1. Molecular Imaging Program at Stanford (MIPS), Canary Center at Stanford for Cancer Early Detection, Department of Radiology and Bio-X Program, School of Medicine, Stanford University, 1201 Welch Road, Lucas P095, Stanford, California 94305-5484, United States
2. Department of Radiology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi 030001, China