1. Department of Diagnostic Radiology, Hiroshima City Hiroshima Citizens Hospital , 7-33 Motomachi, Naka-ku , Hiroshima 730-8518, Japan
2. Department of Diagnostic Radiology, Araki Neurosurgical Hospital , 2-8-7 Kogokita, Nishi-ku , Hiroshima 733-0821, Japan