RU2318465C1 - Method for microwave biotissue diathermocoagulation and device for its implementation - Google Patents

Abstract

FIELD: medicine, veterinary science, surgery.

SUBSTANCE: the present innovation deals with destructing pathologically altered human and animal tissues. The method for microwave biotissue diathermocoagulation is based upon introducing an emitter into biotissue followed by simultaneous microwave heating and supplementing biotissue with NaCl solution, moreover, one should introduce about 20-25%-NaCl solution at the rate of 0.5-1 ml/min in volume being equal to that of the biotissue under destruction, as for heating, it should be fulfilled at output power ranged 20-30 W. The device for microwave biotissue diathermocoagulation contains an emitter connected with a microwave generator, designed as a segment of coaxial line, that forms a working part and includes external and protruding internal conductors at insulation between them. At the end of the internal conductor there is a metal tip fixed by its bottom, designed as a semi-sphere. The emitter mentioned is installed with clearance in a radiotransparent catheter, as for the working part, it is covered with the layer of dielectric at thickness being equal to that of the external conductor of coaxial line. The present innovation enables to increase the volume of the tissue under destruction and decrease traumatism due to improving the efficiency of energy supply from the emitter into the tissue under destruction.

EFFECT: higher efficiency.

2 cl, 3 dwg, 1 ex

Description

The invention relates to the field of medicine and veterinary medicine, mainly to surgery, and can be used to destroy pathologically altered tissues of the human and animal body.

Known chemical and physical methods of irreversible coagulation of proteins (Joli M. Physical chemistry of protein denaturation. M. Mir. 1968.), which are the most important structural and functional molecules of living cells, the combination of which forms various biological tissues.

However, to date, the clinic uses only one method of chemical destruction of biological tissue, namely the injection of ethanol into it (Erce C., Parks RW Interstitial ablative techniques for hepatic tumors. British Journal of Surgery. 2003, 90, 272-289). it is possible to reliably destroy tumors with a diameter of up to 3 cm. Despite the effectiveness and cheapness of the method has significant disadvantages. In order to completely destroy biological tissue, injections have to be repeated many times (up to 10 or more times) due to the unpredictability of the distribution of the introduced alcohol over the volume of biological tissue.

Among physical methods, thermocoagulation is most widely used. Only three heating methods are of practical importance: due to absorption of laser radiation by biological tissue, and also through transmission of high-frequency and microwave currents through biological tissue (Ng KKC et al. Thermal ablative therapy for malignant liver tumors: A critical appraisal. J. gastroenterology and hepatology. 2003, 18, 616-629).

The volume of biological tissue destroyed by these methods is approximately the same and does not exceed 3 cm in diameter. To increase the volume of destruction, the combined action of chemical and physical methods of destruction is of great interest. However, the question of the combined effect of chemical and physical methods of destruction of biological tissue has not been studied sufficiently and is largely unpredictable.

Closest to the proposed is the method of microwave diathermocoagulation of biological tissue according to US patent No. 6692490. The main disadvantage of this method is the small amount of destruction (up to 3 cm in 10-15 minutes). The increase in power transmitted from the generator to the emitter, and the duration of dielectric heating does not increase the amount of destruction. Therefore, to coagulate tissue more than 3 cm in diameter, the procedure for introducing the emitter into the biological tissue with subsequent heating has to be performed repeatedly, which increases the invasiveness of the method.

The objective of the present invention is to reduce the invasiveness of the method by increasing the amount of destructible biological tissue in one procedure.

For this, in the known method of diathermocoagulation of biological tissue, which includes introducing an emitter into the biological tissue and subsequent simultaneous microwave heating and introducing a NaCl solution into the biological tissue, 20-25% NaCl solution is introduced into the biological tissue at a rate of 0.5-1 ml / min volume equal to the volume of destructible biological tissue, and heating is carried out at a power input of 20-30 watts. Our experiments showed that with an increase in the concentration of NaCl up to saturation (26.4% at 20 ° C) in the solution introduced into the biological tissue, the volume of coagulated biological tissue increases. The rate of introduction of the solution in excess of 1 ml / min, often leads to leakage of part of the injected solution to the surface of the organ through the channel formed by the introduction of a monopoly emitter for diathermocoagulation in the biological tissue. This leads to damage to some healthy cells near the surface of the injection channel, which is an undesirable phenomenon.

When biotissue is heated with a power exceeding 30 W, the liquid in the biotissue adjacent directly to the emitter quickly boils, which complicates the further efficient transfer of energy from the emitter to the biological tissue. At a power of less than 20 watts, the volume of coagulated tissue decreases.

The technical result of the implementation of these particular modes is the optimal effect of two destructive factors, which leads to an almost twofold increase in the volume of thermonecrosis of the biological tissue and, thereby, to a decrease in the morbidity, since there is no need to repeat the procedure.

To implement the proposed method, a device is used, the closest analogue of which is the installation containing the emitter connected to the microwave generator, made in the form of a segment of a coaxial line forming the working part and including external and protruding internal conductors with insulation between them. A metal tip made in the form of a hemisphere is attached to the end of the inner conductor with a base.

The known device has several significant disadvantages:

- a small amount of coagulated biological tissue (not more than 3 cm in diameter);

- low coefficient of energy transfer from the emitter to the biological tissue due to poor matching of the wave impedances of the biological tissue and the antenna (standing wave coefficient SWR> 3);

- a large deviation from the spherical volume of the coagulated biological tissue (the ratio of the resulting ellipse is about 1 to 2), while most small tumors and metastases, for example, the liver, have a spherical shape;

- baking coagulated biological tissue to the surface of the conductor, which impairs the transfer of energy to the biological tissue, as well as a very low ignition threshold of the plasma between the outer conductor and the metal tip, which limits the level of power used for coagulation of biological tissues to values not exceeding 10 watts.

The objective of the present invention is to remedy these disadvantages. To do this, in the known device for microwave diathermocoagulation of biological tissue containing an emitter connected to a microwave generator, made in the form of a segment of a coaxial line forming a working part and including an external and protruding inner conductors with insulation between them, a metal tip is attached to the end of the inner conductor, made in in the form of a hemisphere, the emitter is installed with a gap in the radiolucent catheter, and the working part is covered with a dielectric layer with a thickness equal to the thickness the outer conductor of the coaxial line.

The invention is illustrated in figures 1 and 2. As can be seen from figure 1, the device introduced into the biological tissue 1 consists of a radiolucent fluoroplastic catheter 2 and the working part 3 of the microwave emitter. There is a gap between the emitter and the catheter, into which NaCl solution is introduced using a tee 4. The end of the emitter through the connecting flange 5 is connected to a coaxial cable supplying microwave power from a generator (not shown). Figure 2 shows in more detail the device of the working part of the emitter. The device consists of an inner conductor 6, fluoroplastic insulation 7 and an outer conductor 8, forming a coaxial line that supplies energy to the emitter. One end of the inner conductor is connected to the connecting flange, and the other end is to the base of the hemispherical metal tip 9. The entire protruding part, including the tip, is covered with a dielectric layer 10 with a thickness equal to the thickness of the outer conductor of the coaxial line. The length of the radiating part protruding from the coaxial line L depends on the electrophysical properties of the biological tissue and is equal to 17 mm (the wavelength in the liver tissue at a generator frequency of 2450 MHz). The entire emitter is placed in a fluoroplastic catheter 2 and introduced into the destructible biological tissue 1.

The operation of the device can be explained using the block diagram of the installation for microwave coagulation, presented in Fig.Z. The installation comprises a pump 11, a control unit with a temperature indicator 12, and a microwave generator 13 operating at a frequency of 2.45 GHz, to which a radiator 3 is connected via a flexible coaxial cable through a detachable flange 5. Under the control of an ultrasonic scanner, not shown in FIG. 3 , a catheter 2 with a stylet (not shown in Fig. 3) is inserted into the biological tissue 1. Then the stylet is removed and the emitter 3 is inserted in its place. The fluoroplastic catheter 2 is connected to the infusion pump 11 using the tee 14. The pump 11, which feeds the NaCl solution, is turned on, and in the emitter l 3 supplies power from the generator 13. The power transmitted from the emitter to the biological tissue leads to its heating to a coagulation temperature and higher, destroying the biological tissue. Temperature control is carried out by introducing into the biological tissue 1 a temperature sensor 15 connected to the control unit 12, which allows changing the heating mode of the biological tissue.

Tests of the proposed method and device for its implementation were carried out on the liver of a pig. Under general anesthesia, the animal was fixed on the operating table and, using an ultrasound scanner, the emitter was introduced into various lobes of the liver according to the method described above. The 25% NaCl solution was infused at a rate of 1.0 ml / min. The power transmitted to the biological tissue was 30 watts. The heating duration was from 20 to 30 minutes. SWR was measured before and after heating. At the end of the experiment, the animal was sacrificed, the abdominal cavity was opened, and the sizes of the coagulation area were measured.

The test results showed that using the proposed method and device, an almost spherical coagulation volume is achieved. In this case, heating for 20 minutes led to coagulation of tissue with a diameter of about 3.5 cm, which corresponds to a volume of 20 ml, and when heated for 30 minutes, the coagulation diameter slightly exceeded 4 cm, which corresponds to a volume of 30-35 ml. The latter values are more than twice the amount of coagulation achieved using the prototype. The emitter SWR was equal to 1.5 both before and after coagulation, which is also two times less than that of the prototype. Sintering of coagulated biological tissue to the emitter was not observed.

Thus, the use of the proposed method and device significantly increases the volume of destructible biological tissue, reduces the invasiveness of the method and improves the sphericity of coagulation by using the combined action of concentrated NaCl solution and microwave heating, as well as by improving the efficiency of energy transfer from the emitter to the destructible biological tissue.

Patient C., 31 years old, was under treatment in the microsurgery department of Moscow P.A. Herzen with a diagnosis of Hemangiopericytoma of the lower jaw on the right. On examination: The face is asymmetric due to partial paresis of the facial nerve on the right. In the parotid region, a nodular formation of a dense-elastic consistency, with a smooth surface, motionless, painful on palpation, 5 × 6 cm in size is determined on the right. According to computed tomography: A tumor formation with localization in the right parapharyngeal region is determined on the right in the soft tissues of the face.

The tactics of treating the patient were discussed at an interdepartmental consultation with the participation of radiologists and chemotherapists. Given the data on the prevalence of the tumor process and the morphological structure of the tumor, the only possible way to help the patient is an attempt to conduct local thermocoagulation of the primary focus area with subsequent possible chemotherapy with palliative purpose. The patient held a session of microwave diathermocoagulation of the tumor by the proposed method and device. Under local anesthesia, an emitter and a needle temperature sensor were introduced into the tumor tissue at a distance of 2 cm from the emitter using an ultrasound scanner. After introducing the emitter and temperature sensor, the generator was turned on and diathermocoagulation was performed at a power level of 20 W with simultaneous infusion of a 20% NaCl solution at a rate of 1 ml / min for 30 minutes.

At the end of treatment, according to the control examination, after 3 months, the stabilization of the tumor process, the absence of signs of continued tumor growth, a decrease in the tumor mass due to scarring and fibrosis are noted.

Claims (2)

1. The method of microwave diathermocoagulation of biological tissue, comprising introducing an emitter into the biological tissue and subsequent simultaneous microwave heating and introducing a NaCl solution into the biological tissue, characterized in that a 20-25% NaCl solution is introduced at a rate of 0.5-1 ml / min volume equal to the volume of destroyed biological tissue, and heating is carried out at an output power of 20-30 watts. 2. A device for microwave diathermocoagulation of biological tissue, comprising an emitter connected to a microwave generator, made in the form of a segment of a coaxial line forming a working part and including an external and protruding inner conductors with insulation between them, a metal tip made in the form of a hemisphere is attached to the end of the inner conductor with a base characterized in that the emitter is installed with a gap in the radiolucent catheter, and the working part is covered with a dielectric layer with a thickness equal to the thickness no external conductor of the coaxial line.

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