[1] Hosp Univ Penn, Dept Radiol, 3400 Spruce St, Philadelphia, PA 19104 USA
[2] Univ Penn, Div Rheumatol, 3400 Spruce St, Philadelphia, PA 19104 USA
[3] Corporal Michael J Crescenz VA Med Ctr, Div Rheumatol, 3900 Woodland Ave, Philadelphia, PA 19104 USA
[4] Univ Penn, Dept Epidemiol & Biostat, 423 Guardian Dr, Philadelphia, PA 19104 USA
[5] Oslo Univ Hosp, Intervent Ctr, Div Technol & Innovat, Sognsvannsveien 20, N-0372 Oslo, Norway
[6] Oslo Univ Hosp, Div Radiol & Nucl Med, Sognsvannsveien 20, N-0372 Oslo, Norway
[7] Univ Oslo, Inst Clin Med, Fac Med, Problemveien 7, N-0315 Oslo, Norway