Imaging of the aorta in dual-source photon-counting CT: impact of low energy virtual monoenergetic imaging on image quality, vascular contrast and diagnostic assessability
Author Block: I. Yel1, C. Booz1, V. Koch1, L. D. Gruenewald1, L. S. Alizadeh1, S. Martin1, T. J. Vogl1, S. Waldeck2, D. P. Overhoff2; 1Frankfurt/DE, 2Koblenz/DE
Purpose: To evaluate the impact of low energy VMI+ reconstructions on quantitative and qualitative image quality, vascular contrast and diagnostic assessability of the aorta in patients undergoing photon-counting CTA.
Methods or Background: A total of 125 patients (69 male) who had undergone dual-source photon-counting CTA scans of the aorta were retrospectively analysed in this study. 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, SNR and CNR. CT number measurements were performed in the ascending aorta, the aortic arch, the thoracic and infrarenal descending aorta. Qualitative analyses were performed by three board-certified radiologists independently using five-point scales to evaluate image quality, vascular contrast and diagnostic assessability.
Results or Findings: Mean attenuation, CNR and SNR values were highest in 40 keV VMI+ reconstructions (HU, 1312 ± 13; CNR, 32 ± 8; SNR, 34 ± 10) followed by 55-keV VMI+ reconstructions (HU, 731 ± 9; CNR, 24 ± 6; SNR, 27 ± 9); all three mean values at these keV levels were significantly higher compared with the remaining VMI+ series and standard 120 kV CT series (HU, 160 ± 8; CNR, 18 ± 5; SNR, 26 ± 6) (p<.0001). The qualitative analysis showed the 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 regarding image quality, vascular contrast and diagnostic assessability of the aorta (p<.0001).
Conclusion: Low keV VMI+ reconstructions at a level of 40-55 keV significantly improve image quality, vascular contrast and diagnostic assessability of the aorta compared with standard CT series in photon-counting CTA.
Limitations: The single-centre retrospective study design was an identified limitation.
Funding for this study: No funding was received for this study.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: This study was approved by the local IRB.