[1] Rutgers Robert Wood Johnson Med Sch, 675 Hoes Lane West, Piscataway, NJ 08854 USA
[2] Univ Pittsburgh, Sch Med, 3550 Terrace St, Pittsburgh, PA 15261 USA
[3] Stanford Univ, Richard M Lucas Ctr Imaging, MIPS, Sch Med, 1201 Welch Rd, Stanford, CA 94305 USA
[4] Hosp Univ Penn, Dept Radiol, 3400 Spruce St, Philadelphia, PA 19104 USA
[5] Oslo Univ Hosp, Intervent Ctr, Div Technol & Innovat, Rikshosp, Post Box 4950 Nydalen, N-0424 Oslo, Norway
[6] Univ Oslo, Inst Clin Med, Fac Med, Postboks 1078, N-0316 Oslo, Norway