1. From the Departments of Cardiology (T.S., C.F.M., R.H., M.M.Z., J.E.M., D.S., A.C., H.T., S.S., A.K., G.F.T., R.D.B., H.R.H., H.C., S.N.), Biostatistics (V.Z.), and Radiology (S.L.Z.), Johns Hopkins University, Baltimore, MD; and Division of Radiology and Imaging Sciences, NIH Clinical Center, National Institute of Biomedical Imaging and Bioengineering, Bethesda, MD (D.A.B.).