Table 1. Comparison of SD value of background tissue between reconstructed images and real images using 8%PET images as input.

Group	Liver	Lung	Aorta	Lumbar spine
3D Unet-15s	0.20 (0.14, 0.28)*	0.06 (0.05, 0.10)	0.12 (0.09, 0.15)*	0.27 (0.16, 0.37)
P2P-15s	0.31 (0.23, 0.37)*	0.11 (0.09, 0.13)*	0.16 (0.15, 0.23)	0.27 (0.24, 0.34)
8%PET	0.86 (0.64, 1.06)	0.22 (0.16, 0.25)	0.55 (0.46, 0.77)	1.20 (0.75, 1.57)
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	32.13	35.22	35.11	28.65
P	<0.0001	<0.0001	<0.0001	<0.0001

The italic font represents a statistical difference between this value and that of the 8%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.