Vascular origin of the BOLD phenomenon has been the focus of several studies. Differentiation of the macro- versus micro-vascular and parenchyma components in BOLD images remains to be further examined. With the CBF-based Flow-sensitive Alternating Inversion Recovery (FAIR) technique, it is possible to distinguish macrovascular flow from microvascular flow and perfusion. We define here microvasculature as arterioles, capillaries and venules which can not be spatially resolved in MR image. To find whether activation sites determined by the BOLD technique agree with those detected by the FAIR CBF technique, we have studied functional imaging of motor cortical areas using both techniques. Although some of BOLD-based activated pixels were located at the large vessel areas and the edge of the brain, functional sites were in good agreement in both activation maps generated by BOLD and FAIR techniques.
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