Date of Award

January 2026

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Long H. Tu

Abstract

Purpose: Cerebral ischemic infarct results in a rapidly developing core of infarcted brain tissue surrounded by hypoxic but potentially salvageable tissue known as a penumbra. MR perfusion (MRP) is an uncommonly used technique that can be used to define ischemic core and penumbra; its utilization, diagnostic yield, and impact on management, however, are not well-described. This study aims to delineate the use of MRP in acute ischemic stroke and related neurovascular conditions.Methods: This retrospective study examines approximately 11 years of patient encounters (January 1, 2014- November 11, 2024) from a single health system to identify all cases where MR perfusion is used. The study setting sees more than 80,000 inpatient visits, 230,000 ED visits, and 2 million outpatient encounters per year. Patient demographics, imaging indication, patient demographics, scan quality, and ischemic core and penumbra size and location, as well as stroke-related management decisions were evaluated. The influence of age, sex, imaging indication, and clinical setting on diagnostic yield (stroke core and/or penumbra) was assessed. Results: 305 MRP examinations were performed during the study period. MRP represented 0.03% of all MRI exams (961,086 total MRI studies in the same period). The median age of patients in the cases was 64 years old (range 12-95 years old). 39% of patients were male and 61% were female. The most common indications for MRP were ischemic stroke (n = 269, 88%) and moyamoya disease (n = 21, 7%). An ischemic core (i.e., acute stroke) was identified in 220 cases (72% of all cases) and ischemic penumbra was detected in 152 cases (50% of all cases). An ischemic core was significantly more likely in older (p value=0.001) and hospitalized patients (p<0.001). There was no significant association between ischemic penumbra and age, sex, indication, or clinical setting. An ischemic core was more commonly seen within only the anterior circulation compared to posterior circulation and within both anterior and posterior territories (Pearson χ² = 10.87, p value = 0.004). Similarly, ischemic penumbra was most commonly detected in the anterior circulation, specifically the MCA territory. There were 26 cases (9% of all cases) with detection of an ischemic penumbra in patients without an ischemic core. Detection of ischemic penumbra was not associated with increased use of reperfusion therapy. Detection of ischemic core was associated with significantly greater neurologic stroke severity, and worse short-term functional outcomes. Detection of ischemic penumbra was not associated with significant differences in infarct core size, neurologic stroke severity, or short-term functional outcomes. Conclusion: Our analysis finds that perfusion MRI is a rarely used imaging study. In most cases, stroke is known or strongly suspected. Because of patient selection in our study, the diagnostic yield of MRP for ischemic core infarct was high. Use of perfusion MRI in posterior circulation stroke is rare, which may suggest underutilization of perfusion MRI with suspected posterior circulation ischemia. Follow up brain MRI in cases with ischemic penumbra without core infarct is rare. There was no significant association between reperfusion therapy and ischemic penumbra. Detection of an ischemic core was significantly associated with greater neurologic stroke severity, and worse short-term functional outcomes. Ischemic penumbra was not associated with neurologic stroke severity, or short-term functional outcomes. Given the potential utility of perfusion MRI in differentiation of stroke mimics, posterior circulation ischemia, and hyperacute stroke, future prospective studies should be performed to determine the true diagnostic yield of perfusion MRI for evaluation of acute stroke and ischemic penumbra. Clinical Relevance Statement: Our study demonstrates that MR perfusion has high diagnostic yield for acute stroke and that it may be underutilized in posterior circulation ischemia. Detection of ischemic penumbra was not associated with changes in management.

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