Radiofrequency embolization of head and neck tumors (theoretical basis). Head and neck. Russian Journal. 2021;9(4):95–102 (In Russian).

The authors are responsible for the originality of the data presented and the possibility of publishing illustrative material – tables, figures, photographs of patients.

There are two approaches to tumor therapy. The first (radiofrequency ablation — RFA) is based on heating tumor cells to temperatures at which the cells die. The second (embolization) deprives the tumor of blood supply.

Purpose of the study. In this study, we proposed to combine both methods into one and implement total tumor embolization by creating a closed contour of coagulated tissue around it, using the existing RFA equipment. Since the tumor is surrounded by a dense network of capillary vessels passing through the ablastic zone, heating of a part of this zone to coagulation temperature will lead to disruption of blood supply to the tumor, followed by possible apoptosis of tumor cells.

Experimental model. The mathematical model of radiofrequency heating is built considering the following physical processes: absorption of energy of alternating electric current within a tissue, heat transfer and thermal damage to a tissue resulting from heating ablation. Possible schemes for connecting electrodes in azimuthal and transverse fields for 4, 8 and 12 electrodes are discussed. By alternately changing the polarity of the electrodes, it is possible to obtain electric fields directed along the azimuth, and with an increase in the number of electrodes, the radial component of the field tends to zero. Transverse components are created by simultaneously connecting electrodes in two opposite groups.

Calculations and their discussion. The processes of formation of cylindrical and flat surfaces at different diameters of introduction of shaping electrodes were studied. The results of the calculations are presented, indicating the possibility of complete isolation of tumors with diameters up to 80–90 mm.
Conclusion. For the first time, a system of total embolization is discussed where external coagulation of the entire vascular system surrounding the tumor is used instead of internal clogging of blood vessels by emboli. As a result, the processes of transition to cellular apoptosis and replacement of tumor cells with healthy ones is expected. The implementation of total embolization will allow a 100% cure for patients. Calculations carried out using the COMSOL MULTIPHYSICS software package indicate the possibility of embolization of tumors up to 80–90 mm in diameter. Thus, the study indicates the technical feasibility of realizing complete tumor embolization by using standard radio frequency equipment and special multielectrode systems. When using the proposed design, it is potentially possible to improve existing methods of therapy. The design of the electrode system does not require moving the electrodes during the heating procedure. Achieving complete embolization will allow avoiding the spread of cancer cells since, according to the calculations, the volume of coagulation required for heating is reduced by about 60%, and an increase in the generator power and the volume of energy supplied to the tissue, as in the case of the classical ablation method, is not required. In addition to oncology, such systems can be used for denervation of the renal artery due to the possibility of creating a hollow closed circular heating circuit. Key words: ablation, embolization, model, radiofrequency generator, bipolar mode, electrodes, switching circuits

Conflicts of interest. The authors have no conflicts of interest to declare.
Funding. This work was supported by grant No FSFZ-2020-0019.

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