Photon-counting CT of elbow joint fractures: image quality in a simulated post-trauma setting with off-center positioning

European Radiology Experimental

Table 4 SNR and CNR calculations

	Kernel	Position	Dose protocol	PCD-CT (mean ± SEM)	EID-CT (mean ± SEM)	p value
SNR	Br76/Ur77	OH	2 mGy	0.6 ± 0.11	0.3 ± 0.05	< 0.001
			6 mGy	0.7 ± 0.11	0.3 ± 0.04	< 0.001
			12 mGy	0.7 ± 0.11	0.6 ± 0.15	0.001
		ABD	2 mGy	0.5 ± 0.16	0.3 ± 0.05	< 0.001
			6 mGy	0.7 ± 0.16	0.3 ± 0.05	< 0.001
			12 mGy	0.7 ± 0.17	0.4 ± 0.07	< 0.001
	Br89/Ur89	OH	2 mGy	0.3 ± 0.07	0.3 ± 0.01	0.031
			6 mGy	0.4 ± 0.09	0.3 ± 0.02	< 0.001
			12 mGy	0.4 ± 0.12	0.2 ± 0.03	< 0.001
		ABD	2 mGy	0.3 ± 0.58	0.4 ± 0.03	< 0.001
			6 mGy	0.3 ± 0.08	0.3 ± 0.01	0.235
			12 mGy	0.3 ± 0.11	0.3 ± 0.02	0.774
CNR	Br76/Ur77	OH	2 mGy	0.9 ± 0.16	0.4 ± 0.04	< 0.001
			6 mGy	1.0 ± 0.14	0.6 ± 0.05	< 0.001
			12 mGy	1.0 ± 0.15	1.0 ± 0.12	0.013
		ABD	2 mGy	0.5 ± 0.32	0.4 ± 0.10	< 0.001
			6 mGy	0.9 ± 0.20	0.4 ± 0.04	< 0.001
			12 mGy	0.9 ± 0.21	0.5 ± 0.06	< 0.001
	Br89/Ur89	OH	2 mGy	0.4 ± 0.11	0.4 ± 0.03	0.031
			6 mGy	0.6 ± 0.13	0.3 ± 0.02	< 0.001
			12 mGy	0.7 ± 0.18	0.3 ± 0.04	< 0.001
		ABD	2 mGy	0.4 ± 0.71	0.4 ± 0.04	< 0.001
			6 mGy	0.4 ± 0.11	0.1 ± 0.03	< 0.001
			12 mGy	0.5 ± 0.13	0.4 ± 0.02	0.011

Calculations of SNR and CNR after a ROI-based measurement of signal attenuation for different dose protocols, arm scanning positions and reconstruction kernels. The results are given as mean values with the standard error of mean (± SEM). The p value of the Mann-Whitney U test analysis is reported. ABD Abdominal scanning position, CNR Contrast-to-noise ratio, EID-CT Energy-integrating detector computed tomography, OH Overhead scanning position, PCD-CT Photon-counting detector computed tomography, ROI Region of interest, SNR Signal-to-noise ratio