Dual Encoder Fusion U-Net (DEFU-Net) for Cross-manufacturer Chest X-ray Segmentation

Zhang, Lipei; Liu, Aozhi; Xiao, Jing; Taylor, Paul

A number of methods based on the deep learning have been applied to medical image segmentation and have achieved state-of-the-art performance. Due to the importance of chest x-ray data in studying COVID-19, there is a demand for state-of-the-art models capable of precisely segmenting chest x-rays before obtaining mask annotations about this sort of dataset. The dataset for exploring best pre-trained model is from Montgomery and Shenzhen hospital which had opened in 2014. The most famous technique is U-Net which has been used to many medical datasets including the Chest X-ray. However, most of variant U-Net mainly focus on extraction of contextual information and dense skip connection. There is still a large space for improving extraction of spatial feature. In this paper, we propose a dual encoder fusion U-Net framework for Chest X-rays based on Inception Convolutional Neural Network with dilation, Densely Connected Recurrent Convolutional Neural Network, which is named DEFU-Net. The densely connected recurrent path extends the network deeper for facilitating context feature extraction. In order to increase the width of network and enrich representation of features, the inception blocks with dilation have been used. The inception blocks can capture globally and locally spatial information by various receptive fields. Meanwhile, the features fusion of two path by summation preserve the context and the spatial information for decoding part. This multi-learning-scale model are benefiting in Chest X-ray dataset from two different manufacturers (Montgomery and Shenzhen hospital). The DEFU-Net achieves the better performance than basic U-Net, residual U-Net, BCDU-Net, modified R2U-Net and modified attention R2U-Net. This model is proved the feasibility for mixed dataset. The open source code for this proposed framework will be public soon.