Contrast enhancement of hepatic tumors in CT: comparison between bolus and infusion techniques

Pre- and postcontrast CT scans of 125 nonselected patients with histologically verified hepatic neoplasms were analyzed. Sixty patients received an intravenous bolus injection of 50-100 ml diatrizoate 60% in 10-20 sec, and 65 patients an intravenous infusion of 300 ml diatrizoate 30% in 5-10 min. Compared to the precontrast examination, a significant improvement in the visualization of hepatic tumors was obtained with both contrast administration methods when the patients were examined before the equilibrium phase (difference in blood iodine concentration between aorta and inferior vena cava of less than 10 H) is reached. The equilibrium phase is reached 2 min after a contrast material bolus and with termination of an infusion. Scanning in the equilibrium phase does not significantly improve visualization of hepatic tumors when compared to the precontrast examination and carries a considerable risk of partial to complete tumor concealment. For similar reasons, concealment of hepatic tumors might also result when intravenous contrast material is used for another radiographic study preceding the CT examination.