ASSESSMENT OF CEREBRAL BLOOD-FLOW RESERVE USING FUNCTIONAL MAGNETIC-RESONANCE-IMAGING

Imaging of activated brain areas based on changes of blood deoxyhemogl obin levels is now possible with MRI. Acetazolamide (ACZ) increases ce rebral blood now (CBF) without changing cerebral oxygen consumption; t his results in signal changes observed in gradient echo MR images from the areas with an increase in CBF, We assessed signal changes after A CZ application in seven healthy subjects with a conventional 1.5-T MRI scanner. The susceptibility-sensitized three-dimensional fast low-ang le shot (FLASH) sequence was used to visualize signal changes induced by ACZ. We analyzed anatomic localization of different ranges of detec ted signal changes. ACZ caused significant signal changes in the gray matter and at the edge of the cerebral cortex, the latter correspondin g to draining surface veins. No significant differences were seen amon g different brain areas within the same slice. Using the maximum inten sity projection technique, we were able to partially separate signal c hanges originating in draining veins from signal originating in the gr ay matter microvasculature. Signal changes from the microvessels refle ct cerebrovascular reserve, Blood-oxygen-level-dependent (BOLD) based MRI can evaluate CBF reserve with high spatial and temporal resolution , To assess cerebrovascular reserve, it is necessary to separate signa l changes originating in large vessels from signal from brain microvas culature.