V.N. Makarov1, N.A. Boos2

1,2 MIREA – Russian Technological University (Moscow, Russia)

1 Firm "TECHNOSVET" LLC (Moscow, Russia)

One of the main indicators of the effectiveness of RFA is frequency of complete tumor necrosis (i.e., the complete absence of viable tumor cells in the affected area). According to different authors, this indicator varies within 30 - 100%. The inconsistency of these data is explained on the one hand by the difference in approaches to assessing changes in the affected area, on the other hand, by the existence of a number of objective reasons that do not allow the destruction of the tumor in full (the heat-dissipating effect of blood vessels, the difference in the thermal conductivity of tissues, etc.). It is obvious that search and development of ways to reduce the influence of these factors on the treatment result are relevant, because it will increase the effectiveness of radio frequency exposure.

Currently manufacturers of RFA devices are trying to increase the diameter (up to 4.5-6.0 cm) and the volume of destroyed tumors (more than 100 cm3) while ensuring the spherical shape of the heating zone and reducing the procedure time (no more than 6-8 minutes). The issues of ensuring the ablasticity of the procedure are solved by exceeding the diameter of the heating zone over the diameter of the tumor by 0.5-1.0 cm. It is interesting to compare the devices produced in order to determine the main vector of their possible development in the listed directions.

Nowadays, there are two ways of development to solve these problems. The first consists in the creation of complex, divided into several radio-frequency "umbrella" electrodes, operating in a monopolar mode. The second way is to increase the number of inserted electrodes up to 3 or more and switch to a bipolar mode of operation. Due to the need to maintain a constant generator load, the use of switching in a multi-electrode monopolar mode of operation is required, which leads to an increase in heating time and using of programming devices.

Therefore, a natural stage in the development of radio frequency installations is the transition from a monopolar mode of operation to a bipolar one. With bipolar heating, the heating time is shortened, the switching algorithm is simplified, or it becomes possible to abandon it.

Abroad, the leading position in the development of bipolar heating is taken by STARmed (South Korea). In the products of this company, bipolar three-electrode heating is implemented, where there are two oppositely polar zones on each electrode. During the procedure, 2 out of 3 electrodes are simultaneously heated with pairwise switching.

On the domestic market, in the face of the TEKHNOSVET company, a device has been created that surpasses foreign analogues in the number of electrodes (4-12). All electrodes work simultaneously, no switching is required. In addition, the unit is equipped with an additional channel for connecting electrosurgical instruments for coagulation and cutting.

Single-row and multi-row bipolar systems have been developed and tested. It has been established that, in addition to solving the problem of insufficient heating volume, these systems provide a number of advantages, including an increase in the uniformity of the generated thermal field, the possibility of refusing to insert electrodes directly into the tumor, and the elimination of the electrode cooling system, which simplifies and reduces the cost of production and development of equipment for thermal ablation.

Makarov V.N., Boos N.A. Tendency in development of installations for multielectrode radiofrequency ablation. Biomedicine Radioengineering. 2021. V. 24. № 6. Р. 58−68. DOI: https://doi.org/10.18127/j15604136-202106-06 (In Russian)

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