1. From the Joint Center for Radiation TherapyHarvard Medical School, and Departments of Pathology and Urology, Brigham and Women’s Hospital, Boston; Department of Mathematical Sciences, Worcester Polytechnic Institute, Worcester, MA; Departments of Radiation Oncology, Urology, and Pathology, Hospital of the University of Pennsylvania, Philadelphia; and Department of Mathematics, Millersville University, Millersville, PA.