Comparison of Vascular Opacification after Bolus Injection of Iodixanol-320 and Iohexol-350

RATIONALE AND OBJECTIVES: The vascular opacification characteristics of a new nonionic, dimeric contrast agent, iodixanol, have been compared with a nonionic, monomeric agent, iohexol, using ultrafast computed tomography (UFCT). METHODS: In 10 experiments with mongrel dogs, the contrast agents were alternately injected into the animal's left atrium, and UFCT images were obtained at four cross-sectional levels through the carotid arteries. Time-density curves were then obtained for each carotid artery and each agent. The peak height and area under the curves were compared for each agent. RESULTS: Iohexol provided significantly (P < or = .05) greater opacification, determined by paired Student's t tests. CONCLUSION: This result was predicted from the greater iodine concentration of iohexol (350 mg/mL) compared with iodixanol (320 mg/mL); the difference was greater than expected based on iodine content alone.