Three-Dimensional Mapping of Brain Venous Oxygenation Using R2* Oximetry

Purpose Cerebral venous oxygenation (Y-v) is an important biomarker for brain diseases. This study aims to develop an R-2*-based MR oximetry that can measure cerebral Y-v in 3D. Methods This technique separates blood signal from tissue by velocity-encoding phase contrast and measures the R-2* of pure blood by multi-gradient-echo acquisition. The blood R-2* was converted to Y-v using an R-2*-versus-oxygenation (Y) calibration curve, which was obtained by in vitro bovine blood experiments. Reproducibility, sensitivity, validity, and resolution dependence of the technique were evaluated. Results In vitro R-2*-Y calibration plot revealed a strong dependence of blood R-2* on oxygenation, with additional dependence on hematocrit. In vivo results demonstrated that the technique can provide a 3D venous oxygenation map that depicts both large sinuses and smaller cortical veins, with venous oxygenation ranging from 57 to 72%. Intrasession coefficient of variation of the measurement was 3.0%. The technique detected an average Y-v increase of 10.8% as a result of hyperoxia, which was validated by global oxygenation measurement from T-2-Relaxation-Under-Spin-Tagging (TRUST) MRI. Two spatial resolutions, one with an isotropic voxel dimension and the other with a nonisotropic dimension, were tested for full brain coverage. Conclusions This study demonstrated the feasibility of 3D brain oxygenation mapping without using contrast agent. Magn Reson Med 79:1304-1313, 2018. (c) 2017 International Society for Magnetic Resonance in Medicine.