Brain oxygen saturation assessment in neonates using T2-prepared blood imaging of oxygen saturation and near-infrared spectroscopy

Abstract

Although near-infrared spectroscopy is increasingly being used to monitor cerebral oxygenation in neonates, it has a limited penetration depth. The T2-prepared Blood Imaging of Oxygen Saturation (T2-BIOS) magnetic resonance sequence provides an oxygen saturation estimate on a voxel-by-voxel basis, without needing a respiratory calibration experiment. In 15 neonates, oxygen saturation measured by T2-prepared blood imaging of oxygen saturation and near-infrared spectroscopy were compared. In addition, these measures were compared to cerebral blood flow and venous oxygen saturation in the sagittal sinus. A strong linear relation was found between the oxygen saturation measured by magnetic resonance imaging and the oxygen saturation measured by near-infrared spectroscopy ( R2 = 0.64, p < 0.001). Strong linear correlations were found between near-infrared spectroscopy oxygen saturation, and magnetic resonance imaging measures of frontal cerebral blood flow, whole brain cerebral blood flow and venous oxygen saturation in the sagittal sinus ( R2 = 0.71, 0.50, 0.65; p < 0.01). The oxygen saturation obtained by T2-prepared blood imaging of oxygen saturation correlated with venous oxygen saturation in the sagittal sinus ( R2 = 0.49, p = 0.023), but no significant correlations could be demonstrated with frontal and whole brain cerebral blood flow. These results suggest that measuring oxygen saturation by T2-prepared blood imaging of oxygen saturation is feasible, even in neonates. Strong correlations between the various methods work as a cross validation for near-infrared spectroscopy and T2-prepared blood imaging of oxygen saturation, confirming the validity of using of these techniques for determining cerebral oxygenation.

Keywords: Brain imaging; cerebral blood flow; cerebral hemodynamics; magnetic resonance imaging; near-infrared spectroscopy.

Figures

Figure 1.

Neonate with an infarction of the left medial cerebral artery: (a) Conventional T2 weighted image with schematic of the two NIRS sensors. The blue arrows indicate the light emitter (Tx1) and two detectors (Rx1 + Rx2). The orange arches indicated the presumed path that light travels through the brain; (b) SO2-T2-BIOS (indicated by Y in %) map with ROIs and blue arrows indicating the center of the NIRS sensors; (c) a CBF map with blue arrows indicating the center of the NIRS sensors.

Figure 2.

MR sequence chart of the T2-BIOS sequence

Figure 3.

Δb images for each eTE (i.e. 0, 40, 80, and 160 ms), with a single ROI and corresponding curve fit for an exemplary subject.

Figure 4.

(a) Linear regression plot between SO2-T2-BIOS and rScO2-NIRS, (b) Bland–Altman plot with regression line between the average and difference between the two methods, (c) Bland–Altman plot of log-transformed data as mean vs. ratio, (d) Linear regression plot between hematocrit (Hct) and the observed difference bias between SO2-T2-BIOS and rScO2-NIRS, (e) Bland–Altman plot where bias data was corrected for Hct variation, and (f) Bland–Altman plot of log-transformed data where the bias was corrected for Hct variation.

Figure 5.

Scatter plots with regression lines between SO2-T2-BIOS and (a) SvO2-T2-TRIR, (b) whole brain CBF and (c) frontal brain CBF, and scatter plots between rScO2 and (d) SvO2-T2-TRIR, (e) whole brain CBF, and (f) frontal brain CBF.