2008 Volume 20 Issue 1 Pages 23-28
To estimate the biological total body radiation dose for BNCT (boron neutron capture therapy) patients, we investigated the frequency of micronuclei in the peripheral blood lymphocytes after neutron irradiation. After BNCT irradiation, blood samples were obtained from patients. Using cytochalasin B, the frequency of micronuclei present in cytokinesis-blocked cells was investigated. The evidence of acute radiation effect was studied based on a questionnaire answered by the chief physician. In an in-vitro neutron radiation study, we observed standard dose-response model induction and calculated the maximal biological dose estimation as 0.24 Gy-eq for head and neck tumor patients and 0.20 Gy-eq for brain tumor patients. The total body radiation dose obtained by biological estimation using the micronucleus assay correlated with the total effective dose of BNCT that was obtained by thermal neutron fluence and TLD estimation. The increased micronucleus frequency in BNCT patients was less than one-third of that in malignant tumor patients after X-ray radiotherapy. These findings demonstrate the usefulness of BNCT for selective high-LET radiotherapy. Additionally, post-BNCT suggests a low irradiation effect of cytological radiation damage allowing a high tumor target dose for each cancer patient. (Article in Japanese)
