Mass attenuation coefficients, effective atomic numbers and electron densities of some contrast agents for computed tomography

In the clinical computed tomography (CT) examinations, a photon is attenuated as it passes a patient by tissues and contrast agents (CAs). The CM can increase the visibility of internal structures or fluids within the patient. In this work, we have investigated the photon interaction parameters of some CT contrast agents such as iotrolan, iodixanol, iohexol, ioxilan, ioversol, and iomeprol. The mass attenuation coefficients (mu/rho) of these contrast agents have been determined using Geant4 code in the energy range from 1 keV to 1 MeV for total photon interaction. The validity of the Geant4 code was verified by comparing the simulation results with those calculated by the XCOM program. A very good agreement was observed between mu/rho values obtained by both Geant4 and XCOM codes. The mu/rho values were then used to estimate the effective atomic numbers (Z(eff)) and electron densities (N-eff) for the selected CT contrast agents. It was found that the values of mu/rho, Z(eff) and N-eff depend on the photon energy and increase with increasing iodine concentration in the composition of CAs. Also, the Z(eff) values were observed in the range of 6-50 and the N-eff values were observed in the range of 2 - 21 (10(23) electron/g). The present study would be helpful to develop new CT contrast agents to serve in vivo imaging applications.