Multivendor comparison of quantification accuracy of effective atomic number by Dual-Energy CT: A phantom study

Our study aimed to compare the accuracy of the effective atomic number (Z_eff) of five dual-energy CT (DECT) from three vendors and different generations under different scanning parameters.

Z_eff accuracy of five DECT scanners with twelve tube voltage configurations was evaluated by using the TomoTherapy cheese phantom. The potential dose dependence of the Z_eff was investigated using three radiation dose (5, 15, and 25 mGy), and the robustness of Z_eff was simulated for different organs of the body by placing the inserts at different positional depths. Bias and mean absolute percentage error (MAPE) were used to characterize the accuracy of Zeff. Data underwent analysis using one-way ANOVA, followed by the Turky and LSD post hoc tests, simple linear regression, and linear mixed models.

All tube voltage configurations had a bias of less than 1. Dual layer detector DECT (dl-DECT) -140 kV has the lowest MAPE (1.79 %±1.93 %). The third generation dual source DECT (ds-DECT) and the second generation rapid switch DECT (rs-DECT) have higher MAPE than their predecessor DECT. The results of the linear mixed model showed that tube voltage configuration (F=16.92, p < 0.001) and insert type (F=53.26, p < 0.001) significantly affect the MAPE. In contrast, radiation dose only has a significant effect on the MAPE of rs-DECT. The inserts position does not affect the final MAPE.

When scanning different inserts, Z_eff accuracy varies by vendor and DECT generation. Of all the scanners, dl-DECT had the highest Z_eff accuracy. Upgrading DECT generation doesn't lead to higher accuracy, or even lower.