[1] Univ Tubingen, Dept Diagnost Radiol, D-72076 Tubingen, Germany
[2] Univ Tubingen, Inst Med Virol, D-72076 Tubingen, Germany
[3] Univ Tubingen, Dept Diagnost Radiol Neuroradiol, D-72076 Tubingen, Germany
[4] Harvard Univ, Beth Israel Deaconess Med Ctr, Sch Med, Dept Neuroradiol, Boston, MA 02215 USA