1. From the Departments of Radiology (C.J.G.S., T.D.S.L., N.L.R., T.J.B., P.B.S., D.V.) and Medicine (S.K.M.), University of Colorado, Anschutz Medical Campus, 12401 E 17th Ave, Room L517, Aurora, CO 80045; Department of Radiology, University of Texas Health Science Center at Houston, Houston, Tex (D.O.); and Department of Radiology, University of Texas Health Science Center at San Antonio, San Antonio, Tex (C.S.R.).