Balancing act between quantitative and qualitative image quality between nonionic iodinated dimer and monomer at...

Investigate the impact of nonionic dimer and monomer on iodine quantification in different vessel sizes when employing a vascular specific phantom and varying iodinated contrast media (ICM) concentrations during computed tomography (CT).

We created a vascular specific phantom (30 cm) to simulate human blood vessel diameters (25 cylinders of different diameters: 10 × 9mm, 10 × 12mm and 5 × 21mm). The phantom was filled with two ICM separately: Group: Iohexol(monomer)350 mg ml^-1 and B: Iodixanol(Dimer)320 mg ml^-1. Cylinders of same size were filled with increasing ICM concentration(10%-100%) while large cylinders were filled in quartiles(25%-100%). Phantom was scanned with different tube potential (80-140kVp), current (50-400mAs), reconstruction method [filtered back projection (FBP), hybrid-based iterative reconstruction (HBIR) and model-based iterative reconstruction (MBIR)] for each ICM. Chi-square was employed to compare mean opacification, contrast/noise ratio (CNR) and noise. Qualitative analysis was assessed by Visual grading characteristic (VGC) and Cohens-kappa analyses.

At 80 and140kVp significant difference in opacification between Group A (2054 ± 1040HU and 1696 ± 1027HU) and B (2169 ± 1105HU and 1568 ± 1034HU) was demonstrated (p < 0.001). However, at 100 and 120kVp no difference was noted (p > 0.05). When comparing image noise, it was higher in Group A compared to B (p < 0.05). CNR was higher in Group B (119.99 ± 126.10HU) than A (107.09 ± 102.56HU) (p < 0.0001). VGC: Group A outperformed B in image opacification in all vessel sizes and ICM concentrations except at medium vessels with concentration group 2(0.4-0.6 mg ml^-1). Cohens'-kappa: agreement in opacification between each ICM group and iodine concentration 1(0-0.3 mg ml^-1): κ = 0.253 and 0.014 respectively, concentration 2(0.4-0.6 mg ml^-1):κ = -0.017 and -0.005 respectively and concentration 3(0.7-1 mg ml^-1):κ = 0.031 and 0.115 respectively.

Nonionic dimer (Iodixanol) surpasses monomer (Iohexol) in quantitative image quality assessment by having lower image noise and higher CNR during CT.