely made of silicone rubber and may be re-used a plurality of times. The probe has a good anatomic shape and is provided with a protector against rotation. Said protector is important, since a rotary movement results in an anatomically wrong position for the sensors 32, 34, 36 in the patient.

The cooling water is cooled in a cooling system compri¬ sing a heat exchanger complete with cooling system, cooling regulator and circulating pump. The cooling system includes a so called Peltier-system with a plurality of Peltier tran- sitions. The Peltier-system is able to change the temperature of the coolant very rapidly.

Claims

1. An apparatus for the thermal treatment of the pros¬ tate, having a cooled urethral catheter (2) , a microwave emitter (4) being disposed therein for heating a region around the prostatic urethra, a temperature sensor associated with said catheter and having an optical fibre (12) , one end of which being provided with a luminiscent member (16) , which when illuminated emits light, the frequency and/or the wavelength of which being dependent of the temperature of said member, said end being in use disposed in the catheter in the thermal treatment region, characterised in that the outer surface of the catheter (2) is made of a heat sterili- zable material and in that said temperature sensor is remo¬ vably integrated in said catheter (2) .

2. An apparatus as claimed in claim 1, characterized in that said optical fibre (12) is removably disposed in a longitudinal channel (14) provided in a wall in said catheter (2).

3. An apparatus as claimed in claims 1 or 2, charac- terized in that the catheter (2) is made of an autoclavable material.

4. An apparatus as claimed in claim 3, characterized in that the said catheter (2) is made of silicone rubber.

5. An apparatus as claimed in anyone of claims 1-4, characterized in that an alarm is arranged to interrupt the energy supply to said microwave emitter (4) if the temperatu¬ re in urethra detected by said temperature sensor trespasses a predetermined first limit value.

6. An apparatus as claimed in anyone of claims 1-5, characterized in that said luminiscent member is an alumi¬ nium-gallium-arsenide-stack (16) , which, when illuminated, emits light having a frequency which is dependent on the temperature of said stack.

7. An apparatus as claimed in anyone of claims 1-6, characterized in that a measurement unit (18) is connected to the optical fibre (12) , said unit (18) having an optical filter and semiconductor detectors for measuring the in¬ tensity of the luminiscent light for checking the operation of the fibre and or measuring the frequency of the light for determination of the temperature.

8. An apparatus as claimed in anyone of claims 1-7, characterized in that a rectal probe is provided having a plurality of temperature sensors for providing a temperature profile in rectum.

9. An apparatus as claimed in claim 8, characterized in that an alarm is arranged to interrupt the energy supply to the microwave emitter, if the uppermost of the temperatures sensed by the temperature sensors in rectum trespasses a predetermined second limit value.