1. From the Departments of Radiology (S.T., O.O.) and Medicine (S.T.), University of Pittsburgh, Pittsburgh, Pa; Heart, Lung, Blood, and Vascular Medicine Institute, University of Pittsburgh Medical Center, Pittsburgh, Pa (S.T.); and Department of Radiology, UPMC Presbyterian Hospital, 200 Lothrop St, Suite E200, Pittsburgh, PA 15213 (S.T.).