Method for measuring cerebral vascular reactivity using hypoxia as vasoactive agent

Abstract

A method for quantitative measurement of cerebral vascular reactivity (CVR) combines sequential gas delivery with ΔR2*-based perfusion analysis. Sequential gas delivery imposes a first stepwise reoxygenation after a first hypoxic condition and a second stepwise reoxygenation after a second hypoxic condition. In one mode, the second hypoxic condition produces greater vasodilation than the first; in another mode both hypoxia levels are minimal and an independent vasoactive stimulus, such as hypercapnia or acetazolamide, is applied between reoxygenations. MRI gradient-echo imaging records the ΔR2* time course in a target voxel during each reoxygenation. Sigmoid fitting yields perfusion metrics including relative cerebral blood flow, relative cerebral blood volume and mean transit time. Comparison of the metrics derived from the two reoxygenations provides a numerical CVR value that can be reproduced across sessions and subjects.

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