作者单位:Univ Calif San Francisco, Dept Radiol & Biomed Imaging, San Francisco, CA 94109 USA[1]Univ Calif San Francisco, Dept Pediat, 505 Parnassus,M691,Box 0110, San Francisco, CA 94109 USA[2]Univ Calif San Francisco, Dept Pathol, San Francisco, CA 94109 USA[3]