Inclusion Criteria:  Patient whose age ≥ 18 years Patient referred to GHPSJ for suspected stroke Patient who had a brain MRI including the magnetic susceptibility sequence Patient for whom a blood count with hematocrit was performed at the same time (within 7 days between the MRI and the blood test) French-speaking patient  Exclusion Criteria:  Patient under guardianship or curatorship Patient deprived of liberty Patient under court protection Elimination of potential biases: recent injection (48 h) of gadolinium, pathology likely to modify the venous signal in magnetic susceptibility imaging (notably arterial occlusion or stenosis), high flow oxygenation, sickle cell disease, thalassemia. Patient objecting to the use of his/her data for this research