Effect of Gadoxetic Acid Injection Duration on Tumor Enhancement in Arterial Phase Liver MRI

Rapid injection of gadoxetic acid has been shown not to increase tumor enhancement in arterial phase liver MRI for unknown reasons. This study aimed to investigate the effect of injection durations on peak contrast concentration in tumors and to correlate it with signal enhancement in gadoxetic acid-enhanced arterial phase MRI.Gadoxetic acid-enhanced arterial phase MRI was obtained using a bolus-tracking technique with injection durations of 1, 3, and 6s in six rabbits with VX2 liver tumors. The peak concentration of gadoxetic acid in the aorta and tumor was estimated by iopromide-enhanced time-resolved CT using the same injection volume and durations with those for MRI. Signal enhancement on MRI and peak enhancement on CT were compared and correlated.There was no significant difference in MR signal enhancement of tumors among the 3 injection durations (p = 0.87). In CT, shorter injection durations significantly increased peak contrast concentration in the aorta (p0.01) but produced equivalent peak contrast concentration in tumors (p = 0.24). The longer injections resulted in the stronger correlation between peak contrast concentration in CT and MR signal enhancement in tumors (r = 0.31, 0.43, and 0.86 with 1s-, 3s-, and 6s-injection, respectively) with a statistical significance only found with 6s-injection (p = 0.03).Estimation of contrast concentration by CT demonstrated that shorter injections did not increase peak contrast concentration in tumors despite increased peak concentration in the aorta. Furthermore, tumor signal enhancement in gadoxetic acid-enhanced arterial phase MRI was less correlated with the peak contrast concentration with shorter injections.