1. Department of Radiology, Chiba University Hospital, 1-8-1, Inohana, Chuo-ku, Chiba City, Chiba 260-8677, Japan
2. School of Radiological Technology, Health Sciences, Graduate School of Medicine, Tohoku University, 2-1 Seiryo, Aoba, Sendai, Miyagi, 980-8575, Japan
3. Diagnostic Radiology and Radiation Oncology, Graduate School of Medicine, Chiba University, 1-8-1, Inohana, Chuo-ku, Chiba City, Chiba 260-8670, Japan