1. Associate professor, and professor and chairman, respectively, Department of Radiology, The George Washington, University Hospital, Washington, DC 20037, US.
2. Research assistant, and associate professor and chairman, respectively, Department of Radiology/Nuclear Medicine, Uniformed Services University of Health Sciences, F. Edward Hebert School of Medicine, Bethesda, MD, US.
3. Department of Anatomy, Uniformed Services University of Health Sciences, F. Edward Hebert School of Medicine, Bethesda, MD, US.