Assessment of Virtual Monoenergetic Images in Run-off Computed Tomography Angiography: A Comparison Study to Conventional Images From Spectral Detector Computed Tomography

The aims of this study were to evaluate image quality of virtual monoenergetic images (VMIs) compared with conventional images (CIs) from spectral detector CT (SDCT) and to explore the optimal energy level in run-off computed tomography angiography (CTA). METHODS: The data sets of 35 patients who received run-off CTA on the SDCT were collected in this retrospective study. Conventional images were generated via iterative reconstruction algorithm and VMI series from 40 to 120 keV were generated via spectral reconstruction algorithm. The objective indices including vascular attenuation, noise, signal-to-noise ratio, and contrast-to-noise ratio were compared. Two readers performed subjective evaluation using a 5-point scale. RESULTS: The attenuation showed higher values compared with CIs at 40 to 60 keV (P < 0.001). The noise was similar in 60- to 80-keV VMIs and significantly decreased in 90- to 120-keV VMIs (P < 0.001) in comparison with CIs. The signal-to-noise ratio and contrast-to-noise ratio were improved in 40- to 60-keV VMIs compared with CIs (P < 0.05). The score of subjective assessment was higher than that of CIs in 50- to 70-keV VMIs (P < 0.001). CONCLUSIONS: Virtual monoenergetic images can provide improved image quality compared with CIs from SDCT in run-off CTA, and VMIs at 60 keV may be the best choice in evaluating lower extremity arteries.