1UCLADepartment of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, CA, United States, 2Department of Medicine, Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA, United States, 3Division of Cardiology, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, United States, 4Biomedical Physics Inter-Departmental Graduate Program, University of California, Los Angeles, CA, United States