1. From the Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia (D.C.F.); and the Departments of Radiology (R.J.G.), Medicine (J.D.S.), and Pathology (C.K.H.), Massachusetts General Hospital, and the Departments of Radiology (R.J.G.), Medicine (J.D.S.), and Pathology (C.K.H.), Harvard Medical School — both in Boston.