[1] Univ Calif San Francisco, San Francisco Sch Med, Dept Pediat, San Francisco, CA 94143 USA
[2] Univ Calif San Francisco, San Francisco Sch Med, Dept Pathol, San Francisco, CA 94143 USA
[3] Stanford Univ, Sch Med, Dept Pathol, Palo Alto, CA 94304 USA
[4] Stanford Univ, Sch Med, Dept Radiol, Palo Alto, CA 94304 USA
[5] Stanford Univ, Sch Med, Dept Pediat, Palo Alto, CA 94304 USA