1. From the Division of Urology, Surgical Service and Department of Radiology, Brockton/West Roxbury Veterans Administration Medical Center, West Roxbury, Harvard Program in Urology (Longwood Area) and Division of Aging, Harvard Medical School, Joint Departments of Medicine, Brigham and Women’s, and Beth Israel Hospitals, Boston and Department of Mechanical Engineering, Massachusetts Institute of Technology, and Harvard-MIT Division of Health Sciences and Technology, Cambridge, Massachusetts