  Existing image segmentation networks mainly leverage large-scale labeled
datasets to attain high accuracy. However, labeling medical images is very
expensive since it requires sophisticated expert knowledge. Thus, it is more
desirable to employ only a few labeled data in pursuing high segmentation
performance. In this paper, we develop a data augmentation method for one-shot
brain magnetic resonance imaging (MRI) image segmentation which exploits only
one labeled MRI image (named atlas) and a few unlabeled images. In particular,
we propose to learn the probability distributions of deformations (including
shapes and intensities) of different unlabeled MRI images with respect to the
atlas via 3D variational autoencoders (VAEs). In this manner, our method is
able to exploit the learned distributions of image deformations to generate new
authentic brain MRI images, and the number of generated samples will be
sufficient to train a deep segmentation network. Furthermore, we introduce a
new standard segmentation benchmark to evaluate the generalization performance
of a segmentation network through a cross-dataset setting (collected from
different sources). Extensive experiments demonstrate that our method
outperforms the state-of-the-art one-shot medical segmentation methods. Our
code has been released at
https://github.com/dyh127/Modeling-the-Probabilistic-Distribution-of-Unlabeled-Data.
