1. Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE 68105, USA
2. Department of Urology, University of Nebraska Medical Center, Omaha, NE 68105, USA
3. Department of Urology, University of California, Irvine–Health Orange, Orange, CA 92868, USA
4. Physics Department, Creighton University, Omaha, NE 68178, USA