  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\%.
