In vivo MRI measurement of fetal blood oxygen saturation in cardiac ventricles of fetal sheep: A feasibility study

The purpose of this study was to assess the feasibility to determine fetal blood oxygen saturation (sO 2 ) with T 2 ‐weighted MR sequences using a fetal sheep model. T 2 measurements were performed on a 1.5‐T scanner using a T 2 preparation pulse in combination with a three‐dimensional balanced steady‐state free precession sequence repeated at different echo times. Eight sheep fetuses were examined during a control, hypoxic, and recovery phase to perform T 2 ‐weighted scans of the fetal blood in the heart. Signal intensities in the left and right ventricle were measured to calculate the MR blood sO 2 . During each phase, fetal carotid artery sO 2 was directly measured and correlated with MR sO 2 . A Bland‐Altman plot was performed. Fetal carotid artery sO 2 was 69% sO 2 during control, 16% sO 2 during hypoxemia, and 67% sO 2 during recovery. Mean values of the MR sO 2 were 49% sO 2 and 40% sO 2 for control, 6% sO 2 and 3% sO 2 for hypoxemia, and 51% sO 2 and 43% sO 2 for recovery in left ventricle and right ventricle, respectively. Mean values of fetal carotid artery sO 2 and MR sO 2 were highly correlated (left ventricle: r = 0.87, right ventricle: r = 0.89). According to the Bland‐Altman plot, MR sO 2 was lower compared to fetal carotid artery sO 2 (left ventricle: 15%, right ventricle: 20%). Based on our preliminary results, it seems to be possible to assess fetal sO 2 with MR oximetry. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.