氧气刺激的BOLD磁共振成像ΔR2*值评估鼠肝纤维化的初步实验研究

Assessment of rat liver fibrosis with ΔR2* value in oxygen-challenge BOLD MR imaging: a preliminary study

目的：探讨氧气刺激的血氧水平依赖（BOLD）磁共振成像△R2^＊值与大鼠肝纤维化程度的关系，初步探讨应用△R2^＊值评估肝纤维化的潜在价值。方法：腹腔注射CCl4法建立大鼠肝纤维化模型（90只）和对照组（10只）进行吸氧前、后的BOLD磁共振成像，测算吸氧前后肝脏R2^＊值的变化量（△R2^＊）。以肝纤维化病理分期为基础将其划分为：A组：无纤维化组（SO），B组：轻中度纤维化组（S1～S2），C组：重度纤维化／肝硬化组（S3～S4），采用单因素方差分析比较各组间的△R2^＊值的差异，采用非参数Spearman检验分析△R2^＊值与病理肝纤维化程度的相关性。结果：模型组32只和对照组10只共42只大鼠完成MR检查。大鼠吸氧后R2^＊绝对值不同程度减低，A组、B组及C组的平均△R2^＊值分别为（24．05±4．65）Hz、（17．18±4．50）Hz、（8．09±5．17）Hz，经统计学分析，A组、B组、C组的△R2^＊值差异均有统计学意义（P〈0．05）；△R2^＊值随肝纤维化程度的加重逐渐减小，与纤维化程度呈负相关（r=-0．827，P〈0．001）。结论：氧气刺激的BOLD磁共振成像的△R2^＊值可反映纤维化进程中肝脏血流动力学及血氧含量的综合变化．在肝纤维化的检出及严重程度评价中有潜在的应用价值。

Objective： To explore the relationship between △R2^＊ value in oxygen-challenge blood oxygen level-dependent （BOLD） MRI and the severity of liver fibrosis in a rat model, and assess the potential value of diagnosis of the disease using △R2^＊ value. Methods： Liver fibrosis was induced in 90 rats by means of weekly intraperitoneal injection with a mixture of carbon tetrachloride and olive oil. Ten healthy rats were used as controls. BOLD-MRI study was performed on the rats under anesthesia at steady normoxia state by inhaling room air and hyperoxia state by inhaling oxygen. The changes in R2^＊ values （△R2^＊） during the oxygen challenge were quantified on the post-processing workstation. According to the pathological results, the rats were divided into three groups： A： without fibrosis （SO）, B： mild and moderate fibrosis （S1-S2）, C： severe fibrosis and cirrhosis （S3-S4）. The differences of △R2^＊ among the groups were tested by ANOVA and the correlation between liver fibrosis degree and △R2^＊ were analyzed by Spearman-test. Results： Thirty-two liver fibrosis model rats and 10 healthy rats were performed BOLD-MRI. Absolute values of R2^＊ decreased after oxygen challenge in all rats. A statistically significance（P〈0.05） in △R2^＊ were observed between group A（（24.05±4.65）Hz）, group B （（17.18±4.50）Hz） and group C（（8.09±5.17）Hz）. △R2^＊ decreased during liver fibrosis progression and was negatively correlated with liver fibrosis degree （r=-0.827, P〈0.001）. Conclusion： △R2^＊ in oxygen-challenge BOLD-MRI can reflect hemodynamic and oxygenation aherations during the progression of liver fibrosis, and has the potential to serve as a noninvasive method for liver fibrosis diagnosis and severity evaluation.