Purpose: The aim of this study was to establish a new method of real-time, in vivo detection of radiation damage and recovery. Methods: The thymus was observed under fluorescent light in a green fluorescent protein transgenic medaka. After irradiation, medaka thymus images were analyzed to quantify the effects of radiation by measuring changes in thymus size. A single acute irradiation of X-rays (0-30 Gy) or heavy Fe ions (0-10 Gy) was delivered to the medaka. Images were captured 0, 1, 2, 3, 5, 7, 11, and 21 d after irradiation. Dose-response assessment was conducted to provide a direct measurement of the effects of the radiation. Conclusion: A biomonitoring system to detect the effects of radiation in real time was established. Using this system, the threshold doses for the induction of thymic atrophy by acute X-rays and Fe ions were 2-5 Gy and 0.5-1 Gy, respectively. The Relative Biological Effectiveness (RBE) of Fe-ion to X-rays was estimated to be around 3. This system may be used to evaluate the risk from concurrent exposure to hazards, such as chemicals and radiation, and for aging research.
Keywords: RBE; Thymus; high linear energy transfer (LET); medaka; radiation effects.