1. From the Applied Imaging Science Laboratory (A.R.H., M.T.L., F.J.R.), the Thoracic Imaging Section (A.R.H.), Department of Radiology, and Cardiovascular Medicine (S.Z.G.), Brigham and Women's Hospital and Harvard Medical School, Boston Mass; the Department of Radiology (M.T.L.), University of California San Francisco; and the Noninvasive Cardiovascular Imaging Program (F.J.R.), Brigham and Women's Hospital, Boston, Mass.