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Sato, Tatsuhiko; Hamada, Nobuyuki*; Kumada, Hiroaki*; Hasegawa, Sumitaka*; Sakashita, Tetsuya*
no journal, ,
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.
Nagai, Haruyasu; Terada, Hiroaki; Tsuzuki, Katsunori; Katata, Genki; Ota, Masakazu; Furuno, Akiko; Kadowaki, Masanao; Akari, Shusaku*
no journal, ,
no abstracts in English
Kinase, Sakae; Takahashi, Tomoyuki*; Ando, Masaki; Mikami, Satoshi; Yamamoto, Hideaki; Saito, Kimiaki
no journal, ,
no abstracts in English
Ishimori, Yuu
no journal, ,
The average of indoor radon concentrations in Japan is one fifth of that in Nordic countries, and no regulations of indoor radon have been introduced in Japan. Even if the regulation of 100-200 Bq/m
is implemented in Japan, it would not contribute to the significant reduction of lung cancers. Since so-called "radon exposure" is the internal (lung) exposure not from radon itself but from its progeny, there have not been much data on the distribution of radon in the body. Measured data by Nussburm & Hursh (1957) is the sole source of information and is still used. Recently we obtained partition coefficients of radon using mice. In our experiment system, doses from the radon exposure with 2000 Bq/m for 24h are the order of 1
Gy in lung and 0.1Gy in others. The observed activation of antioxidant enzymes following the radon inhalation may be attributed to the local energy transfer at cell and molecular levels. To discuss these biological responses in comparison to the LNT model, the dose-response relationship must be offered.