Procedure for Normalization of Cerebrovascular Reactivity in Bilateral and Indeterminate Patterns of Hypoperfusion using Dynamic BOLD-CVR

Motivation: The BOLD response to acetazolamide offers robust estimation of cerebrovascular reactivity (CVR) with dynamic interrogation for maximal (CVRmax) augmentation. The lack of physiologic units limits use to relative CVR reductions versus normal hemispheres, confounding use for bilateral steno-occlusive disease (SOD). Goal(s): Develop normal voxel search procedure for BOLD-CVR informed by DSC perfusion in SOD. Approach: DSC in unilateral SOD patients undergoing BOLD-CVR were used to train random forest classifiers and identify voxels with CVRmax within 10% of ground-truth normal hemispheric CVRmax. Results: Median percent-differences <8% from ground-truth were achieved, indicating robust performance for extension of BOLD-CVR to bilateral SOD. Impact: We demonstrate the feasibility of a random forest classifier as a normal voxel search algorithm, in order to identify candidate voxels serving as an auto-normalization for CVR studies in settings of bilateral or indeterminate patters of steno-occlusive disease.