Vessel-specific quantification of cerebral venous oxygenation with velocity-encoding preparation and rapid...

Non-invasive measurement of cerebral venous oxygenation (Y_v) is of critical importance in brain diseases. The present work proposed a fast method to quantify regional Y_v map for both large and small veins.

A new sequence was developed, referred to as TRU-VERA (T₂ relaxation under velocity encoding and rapid acquisition, which isolates blood spins from static tissue with velocity-encoding preparation, modulates the T₂ weighting of venous signal with T₂-preparation and utilizes a bSSFP readout to achieve fast acquisition with high resolution. The sequence was first optimized to achieve best sensitivity for both large and small veins, and then validated with TRUST (T₂ relaxation under spin tagging), TRUPC (T₂ relaxation under phase contrast), and accelerated TRUPC MRI. Regional difference of Y_v was evaluated, and test-retest reproducibility was examined.

Optimal Venc was determined to be 3 cm/s, while recovery time and balanced SSFP flip angle within reasonable range had minimal effect on SNR efficiency. Venous T₂ measured with TRU-VERA was highly correlated with T₂ from TRUST (R² = 0.90), and a conversion equation was established for further calibration to Y_v. TRU-VERA sequences showed consistent Y_v estimation with TRUPC (R² = 0.64) and accelerated TRUPC (R² = 0.79). Coefficient of variation was 0.84% for large veins and 2.49% for small veins, suggesting an excellent test-retest reproducibility.

The proposed TRU-VERA sequence is a promising method for vessel-specific oxygenation assessment.