Fig. 2

Overview of the CNN structure. The model consists of four resolution hierarchies with three skip connections. The input image has the voxel size of \(3\times 3\times 3\) mm³. The input image size is 189 \(\times 162\times 162\) , and the output image size is 163 \(\times 136\times 136\) . The up- and down-sampling rate is three, and the up-sampling is implemented by repetition. The convolutional kernel size for all layers is 3 × 3 × 3