Repeatability and reliability of cerebrovascular reactivity in young adults using multi-echo, multi-contrast MRI.

Cerebrovascular reactivity (CVR) shows promise as a biomarker of vascular integrity and may benefit from a repeatable, reliable, and microvasculature-sensitive acquisition. A combined spin- and gradient-echo (SAGE) functional MRI (fMRI) acquisition may improve repeatability and reliability compared to single spin- (SE) and gradient-echo (GRE) fMRI and provide a microvascular-weighted analysis. The most repeatable and reliable MRI acquisition CVR maps were compared across three CVR paradigms: a breath-hold task, a breath modulation task, and a resting state acquisition. SAGE-fMRI data was acquired in fifteen young adults at two timepoints. Mean gray matter (GM) within-subject coefficient of variation (wCV) and intraclass correlation coefficient (ICC) were compared within the quantitative and weighted SAGE-fMRI CVR maps and single GRE- and SE-fMRI CVR. Total and microvascular MRI inputs with lowest wCV and highest ICC were used to compare three CVR paradigms. Total and microvascular weighted SAGE-fMRI CVR had the lowest wCV and highest ICC across paradigms. The breath-hold paradigm produced significantly higher GM CVR estimates. SAGE repeatably and reliably measures CVR and offers a simultaneous, complementary analysis on total and microvascular scales. The breath-hold paradigm showed significantly higher CVR estimates, but less compliance-dependent protocols may be ideal for applications in patient populations.