1. Department of Radiology, Leeds Teaching Hospitals, Musculoskeletal Centre, Chapel Allerton Hospital, Leeds LS7 4SA, UK.
2. National Institute for Health Research Leeds Biomedical Research Centre, Chapel Allerton Hospital, Leeds, UK.
3. Department of Radiology, University of Washington, Seattle, WA.
4. Department of Radiological Sciences, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA.
5. Department of Radiology, University of Michigan Medical Center, Ann Arbor, MI.