BIOLOGICAL EFFICIENCY OF THE PROTON SCANNING BEAM OF THE THERAPEUTIC COMPLEX "PROMETHEUS" OF THE A.F. TSYB MEDICAL RADIOLOGICAL RESEARCH CENTER IN STUDIES ON CELL CULTURE OF MURINE MELANOMA B-16

The basis for the use of protons for radiation therapy tasks is a fixed conventional value of their relative biological efficiency equal to 1,1. Numerous studies have showed that RBE of proton radiation is not a constant value and depends on a number of factors. The purpose of this study was to determine RBE of a thin scanning proton beam at the center of the distributed Bragg peak in experiments on the culture of murine B-16 melanoma cells. The cell suspension was irradiated in an aqueous phantom by a horizontal proton beam from three directions (0,90 and 180°) in doses from 2 to 8 Gy. Modulation of the energy of proton radiation was 47,5÷92,0 MeV. RBE protons were determined from the clonogenic activity of the cells compared with 60Co gamma quanta. A linear-quadratic model was used to construct the dose dependencies. Obtained RBE values of proton radiation (LET 3÷8 keV/μm) differed in the big party from the generally accepted value and was at the level of 10% survival rate of 1.5. The results obtained generally coincided with data of foreign authors performed on different facilities.