Diagnosis and measurement of liver fibrosis by MRI in bile duct ligated rats.

The noninvasive evaluation of liver fibrosis is a major clinical goal in liver diseases. Our aim was to identify MRI parameters to quantify liver fibrosis in vivo in an animal model of liver fibrosis with slight inflammation. We evaluated serum hyaluronate, liver hydroxyproline, area of liver fibrosis (image analysis), and 1.5-T MRI in 10 sham rats and 24 bile duct ligated rats with different stages of liver fibrosis. Liver signal intensity (SI)/muscle SI ratio and liver relaxation times (rT) were measured on T1 and T2 weighted sequences at different echo (TE) or recovery (RT) times of MRI. Among the 66 MRI parameters tested, the highest correlation with the area of fibrosis was observed for rT2 (r=0.78, P < 0.01). The area of liver fibrosis was independently predicted by five MRI variables (adjusted R (2)=0.78, with R (2)=0.64 for rT2 and rT1). Diagnostic accuracy for liver fibrosis was 100% using two variables: liver/muscle SI ratio on T2 at 30-ms TE and liver/muscle SI ratio on T1 at 50-ms RT. We conclude that in this animal model, fibrosis could be diagnosed with an accuracy of 100% using two MRI parameters. The quantification of liver fibrosis was very accurate either with only one MRI parameter (r=0.78 for rT2) or with five parameters (r=0.90) in this cholestatic model.