[1] Queens Univ, Kingston Gen Hosp, Dept Diagnost Radiol, Kingston, ON K7L2V7, Canada
[2] Queens Univ, Sch Med, Kingston, ON K7L3N6, Canada
[3] Univ British Columbia, Sch Populat & Publ Hlth, Vancouver, BC V6T 1Z3, Canada
[4] Univ Toronto, Dalla Lana Sch Publ Hlth, Div Epidemiol, Toronto, ON M5S 1A1, Canada
[5] Univ Hlth Network, Toronto Western Hosp, Res Inst, Div Hlth Care & Outcomes Res, Toronto, ON M6J 3S3, Canada
[6] St Pauls Hosp, Ctr Hlth Evaluat & Outcome Sci, Vancouver, BC V6Z 1Y6, Canada