Dose Assessment by Chromosomal Damage in Persons Heavily Exposed to Radiation in JCO Criticality Accident

The dose assessment of unpredicted exposure to radiation is essential for the setting of medical care and risk management. Chromosome aberration analysis in peripheral blood lymphocytes has been used as the most sensitive biological measure of radiation dose. The standardized protocols for the chromosomal dose assessment have been proposed by the International Atomic Energy Agency (IAEA).1,2) However, the current methods can only provide a dose equivalent to the average total body absorbed dose (ETD). Generally, in the case of human exposure, including radiation emergency, the dose distribution over body is rarely homogeneous; being spread in gradient ranging from high to low or zero dose. Such dose inhomogeneity is also the case for internal and external exposure to radiation of high linear energy transfer (LET). For the estimation of the late effects of radiation, such as development of cancer, the ETD may be informative because cancer risk is nearly proportional to the dose. However, for the immediate early setting of medical care in the radiation emergency, the information on the dose gradient is essential, particularly on the localization of doses which require medical treatment. Recently, we developed a novel biodosimetry system which involved a global fi