氢质子MR波谱及多回波Dixon技术对非酒精性脂肪性肝病脂肪变定量诊断及分级的价值

The value of quantitative diagnosis and grading of steatosis of nonalcoholic fatty liver disease by hydrogen proton MR spectroscopy and multi-echo Dixon technique

目的探讨氢质子MR波谱（1H-MRS）及Dixon序列检查评价非酒精性脂肪性肝病（NAFLD）患者脂肪变定量诊断及分级的价值。方法前瞻性收集2015年10月至2017年5月杭州师范大学附属医院行肝穿刺活检证实的NAFLD患者67例。患者均于肝穿刺活检后7 d内行肝脏1H-MRS和Dixon序列扫描，分别获得基于1H-MRS的氢质子密度脂肪分数值（MRS-PDFF）和基于Dixon扫描的氢质子密度脂肪分数值（MRI-PDFF）。根据肝脏穿刺病理脂肪百分比结果进行脂肪变分级。采用Pearson相关性检验分析MRS-PDFF及MRI-PDFF与病理脂肪变的相关性；采用单因素方差分析比较不同病理脂肪变严重程度分级间PDFF值的差异；采用ROC分析MRS-PDFF和MRI-PDFF值鉴别诊断S1、S3级脂肪变的效能。结果病理组织活检示脂肪变分级S1级36例、S2级16例、S3级15例，S1、S2、S3级患者的MRS-PDFF值分别为（8.25±4.32）%、（15.67±4.54）%和（23.46±5.82）%，MRI-PDFF值分别为（6.31±2.94）%、（15.42±5.07）%和（24.47±6.31）%，不同脂肪变分级患者间的MRS-PDFF、MRI-PDFF值差异均有统计学意义（P均〈0.01）。MRS-PDFF、MRI-PDFF值与病理脂肪变分级均呈正相关（r值分别为0.840、0.892，P均〈0.01），MRS-PDFF和MRI-PDFF值间也具有相关性（r=0.930，P〈0.01）。MRS-PDFF和MRI-PDFF值鉴别诊断S1级脂肪变的ROC下面积分别为0.955、0.976，鉴别诊断S3级脂肪变的ROC下面积分别为0.972和0.978。结论1H-MRS及Dixon序列诊断脂肪变含量及分级具有价值，且两者诊断效能相仿。

ObjectiveTo investigate the value of hydrogen proton MR spectroscopy （1H-MRS） and Dixon sequence for the quantitative diagnosis and classification of steatosis in patients with non-alcoholic fatty liver disease （NAFLD）.MethodsSixty seven patients with NAFLD confirmed by liver biopsy were prospectively collected from October 2015 to May 2017 in Hangzhou Normal University Hospital. All patients underwent 1H-MRS and Dixon sequence scan within 7 days after liver biopsy, 1H-MRS-based hydrogen proton density fraction （MRS-PDFF） and Dixon-based hydrogen proton density fraction （MRI-PDFF） were obtained. Fat grading based on the fat percentage obtained from liver biopsy. Pearson correlation analysis was performed to analyze the correlation among pathological steatosis and MRS-PDFF, MRI-PDFF. One-way ANOVA analysis was performed to compare the difference of PDFF between patients with different degrees of severity of fatty liver. And the ROC curve analysis was performed to generate the thresholds of MRS-PDFF and MRI-PDFF for determining the presence of fatty liver.ResultsThe steatosis grade of pathological biopsy showed grade S1 in 36 cases, grade S2 in 16 cases, grade S3 in 15 cases, the MRS-PDFF values of S1, S2 and S3 patients were （8.25±4.32）%, （15.67±4.54）%, （23.46±5.82）% and the MRI-PDFF values were （6.31±2.94）%, （15.42±5.07）%, （24.47±6.31）%. Statistically significant differences were observed among them （P〈0.01）. Both MRS-PDFF and MRI-PDFF were positively correlated with histological fat percentage （r values were 0.840 and 0.892,all P〈0.01）, there was also a correlation between MRS-PDFF and MRI-PDFF （r=0.930, P〈0.01）. Area under ROC curve of MRS-PDFF and MRI-PDFF for differential diagnosis of grade S1 steatosis were 0.955 and 0.976, and area under ROC curve for differential diagnosis of grade S3 steatosis were 0.972 and 0.978.Conclusion1H-MRS and Dixon sequces have high value in liver fat content detection and classification of patients with NAFLD, and both have similar diagnostic efficacy.