Multidetector CT in the liver: optimization of iodine concentration and scan timing for the diagnosis of hepatic tumors

Abstract

To optimise iodine concentration in contrast-enhanced multidetector CT of hepatic tumors. In this multicenter, double-blind, randomized, parallel group comparison, clinical phase IV study 91 patients with the diagnosis of abdominal tumors were included, 60 patients suspicious of focal liver lesions. All patients underwent multidetector helical CT using biphasic contrast-enhanced technique. Iomeprol was administered intravenously in three different concentrations (300, 350 and 400 mg iodine/ml) via an automatic power injector. The overall iodine dose (36 g) was equal within the groups: Group 1, 120 ml Iomeprol 300; Group 2, 105 ml Iomeprol 350; Group 3, 90 ml Iomeprol 400. Injection rate for all three groups was 4 ml/s for arterial phase and 2 ml/s for portal-venous phase imaging. For normal liver tissue in the arterial phase contrast density was 61.3, 64.8 and 72.7 for Iomeprol 300, 350 and 400 ( p=0.01). Iomeprol 400 led to higher contrast densities of normal liver tissue enhancement. Median contrast density of lesion-surrounding tissue tended to be higher for Iomeprol 400 than for the other groups at arterial (74 HU versus 64 and 66) and portal-venous phase (113 HU versus 99 and 102). This difference cannot be considered statistically relevant, but led to far higher contrasts of Iomeprol 400 versus 300 and 350 for subgroups of patients with certain lesions: primary liver carcinoma (45, 48 and 71 HU), cholangio carcinoma (64, 65 and 84 HU). Higher Iomeprol concentrations showed no significant differences in the patients' sensation and were as tolerable as the low concentration. High concentration contrast medium showed advantages in demarcation and delineation compared to lower iodine-concentrated contrast agents for the diagnosis of abdominal tumors especially of hypervascularized lesions.