From the Division of Neurology (J.O.), St. Michael's Hospital, University of Toronto, Canada; Department of Neurology (J.O., P.A.C., B.D., D.S.R.), Johns Hopkins University, Baltimore, MD; Mellen Center for Multiple Sclerosis (D.O.), Cleveland Clinic, OH; Department of Neurology (C.A., D.P.), University of Southern California, Los Angeles; Department of Neurology (E.C.K.), Massachusetts General Hospital, Harvard Medical School, Boston; Translational Neuroradiology Unit (M.A., G.N., P.S., D.S.R.), National Institute of Neurological Disorders and Stroke, Bethesda, MD; Brain Imaging Centre (D.L.A., S.N.), Montreal Neurological Institute, McGill University, Canada; Departments of Neurology (R.B.) and Radiology (R.B.), Brigham and Women's Hospital, Harvard Medical School, Boston; Department of Biostatistics (C.C.), Johns Hopkins School of Public Health, Baltimore, MD; Department of Neurology (L.F.), University of Texas Health Science Center at Houston; Department of Neurology (S.G., Y.W.), Weill Cornell Medical College, Cornell University, Ithaca, NY; Department of Neurology (R.H.), University of California at San Francisco; Department of Neurology (M.I., A.T.), Mount Sinai Hospital, New York, NY; Division of Neurology, Department of Medicine (S.K., D.K.B.L.), Department of Radiology (S.K., D.K.B.L., A.R.), Department of Physics and Astronomy (S.K., A.R., A.T., Y.Y.), MS/MRI Research Group (S.K., D.K.B.L., A.T., Y.Y.), MRI Research Centre (S.K., D.K.B.L., A.R.), and Department of Pediatrics (A.R.), University of British Columbia, Vancouver, Canada; A. A. Martinos Center for Biomedical Imaging (C.M.), Department of Radiology, Massachusetts General Hospital, Boston; Centre for Functional and Metabolic Mapping (R.S.M.), Robarts Research Institute, Western University, London, CA; Department of Neurology (F.N.), University of Minnesota, Minneapolis; Advanced Imaging Research Center (W.R., D.S., I.T.), Oregon Health & Science University, Portland; Department of Biostatistics, Epidemiology, and Informatics (R.T.S.), University of Pennsylvania Perelman School of Medicine, Philadelphia; Division of Neuroradiology and Neurophysics (T.Y.), University College London Institute of Neurology, UK; Department of Radiology (Y.Z.) and Department of Clinical Neurosciences and Hotchkiss Brain Institute (Y.Z.), University of Calgary, Canada; and Department of Neurology (N.L.S.), Cedars-Sinai Medical Center, Los Angeles, CA. ohjiw@smh.ca. From the Division of Neurology (J.O.), St. Michael's Hospital, University of Toronto, Canada; Department of Neurology (J.O., P.A.C., B.D., D.S.R.), Johns Hopkins University, Baltimore, MD; Mellen Center for Multiple Sclerosis (D.O.), Cleveland Clinic, OH; Department of Neurology (C.A., D.P.), University of Southern California, Los Angeles; Department of Neurology (E.C.K.), Massachusetts General Hospital, Harvard Medical School, Boston; Translational Neuroradiology Unit (M.A., G.N., P.S., D.S.R.), National Institute of Neurological Disorders and Stroke, Bethesda, MD; Brain Imaging Centre (D.L.A., S.N.), Montreal Neurological Institute, McGill University, Canada; Departments of Neurology (R.B.) and Radiology (R.B.), Brigham and Women's Hospital, Harvard Medical School, Boston; Department of Biostatistics (C.C.), Johns Hopkins School of Public Health, Baltimore, MD; Department of Neurology (L.F.), University of Texas Health Science Center at Houston; Department of Neurology (S.G., Y.W.), Weill Cornell Medical College, Cornell University, Ithaca, NY; Department of Neurology (R.H.), University of California at San Francisco; Department of Neurology (M.I., A.T.), Mount Sinai Hospital, New York, NY; Division of Neurology, Department of Medicine (S.K., D.K.B.L.), Department of Radiology (S.K., D.K.B.L., A.R.), Department of Physics and Astronomy (S.K., A.R., A.T., Y.Y.), MS/MRI Research Group (S.K., D.K.B.L., A.T., Y.Y.), MRI Research Centre (S.K., D.K.B.L., A.R.), and Department of Pediatrics (A.R.), University of British Columbia, Vancouver, Canada; A. A. Martinos Center for Biomedical Imaging (C.M.), Department of Radiology, Massachusetts General Hospital, Boston; Centre for Functional and Metabolic Mapping (R.S.M.), Robarts Research Institute, Western University, London, CA; Department of Neurology (F.N.), University of Minnesota, Minneapolis; Advanced Imaging Research Center (W.R., D.S., I.T.), Oregon Health & Science University, Portland; Department of Biostatistics, Epidemiology, and Informatics (R.T.S.), University of Pennsylvania Perelman School of Medicine, Philadelphia; Division of Neuroradiology and Neurophysics (T.Y.), University College London Institute of Neurology, UK; Department of Radiology (Y.Z.) and Department of Clinical Neurosciences and Hotchkiss Brain Institute (Y.Z.), University of Calgary, Canada; and Department of Neurology (N.L.S.), Cedars-Sinai Medical Center, Los Angeles, CA.