[1] McGill Univ, Ctr Hlth, Dept Radiol, Montreal, PQ, Canada
[2] Mem Univ Newfoundland, Dept Med, St John, NF, Canada
[3] Royal Victoria Hosp, Montreal, PQ H3A 1A1, Canada
[4] Univ British Columbia, Fac Med, Dept Radiol, Vancouver, BC, Canada
[5] Univ Alberta, Dept Radiol & Diagnost Imaging, Edmonton, AB, Canada