[1] Brown Univ, Warren Alpert Med Sch, Providence, RI 02903 USA
[2] Hosp Univ Vall dHebron, Dept Radiol, Magnet Resonance Unit, Barcelona, Spain
[3] Univ Brest, CNRS, LEMAR, Inst Univ France, F-29280 Plouzane, France
[4] Univ Brest, UMR 6521, CNRS, CEMCA,Chem Dept, F-29238 Brest 3, France
[5] Univ Brest, Neuroradiol, CHU Brest, UMR 1101,INSERM,LaTIM, F-29609 Brest, France