Multi-task Learning for Brain Tumor Segmentation

Accurate and reproducible detection of a brain tumor and segmentation of its sub-regions has high relevance in clinical trials and practice. Numerous recent publications have shown that deep learning algorithms are well suited for this application. However, fully supervised methods require a large amount of annotated training data. To obtain such data, time-consuming expert annotations are necessary. Furthermore, the enhancing core appears to be the most challenging to segment among the different sub-regions. Therefore, we propose a novel and straightforward method to improve brain tumor segmentation by joint learning of three related tasks with a partly shared architecture. Next to the tumor segmentation, image reconstruction and detection of enhancing tumor are learned simultaneously using a shared encoder. Meanwhile, different decoders are used for the different tasks, allowing for arbitrary switching of the loss function. In effect, this means that the architecture can partly learn on data without annotations by using only the autoencoder part. This makes it possible to train on bigger, but unannotated datasets, as only the segmenting decoder needs to be fine-tuned solely on annotated images. The second auxiliary task, detecting the presence of enhancing tumor tissue, is intended to provide a focus of the network on this area, and provides further information for postprocessing. The final prediction on the BraTS validation data using our method gives Dice scores of 0.89, 0.79 and 0.75 for the whole tumor, tumor core and the enhancing tumor region, respectively.