1. From the Noninvasive Cardiac Imaging Laboratory, University of Chicago, Chicago, Ill (V.M.-A., L.S., L.W., P.M., E.G.C., R.K., R.M.L.); Dipartimento di Bioingegneria, Politecnico di Milano, Milan, Italy (E.G.C.); and Philips Medical Systems, Andover, Mass (I.S.S.).