Table 3. Comparison of SD value of background tissue between reconstructed images and real images using 17%PET images as input.

Group	Liver	Lung	Aorta	Lumbar spine
3D Unet-30s	0.19 (0.15, 0.24)*	0.06 (0.05, 0.09)	0.12 (0.10, 0.14)*	0.26 (0.20, 0.43)
P2P-30s	0.28 (0.25, 0.33)*	0.10 (0.07, 0.13)*	0.16 (0.13, 0.20)	0.29 (0.22, 0.37)
17%PET	0.45 (0.38, 0.67)	0.12 (0.11, 0.16)	0.35 (0.25, 0.42)	0.66 (0.45, 0.90)
s-PET	0.25 (0.19, 0.29)	0.08 (0.06, 0.09)	0.19 (0.16, 0.20)	0.27 (0.23, 0.41)
H	29.46	25.18	32.96	19.93
P	<0.0001	<0.0001	<0.0001	<0.0001

The italic font represents a statistical difference between this value and that of the 17%PET group. And * indicates that the value is statistically significant compared with the s-PET group. SD, standard deviation; PET, positron emission tomography; s-PET, standard positron emission tomography (per bed time: 90 s); 3D Unet, a deep network model based on CNN; P2P, Pixel2Pixel deep network model based on GAN; H, H value for the Kruskal-Wallis method; CNN, convolutional neural network; GAN, generative adversarial network.