Fig. 3.

Obtain background and mask. In A, we obtain a bone window image (to the left of the arrow) and use the corresponding mask to remove the nodule information, resulting in a clean background (to the right of the arrow). In B, ‘Process’ means randomly resizing the input mask and introducing random spikes or dents; ‘Add’ refers to combining the mask with a bone window image used as the background; ‘Delete’ means removing the overlapping regions between the mask and the bone