MRI-Based Classification of Cerebral Hemodynamic Failure With Resting Perfusion Metrics and Cerebrovascular Reactivity

BACKGROUND: The inability to augment regional cerebral blood flow (CBF) in the setting of steno-occlusive disease involving large brain-supplying arteries is a risk factor for stroke. The gold standard for detecting such hemodynamic impairment requires the application of a vasodilatory stimulus while measuring changes in CBF. Resting blood flow metrics derived from computed tomography or magnetic resonance imaging (MRI) perfusion methods have been applied as surrogates for assessing hemodynamic insufficiency including relative CBF, relative cerebral blood volume, and mean transit time (MTT). The purpose of this study, therefore, was to compare the sensitivity and specificity of MRI resting perfusion metrics with cerebrovascular reactivity (CVR). MRI CVR mapping was used as a reference standard for comparing MRI perfusion–derived CBF, CBV, and MTT. METHODS: MRI resting perfusion metrics were measured using a recently reported noninvasive method that induces a bolus of hypoxia-induced deoxyhemoglobin as the dynamic susceptibility contrast in place of the gadolinium-based contrast agents. CVR was measured using a standardized hypercapnic vasoactive stimulus during blood oxygen level–dependent MRI as a surrogate for CBF. RESULTS: Twenty-two patients with large artery steno-occlusive disease (mean age±SD, 46±17.8 years; 60% female), 24 healthy participants for the CVR atlas (35.1±13.8 years; 33% female), and 25 for the perfusion atlas (38.4±17.6 years; 24% female) were recruited. Significant differences in mean hemispheric middle cerebral artery perfusion (MTT, relative CBF) and CVR metrics in gray matter ( P <0.05) were observed between patients and healthy participants. Comparisons between affected and unaffected hemispheres in patients showed significant differences only for MTT and CVR in gray matter ( P <0.05). Receiver-operating characteristic curves identified CVR as the most sensitive predictor for hemodynamic impairment followed by MTT. CONCLUSIONS: CVR remains a more accurate test for assessing hemodynamic impairment compared to resting blood flow metrics.