Table 4.

Differences between linear measurements obtained by the reference protocol (reference dose/filtered back-projection) and the various test protocols

	Mean difference (mm)*	Standard deviation of difference (mm)	95% confidence interval limits (mm)		Significance (linear regression)
			Lower limit	Upper limit
LD1/FBP	− 0.2083	0.61128	− 0.3662	− 0.0504	0.605
LD1/ASIR 50	− 0.2817	0.66498	− 0.4534	− 0.1099	0.394
LD1/ASIR 100	− 0.3467	0.61959	− 0.5067	− 0.1866	–
LD1/MBIR	− 0.4667	1.01508	− 0.7289	− 0.2044	–
LD2/FBP	− 0.2500	0.76878	− 0.4486	− 0.0514	0.584
LD2/ASIR 50	− 0.6367	1.47269	− 1.0171	− 0.2562	–
LD2/ASIR 100	− 0.4050	0.55736	− 0.5490	− 0.2610	–
LD2/MBIR	− 0.4583	1.05899	− 0.7319	− 0.1848	–

– Bland–Altman plot and linear regression were not performed because the one-sample t test demonstrated a mean difference greater than ± 0.3 mm with 95% confidence limits greater than ± 0.5 mm

LD low-dose protocol, FBP filtered back-projection, ASIR adaptive statistical iterative reconstruction, MBIR model-based iterative reconstruction

*All mean differences were statistically significant (p < 0.05)