Impact of acquisition and reconstruction parameters on quantitative accuracy in dual-layer spectral CT: A phantom...

This study aims to systematically evaluate the impact of different CT acquisition and reconstruction parameters on the accuracy of dual-layer spectral CT-based functional imaging, including effective atomic number (Z_eff) maps, relative electron density (RED) maps, and virtual monochromatic images (VMIs).

A standardized phantom equipped with various material inserts, including air, soft-tissue-equivalent, polymer, and bone-equivalent materials, was scanned using a dual-layer spectral CT system. The investigated acquisition and reconstruction parameters included tube voltage, tube current-time product (mAs), reconstruction thickness, pitch, and reconstruction filter. Quantitative accuracy was assessed for RED and Z_eff by comparison with manufacturer-provided reference values, using Bland-Altman analysis. Comparative analyses were performed between VMIs at 40, 70, and 100 keV and conventional CT (120 kVp single-energy reconstruction from the dual-layer system) by calculating the mean and standard deviation of Hounsfield units (HU) differences, to evaluate the dependence of CT number stability on acquisition and reconstruction parameters.

Across all acquisition and reconstruction parameters, RED and Z_eff measurements remained accurate, with signed differences within 2.4% and 0.4%, respectively. Compared with conventional CT, VMIs demonstrated greater robustness to parameter change. At 70 keV, HU variations did not exceed 8 HU, whereas conventional CT exhibited deviations up to 118 HU. Low-energy VMIs (40 keV) showed greater variability, with a maximum difference of 27 HU. Among the investigated parameters, tube voltage exerted the most evident influence.

Dual-layer spectral CT demonstrated quantitative accuracy in functional imaging (ED, Z_eff, and VMIs) across diverse acquisition and reconstruction parameters.