[1] Univ Vermont, Coll Med, Med Ctr Hosp,Fletcher Allen Hlth Care, Dept Radiol Patrick 113, Burlington, VT 05401 USA
[2] Univ Pittsburgh, Med Ctr, Dept Radiol, Pittsburgh, PA 15213 USA
[3] Stanford Univ, Med Ctr, Dept Radiol, Palo Alto, CA 94305 USA
[4] Washington Univ, Sch Med, Edward Mallinckrodt Inst Radiol, St Louis, MO 63110 USA
[5] Georgetown Univ, Med Ctr, Dept Radiol, Washington, DC 20007 USA