Gadolinium as a CT contrast agent: Assessment in a porcine model

PURPOSE: To investigate the use of gadolinium as a computed tomographic (CT) contrast agent. MATERIALS AND METHODS: In vitro attenuation measurements of multiple dilutions of gadodiamide and ioversol were compared. In three pigs, 50-mL boluses of undiluted gadodiamide were injected intravenously at 2 mL/sec, and repeated single-level scans were obtained through the lung bases, liver, and kidneys. The doses of 0.8-1.0 mmol of gadolinium per kilogram of body weight were approximately three times the highest doses currently used in patients. Enhancement was determined from attenuation measurements in the aorta, pulmonary arteries, liver, and kidneys. RESULTS: In vitro, the attenuation of undiluted gadodiamide (3,069 HU) was equivalent to that of ioversol diluted to 106 mg of iodine per milliliter and at equimolar concentrations was 50% greater than that of ioversol. The magnitude of and time to peak enhancement were 141 HU and 27 seconds (n = 3) for the aorta; 168 HU and 21 seconds (n = 3) for the pulmonary arteries; 23 HU and 65 seconds (n = 2) for the liver; and 63 HU and 32 seconds (n = 1) for the kidneys. Time-attenuation curves revealed a useful duration of enhancement of 20-30 seconds for the aorta and pulmonary arteries. CONCLUSION: Gadolinium produces good vascular enhancement, adequate renal enhancement, and suboptimal hepatic enhancement. Further study is needed to determine the safety of the gadolinium dose required to produce similar enhancement in patients.