1. University of Nebraska Medical Center, Department of Radiology, Omaha, Nebraska 68198‐1045
2. The University of Michigan Medical School, Department of Internal Medicine, Ann Arbor, Michigan 48109
3. Duke University Medical Center, Department of Radiology, Durham, North Carolina 27710
4. The Department of Clinical Oncology, The Royal Free Hospital School of Medicine, London, NW3 2PF, United Kingdom
5. Michael Reese/University of Chicago, Center for Radiation Therapy, Chicago, Illinois 60637