[1] Univ Calif San Francisco, Sch Med, Dept Radiat Oncol, San Francisco, CA 94143 USA
[2] Univ Calif San Francisco, Sch Med, Dept Neurol, San Francisco, CA 94143 USA
[3] Univ Calif San Francisco, Sch Med, Dept Neurol Surg, San Francisco, CA 94143 USA