1. From the Departments of Diagnostic and Interventional Imaging (P.A.N., I.C., S.J.S., R.E.G.) and Neurology (J.S.W.), McGovern Medical School, University of Texas Health Science Center, 6431 Fannin St, Houston, TX 77030; and Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574 (F.D.L.).