1. Department of Environmetrics and Biometrics, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
2. Department of Radiation Biophysics, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
3. Department of Epidemiology, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
4. Division of Radiation Information Registry, Research Institute of Radiation Biology Medicine, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan