1. Department of Neurology, Medical Center of Central Massachusetts-Memorial, University of Massachusetts Medical School, Worcester, Massachusetts, U.S.A.
2. Department of Biomedical Engineering, Worcester Polytechnic Institute, University of Massachusetts Medical School, Worcester, Massachusetts, U.S.A.
3. Departments of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts, U.S.A.
4. Departments of Neurology, University of Massachusetts Medical School, Worcester, Massachusetts, U.S.A.