Comparison of iodine quantification results accuracy between 3 different dual-energy CT systems: a phantom study

Introduction

Dual-energy CT seems to be acquiring significant attention in the field of medical imaging. Iodine mapping, specifically, has emerged as a valuable application, enabling the quantification of contrast agent concentration throughout the images. CT users lack robust criteria to assess the accuracy of iodine maps generated by various CT systems. This study seeks to compare the performances of iodine quantification on 3 recent CT systems employing different emission-based technologies, positioned in our hospital.

Methods

A specific home-made phantom was used for this study, with 12 known concentrations of iodinated contrast agent: from 0.4 to 50.0 mgI/mL. Three different dual-energy scanners were tested: one employing dual-source technology and two systems equipped with Fast kilovolt-peak switching solution from two different manufacturers. Helical scans were performed for each system following specific spectral acquisition protocols. Eight acquisitions were performed for each concentration (mgI/mL) on each CT system, resulting in 24 measurements for each concentration and CT. Mean measured values were compared to the known concentrations, and the absolute quantification error (AQE) and the relative percentage error (RPE) were used to compare the performances of each CT.

Results

The obtained measurements' accuracy varied depending on the studied model but not on the acquisition mode. The quantification was more precise at high concentrations (≥5.0 mgI/mL). The accuracy of measured values at low concentrations (<4.0 mgI/mL) varied considerably from one device to another.

Conclusions

We identified variability in the results accuracy depending on the CT model, with sometimes significant deviation. Therefore, a comprehensive evaluation of the performances of all CT systems may be necessary before routinely conducting iodine mapping.

The radiographer role is to be attentive to the performances of imaging systems, especially when dealing with quantitative data such as iodine-quantification.