DWI多b值水通道蛋白分子成像在肝纤维化早期诊断的价值

目的：探讨磁共振弥散加权成像（MR diffusion weighted imaging,MR-DWI）多b值水通道蛋白（Aquaporin,AQP）分子成像技术在肝纤维化早期诊断的价值.方法：应用乙酰唑胺作为水通道蛋白抑制剂,将对照组及肝纤维化模型组大鼠分别于乙酰唑胺静脉注射抑制前后进行常规MRI及DWI扫描.DWI扫描多b值包括0～4 500 s/mm2共18个不同b值,先按照常规方法获得“标准”表观弥散系数（ADC）值,然后再分别以200、1 500作为界值将其分为低、中和高b值.以病理学肝纤维化分期将大鼠分为S0、S1、S2、S3、S4期,比较低、中、高b值下,不同纤维化分期大鼠肝脏ADC值,并观察同一分期大鼠乙酰唑胺抑制前后,肝脏组织细胞膜上AQP表达量和活性变化情况.结果：“标准”ADC值在各分期之间均无显著性差异.在肝纤维化早期,随着肝纤维化程度的进展,肝脏组织细胞膜上AQP1表达相应增加.乙酰唑胺抑制前,在高b值下,S0期ADC值显著低于S3、S4期（P＜0.05）,其余各组比较均无明显统计学差异;但乙酰唑胺抑制后,高b ADC值比较,S0与S1比较无明显统计学差异,S0与其他各期比较、S1与S2、S1与S3/S4比较,均有明显统计学差异（均P＜0.05）.各组内乙酰唑胺抑制前后自身比较,SO、S1期抑制率分别为15.5％、16.0％,S2期抑制不明显1.9％,S3＋S4期为11.7％.结论：初步实验表明,常规方法获得“标准”ADC值并不能发现肝脏纤维化早期病变,也不能有效对其分期.磁共振DWI多b值扫描,主要是高b值下ADC值变化与肝脏细胞膜上AQP表达相关,该技术可以用于评价早期肝纤维化和对肝脏纤维化分期.

Assessment of aquaporins function of early-stage liver fibrosis using multi-b diffusion weighted magnetic resonance imaging

Objective：To investigate the value of aquaporins（AQP） function in the diagnosis of early liver fibrosis by using multiple b-value （multi-b） diffusion weighted magnetic resonancce imaging （MR-DWI）.Methods：Using acetazolamide as AQP inhibitor,rats of control group and rats of developed model of liver fibrosis undertook conventional MR scans and a multi-b DWI before and after inhibition.The DWI was carried out with 18 different b values selected from 0 to 4 500 s/mm2.First of all,we obtained the standard ADC value in accordance with conventional methods,and then the multi-b values were divided into low-b,middle-b and high-b domains with 200 s/mm2 and 1 500 s/mm2 as thresholds.According to histological fibrosis stage,rats were divided into four groups：S0,S1,S2,S3＋S4.With multiple b values,the result of apparent diffusion coefficience （ADC） and the expression and activity of AQP in four groups were compared.Results：There was no significant difference between each group in standard ADC.The AQP1 expression in the liver endothelial cells significantly increased with aggravation of liver fibrosis in early stage.Before inhibition,significant difference was observed between S0 and S3＋S4 at high b value.While after inhibition,each group could be distinguished except S0 and S1.The high-b ADC value decreased 15.5％ at S0,16％ at S1,while no obvious decrease was observed at S2 with the addition of inhibitor.The inhibition rate increased to 11.7％ at S3＋S4.Conclusion：Our preliminary experimental results indicate that the standard ADC value obtained by conventional method can not detect and stage early liver fibrosis,while the high-b ADC values are correlated with AQP expression,so the multi-b MR-DWI technique is capable to detect and stage early liver fibrosis.