Table 2. Numerical analysis of sequential and non-sequential transfer learning images.

Transfer learning methods	Day 3	Day 4	Day 5
Sequential freezing	SSIM: 0.956; PSNR: 38.38	SSIM: 0.941; PSNR: 35.47	SSIM: 0.950; PSNR: 37.14
All-data freezing	SSIM: 0.957; PSNR: 38.33	SSIM: 0.946; PSNR: 35.64	SSIM: 0.950; PSNR: 37.47
Sequential tuning	SSIM: 0.950; PSNR: 37.86	SSIM: 0.945; PSNR: 35.97	SSIM: 0.950; PSNR: 37.19
All-data tuning	SSIM: 0.954; PSNR: 37.96	SSIM: 0.944; PSNR: 35.58	SSIM: 0.943; PSNR: 36.83
Basic U-Net	SSIM: 0.922; PSNR: 33.62	SSIM: 0.936; PSNR: 34.75	SSIM: 0.892; PSNR: 32.06

PSNR, peak signal-to-noise ratio; SSIM, structure similarity index matrix.