Primary Outcomes. CBF (measured at baseline, after the 12 week intervention and after 6 month follow-up). All participants will be screened for contraindications to MRI using standard clinical screening questionnaires. Participants will undergo MRI on a 3.0 Tesla X750 GE Discovery scanner with an 8-channel array head coil. Scan time is ~45 minutes and will include scans relevant to the primary outcome measure of micro- and macro-vessel CBF. Additional scans will include a 3D T1-weighted volume, and T2 FLAIR to assess ischemic lesion burden.