Technical field

The invention concerns the method of carrying out cryosurgical interventions based on the destruction of the pathological tissue consisting of freezing the biological tissue below -25°C with its subsequent rewarming up to the body temperature and the device for carrying out ' this method consisting of operating apparatus with a built in container of cooling medium and operating instrument and control unit.

Background of the invention

In the destruction of the pathological tissue by the local deep undercooling for the therapeutic treatment of bening as well as malignant tumors in the proctology, gynaecology, oncological surgery, etc. , the biological tissue has been yet exposed to the action of low temperature below -25°C. After that, the biological tissue is rewarmed up to the initial body temperature. In the still known methods rapid freezing wj th subsequent rewarming up at a comparable speed is performed .

The disadvantage of this known procedure is particularly a too high speed when rewarming the tissue up to the initial temperature. For achieving a reliable cryodestruction, in the literature, as well as in accordance with experience in practice rapid cooling is recommended down to temperatures below -25°C at a rate of about 200 K/min or above with a subsequent moderate rewarming up to the body temperature at a rate of 10 to

20 K/min. Vith respect to the necessary rewarming ra ^* te, ^* the whole operation would be very time consuming and this approach is not feasible with respect to the fact that the intervention calls for a high degree of ^* the concentration.

For the methods mentioned, devices have been yet known consisting of an operation apparatus with a built in container of the cooling medium, most typically liquid nitrogen. To the operation apparatus,an operation instrument is attached having at its end a heat exchanger or applicator arranged for fitting operating tips.

This device makes possible only rapid cooling and comparably rapid rewarming of the tissue. Thus, the drawback is in the impossibility of a suitable continuous control of the cooling and particularly rewarming rates. The temperature control is implemented by the maximum rate given by the heating power of relevant heat exchangers of the operating apparatus and by their instantaneous thermal load. A further disadvantage is in the impossibility of checking proper fitting of tips to the operation instrument and thus also the impossibility of checking the necessary contact between the operation tip and tissue. The impossibility is also disadvantageous of the preliminary determination of the cooling power in the still existing devices.

Summary of the invention

The above mentioned disadvantages are to a considerable extend avoided by a method of performing the cryosurgical intervention consisting of cooling the biological tissue below -25 C with its subsequent rewarming to the body temperature in accordance with the

invention. Its principle is in that the contact area of the biological tissue is cooled down at a rate of at least 180 K/min to -190 to -160°C , _ after that it is rewarme at a rate of 100 to 240 K/min to -70 to -20°C. Then the contact area of the biological tissue is rewarmed at a rate of 10 to 25 K/min to -5 to +5°C with a subsequent continuation of the rewarming procedure up to the body temperature. A considerable advantage of this method is that the total time of the controlled rewarming procedure is shorter than 5 min, which can be provided.

For perfoming the described method it is suitable to use the device consisting of an operation apparatus with a built in container of the cooling medium and operation instrument, and of the controlling unit in accordance with the invention. Its principle is that the control unit is formed by a controlling microprocessor coupled to electronical switches of an electromagnetic valve of heat exchanger, heating of heat exchanger, additional heating of heater of output gases and pressurizing heating. The controlling mikroprocessor is further coupled to a measuring unit connected wiht the heat exchanger thermometer, further thermometer of the outlet gas heater, nanometer of the container, indicator of the cooling medium level and a further thermometer of the pressurizing heating. The controlling microprocessor can be preferably connected to a power supply and memory with its further connection to a display unit and keyboard. The method described makes possible a high-quality cryosurgical intervention in a suitable time interval with adhering to all the cryobiological requirements.

The device corresponding to the invention makes it possible to essure the freezing power of the coolant prior to the intervention itself. Prior to the

intervention, it is also possible to automatically establish the quality of the thermal contact between the heat exchanger-applicator and operating tip. In the course of the intervention it is possible to automatically check the quality of the thermal contact between the operating tip and contact area of the biological tissue for possible ocurrence of breaking off of the operation tip from the contact area of the tissue,i.e. sudden deterioration of the thermal contact by the action of microscopic cracks between the operating tip and contact area of the tissue.The further advantage is a possibility of automatical providing of the tissue rewarnimg in accordance with cryobiological requirements after the cooling, i.e. rewarming at a rate of at most 10 to 25 K/min in a temperature interval of -25 to 0°C. The total rewarming time will not exceed 4 min, which is a suitable time delay from the standpoint of the concentration for the given intervention.

Brief description of the drawings

The device for carrying out the cryosurgical intervention is described in details with the help of a drawing of a particular implementation, where Fig.l shows a schematic diagram of a sample performance of the device in accordance with the invention and Fig. 2 shows a schematic diagram of the connection of particular elements of the control unit of this device.

Detailed description of the preferred embodiments

One example of performing the cryosurgical intervention consisting in cooling the biological tissue below -25°C with its subsequent rewarming to the body temperature was based on the fact that the contact area of the biological tissue was cooled down at a rate of 200 K/min to a temperature of -180°C. After that it was rewarmed at rate of 150 K/min to -50°C with further rewarming at a rate of 20K/min to +5°C. After that, continuous rewarming occured up to the body temperature at a rate of 200 K/min. At a contact area of 25 mm in diameter, the biological tissue of a diameter of about 28 mm and depth 4 mm was involved.The total rewarminng time was shorter than 4 in.

In a further case, the contact area of the biological tissue was cooled down at a rate of 3 000 K/min to -170°C and this temperature was kept for 45 s. The biological tissue was then rewarmed in the same way as in the first case.For a contact area of 5 mm in diameter, the biological tissue of a diameter of about 7 mm and depth of 3 mm was involved . In a further particular case, the contact area of the biological tissue was cooled down at a rate of 600 K/min to -180°C, this temperature being kept for 30 s.After that, the biological tissue was rewarmed at a rate of 200 K/min to -30°C with a subsequent rewarming in the same way as in the above mentioned cases. For a contact area of 12 mm in diameter, the biological ^* tissue of a diameter of about 15 mm and depth of 4 mm was involved.

In the last particular case, the contact area of the

biological tissue was cooled down at a rate of 200 K/min to -160°C and it was kept at this temperature for 120s. The biological tissue was then rewarmed in the same way as in the first example. For a contact area of 25 mm in diameter, with outputs arranged into seven points, 14 mm long and 3 mm in diameter, the biological tissue of a diameter of about 28 mm and depth of 17 mm was involved. The sample device for carrying out this method consists of an operating apparatus 21. wiht a built in container 15 _. of the cooling medium and and operating instrument _. 19 _. and control unit .20 _. . The control unit 20 consists of a control microprocessor , attached to a block 4_ of electronic switches, which are connected with an electromagnetic valve 8.. of the heat exchanger 1.7.,heating 9. of the exchanger 1/7 _. , additional heating 11 of heater .13. of outlet gases and pressurized heating, and the controlling mikroprocessor 1 _. is further coupled to a measuring unit 5_, connected to a thermometer i0_ of the heat exchanger 17, further thermometer Yl_ of the heater of outlet gases, manometer A_ of the container, level indicators _. 15. and a further thermometer 16 of the pressurized heating. The controlling microprocessor 1 is coupled to an independent power supply 3_ and external memory 2 and it is further connected to the display unit 6_ and keyboard 7 _. .

Before carrying out the operating intervention itself, the freezing power of the equipment for the cryosurgical intervention and the quality of the thermal contact between the heat exchanger 1/7 and tip is checked. In the course of the operation intervention, it is possible to control the rewarming rate in accordance with the dependence recommended.The cooling power should be evaluated depending on the heat exchanger 1/7 _. cooling course expressing the time dependence of the heat exchanger 1/7. temperature at the cooling stage without

the contact with the tissue and without the passive tip. For this evaluation, two suitably chosen points of the course are sufficient (t^, T^) and (t2_T2), determining the rate of cooling the heat exchanger 1/7 and the cooling power is determined from the known capacity of the heat exchanger 1J _. . For achieving as precise measurement as possible an for simultaneous checking of the function of the instrument 1£ even at the lowest temperature, it is suitable to choose the origin of cooling as the first point (0.+36) and (t,-185) as the second point. Instead of the value of the cooling power, it is also possible to directly present the measured cooling rate. In practice, this means that after pressing the switch for testing the power the time measurement is started and freezing is switched on, i.e. the electromagnetic valve 8. is switched on and heating £ of the heat exchanger 1/7 is switched off. After achieving the temperature chosen, for example -185°C, corresponding time is recorded and freezing is switched off. It is advantageous to wait for a certain time interval, for example one s, in order that the temperature in the heat exchanger 1/7 could be uniformly distributed and to use a steady state value after determining the cooling rate. The normal rewarming to the initial temperature is then adopted, i.e. the control of heating £ of the exchanger is switched to +36°C.

Before starting the intervention itself, it is also possible to establish the quality of the thermal contact between the heat exchanger 1/7 and tip of the cryodevice. After pressing the button test, freezing is started, which means that the electromagnetic valve 8. is switched on and heating £ of the heat exchanger 1/7 is switched off. After achieving a certain temperature recorded by a thermometer 10 _. of the heat exchanger 1/7, for example -30

°C, the freezing process is terminated, the lowest achieved temperature T^ is recorded and after a stabilization for about 10 s, temperature T _β is measured. Their mutual ratio is a measure of the quality of the thermal contact.

However, in order that comparable data could be obtained for all the sizes of the tips, the thermal capacity of the tip togehter with the heat exchanger 1/7. is further measured during heating with a defined heating power for the whole time. From these data, a number in interval of 0 to 100 is obtained, characterizing the quality of the thermal contact.

During the implementation of the intervention itself, the tip can be broken off from the tissue, which is manifested by a subsequent deterioration of the thermal contact resulting from the action of microscopic cracks between the tip and tissue. This breaking off exerts an adverse effect on the cooling rate and thus also on the quality of the cryodestruction. This is manifested by a reduced depth of freezzing and lower probability of the tumorous cell destruction. In addition the healing process is also deteriorated. Thus, it is necessary to check the possible occurrence of this breaking off. This checking is performed by following the time course of the heat exchanger 1/7 in a regime with a controlled inlet of the coolant into the exchanger 1/7. after achieving a given exchanger .17. temperature. In the case of breaking off the tip, a sudden change of the nature of regulation cycles occurs. The cooling course is then steeper and, in contrast to this, the course of the rewarming process is less steep, the resulting regulation period being longer after breaking off the tip. The change of the course is evaluated and breaking off of the tip from the tissue is signalized. In this case it is possible

00004

to interrupt the power, to wait for the tissue and tip heating and to repeat the whole operation intervention. ,_ ₌ -

It is of a high importance to adhere to the recommended tissue rewarming rate in a range of temperature of -25 to 0° C, in the whole volume of the tissue to be destructed as far as possible, provided that the total time of controlled rewarming does not exceed four min. The control of the rewarming rate is provided with the help of the microprocessor 1 _. controlling electronic switches 4_ and output data are shown on the display 6 _. .

Industrial applicability

The method of performing cryosurgical interventions and device for porforming this method in accordance with the invention will find its application particularly in the treatment of pahological formations in the proctology, gyneacology and oncological surgery and further in dermatology, orofacial surgery, otrinolaringology, pneumology, urology, cardiosurgery, etc.