Comparison of Low-Iodine Concentration Quantification Accuracy and Contrast-To-Noise Ratio Across Three Dual-Energy...

Dual-energy computed tomography (DECT) enables improved tissue characterisation and the potential to reduce contrast media dose, yet clinical practice often still uses contrast volumes comparable to single-energy CT. This study evaluates the accuracy of low-concentration iodine quantification and image quality across three DECT techniques, with specific objectives to identify the lowest reliably measurable iodine concentration and to compare normalised contrast-to-noise ratios (CNR_norm) using a clinical abdominal CT protocol.

A Multi-Energy CT Quality Assurance Phantom (CIRS Model 662) filled with iodinated contrast (Iopamiro 370 mgI/mL) at concentrations of 0.025-10 mgI/mL was scanned three times using the clinical abdominal imaging protocol at the study site, without parameter adjustment. Iodine maps and virtual monoenergetic images (VMI) were analyzed using regions of interest to evaluate iodine measurement accuracy for limit of detection (LOD) and limit of quantification (LOQ) and normalised CNR across the DECT techniques.

For VMI at 40 keV, all DECT techniques demonstrated high iodine measurement accuracy (R² > 0.99). The LODs for rapid kV-switching, dual-layer detector, and dual-source DECT were 0.205, 0.436 and 0.411 mg/mL, respectively. Corresponding LOQs were 0.621, 1.321 and 1.246 mg/mL. The rapid kV-switching system consistently achieved the lowest LOD and LOQ, while the dual-layer detector yielded the highest CNR_norm, followed by dual-source DECT and rapid kV-switching.

All DECT techniques accurately quantified iodine on iodine maps. Rapid kV-switching provided the lowest LOD and LOQ, whereas the dual-layer detector offered superior image quality in terms of CNR_norm derived from VMI at 40 keV in CT abdominal protocol setting.