Table 1. Brain phantom reconstruction results comparison with different counting rates.

Counting Rate	ROI	SNR		Bias		Variance
		MLEM	MLEM+SAE	MLEM	MLEM+SAE	MLEM	MLEM+SAE
5 × 104	Total	66.39	69.30	0.0516	0.0409	0.0146	0.0076
	ROI 1	66.49	68.98	0.0860	0.0715	0.0148	0.0082
	ROI 2	56.58	61.70	0.3588	0.1638	0.1428	0.0439
	ROI 3	76.01	76.37	0.0317	0.0295	0.0016	0.0014
1 × 105	Total	65.76	69.20	0.0548	0.0410	0.0172	0.0078
	ROI 1	66.28	69.18	0.0872	0.0721	0.0153	0.0077
	ROI 2	55.83	61.66	0.3952	0.1639	0.1698	0.0443
	ROI 3	76.65	77.37	0.0290	0.0272	0.0014	0.0012
5 × 105	Total	67.69	69.60	0.0434	0.0378	0.0100	0.0071
	ROI 1	66.54	67.69	0.0780	0.0737	0.0144	0.0111
	ROI 2	59.04	62.21	0.2559	0.1533	0.0809	0.0391
	ROI 3	73.19	77.88	0.0484	0.0251	0.0031	0.0011
1 × 106	Total	69.17	70.42	0.0387	0.0365	0.0079	0.0073
	ROI 1	66.97	69.81	0.0782	0.0573	0.0132	0.0068
	ROI 2	59.75	61.73	0.2325	0.1640	0.0687	0.0436
	ROI 3	79.57	80.19	0.0218	0.0162	0.0027	0.0017