1. Institute of Nuclear Energy Research, Health Physics Division P.O. Box 3–10, Longtan 32546, Taiwan
2. National Tsing Hua University Department of Biomedical Engineering and Environmental Science No. 101, Sec. 2, Kuang-Fu Road, Hsinchu 30013, Taiwan
3. Chang Gung University Department of Medical Imaging and Radiological Sciences 259, Wen-Hua 1st Road, Kwei-Shan, Tao-Yuan 333, Taiwan