AGE-RELATED VASODILATORY RESPONSE TO ACETAZOLAMIDE CHALLENGE IN HEALTHY-ADULTS - A DYNAMIC CONTRAST-ENHANCED MR STUDY

PURPOSE: We examined age-related changes in baseline regional cerebral blood volume (rCBV) and response to acetazolamide stimulation by usin g dynamic contrast-enhanced MR imaging. METHODS: Thirty healthy volunt eers ranging widely in age (23 to 82 years) were examined before and a fter intravenous injection of acetazolamide with dynamic susceptibilit y contrast-enhanced MR imaging. rCBV values were normalized for inters ubject and intrasubject comparison by estimating an arterial input fun ction directly from the imaging data. Preacetazolamide baseline rCBV a nd the percentage volume change index (PVCI) of the postacetazolamide to preacetazolamide state were calculated and examined as a function o f age. RESULTS: Older adults (>50 years) had lower baseline rCBV per u nit tissue than did younger adults (<50 years), but higher rCBV after acetazolamide stimulation, Baseline rCBV tended to decrease with age i n the medial frontal and frontoparietal gray matter regions. Response to acetazolamide stimulation, measured by PVCI, showed a significant a ge-related increase in gray matter, approximately 0.5% per year. CONCL USION: rCBV can be significantly increased after acetazolamide stimula tion in the healthy aged. These results support the notion that age-re lated decreases in rCBV measured at rest reflect reduced regional meta bolic requirements rather than reduced capacity for regional substrate delivery. These data serve as a normative baseline for comparison stu dies of rCBV vascular reserve in aging persons with various cerebrovas cular disorders.