Vessel-specific quantification of neonatal cerebral venous oxygenation

Purpose: Noninvasive measurement of cerebral venous oxygenation (Y_v) in neonates is important in the assessment of brain oxygen extraction and consumption, and may be useful in characterizing brain development and neonatal brain diseases. This study aims to develop a rapid method for vessel-specific measurement of Y_v in neonates. Methods: We developed a pulse sequence, named accelerated T₂-relaxation-under-phase-contrast (aTRUPC), which consists of velocity-encoding phase-contrast module to isolate pure blood signal, flow-insensitive T₂-preparation to quantify blood T₂, and turbo-field-echo (TFE) scheme for rapid image acquisition, which is critical for neonatal MRI. A series of studies were conducted. First, the pulse sequence was optimized in terms of TFE factor, velocity encoding (VENC), and slice thickness for best sensitivity. Second, to account for the influence of TFE acquisition on T₂ quantification, simulation and experiments were conducted to establish the relationship between TFE-T₂ and standard T₂. Finally, the complete aTRUPC sequence was applied on a group of healthy neonates and normative Y_v values were determined. Results: Optimal parameters of aTRUPC in neonates were found to be a TFE factor of 15, VENC of 5 cm/s, and slice thickness of 10 mm. The TFE-T₂ was on average 3.9% lower than standard T₂. These two measures were strongly correlated (R²= 0.86); thus their difference can be accounted for by a correction equation, T_2,standard = 1.2002 × T_2,TFE− 10.6276. Neonatal Y_v values in veins draining cortical brain and those draining central brain were 64.8 ± 2.9% and 70.2 ± 3.3%, respectively, with a significant difference (P =.02). Conclusion: The aTRUPC MRI has the potential to provide vessel-specific quantification of cerebral Y_v in neonates.