Abstract
Rationale and Objectives To investigate the utility of intravoxel incoherent motion MRI (IVIM-MRI) and R2⁎ mapping in diagnosing early stage liver fibrosis in a radiation-induced rat model. Materials and Methods Thirty rats were randomly divided into three groups with 10 rats in each group. Liver fibrosis was induced by exposure of right lobe of liver in each animal to 20 Gy of radiation. MRI examination was conducted at baseline, one month, two months, and three months after radiation using T1WI, T2WI, IVIM-DWI, and R2⁎ sequences. The pathological examination included hematoxylin eosin, masson trichrome, and prussian blue staining. D, D⁎, f, and R2⁎ values were measured in both left and right lobes for quantitative analysis. Results Regarding the surviving 23 rats, eight rats were diagnosed with stage F0, ten with stage F1, and five with stage F2 liver fibrosis using METAVIR Scores. The D values of right lobes decreased (P<0.05), and R2⁎ values increased (P<0.01) significantly as fibrosis levels increased. But there was no statistical difference in D⁎ (P=0.970) and f values (P=0.079). R2⁎ value showed a strong positive correlation (r=0.819, P<0.001), while D value showed a negative correlation with fibrosis stages (r=-0.424, P<0.001). D⁎ (r=0.029, P=0.744) and f values (r=-0.055, P=0.536) were poorly correlated with fibrosis levels. Conclusion IVIM-MRI and R2⁎ mapping are useful techniques for evaluating the severity of liver fibrosis in a radiation-induced rat model, and R2⁎ value is the most sensitive parameter in detecting early stage fibrosis.
Highlights
Liver cancer is one of the most fatal cancers in the world
Out of 30 rats, only 23 rats were studied for radiation induced liver fibrosis
4 rats died within 48 h after irradiation due to intolerance to the irradiation, while 3 rats died during scanning because of anesthetic accidents
Summary
The incidence rate and death rate due to liver cancer are increasing in recent years [1]. With widespread use of radiotherapy in the treatment of liver cancer, radiation induced liver injury (RILI) has become more common [2]. The pathological changes of RILI originate from an inflammatory response induced by radiation, progress into liver fibrosis, leading to the development of cirrhosis. An accurate and early diagnosis of liver fibrosis may help reduce the risk of radiotherapy-related complications and achieve a better prognosis [3]. Clinical adoption of liver biopsy has been limited due to poor repeatability, lack of localization, risks of bleeding and infection, and strong subjective bias in reading the results [4]. With recent advancement in magnetic resonance (MR) techniques, two novel sequences including intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) and R2∗ mapping, have been applied to detect the molecular and hemodynamic changes in various kinds of liver diseases
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