Quantitative oxygenation venography from MRI phase

Purpose To demonstrate acquisition and processing methods for quantitative oxygenation venograms that map in vivo oxygen saturation (SvO₂) along cerebral venous vasculature. Methods Regularized quantitative susceptibility mapping (QSM) is used to reconstruct susceptibility values and estimate SvO ₂ in veins. QSM with ℓ₁ and ℓ₂ regularization are compared in numerical simulations of vessel structures with known magnetic susceptibility. Dual-echo, flow-compensated phase images are collected in three healthy volunteers to create QSM images. Bright veins in the susceptibility maps are vectorized and used to form a three-dimensional vascular mesh, or venogram, along which to display SvO₂ values from QSM. Results Quantitative oxygenation venograms that map SvO₂ along brain vessels of arbitrary orientation and geometry are shown in vivo. SvO₂ values in major cerebral veins lie within the normal physiological range reported by ¹⁵O positron emission tomography. SvO₂ from QSM is consistent with previous MR susceptometry methods for vessel segments oriented parallel to the main magnetic field. In vessel simulations, ℓ₁ regularization results in less than 10% SvO₂ absolute error across all vessel tilt orientations and provides more accurate SvO₂ estimation than ℓ₂ regularization. Conclusion The proposed analysis of susceptibility images enables reliable mapping of quantitative SvO₂ along venograms and may facilitate clinical use of venous oxygenation imaging.