1. Department of Radiology and Biomedical Imaging, University of California San Francisco (UCSF), 1700 fourth St., Byers Hall 203, San Francisco, California 94158; Department of Biomedical Engineering, University of North Carolina—Chapel Hill (UNC), 152 MacNider Hall, Campus Box 7575, Chapel Hill, North Carolina, 27599; and GE Healthcare, 333 Ravenswood Ave., Building 207, Menlo Park, California 94025