Changes in coronary plaque component volumes comparing different virtual monoenergetic images using photon-counting computed tomography

Abstract

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): BV was supported by the ÚNKP-22-3-II-SE New National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund. Introduction Photon-counting CT (PCCT) allows virtual monoenergetic images (VMIs) which may aid more precise assessment of coronary plaques. We aimed to analyze how plaque component volumes change on different VMIs. Methods Coronary CT angiography images were acquired using a dual-source PCCT and VMIs were reconstructed between 40–180 keV in 10 keV increments. Polychromatic images at 120 kVp (T3D) were also reconstructed and used as reference. Quantitative image quality analysis was performed on all reconstructed images. Quantitative plaque assessment was performed on T3D images and segmentation masks were copied to all VMI images. Calcified plaque (CP; >350 Hounsfield units, HU), non-calcified plaque (NCP; 30–350HU) and low-attenuation NCP (LAP; −100-30HU) volumes were calculated. Results We analyzed 51 plaques from 51 patients (67% male, mean age 65±12 years). Average attenuation and contrast-to-noise ratio (CNR) decreased significantly with increasing keV levels, with similar values observed between T3D and 70 keV images (299±209 vs 303±225 HU, p = 0.15 for mean HU; 15.5±3.7 vs. 15.8±3.5, p = 0.32 for CNR). Mean NCP volume was comparable between T3D and 100–180 keV reconstructions. There was a graded decrease in mean CP volume, with a significant difference between all VMI images and T3D (p<0.05). LAP volume increased with increasing VMI energy levels and all VMI images showed a significant difference compared to T3D, except for 50 keV (28.0±30.8 mm3 and 28.6±30.1 mm3, respectively, p = 0.63). Conclusion Fixed threshold settings result in significantly different plaque volumes when using VMIs as compared to T3D images. Normalization protocols are needed to have comparable results between future studies.