1. From the Department of Radiology (A.R.S., M.M.C., T.J.Z., F.T.L.), Research Animal Resource Center (A.G.F.), Department of Statistics (C.G.), and Department of Biomedical Engineering (F.T.L.), University of Wisconsin, 600 Highland Ave, Madison, Wis 53792; Department of Biomedical Engineering and Mechanics, Virginia Polytechnic and State University, Blacksburg, Va (E.V.); and HistoSonics, Ann Arbor, Mich (E.V., J.C.).