Quantification of Liver Fibrosis at T1 and T2 Mapping with Extracellular Volume Fraction MRI: Preclinical Results

Abstract

Purpose To evaluate MRI T1 and T2 mapping with calculation of extracellular volume (ECV) for diagnosis and grading of liver fibrosis. Materials and Methods Different grades of fibrosis were induced in 60 male Sprague-Dawley rats by bile duct ligation (BDL) and carbon-tetrachloride (CCl₄) intoxication. Portal pressure was measured invasively, whereas hepatic fibrosis was quantified by hydroxyproline content, Sirius red staining, and α smooth muscle actin staining. T1 values, T2 values, and ECV were assessed by using quantitative MRI mapping techniques. Results T1 values in animals 4 weeks after BDL were greater than in control animals (718 msec ± 74 vs 578 msec ± 33, respectively; P < .001). T2 values at 4 weeks were also greater in animals that underwent BDL than in control animals (46 msec ± 6 vs 29 msec ± 2, respectively; P < .001). Similar T1 and T2 findings were observed after CCl₄ intoxication. ECV was greater in animals 4 weeks after BDL compared with control animals (31.3% ± 1.3 vs 18.2% ± 3.5, respectively; P < .001), with similar results after CCl₄ intoxication. High correlations were found between ECV and hepatic hydroxyproline content (BDL: r = 0.68, P < .001; CCl₄: r = 0.65, P < .001), Sirius red staining (BDL: r = 0.88, P < .001; CCl₄: r = 0.82, P < .001), α smooth muscle actin staining (BDL: r = 0.70, P < .001; CCl₄: r = 0.73, P < .001), and portal pressure (BDL: r = 0.54, P = .003; CCl₄: r = 0.39, P = .043). Conclusion Elevation of T1 and T2 values and ECV was associated with severity of liver fibrosis and portal hypertension in an experimental animal model.