1. From the Radiology Service (L.B., V.R., G.A.-B., D.S.), VA Medical Center, and the Departments of Radiology (L.B., A.M., R.H., D.S.), Biostatistics (C.M.), Neurological Surgery (M.L., R.H., W.L.Y.), Neurology (R.H., W.S.S., W.L.Y.), and Anesthesia and Perioperative Care (R.H., W.L.Y.), University of California, San Francisco.