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Introduction: The value of perfusion MRI for identifying the tissue at risk has been questioned. Our objective was to assess baseline perfusion-weighted imaging parameters within infarct progression areas. Methods: Patients with anterior circulation stroke without early reperfusion were included from a prospective MRI database. Sequential MRI examinations were performed on admission, 2-3 h (H2), 2-3 days (D2), and between 15 and 30 days after the initial MRI. Maps of baseline time-to-peak (TTP), mean transit time (MTT), cerebral blood volume (CBV), and cerebral blood flow (CBF) were calculated. Lesion extension areas were defined as pixels showing de novo lesions between each MRI and were generated by subtracting successive lesion masks: V, baseline diffusion-weighted imaging (DWI) lesion; V, lesion extension between baseline and H2 DWI; V, lesion extension from H2 to D2 DWI; and V, lesion extension from D2 DWI to final FLAIR. Repeated measures analysis was used to compare hemodynamic parameters within the baseline diffusion lesion and subsequent lesion extension areas. Results: Thirty-two patients were included. Baseline perfusion parameters were significantly more impaired within the acute DWI lesion compared to lesion extension areas (TTP, p < 0.0001; MTT, p < 0.0001; CBF p < 0.0001; CBV, p < 0.0001). A significant decrease in MTT ( p = 0.01) and TTP ( p = 0.01) was found within successive lesion growth areas. Conclusion: A decreasing gradient of severity for TTP and MTT was observed within successive infarct growth areas. [ABSTRACT FROM AUTHOR]