Estimation of liver iron concentration by dual energy CT images: Influence of X-ray energy on sensitivity

In hemochromatosis an abnormal accumulation of iron is present in parenchymal organs and especially in liver. Among the several techniques employed to diagnose the iron overload, magnetic resonance imaging (MRI) and Computed Tomography (CT) are the most promising non-invasive ones. MRI is largely used but shows limitation including an overestimation of iron and inability to quantify iron at very high concentrations. Therefore, some research groups are focusing on the estimation of iron concentration by CT images. Single X-ray CTs are not able to accurately perform this task in case of the presence of confounding factors (e.g., fat). A potential solution to overcome this concern is the employment of Dual-Energy CT (DECT). The aim of this work is to investigate influence of the kVp and mAs on CT number sensitivity to iron concentration. A phantom with test tubes filled with homogenized porcine liver at different iron concentrations, has been scanned with DECT at different mAs. The images have been analyzed using an ad-hoc developed algorithm which allows minimizing the influence of air bubbles present in the homogenized. Data show that the sensitivity is strongly influenced by kVp (its value almost halves from 80 kVp to 140 kVp; e.g. 0.41 g·μmol^-1 and 0.19 g·μmol^-1 at 80 kVp/120 mAs and 140 kVp/60 mAs respectively), on the other hand the influence of mAs value is negligible.