Table 4. aPSNR values of different down-sampling methods.

Cases			DLFBP Sinogram			DLFBP CT Image
			Max-pooling	Mean-pooling	Strided-Conv.	Max-pooling	Mean-pooling	Strided-Conv.
Sparse-view	Synthetic aPSNR(dB)	90 views	52.57	52.86	53.29	38.50	37.42	39.01
		60 views	46.40	45.87	46.47	34.97	35.21	35.52
	Experimental aPSNR(dB)	90 views	52.54	51.21	53.15	39.67	39.10	40.22
		60 views	48.33	48.62	49.30	36.54	35.44	37.21
Limited-view	Synthetic aPSNR(dB)	[0 − 120°]	38.49	38.35	39.74	33.01	33.65	33.78
		[0 − 90°]	38.23	38.54	38.99	31.98	32.14	32.38
	Experimental aPSNR(dB)	[0 − 120°]	46.54	46.87	47.03	45.32	45.11	46.93
		[0 − 90°]	43.21	44.43	44.50	42.88	43.20	43.69