1. Department of Radiology and the Surgery Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland; Georgetown University School of Medicine, Washington, DC.; Department of Radiology, National Institutes of Health, Clinical Center, Bldg 10, Room 1C660, Bethesda, MD 20892.
2. Department of Radiology and the Surgery Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland; Georgetown University School of Medicine, Washington, DC.