[1] Univ Penn, Perelman Sch Med, Philadelphia, PA 19107 USA
[2] Univ Penn, Perelman Sch Med, Dept Surg, Philadelphia, PA 19107 USA
[3] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Epidemiol, Baltimore, MD USA
[4] Univ Washington, Dept Surg & Global Hlth Med, Seattle, WA 98195 USA
[5] Univ Penn, Perelman Sch Med, Dept Biostat Epidemiol & Informat, Philadelphia, PA 19107 USA
[6] Penn Hosp, Dept Radiol, Philadelphia, PA 19107 USA