[1] Duke Univ, Sch Med, Durham, NC USA
[2] Duke Clin Res Inst, 2400 Pratt St,NP-8064, Durham, NC 27705 USA
[3] Duke Univ, Sch Med, Dept Med, Durham, NC 27706 USA
[4] Univ Brescia, Inst Cardiol, Dept Med & Surg Specialties, Radiol Sci & Publ Hlth, Brescia, Italy