Comparison of dicentric dose response curves of 6MV LINAC X-rays and Co γ-rays for biodosimetry application.

In vitro Dicentric (DC) dose response curves of 6MV X-rays (3Gy/min) and Co γ-rays (0.63Gy/min) were generated and compared (intra-laboratory) to understand their similarities and differences. Human peripheral blood samples exposed to ten different doses (0, 0.05, 0.1, 0.25, 0.5, 1, 2, 3, 4 and 5Gy) of 6MV X-rays and Co γ-rays were subjected to Dicentric Chromosome Assay (DCA) and dicentrics, excess acentric fragments (AF) and chromatid breaks (CB) were scored. Totally about 31,553 metaphase spreads were scored for the purpose. Dose response curves of both radiation qualities were almost same except for a 13.8% higher β value for 6MV X-rays. However, blind tests results revealed that both these curves are biologically equivalent and exhibited good dose prediction accuracy for the entire dose range. This demonstrated the feasibility of interchangeable use of these curves in biodosimetry. Consequently it has been suggested that LINAC facilities worldwide can be roped in for biodosimetry capacity augmentation towards managing nuclear emergency situations involving γ-radiation exposures.