Fig. 2.

Examples in the image preprocessing. a Original chest CT image. b, c Segmented chest after binarization, a series of morphological erosion, opening and closing operations, remove_small_objects operation and FloodFill operation. d Mapping the original image to the area with pixel value of 1 in the binary image, and getting the original chest part. e, f Segmented lung with another binarization, followed erosion, opening and closing operation. g Mapping the original image to the area with pixel value 1 on binary image, and getting the lung region that we want