Abdominal Radiology | 2021
Contrast media injection protocol for portovenous phase abdominal CT: does a fixed injection duration improve hepatic enhancement over a fixed injection rate?
Abstract
Purpose To assess whether a fixed contrast media (CM) injection duration improves the magnitude and inter-patient variability in hepatic enhancement over a fixed injection rate. Methods Outpatients who underwent portovenous phase abdominal CT (fixed duration, February–November 2018; fixed rate, January–July 2020) with 1.22\xa0mL/kg iohexol 350 were included. Subjects with liver, kidney or heart disease were excluded. The number of subjects and injection protocols were as follows: fixed duration arm, 56 women, 60 men, 35\xa0s injection duration; fixed rate arm, 66 women, 62 men, 3\xa0mL/s injection rate. Liver attenuation measurements were obtained from regions of interest on pre- and post-contrast images. Mean hepatic enhancement (MHE) and MHE normalized to iodine dose (MHE/I) were compared (unpaired t -tests and F -tests). Results There was no statistically significant difference in age, weight, body mass index or CM dosing ( p \u2009>\u20090.05). Enhancement indices were significantly lower in the fixed rate group as compared to the fixed duration group, as follows: MHE, 50.0\u2009±\u200912 vs. 54.8\u2009±\u200911 HU ( p \u2009=\u20090.001); and MHE/I, 1.53\u2009±\u20090.43 vs. 1.66\u2009±\u20090.51 HU/g, ( p \u2009=\u20090.04). However, there was no significant difference in the variances of MHE ( p \u2009=\u20090.51) and MHE/I ( p \u2009=\u20090.08). Conclusion A fixed CM injection duration yields a greater magnitude in hepatic enhancement indices than a fixed injection rate. Inter-patient variability in hepatic enhancement indices do not significantly differ between the two injection protocols.