TABLE 3. Relative Noise Estimation.

Estimates of relative noise between corresponding iBH- and eBH-CT were determined by regional assessment of the distribution of image intensities within manually placed ROIs. The ratio of COVs was calculated from these measurements as a surrogate for the relative noise between image pairs. On average, the estimated eBH-CT noise is 2.2× that of the corresponding iBH-CT.

Case Number	Inhale COV	Exhale COV	Ratio (Exhale / Inhale)
1	0.011	0.018	1.64
2	0.028	0.042	1.50
3	0.015	0.031	2.07
4	0.012	0.024	2.00
5	0.016	0.031	1.94
6	0.008	0.019	2.37
7	0.014	0.037	2.64
8	0.012	0.026	2.17
9	0.014	0.039	2.78
10	0.013	0.037	2.85
		Average Ratio	2.20