[1] UNIV CALIF SAN FRANCISCO,DEPT RADIOL,SAN FRANCISCO,CA 94143
[2] CHR TOULOUSE,SERV NEURORADIOL,TOULOUSE,FRANCE
[3] TORONTO GEN HOSP,TORONTO M5G 1L7,ONTARIO,CANADA
[4] CHU VAUDOIS,SERV RADIODIAG,CH-1011 LAUSANNE,SWITZERLAND
[5] UNIV CALIF SAN FRANCISCO,DEPT NEUROSURG,SAN FRANCISCO,CA 94143