1. From the Laboratories of Molecular Imaging, Department of Radiology (H.Z., H.Q., R.S.F., B.H., R.Z.), Department of Bioengineering (H.Z., S.M., R.Z.), Department of Medicine, Division of Cardiovascular Medicine (V.A.F., J.A.E.), and the Cardiovascular Institute (H.Z., H.Q., V.A.F., J.A.E.), Department of Biostatistics and Epidemiology (K.P.), and Department of Cell and Developmental Biology (J.A.E.), University of Pennsylvania, Philadelphia, PA.