Inclusion Criteria1. first ever stroke within 4.5h-72h from onset, confirmed by diffusion weighted imaging (DWI).
2. stable vital signs.
3. the patients who have underwent thrombolytic/intravascular therapy are allowed to enroll in the study.
Exclusion Criteria1. has absolute/relative contraindication to MRI (including but not confined to metal in the body and claustrophobia).
2. Extremely agitated, and cannot comply with MRI exam.
3. Declined the consent.