Assessment of diffusion tensor MR imaging (DTI) in liver fibrosis with minimal confounding effect of hepatic steatosis

Abstract

Purpose Given the potential confounding effect of fat on apparent diffusion coefficient (ADC) in the liver, we have assessed diffusion tensor imaging in liver fibrosis with minimal effect of fat on ADC and fractional anisotropy (FA). Methods Thirty-six mice were used, among which 20 mice were CCl4 treated for fibrosis induction. Diffusion tensor imaging was performed at 9.4T using a spin-echo diffusion tensor imaging sequence with six gradient directions. Hepatic fat fraction obtained by MR spectroscopy was used as hepatic fat content. Fibrosis scores were obtained from histopathology. Results The hepatic fat fractions of the two animal groups were below 5.5% and not different (5.3±1.5 vs. 4.6±1.1%; P=0.115). Fibrosis scores were higher in CCl4-treated mice (0.0±0.0 vs. 2.1±0.7; P<0.001). Nonetheless, there was no difference in ADC between the two groups (0.711±0.068×10-3 vs. 0.718±0.095×10-3 mm2 s-1; P=0.911). The treated group had a lower FA than control (0.552±0.050 vs. 0.586±0.013; P=0.023). ADC was not correlated with hepatic fat fraction and fibrosis. FA was correlated with hepatic fat fraction (r=0.418, P=0.011) and fibrosis (r=-0.411, P=0.012). Conclusion FA may be more sensitive to mild-to-moderate liver fibrosis than ADC. In addition to ADC, FA may also be sensitive to hepatic fat content, and therefore need careful interpretation in liver fibrosis with concomitant fatty liver.