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The fetal brain undergoes extensive morphological changes throughout pregnancy, which can be visually seen in ultrasound acquisitions. We explore the use of convolutional neural networks (CNNs) for the segmentation of multiple fetal brain structures in 3D ultrasound images. Accurate automatic segmentation of brain structures in fetal ultrasound images can track brain development through gestation, and can provide useful information that can help predict fetal health outcomes. We propose a multi-task CNN to produce automatic segmentations from atlas-generated labels of the white matter, thalamus, brainstem, and cerebellum. The network as trained on 480 volumes produced accurate 3D segmentations on 48 test volumes, with Dice coefficient of 0.93 on the white matter and over 0.77 on segmentations of thalamus, brainstem and cerebellum.

For many medical applications, large quantities of imaging data are routinely obtained but it can be difficult and time-consuming to obtain high-quality labels for that data. We propose a novel uncertainty-based method to improve the performance of segmentation networks when limited manual labels are available in a large dataset. We estimate segmentation uncertainty on unlabeled data using test-time augmentation and test-time dropout. We then use uncertainty metrics to select unlabeled samples for further training in a semi-supervised learning framework. Compared to random data selection, our method gives a significant boost in Dice coefficient for semi-supervised volume segmentation on the EADC-ADNI/HARP MRI dataset and the large-scale INTERGROWTH-21st ultrasound dataset. Our results show a greater performance boost on the ultrasound dataset, suggesting that our method is most useful with data of lower or more variable quality.