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

摘要

The purpose of this study was to assess the feasibility to determine fetal blood oxygen saturation (sO₂) with T₂-weighted MR sequences using a fetal sheep model. T₂ measurements were performed on a 1.5-T scanner using a T₂ 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 T₂-weighted scans of the fetal blood in the heart. Signal intensities in the left and right ventricle were measured to calculate the MR blood sO₂. During each phase, fetal carotid artery sO₂ was directly measured and correlated with MR sO₂. A Bland-Altman plot was performed. Fetal carotid artery sO₂ was 69% sO₂ during control, 16% sO₂ during hypoxemia, and 67% sO₂ during recovery. Mean values of the MR sO₂ were 49% sO₂ and 40% sO₂ for control, 6% sO₂ and 3% sO₂ for hypoxemia, and 51% sO₂ and 43% sO₂ for recovery in left ventricle and right ventricle, respectively. Mean values of fetal carotid artery sO₂ and MR sO₂ were highly correlated (left ventricle: r = 0.87, right ventricle: r = 0.89). According to the Bland-Altman plot, MR sO₂ was lower compared to fetal carotid artery sO₂ (left ventricle: 15%, right ventricle: 20%). Based on our preliminary results, it seems to be possible to assess fetal sO₂ with MR oximetry. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.