[1] VET ADM HOSP, RADIOL SERV, SAN FRANCISCO, CA 94121 USA
[2] UNIV CALIF SAN FRANCISCO, SCH MED, DEPT NEUROL, SAN FRANCISCO, CA 94143 USA
[3] UNIV CALIF SAN FRANCISCO, SCH MED, DEPT RADIOL, SAN FRANCISCO, CA 94143 USA
[4] UNIV CALIF SAN FRANCISCO, SCH MED, DEPT NEUROSURG, SAN FRANCISCO, CA 94143 USA
[5] KAISER FDN HOSP, DEPT RADIOL, REDWOOD CITY, CA USA