Theoretical study on the relative biological effectiveness of branchytherapy and BNCT

Sato, Tatsuhiko   ; Hamada, Nobuyuki*; Kumada, Hiroaki*; Hasegawa, Sumitaka*; Sakashita, Tetsuya*

In order to evaluate the relative biological effectiveness (RBE) of branchytherapy and BNCT, we improved our established model DSMK to be capable of estimating cell surviving fractions due to internal exposure. Using the improved DSMK, we calculated the surviving fractions of cells containing I-131 or Ra-224 inside their cell nucleus, cytoplasm, or external cellular region. The calculated RBE10 are approximately 1.6 and 4.8 times higher when all radioisotopes are concentrated inside cell nucleus. This result quantitatively suggests that the therapeutic effect of branchytherapy and BNCT would be improved if one can succeed in developing medicine that tends to accumulate in cell nucleus.