1. Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
2. Department of Radiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado
3. Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
4. Department of Public Health Sciences, Penn State University, University Park, Pennsylvania
5. Department of Biostatistics, University of Virginia, Charlottesville, Virginia
6. Department of Anesthesiology and Pain Management, University of Texas Southwestern, Dallas, Texas