Table 1.

Comparison of image-quality parameters in polyenergetic and virtual monoenergetic reconstructions. Data are presented as mean ± standard deviation in Hounsfield units (HU); SNR and CNR are dimensionless. GM: gray matter; WM: white matter; SNR: signal-to-noise-ratio; CNR: contrast-to-noise-ratio; SAI: subcalvarial artifact index; PFAI: posterior fossa artifact index. The keV levels are chosen to represent the ends of the spectrum for signal and noise, the highest values for SNR and CNR for comparison of these in MERs and PERs, and both the spectrum and the lowest values for the SAI and PFAI because they are superior to the parameters of the PER.

Image-Quality Parameter	Polyenergetic Reconstruction	Monoenergetic Reconstruction	p Value
GM Signal	41.93 ± 1.78	40 keV: 42.41 ± 6.17 120 keV: 32.93 ± 2.07	p = 0.540 p < 0.001
WM Signal	33.37 ± 1.84	40 keV: 26.87 ± 3.99 120 keV: 30.92 ± 2.05	p < 0.001 p < 0.001
GM Noise	2.21 ± 0.53	40 keV: 5.09 ± 1.36 120 keV: 2.63 ± 0.69	p < 0.001 p < 0.001
WM Noise	2.07 ± 0.41	40 keV: 4.8 ± 1.07 120 keV: 2.53 ± 0.6	p < 0.001 p < 0.001
GM SNR	20.08 ± 5.5	70 keV: 15.59 ± 4.22	p < 0.001
WM SNR	16.77 ± 4.16	70 keV: 12.8 ± 2.47	p < 0.001
GM-WM CNR	2.90 ± 0.92	65 keV: 2.28 ± 0.77	p < 0.001
SAI	3.90 ± 1.48	40 keV: 9.82 ± 5.19 70 keV: 3.57 ± 1.22 120 keV: 2.49 ± 0.58	p < 0.001 p = 0.324 p < 0.001
PFAI	9.67 ± 3.61	40 keV: 13.84 ± 7.77 85 keV: 3.8 ± 0.82 120 keV: 4.31 ± 1.39	p < 0.001 p < 0.001 p < 0.001