1. From the Departments of Bioengineering (Z.C., F.C., E.M.) and Mechanical and Aerospace Engineering (A.M.), UC San Diego School of Engineering, La Jolla, Calif; and Departments of Radiology (F.C., S.K., E.M.), Cardiology (A.M.K., E.M.), and Pediatrics (H.K.N.), UC San Diego School of Medicine, 9452 Medical Dr, La Jolla, CA 92037.