Low-dose CT image denoising using deep convolutional neural networks with extended receptive fields

How to reduce radiation dose while preserving the image quality as when using standard dose is an important topic in the computed tomography (CT) imaging domain because the quality of low-dose CT (LDCT) images is often strongly affected by noise and artifacts. Recently, there has been considerable interest in using deep learning as a post-processing step to improve the quality of reconstructed LDCT images. This paper provides, first, an overview of learning-based LDCT image denoising methods from patch-based early learning methods to state-of-the-art CNN-based ones and, then, a novel CNN-based method is presented. In the proposed method, preprocessing and post-processing techniques are integrated into a dilated convolutional neural network to extend receptive fields. Hence, large distance pixels in input images will participate in enriching feature maps of the learned model, leading to effective denoising. Experimental results showed that the proposed method is light, while its denoising effectiveness is competitive with well-known CNN-based models.