Experiments and simulation were done to study the impact of contrast agent when CT scan was used to attenuation correction for PET images in PET/CT system. Whole body phantom was imaged with various concentration of iodine-based contrast agent using CT. Mathematical emission and transmission density map with liver were made to simulate for whole body FDG imaging. A variety of factors were estimated, including non-uniform enhancement of contrast agent, concentration and distribution size of contrast agent, noise level, image resolution, reconstruction algorithm, hypo-attenuation of contrast agent, and different time phases for contrast agent. Experimental studies showed that Hounsfield unit depends on the concentration of contrast agent and tube voltage. From the simulation data, contrast agents introduced artifacts and degraded image quality on the attenuation-corrected PET images. The severity of these effects depends on a variety of factors, including the concentration and distribution size of contrast agent, the noise levels, and the image resolution. These results indicated that the impact of contrast agents should be considered with a full understanding of their potential problems in clinical PET/CT images.

KeywordsPET/CT, Attenuation correction, Artifacts, Contrast agents