TABLE II. Image Quality Evaluation Results of Synthetic CT Images (The Best Evaluation Score is Marked in Bold. 
Means Higher Number is Better, and 
Indicates Lower Number is Better.).
| Categories | Complemented images | Lung only images | ||||||
|---|---|---|---|---|---|---|---|---|
| Metrics | FID ( ) |
PSNR ( ) |
SSIM ( ) |
RMSE ( ) |
FID ( ) |
PSNR ( ) |
SSIM ( ) |
RMSE ( ) |
| OURS | 0.0327 | 26.89 | 0.8936 | 0.0813 | 0.3641 | 28.17 | 0.8959 | 0.2747 |
| SEAN [15] | 0.0341 | 26.69 | 0.8922 | 0.0837 | 0.3575 | 28.02 | 0.8952 | 0.2795 |
| SPADE [14] | 0.0389 | 26.50 | 0.8903 | 0.0854 | 0.4812 | 27.79 | 0.8928 | 0.2864 |
| Pix2pixHD [13] | 0.0430 | 26.63 | 0.8893 | 0.0840 | 0.4283 | 27.82 | 0.8910 | 0.2856 |
| Pix2pix [12] | 0.0611 | 26.56 | 0.8870 | 0.0913 | 8.4077 | 26.56 | 0.8855 | 0.3301 |