Accuracy of iodine quantification and CT numbers using split-filter dual-energy CT: influence of phantom diameter

Dual-energy computed tomography (DECT) generates virtual monochromatic images (VMI) and material decomposition images (MDI), facilitating enhanced tissue contrast and quantitative material assessment. However, the accuracy of these measurements may be influenced by object size due to beam hardening and associated spectral changes. To evaluate the impact of object size on the accuracy of iodine quantification and CT numbers in virtual monochromatic images (VMI) using split-filter dual-energy CT (SFDE), and to compare its performance with sequential acquisition dual-energy CT (SADE). CT scans were performed on phantoms with diameters ranging from 16 to 36 cm using both SFDE and SADE techniques. Virtual monochromatic images and material decomposition images were generated. CT numbers and iodine concentrations were measured from embedded iodine rods, and relative errors were calculated using the 16 cm phantom as a reference. CT numbers in VMI obtained from SFDE exhibited increasing variability with larger phantom sizes, particularly at both low and high energy levels. Iodine quantification errors with SFDE exceeded 10% in all phantom sizes and reached approximately 60% in the 36 cm phantom. In contrast, SADE consistently maintained measurement errors within 10%. Object size significantly influences the accuracy of CT numbers and iodine quantification using SFDE, with larger phantoms showing marked overestimation. These results suggest that careful interpretation is necessary when applying SFDE-based quantitative imaging in patients with larger object sizes.