The effect of spatially nonuniform electromagnetic field and antitumor drug on growth of maglinant tumor

Abstract

The effect of spatially nonuniform electromagnetic field on transformation of radio waves and thermal descriptions in phantoms and malignant tumour during electromagnetic irradiation was investigated. It is shown that the structure of heat formation on the surface of phantoms depends on the degree of nonuniformity of electromagnetic field (EF) and it is similar to computed EF distribution. Output descriptions of magnetic component after EF transformation in a phantom more depended on phantom' size and spatial heterogeneity than electric component. The treatment of experimental animals was carried out with DOXO in the dose 1.5 mg/kg. The animal tumors were exposed by EF with the frequency 40 MHz inside using two types of loop elliptic applicators. First type of applicator with straight profile (ASP) had small asymmetry of electric component aE = - 0.03 a.u., magnetic component aH = 0.16 a.u. and specific adsorption rate (SAR) = 8.8 W/kg. Second type with the circular arc in profile (ACAP) had increased asymmetry of EF aE = 0.89 a.u., a H = 0.48 a.u. and SAR = 1.6 W/kg. The temperature inside tumor was nonlinearly increased up to 39.1°C during 15 min electromagnetic irradiation (EI) by ASP and up to 37.9°C with the use of ACAP. Animals were housed in 4 groups: 1 - control (no treatment); 2 - DOXO-administration; 3 - DOXO-administration + EI by ASP; 4 - DOXO-administration + EI by ACAP. The maximal inhomogeneity in thermograms' structure of tumor surface visualized after EI by EF with increased asymmetry. Since 14th day after tumor transplantation the tumor volumes for animals from 4 group was statistically significant decreased in comparison with the animals of 1, 2 and 3 groups on 88%, 79% and 82% (p < 0.05) accordingly in average. At the same time, the complete resorption on 20th day after tumor transplantation for 40% animals from 4 group were observed. © 2009 Springer-Verlag.