COVID TV-UNet: Segmenting COVID-19 Chest CT Images Using Connectivity Imposed U-Net

TL;DR

This paper introduces TV-UNet, a novel segmentation model that incorporates connectivity regularization to improve COVID-19 infected region detection in chest CT images, achieving high accuracy and better connectedness of segmented regions.

Contribution

The paper proposes a connectivity-imposing regularization term in a U-Net based model, enhancing segmentation of COVID-19 regions in CT images with a 2 ext{%} performance gain.

Findings

Achieved over 99 ext{%} mean Intersection over Union (mIoU)

Attained approximately 86 ext{%} Dice score

Demonstrated improved connectedness of segmented regions

Abstract

The novel corona-virus disease (COVID-19) pandemic has caused a major outbreak in more than 200 countries around the world, leading to a severe impact on the health and life of many people globally. As of mid-July 2020, more than 12 million people were infected, and more than 570,000 death were reported. Computed Tomography (CT) images can be used as an alternative to the time-consuming RT-PCR test, to detect COVID-19. In this work we propose a segmentation framework to detect chest regions in CT images, which are infected by COVID-19. We use an architecture similar to U-Net model, and train it to detect ground glass regions, on pixel level. As the infected regions tend to form a connected component (rather than randomly distributed pixels), we add a suitable regularization term to the loss function, to promote connectivity of the segmentation map for COVID-19 pixels. 2D-anisotropic total-variation is used for this purpose, and therefore the proposed model is called "TV-UNet". Through experimental results on a relatively large-scale CT segmentation dataset of around 900 images, we show that adding this new regularization term leads to 2\% gain on overall segmentation performance compared to the U-Net model. Our experimental analysis, ranging from visual evaluation of the predicted segmentation results to quantitative assessment of segmentation performance (precision, recall, Dice score, and mIoU) demonstrated great ability to identify COVID-19 associated regions of the lungs, achieving a mIoU rate of over 99\%, and a Dice score of around 86\%.