Author: Xinhua Li, Vu Nguyen, Yifang (Jimmy) Zhou 👨🔬
Affiliation: Cedars-Sinai Medical Center 🌍
Purpose: Assessing iodine concentration in liver lesions is essential for evaluating contrast enhancement in multi-phase liver CT and for accurate disease diagnosis. This study aims to evaluate the assessment accuracy of low iodine concentration in liver lesions using different beam options of dual-energy CT.
Methods: A medium-sized (25×32.5 cm2) liver phantom was custom-designed and industry-fabricated. Shaped in realistic liver, the anthropomorphic phantom consisted of three segments, representing early arterial phase (no iodine), late arterial phase (iodine concentration 0.68 mg/cm3), and venous phase (1.89 mg/cm3) in multi-phase liver CT scans. Each segment contained multiple iodine inserts in different shapes (sphere, ellipsoid, lobulated), volumes (0.092 – 8.57 cm3), and concentrations (0.05 – 2.31 mg/cm3). The phantom was scanned on both GE Revolution (fast kV switch, 80/140 kV; Slice thickness 2.5 mm) and Siemens Force (dual source, 80/150 Sn kV, 100/150 Sn kV; 3 mm) with CTDIvol of 14 mGy. Iodine concentration was assessed using the vendor workstations and the mean of three repeated scans was compared with the ground truth.
Results: Using the choice of 80/150 Sn kV, twelve discernible iodine inserts yielded iodine concentration assessments with a root-mean-square (RMS) error of 0.17 mg/cm3. At 100/150 Sn kV, four inserts were non-discernible, and the other 8 inserts yielded iodine concentration assessments with an RMS error of 0.21 mg/cm3. With fast kV switch (100/140 kV), two of twelve inserts were non-discernible, and the other 10 inserts yielded iodine concentration assessments with an RMS error of 0.45 mg/cm3.
Conclusion: Dual-energy CT is valuable for assessing liver lesion iodine concentrations, even at low levels (<2 mg/cm3), in multi-phase liver scans. Among three dual-energy beam choices evaluated in this study, 80/150 Sn kV demonstrated the highest accuracy for lesions in the medium-sized liver phantom.