1. From the Departments of Radiology (V.A.W., M.D.C.F., D.L.G.S., K.D., A.F.R., P.J.S.) and Pathology (I.M., A.S.), Boston Medical Center, Boston University Chobanian & Avedisian School of Medicine, 820 Harrison Ave, FGH Building, 4th Floor, Boston, MA 02118.