EP04.02: Fetal brain imaging in 3D: a direct comparison between same day MRI and ultrasound volumetric measures

Fetal brain structures appear radically different when imaged using ultrasound (US) and Magnetic Resonance Imaging (MRI). Using same-day US and MRI we investigated differences in volume measurements derived from each modality. We used 110 same-day MRI and US scans, from singleton pregnancies scanned between 18 and 27 gestational weeks, from the iFIND2 study. Modality-specific deep learning pipelines were used to segment each scan into 8 regions (see figure 1a). Poor quality segmentations were rejected through manual inspection, resulting in 93 paired scans. The volume measurements were found to strongly agree between the two modalities, except brain stem (BS), intracranial volume (ICV), cortical plate (CP) (see figure 1b). Differences in BS volume was expected, as MRI scans contain a larger proportion of the structure (see figure 1a). The volume measurements between the two modalities were found to correlate significantly (p < 0.001) for all structures except the ventricular system (see figure 1c). The growth trajectories of most brain structures were found to be consistent between the two modalities. However, the derived volume measurements from ICV, CP, thalamus and white/deep grey matter were larger in US, likely due to how each modality interacts with soft tissue boundaries. This shows that volume measurements derived from one modality cannot always be directly compared to the other without adjusting for the differences in image acquisition. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.