Mechanical thrombectomy (MT) is a highly effective treatment that retrieves large blood clots in acute stroke patients. Yet even when the blocked artery is fully reopened, many patients remain disabled. One reason is the No-Reflow phenomenon: tiny brain vessels stay blocked or damaged, so blood cannot reach the tissue. This project will, for the first time, study No-Reflow in patients using advanced MRI scans, blood samples taken directly during MT. The scientistst will test how these markers identify No-Reflow and predict recovery. The results will provide the first clear definition of No-Reflow and open the door to new treatments that improve outcomes after stroke.