From the Athinoula A. Martinos Center for Biomedical Imaging (S.T.C., H.D.R.), Department of Radiology, and Department of Neurology (N.D.M., S.M.H., H.D.R.), Massachusetts General Hospital, Boston; Voyager Therapeutics (S.M.H.); and Praxis Medicines (B.R.), Cambridge, MA.