Age-Related Changes of Cerebral Autoregulation: New Insights with Quantitative T2′-Mapping and Pulsed Arterial Spin-Labeling MR Imaging

BACKGROUND AND PURPOSE: Cerebral perfusion and O₂ metabolism are affected by physiologic age-related changes. High-resolution motion-corrected quantitative T2′-imaging and PASL were used to evaluate differences in deoxygenated hemoglobin and CBF of the gray matter between young and elderly healthy subjects. Further combined T2′-imaging and PASL were investigated breathing room air and 100% O₂ to evaluate age-related changes in cerebral autoregulation.

MATERIALS AND METHODS: Twenty-two healthy volunteers 60–88 years of age were studied. Two scans of high-resolution motion-corrected T2′-imaging and PASL-MR imaging were obtained while subjects were either breathing room air or breathing 100% O₂. Manual and automated regions of interest were placed in the cerebral GM to extract values from the corresponding maps. Results were compared with those of a group of young healthy subjects previously scanned with the identical protocol as that used in the present study.

RESULTS: There was a significant decrease of cortical CBF (P < .001) and cortical T2′ values (P < .001) between young and elderly healthy subjects. In both groups, T2′ remained unchanged under hyperoxia compared with normoxia. Only in the younger but not in the elderly group could a significant (P = .02) hyperoxic-induced decrease of the CBF be shown.

CONCLUSIONS: T2′-mapping and PASL in the cerebral cortex of healthy subjects revealed a significant decrease of deoxygenated hemoglobin and of CBF with age. The constant deoxyHb level breathing 100% O₂ compared with normoxia in young and elderly GM suggests an age-appropriate cerebral autoregulation. At the younger age, hyperoxic-induced CBF decrease may protect the brain from hyperoxemia.