From the Mathematical Sciences Department (D.T., Z.T., X.H.), Worcester Polytechnic Institute, Mass; the Department of Radiology (G.C., M.F., C.Y.), University of Washington, Seattle; the School of Mathematics (C.Y.), Beijing Normal University, China; and Mallinkcrodt Institute of Radiology (J.Z., P.K.W.), Washington University, St. Louis, Mo. (At 2009-10)
