1. From the Division of Image Processing (I.M.A., P.J.H.d.K., B.P.F.L., J.H.C.R., R.J.v.d.G), Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands, and the Russell H. Morgan Department of Radiology and Radiological Sciences (B.A.W.), Johns Hopkins Hospital, Baltimore, Md.