Assessing cerebral perfusion: analysis of the BOLD response to a hypoxia-induced step change in deoxyhemoglobin

Motivation: Provide direct measurements of cerebral perfusion metrics, relative cerebral blood flow and volume, and mean transit time. Goal(s): Generate a known step susceptibility contrast input rather than requiring back calculation of an arterial input function Approach: We used a step reoxygenation of previously deoxygenated lung alveoli to induce a step increase in oxyhemoglobin in arterial blood and analyzed the T2*-weighted signal for each voxel. Perfusion metrics from step deoxyhemoglobin changes were compared to those from conventional analysis using a gadolinium contrast agent in healthy volunteers. Results: The perfusion metrics from the step deoxyhemoglobin method were similar to those from Gadolinium injection. Impact: Perfusion metrics can be measured directly from a non-invasive test using a step decrease in deoxyhemoglobin generated by instantaneous reoxygenation from a brief hypoxia. They correspond to those calculated indirectly from an intravenously injected Gadolinium contrast agent involving complex analysis.