Assessing Liver Function by T1 Maps on Gd-EOB-DTPA-Enhanced MRI for up to 50 Min in Rat Models of Liver Fibrosis: A Longer Hepatobiliary Time Period may Help

Objectives To investigate whether a longer time period of gadolinium ethoxybenzyl diethylenetriaminepen-taacetic acid (Gd-EOB-DTPA)-enhanced T1 mapping scanning, as well as dynamic contrast-enhanced (DCE) and multiple hepatobiliary phase magnetic resonance imaging (MRI) have the potential to provide information about liver function in rats with liver fibrosis. Methods Forty rats were divided into the carbon tetrachloride-induced hepatic injury groups [carbon tetrachloride for four (n=14), eight (n=8), or twelve (n=8) weeks] and the control group (n=10). Gd-EOB-DTPA-enhanced MRI was performed including T1-mapping (delayed to 50 min), DCE, and multiple hepatobiliary phases. Indocyanine green retention rate at 15 min (ICG-R15) was determined. Parameters such as T1 reduction rate (ΔT1), elimination half-life of ΔT1 (T_{ΔT1 1/2}), relative enhancement (RE), time to maximum RE (T_max), and perfusion parameters were calculated. Pearson correlation analysis was used for correlation analysis between ICG-R15 and each MRI indices. Results ΔT1 at 30, 40, and 50 min showed significant positive correlations with ICG-R15 ( r=0.784, 0.653, 0.757, P=0.007, 0.041, 0.030). T_{ΔT1 1/2} showed a significant positive correlation with ICG-R15 (r=0.685, P=0.029). T_maxshowed a significant positive correlation with ICG-R15 (r=0.532, P=0.019). Conclusions ΔT1 in the late hepatobiliary phase and T _{ΔT1 1/2} exhibited moderate correlations with liver function. The longer time period of Gd-EOB-DTPA-enhanced T1 mapping scanning, as well as DCE and multiple hepatobiliary phases, may be of some value for estimating liver function in rats with liver fibrosis.