Assessment of liver fibrosis in rats by MRI with apparent diffusion coefficient and T1 relaxation time in the rotating frame

Purpose To explore the value of T1 relaxation times in the rotating frame (T1ρ or T1rho) for evaluating liver fibrosis stage, compared to apparent diffusion coefficients (ADCs). Materials and Methods Liver fibrosis in model rats (n = 50) was produced by carbon tetrachloride (CCl4) injection. Five rats died during the experiment. Surviving model rats (n = 45) and controls (n = 15) were subjected to 3.0T MRI and the ADCs (b-values: 0, 800 s/mm2) and T1ρ values were determined. Liver fibrosis stage (F0–F4) was defined based on METAVIR scoring. Nonparametric statistical methods and receiver operating characteristic (ROC) curve analyses were employed to determine diagnostic accuracy. Results Mean ADC and T1ρ associated negatively (r = −0.732 P < 0.001) and positively (r = 0.863 P < 0.001), respectively, with severity of fibrosis stage. Analysis of ROC curves for fibrosis staging showed that the area under the curve (AUC) for T1ρ (stage F0 vs. F1–F4 = 0.976, stage F0–F1 vs. F2–F4 = 0.920, stage F0–F2 vs. F3–F4 = 0.938, and stage F0–F3 vs. F4 = 0.931) was larger than that for ADCs (0.917, 0.924, 0.842, and 0.781, respectively). Conclusion ADC and T1ρ values correlate with liver fibrosis stage. The performance of the T1ρ parameter was superior to that of the ADC parameter in the differentiation of liver fibrosis stages in a CCl4 rat model. J. Magn. Reson. Imaging 2016;43:1082–1089.