[Medical Devices for Evaluating Cerebral Blood Flow and its Evaluation Method]

Neuroimaging studies prior to endovascular treatment for acute ischemic stroke provide essential information for determining eligibility (treatment triage) and procedural strategies. A fundamental concept of recanalization therapy is the mismatch between the ischemic core (irreversibly damaged tissue) and ischemic penumbra (severely hypoperfused, functionally impaired, at-risk, but not yet infarcted tissue). The goal of recanalization therapy is to recanalize an occluded blood vessel, restore blood flow to penumbral tissue before the ischemic core expands, and save the penumbra tissue. Perfusion imaging allows noninvasive evaluation of the ischemic core and penumbral tissue, although the ischemic penumbra is difficult to discern clinically or based on noncontrast imaging alone. Automated postprocessing software can quickly calculate the location and volume of the ischemic core and penumbra. Optimal thresholds vary depending on the specific perfusion software platform. CT perfusion occasionally overestimates or underestimates ischemic core volume. Discordance among CT perfusion findings, clinical symptoms, and CT angiography findings can provide an additional suggestion for the diagnosis of a stroke mimic.