1. Department of Radiation Oncology, E-Da Hospital, Kaohsiung 824, Taiwan
2. Department of Medical Imaging and Radiological Science, Central Taiwan University of Science and Technology, Taichung 411, Taiwan
3. Medical Physics & Informatics Laboratory, Department of Electronics Engineering, National Kaohsiung University of Applied Sciences, 415 Chien Kung Road, Kaohsiung 807, Taiwan
4. Department of Medical Imaging and Radiological Sciences, I-Shou University, Kaohsiung 824, Taiwan