Effect of oral contrast agents on computed tomography-based positron emission tomography attenuation correction in dual-modality positron emission tomography/computed tomography imaging

Rationale and Objectives: To evaluate the effect of iodine- and barium-based contrast agents on the computed tomography (CT)-based positron emission tomography (PET) attenuation correction in dual-modality PET/CT. Methods: Experiments were conducted on a Society of Nuclear Medicine/National Electrical Manufacturers Association-PET phantom equipped with cylinders containing [F-18]-2-fluoro-2-desoxy-D-glucose. The main compartment was filled with iodine (0.5-10%), barium (0.5-50%), or water (negative control). The error in attenuation correction was determined by comparison of measured tracer quantities in the presence of contrast agents with expected quantities. Contrast agent attenuation was demonstrated to be comparable to in vivo conditions. Results: The presence of contrast agents resulted in an overestimation of the intracylindrical activity concentration on PET images and overestimation directly related to contrast concentrations (iodine 5-38%; barium 15-580%). Iodine and barium concentrations in clinical use resulted in an activity overestimation of 20 +/- 1.8% for iodine and 21 +/- 2.9% for barium. Conclusion: An overestimation of the tracer activity concentration is to be expected in the presence of oral contrast agents, if PET attenuation correction is attained CT-based.