V.N. Makarov –  Dr. Sc. (Phys-Math.), Professor, Russian Technological University (MIREA) (Moscow)  E-mail: makarov_vn@bk.ru

M.A. Makhov –  Vice Director, Company «TECHNOSVET» (Moscow) E-mail: technosvet@bk.ru

D.V. Shmeleva –  Ph.D. (Phys.-Math.), Associate Professor, Department of Bio-Cybernetic Systems  and Technologies, Russian Technological University (MIREA) (Moscow)  E-mail: shmeleva@mirea.ru

K.O. Kuchin –  Undergraduate, Department of Bio-cybernetic Systems and Technologies, 

Russian Technological University (MIREA) (Moscow) E-mail: technosvet@bk.ru

In order to obtain large volumes of heating during radiofrequency ablation of tumors, a thermal imaging study of temperature fields created in a bioobject simulator by multielectrode systems was carried out. In the experiments, a domestic four-channel installation for ablation of METATOM-3 tumors was used, allowing to connect from 1 to 12 electrodes with thermocouples to the generator and to control their temperature, setting in advance one or another profile of temperature change over time on the control unit. For the first time, potato tubers were used as a simulator that performs the indication of a thermal field in radio frequency heating. The essence of thermal fixation was that when heated in the range from 58 to 62, potato starch changes its structure from coarse-grained to fine-grained. The resulting sponge draws water from the surrounding volume, and the volumetric pattern of heating has clearly limited boundaries that persist for a long time. The picture of the temperature field obtained on flat potato slices using a thermal imager made it possible to judge not only the lateral temperature distribution, but also the longitudinal distribution. Research results showed that, depending on the location of bipolar electrodes, two configurations of the thermal field can be created in the simulator: in the form of a cylindrical tube with a wall width of 10 to 20 mm and a solid circular cylinder whose height is equal to the length of the working part of the applied electrodes. The latter configuration allows the introduction of electrodes into the ablastic zone to destroy tumors with a diameter greater than 70 mm in a time not exceeding 15 minutes. The results obtained in this work indicate the technical possibility of a substantial increase in the volume of tissue being destroyed during RFA by increasing the number of electrodes and placing the electrodes in the tumor volume closer to the periphery, including the ablastics zone. As a result, it becomes possible to heat tumors from their periphery without contact of the electrodes with the tumor with a significant reduction in the risk of distant metastasis. The increase in the number of heat sources allows not only to reduce the load on the electrodes, but also to reduce the time of the procedure. Clinical testing carried out in a number of oncological centers confirmed the results of experimental studies obtained on bioobject simulators.

1. Makarov V.N., Mahov M.A., Miroshnik V.I. Primenenie mnogoehlektrodnyh sistem v radiochastotnyh ustrojstvah dlya ab-lyacii tkanej // Biomedicinskaya radioehlektronika. 2017. № 4. S. 55–62.
2. Makarov V.N. Apparatnoe i ehlektrodnoe obespechenie zarubezhnyh i otechestvennyh ustanovok dlya radiochastotnoj ablya-cii // XIX nauch.-tekhn. konf. «Mediko-tekhnicheskie tekhnologii na strazhe zdorov'ya» MEDTEKH-2017: Sb. trudov. NII RL im. N.EH. Baumana. M. 2017. S. 91–100.
3. Makarov V.N., Mahov M.A, Miroshnik V.I. Issledovanie mnogoehlektrodnoj radiochastotnoj ablyacii v bipolyarnom re-zhime pri temperaturnom upravlenii processom nagreva // Biomedicinskaya radioehlektronika. 2017. № 12. S. 50–59. 
4. Reshetov I.V., Makarov V.N. Radiochastotnaya ablyaciya opuholej golovy i shei bez kontakta s ehlektrodami // Head and neck. Russian Journal. 2018. V. 6(3). P. 20–27.
5. Chang W., Lee J.M., Lee S.M. et al. No-Touch Radiofrequency Ablation: Comparison of Switching Bipolar and Switching Mono-polar Ablation in Ex Vivo Bovine Liver // Korean J. Radiol. 2017. V. 18(2). P. 279–288l. 
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8. Wu L.W., Chen C.Y., Liu C.J. et al. Multipolar radiofrequency ablation with non-touch technique for hepatocellular carcinoma ≤ 3 cm: a preliminary report // Adv. Dig. Med. 2014. V. 1. P. 80–85.
9. Makarov V.N. Primenenie raspredelennogo nagreva dlya teplovogo razrusheniya opuholej (kratkij obzor) // Biomedicin-skaya radioehlektronika. 2018. № 1. C. 54–60.
10. Makarov V.N., Mahov M.A., Miroshnik V.I. CHetyrekhkanal'naya ustanovka dlya radiochastotnoj ablyacii opuholej // XX nauch.-tekhn. konf. «Medikotekhnicheskie tekhnologii na strazhe zdorov'ya «MEDTEKH-2018»: Sb. trudov. NII RL im. N.EH. Baumana. M. 2018. S. 57–65.
11. Makarov V.N., Hitrov YU.A., Korepanova E.A. Termoindikatornye sostavy dlya ob"emnoj vizualizacii teplovyh polej pri nagreve ehlektromagnitnymi polyami // EHlektronnaya obrabotka materialov. 1990. № 1/151. S. 79–81. 
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