1 From the Departments of Medicine (A.J.F., I.T.L.), Radiology (J.-A.O.S.), Surgery (L.Y.S.), and Pathology (A.R.S.), Massachusetts General Hospital, and the Departments of Medicine (A.J.F., I.T.L.), Radiology (J.-A.O.S.), Surgery (L.Y.S.), and Pathology (A.R.S.), Harvard Medical School - both in Boston.