Accuracy of the raw-data-based effective atomic numbers and monochromatic CT numbers for contrast medium with a dual-energy CT technique

Objective:To evaluate the accuracy of raw-data-based effective atomic number (Zeff) values and monochromatic CT numbers for contrast material of varying iodine concentrations, obtained using dual-energy CT.Methods:We used a tissue characterization phantom and varying concentrations of iodinated contrast medium. A comparison between the theoretical values of Zeff and that provided by the manufacturer was performed. The measured and theoretical monochromatic CT numbers at 40–130 keV were compared.Results:The average difference between the Zeff values of lung (inhale) inserts in the tissue characterization phantom was 81.3% and the average Zeff difference was within 8.4%. The average difference between the Zeff values of the varying concentrations of iodinated contrast medium was within 11.2%. For the varying concentrations of iodinated contrast medium, the differences between the measured and theoretical monochromatic CT values increased with decreasing monochromatic energy. The Zeff and monochromatic CT nu...