1. Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee
2. Department of Radiology, Vanderbilt University School of Medicine, Nashville, Tennessee
3. Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee
4. Department of Biostatistics, Vanderbilt University School of Medicine, Nashville, Tennessee
5. National Institute of Drug Abuse, Bethesda, Maryland
6. Department of Medicine, Washington University School of Medicine, St. Louis, Missouri