  We propose an algorithm for calculating the cardiothoracic ratio (CTR) from
chest X-ray films. Our approach applies a deep learning model based on U-Net
with VGG16 encoder to extract lung and heart masks from chest X-ray images and
calculate CTR from the extents of obtained masks. Human radiologists evaluated
our CTR measurements, and $76.5\%$ were accepted to be included in medical
reports without any need for adjustment. This result translates to a large
amount of time and labor saved for radiologists using our automated tools.
