Dual-source photon-counting CTA of the thorax: impact of low energy virtual monoenergetic imaging on image quality, vascular contrast and diagnostic assessability
Author Block: C. Booz1, I. Yel1, V. Koch1, L. D. Gruenewald1, L. S. Alizadeh1, S. Martin1, T. J. Vogl1, D. P. Overhoff2, S. Waldeck2; 1Frankfurt a. Main/DE, 2Koblenz/DE
Purpose: The aim of this study was to evaluate the impact of low energy VMI+ reconstructions on quantitative and qualitative image quality, vascular contrast and diagnostic assessability of thoracic arteries in photon-counting CTA.
Methods or Background: A total of 120 patients (66 male) who had undergone dual-source photon-counting CTA scans of the thorax were retrospectively analyzed. Standard 120 kV CT images and low keV VMI+ series from 40 to 100 keV with an interval of 15 keV were reconstructed. Quantitative analyses included evaluation of vascular CT numbers, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). CT number measurements were performed in the ascending and descending aorta, the aortic arch, the common carotid artery, the subclavian artery and the coronaries. Qualitative analyses were performed by three board-certified radiologists independently using five-point scales to evaluate image quality, vascular contrast and diagnostic assessability of thoracic arteries.
Results or Findings: Mean attenuation, CNR and SNR values were highest in 40 keV VMI+ reconstructions (HU, 1205 ± 11; CNR, 29 ± 7; SNR, 30 ± 9) followed by 55-keV VMI+ reconstructions (HU, 679 ± 8; CNR, 23 ± 6; SNR, 24 ± 7); all three mean values at these keV levels were significantly higher compared with the remaining VMI+ series and standard 120 kV CT series (HU, 169 ± 7; CNR, 19 ± 5; SNR, 27 ± 7) (p<.0001). The qualitative analysis showed highest rating scores for 55 keV VMI+ reconstructions followed by 40 keV and 70 keV VMI+ series with a significant difference compared to standard 120 kV CT images series (p<.0001).
Conclusion: Low keV VMI+ reconstructions at a level of 40-55 keV significantly improve image quality, vascular contrast and the diagnostic assessability of the thoracic arteries compared with standard CT series in photon-counting CTA.
Limitations: Single-center retrospective study design
Funding for this study: No funding was receidved for this study.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: The local IRB approved this study.