Improving image quality and diagnostic usability in photon-counting coronary CT angiography using a novel reconstruction algorithm.

Purpose: Qualitative comparison of image quality and diagnostic usability of the recently introduced ZeeFree (ZF) reconstruction algorithm for photon-counting coronary CT angiography (cCTA) with Standard (SD) and TrueStack (TS) reconstruction algorithms.

Methods and materials: This retrospective single-center study included 59 patients (mean age 62.5 ± 13.7, 37 males) who were referred for cCTA on a clinical photon-counting CT scanner between July and December 2023. Curved planar reformations were reconstructed for coronary arteries using ZF, SD, and TS algorithms. Three blinded radiologists individually evaluated image quality on a 5-point Likert scale (5 = excellent; median and interquartile range). Differences were evaluated using Friedman's test with pair-wise post-hoc testing. Readers were advised to assess the image quality to be diagnostic using a dichotomous yes/no question, with results being presented as percentages and significance evaluated by the Pearson Chi-Square test. Interrater reliability for image quality used Gwet's AC2 coefficient with ordinal weights, and Gwet's AC1 coefficient for diagnostic usability.

Results: ZF showed superior quality (4 (2)) compared to SD (4 (2), p = 0.03) and TS (4 (1), p < 0.001) while a substantial inter-rater agreement was observed for all algorithms (0.70-0.74). Furthermore, ZF obtained the highest diagnostic usability compared to SD (82.5% vs. 77.0%, p < 0.001) and TS (75.5%, p < 0.001) while yielding an almost perfect inter-rater agreement (0.84).

Conclusion: Compared to SD and TS, the novel ZF image reconstruction algorithm for photon-counting cCTA provides improved image quality and diagnostic usability, suggesting its primary use for clinical assessment.

Key points: Question How well does the novel ZeeFree algorithm address motion artifacts in photon-counting coronary CT angiography? Findings ZeeFree significantly outperformed Standard and TrueStack reconstruction algorithms for image quality and diagnostic usability. Clinical relevance Enhanced image quality with ZeeFree could improve the diagnosis of coronary artery disease.