[Value of susceptibility weighted imaging in hepatic fibrosis staging by using MR in a rabbit model]

To assess the feasibility of susceptibility weighted imaging (SWI) in staging hepatic fibrosis(HF).

Sixty healthy rabbits were divided into three groups: HF group(n=32), control group(n=16), supplementary group(n=12). Rabbits in HF group and supplementary group were injected subcutaneously with 50% CCl4 oil solution to establish hepatic fibrosis model. On the basis of preliminary test, eight rabbits from HF group and four rabbits from control group underwent liver conventional MR scans and SWI once a time at 4, 5, 6, 10 weeks after CCl4 administration.After MR scans at each time point, rabbits were killed to detect pathological staging with Scheuer staging.The liver signal intensity (SI) and liver-to-muscle SI ratios (SIR) were measured. According to the Scheuer classification of histological fibrosis stages, the correlation about the SI value, SIR value and the histological fibrosis stages was investigated by using the Spearman correlation test. The receiver operating characteristic (ROC) curve was used to evaluate the diagnostic performance of SWI for staging HF on the basis of the histopathologic analysis of HF.

There were fifteen rabbits in pathological staging F0, the value of SIR and SI was 0.974 ± 0.018, 374±44, SIR values of pathological staging from F1 to F4 were 0.963 ± 0.018, 0.796 ± 0.023, 0.786 ± 0.025, 0.512±0.024 respectively. SI values of pathological staging from F1 to F4 were 372±18, 376±22, 346±15, 288±19 respectively. In the early period of liver fibrosis, there were no statistical differences in the SI value between F0 and F1, F1 and F2 stage.With progression of hepatic fibrosis, from F2 to F4, SI value decreased, the difference was statistically significant (P<0.05). With the progress of liver fibrosis, SIR value was reduced. It was negatively correlated with the HF stages and SIR value(r=-0.896, P<0.05). ROC curve analysis showed that the efficiency of SI value diagnosis in liver fibrosis was high in the late stage of liver fibrosis, but it was low in the early stage.The performance of liver-to-muscle SI ratio on SWI was high in the early stage. Liver-to-muscle SI ratio had a higher diagnostic performance than SI in the diagnosis of liver fibrosis stages.

SWI can be a safe, reliable method for staging hepatic fibrosis and provide quantitative imaging basis for clinical treatment.