Rapid measurement of major cortical and subcortical venous oxygenation using EPI-based...

Cerebral venous oxygenation (Y_v) is an important physiological parameter indicating the brain's homeostasis of oxygen demand and supply. This study aims to develop a quantitative MRI technique to provide regional Y_v assessment in approximately 1 min.

The new pulse sequence is referred to as EPI-based T₂-relaxation-under-phase-contrast (EPI-TRUPC). It consists of a phase-contrast module to isolate pure blood signal, a T₂-preparation module to modulate the T₂-weighting of the signal, and a post-saturation module to reset spin history. An EPI phase-contrast scheme was used for rapid data acquisition. Two experimental studies were conducted. In the first study (four males and four females, 26.1 ± 5.3 y), we quantified Y_v values in regional veins of the brain and compared the sequence to existing techniques in terms of accuracy and test-retest reproducibility. In the second study (four males and four females, 24.4 ± 2.7 y), we demonstrated its sensitivity in detecting Y_v increases and decreases by applying O₂ and caffeine challenge, respectively.

Y_v values of five major cerebral veins, specifically internal cerebral vein (ICV), straight sinus (SS), posterior superior sagittal sinus (SSS), middle SSS, and anterior SSS, were found to be 72.7 ± 4.0% (mean ± SD across participants), 68.2 ± 4.3%, 66.1 ± 6.0%, 69.8 ± 4.4%, and 72.6 ± 2.5%, respectively. The intra-session coefficient of variance (CoV) in Y_v measured by EPI-TRUPC of all cortical and subcortical veins was around 2%-3%. Y_v increased during O₂ inhalation, with an average increase of 6.4% in absolute value. Following caffeine challenge, Y_v revealed a gradual decrease over a period of 40 min.

EPI-TRUPC MRI has the potential to provide quantitative and reliable measurement of cortical and subcortical venous oxygenation within clinically feasible scan time.