[History and Clinical Significance of Perfusion Imaging in Acute Ischemic Stroke:From the Penumbra Concept to Tissue-Based Patient Selection].

Perfusion imaging has transformed acute ischemic stroke management by enabling a paradigm shift from a time-based to a tissue-based treatment. The concept of the ischemic penumbra, originally established through experimental studies and positron emission tomography (PET), provided the physiological basis for identifying potentially salvageable brain tissue. Subsequent advances in computed tomography and magnetic resonance perfusion imaging have allowed quantitative assessment of cerebral hemodynamics in clinical practice. The introduction of perfusion mismatch enables the estimation of ischemic core and penumbra, facilitating individualized patient selection for reperfusion therapy. Landmark trials, including DAWN and DEFUSE 3, have demonstrated that treatment decisions based on tissue viability, rather than the time from symptom onset, can safely extend the therapeutic window. More recently, studies involving large ischemic cores, such as the RESCUE-Japan LIMIT, have challenged traditional treatment boundaries and refined the concept of malignant profile. Despite these advances, the implementation of perfusion imaging in Japan remains limited, because of insufficient reimbursement and restricted access to automated analysis software. This review summarizes the historical evolution, physiological basis, clinical applications, and future perspectives of perfusion imaging and highlights its pivotal role in modern tissue-based stroke care.