Liver Segmentation in CT Images Using a Non-Local Fully Convolutional Neural Network

Liver segmentation is a critical step in diagnosing various kinds of hepatic diseases. Based on the segmentation results, physicians can make further assessments more accurately. Although deep learning methods have achieved excellent performance in liver segmentation tasks, the traditional convolution encoder-decoder architecture may easily loss the spatial information due to the stacked convolution and pooling layers. In this paper, we present a non-local spatial feature based neural network (referred as NL-Net) to learn more spatial features of liver for more accurate segmentation. The NL-Net consists of an encoder block, a non-local spatial feature learning block and a decoder block. We utilized the pretrained ResNet model with transfer learning as the encoder. The non-local block can learn long range dependencies of the liver pixel position by computing the response at a position as a weighted sum of the responses at all positions, which can help the network learn more robust features. We applied the proposed model to ISBI 2019 CHAOs liver Segmentation Challenge task and evaluated it on the testing set. Experimental results show that the proposed NL-Net achieved an average dice of 0.972, RAVD of 1.593, ASSD of 1.926 and MSSD of 110.658 on the segmentation results.