Coronary artery calcium scoring: expanding the new standard by photon-counting detector CT-Part I: Impact of tube voltage, tube current, slice thickness, and quantum iterative reconstructions

OBJECTIVES: Coronary artery calcium (CAC) scoring is a well-established method for cardiovascular risk assessment but has limited reproducibility. For energy-integrating detector (EID)-CT, a new, multivendor validated protocol has been proposed. This study aimed to investigate the variability of photon-counting detector (PCD)-CT-based CAC scoring and propose a new protocol with decreased variability.

MATERIALS AND METHODS: A chest phantom containing nine calcifications was scanned on a PCD-CT using various settings: tube voltages (90 kVp, 120 kVp), tube currents (100% to 25% dose), slice thickness (3 mm, 1 mm), quantum iterative reconstruction (IR, 1-4). To evaluate interscan variability, phantoms were scanned five times per protocol with slight translational (5 mm) and rotational (2°) movements. The standard PCD-CT protocol used 120 kVp, 100% dose, 3 mm slices. CAC scores, image noise, and calcification detectability were assessed. Results were compared to the standard PCD-CT, and standard and proposed EID-CT protocols.

RESULTS: Compared to the standard PCD-CT protocol, score variability decreased by 37% using a thin-sliced protocol at 120 kVp, 25% dose reduction and IR2. Compared to the proposed EID-CT protocol, variability was 66% lower. The optimized PCD-CT protocol met noise targets, eliminating the risk of false-positives. While 6.0 ± 0.0 and 7.0 ± 0.4 calcifications were detected using the PCD-CT standard and the proposed EID-CT protocol, respectively, 7.1 ± 0.7 calcifications were detected with the optimized PCD-CT protocol. Volume and mass scores were closer to physical reference.

CONCLUSIONS: A thin-slice, 25%-dose-reduced PCD-CT protocol at 120 kVp improves CAC score reproducibility and outperforms the proposed EID-CT protocol, possibly offering more reproducible CAC quantification at lower radiation doses.

KEY POINTS: Question Coronary artery calcium scoring is used for cardiovascular risk stratification. However, the current standard method lacks score reproducibility. Findings A thin-slice, 25%-dose-reduced photon-counting detector CT protocol at 120 kVp significantly reduces score variability compared to previous protocols, including the proposed energy-integrating detector CT protocol. Clinical relevance Improved reproducibility of coronary artery calcium scoring may enable more consistent cardiovascular risk prediction and provide a robust technical basis for further in vivo studies.