Diagnostic accuracy of dual-layer spectral computed tomography virtual monoenergetic imaging with multiplanar reformation for T-staging of colorectal cancer

Table 3 Subjective and objective image quality assessments of 40-70 keV virtual monoenergetic images and polyenergetic images in colorectal cancer evaluation (n = 157)

Subjective/objective	PEIs	40 keV VMIs	50 keV VMIs	60 keV VMIs	70 keV VMIs	Z value	P value
Noise	8.53 ± 2.90	8.17 ± 3.63	7.27 ± 3.18	6.83 ± 2.73	6.57 ± 2.58	74.521	< 0.001
SNR	8.41 ± 2.45	18.13 ± 7.09	14.81 ± 5.09	12.60 ± 4.05	10.73 ± 3.26	427.420	< 0.001
CNR	23.09 ± 8.95	45.69 ± 22.76	37.85 ± 18.12	31.58 ± 13.60	27.89 ± 12.11	275.540	< 0.001
Subjective scores	3.97 ± 0.42	4.88 ± 0.33	4.85 ± 0.36	4.69 ± 0.50	4.11 ± 0.49	376.086	< 0.001

Objective image quality parameters (noise/contrast-to-noise ratio/signal-to-noise ratio): Reported as median ± interquartile range due to non-normal distribution. Subjective scores: Reported as mean ± SD. CNR: Contrast-to-noise ratio; SNR: Signal-to-noise ratio; PEI: Polyenergetic image; VMI: Virtual monoenergetic image.