[1] Mayo Clin, Dept Radiol, Rochester, MN USA
[2] Mayo Clin, Dept Neurol Surg, 200 First St SW, Rochester, MN 55905 USA
[3] Mayo Clin, Mayo Med Sch, Rochester, MN USA
[4] Hosp Niguarda, Dept Radiol, Milan, Italy
[5] Gemelli Hosp, Dept Radiodiag, Rome, Italy