Table 2.

Example 2—SNR and SSIM of Noisy and Denoised Signals^a

data averaging		SNR		SSIM
		noisy	NERD	noisy	NERD
18-scan	signal	73	1.1 × 108	NA	NA
	peak 1	38	6.1 × 107	NA	NA
	peak 2	17	2.5 × 107	NA	NA
	peak 3	2.7	5.1 × 106	NA	NA
	peak 4	32	5.3 × 107	NA	NA
	peak 5	13	2.4 × 107	NA	NA
	peak 6	9	1.4 × 107	NA	NA
4-scan	signal	33	1.1 × 105	0.8830	0.9968
	peak 1	17	6.04 × 104	0.9073	0.9934
	peak 2	8	2.5 × 104	0.9269	0.9899
	peak 3	3	5.8 × 103	0.8741	0.9753
	peak 4	14	5.3 × 104	0.9208	0.9964
	peak 5	7	2.4 × 104	0.9182	0.9982
	peak 6	6	1.3 × 104	0.8971	0.9945
1-scan	signal	21	3.2 × 104	0.6938	0.9946
	peak 1	9	1.7 × 104	0.7684	0.9978
	peak 2	4	8.1 × 103	0.7324	0.9804
	peak 3	2	2.1 × 103	0.6554	0.9391
	peak 4	9	1.5 × 104	0.8018	0.9935
	peak 5	4	5.7 × 103	0.7827	0.9866
	peak 6	5	4.6 × 103	0.6823	0.9895

^aSNR is calculated at 18-, 4-, and 1-scan at different peaks, whereas SSIM is obtained for 4- and 1-scan because denoised NERD data at 18-scan are used as the reference. Hence, not applicable (NA) is noted for 18-scan SSIM values for noisy and denoised data. SSIM constant parameters are selected as c₁ = c₁ = 10⁻¹³ in order to measure the small differences in the spectrum. Signal refers to the complete spectrum for which the SNR and SSIM are obtained, and peak refers to SNR and SSIM values for individual peak regions.