Estimating blood oxygen saturation through susceptibility sources separation: a new standpoint on quantitative BOLD models

Motivation: MR methods have been proposed to estimate blood oxygen saturation (SO2) in cerebral tissues by exploiting the magnetic susceptibility difference between oxy and deoxyhemoglobin. These models neglect the contribution of extravascular susceptibility sources leading to inaccurate measurements. Goal(s): Recent approaches tried to combine quantitative BOLD and QSM methods but the model neglects the impact of the geometrical arrangements of extravascular sources on signal decay. Approach: Consequently, we propose a new model to unravel signal contributions of both intravascular and extravascular compartments. Results: When applied to rat data, SO2 measurements were improved in myelin-rich structures and stroke lesions compared to models neglecting extravascular sources. Impact: Unraveling extravascular and intravascular signal contributions using our new model holds promise for the characterization of tissular magnetic properties and oxygenation which may serve as biomarkers of hypoxia and predictive tools of damage reversibility in clinical ischemic stroke.