T2-prepared velocity selective labelling: A novel idea for full-brain mapping of oxygen saturation


Background and aim: Disturbances in cerebral oxygenation saturation (SO2) have been linked to adverse outcome in adults, children, and neonates. In intensive care, the cerebral SO2 is increasingly being monitored by Near-InfraRed Spectroscopy (NIRS). Unfortunately NIRS has a limited penetration depth. The “modified T2-prepared Blood Imaging of Oxygen Saturation” (T2-BIOS) MR sequence provides a step towards full brain SO2 measurement. Materials and methods: Tissue SO2, and venous SO2 (SvO2) were obtained simultaneously by T2-BIOS during a respiratory challenge in ten healthy volunteers. These two measures were compared to SO2 that was obtained by a single probe MR-compatible NIRS setup, and to cerebral blood flow and venous SO2 that were obtained by arterial spin labelling and T2-TRIR, respectively. Results: SO2-T2-BIOS and SO2-NIRS had a mean bias of -4.0% (95% CI -21.3% to 13.3%). SvO2-T2-BIOS correlated with SO2-NIRS (R2 = 0.41, p = 0.002) and SvO2-T2-TRIR (R2 = 0.87, p = 0.002). In addition, SO2-NIRS correlated with SvO2-T2-TRIR (R2 = 0.85, p = 0.003) Frontal cerebral blood flow correlated with SO2-T2-BIOS (R2 = 0.21, p = 0.04), but was not significant in relation to SO2-NIRS. Discussion/conclusion: Full brain SO2 assessment by any technique may help validating NIRS and may prove useful in guiding the clinical management of patient populations with cerebral injury following hypoxic-ischaemic events. The agreement between NIRS and T2-BIOS provides confidence in measuring cerebral SO2 by either technique. As it stands now, the T2-BIOS represents a novel idea and future work will focus on improvements to make it a reliable tool for SO2 assessment.