Perfusion MRI of Infarcted and Noninfarcted Brain Tissue in Stroke

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Abstract
To investigate the hemodynamics of infarcted and noninfarcted regions of the brain in patients with stroke secondary to a complete middle cerebral artery occlusion. Also, to compare factor analysis, a novel method of analyzing perfusion-weighted images, with more conventional techniques. Twenty-two patients with complete unilateral occlusion of the middle cerebral artery were examined by T1-weighted, contrast-enhanced, perfusion-weighted imaging, diffusion-weighted imaging, and magnetic resonance angiography. Quantitative cerebral blood volume (CBV), cerebral blood flow (CBF), and time-to-peak-intensity (TTP) images were generated. Factor analysis of dynamic studies (FADS) was used to generate "early" and "late" images. The hemodynamic parameters for the infarcted and noninfarcted regions of the occluded territory were compared with those for the brain territory on the nonoccluded side. Three regions were shown: (1) Normal tissue on the unaffected side; (2) an infarcted region, which was characterized by reduced CBV, CBF, and early FADS values with increased TTP values; and (3) a noninfarcted region with reduced early FADS and increased late FADS and TTP values compared with the normal region. Cerebral blood volume and CBF values were not reduced significantly in the noninfarcted region. The differences in parameters such as TTP, CBV, and CBF are significant, and it is necessary to use more than one parameter when interpreting magnetic resonance imaging perfusion data. Factor analysis of dynamic studies provides additional information to conventional methods of analyzing perfusion data.