OC48: Comparison of 3D ultrasound and MRI in assessing lung volumes in fetuses with diaphragmatic hernia

Objective: To compare three dimensional ultrasound (3D-US) and magnetic resonance imaging (MRI) in the assessment of lung volumes in fetuses with congenital diaphragmatic hernia (CDH). Methods: Left and right lung volumes were measured using the 30◦ Virtual Organ Computer-aided AnaLysis 3D-US and the multiplan T2 WI MRI technique on a total of 78 fetuses with CDH at 18–38 (median 28) weeks of gestation. Measurements with both methods were done within 4 hours from each other. Regression analysis was used to determine the significance of association between the two methods. Results: There were 67 fetuses with left-sided and 11 with right-sided CDH. Intrathoracic herniation of the liver was observed in 66 of the examinations. In all 78 cases it was possible to visualize and measure both ipsiand contralateral lungs by MRI. In contrast, with 3D-US all contralateral lungs but 44% of ipsilateral lungs (n = 34) could not be adequately visualized. For contralateral lungs there was a significant association between 3D-US and MRI measurements (r = 0.86; p < 0.001). 3D-US volumes were on average 26% lower than those obtained by MRI, independent of lung size, site of CDH or the presence of intrathoracic herniation of the liver. The mean deficit in the measured volume in fetuses with CDH compared to the appropriate normal mean for gestation by the same method and established in previous studies, was not significantly different for 3D-US and MRI. For ipsilateral lungs where both methods yielded a result (56%) there was a much poorer association between 3D-US and MRI (r = 0.39; p < 0.05). Moreover, 3D-US volumes were on average 22% higher than those obtained by MRI. Conclusions: In the assumption that MRI provides an accurate measurement of fetal lungs, in CDH 3D-US provides a reliable measurement of the contralateral but not of the ipsilateral lung.