Hepatic helical CT: effect of reduction of iodine dose of intravenous contrast material on hepatic contrast enhancement.

Abstract

To evaluate the effect of a reduction in iodine dose by altering volume and/or concentration of contrast material on hepatic contrast enhancement (HCE) values during hepatic helical computed tomography (CT). One hundred eleven patients were randomized into four contrast material protocols according to concentration (in milligrams of iodine per milliliter)/volume (in milliliters)/grams of iodine: group 1, ioversol, 320/150/48; group 2, ioversol, 320/100/32; group 3, iohexol, 300/150/45; group 4, ioversol, 300/100/30. Helical CT protocols were identical for the four groups. Time-attenuation curves were constructed; the mean HCE, contrast enhancement index (CEI), and optimal liver scanning interval (OLSI) were calculated; and the results were compared statistically. RESULTS;: Time-attenuation curves, mean HCE, CEI, and OLSI of groups 1 and 3 were significantly superior to those for groups 2 and 4. Decrease in volume from 150 to 100 mliters decreased mean HCE by 27%, CEI by 69%, and OLSI from 80%-100% to 0%-43% at threshold levels of 40-60 HU. Decrease in iodine dose from 45-48 g to 30-32 g significantly decreases all HCE values, which potentially decreases detection of focal hypovascular hepatic lesions.