1. Department of Neurosurgery, Chang Gung Memorial Hospital, Linkou Medical Center and School of Medicine, Chang Gung University, Taoyuan 333, Taiwan
2. Department of Neurosurgery, Chang Gung Memorial Hospital, Keelung 204, Taiwan
3. Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan
4. Department of Electrical Engineering, Chang Gung University, Taoyuan 333, Taiwan
5. Medical Imaging Research Center, Institute for Radiological Research, Chang Gung University, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan