[1] Univ Washington, Dept Neurol & Epidemiol, Seattle, WA 98104 USA
[2] Univ Washington, Dept Biostat, Seattle, WA 98104 USA
[3] NHLBI, Div Epidemiol & Clin Applicat, Bethesda, MD 20892 USA
[4] Wake Forest Univ, Bowman Gray Sch Med, Dept Publ Hlth Sci, Winston Salem, NC 27103 USA
[5] Johns Hopkins Univ, Sch Med, Dept Radiol, Baltimore, MD 21205 USA
[6] Johns Hopkins Univ, Sch Med, Dept Med, Baltimore, MD 21205 USA
[7] Univ Pittsburgh, Med Ctr, Dept Radiol, Neuroradiol Div, Pittsburgh, PA USA
[8] Univ Pittsburgh, Med Ctr, Dept Neurol Surg, Neuroradiol Div, Pittsburgh, PA USA
[9] Tufts Univ, New England Med Ctr, Dept Radiol, Boston, MA 02111 USA
[10] Univ Arizona, Resp Sci Ctr, Tucson, AZ 85721 USA