Inclusion Criteria1. patients with ischemic stroke and hospitalized during 4.5-72 hours after onset , confirmed by diffusion weighted imaging (DWI).
2. patients with stable vital signs.
3. patients who have underwent thrombolytic/intravascular therapy are allowed to enroll in the study.
Exclusion Criteria1. patients with absolute/relative contraindication to MRI (including but not confined to metal in the body and claustrophobia).
2. patients who is extremely agitated, and cannot comply with MRI exam.
3. patients who declined the consent.