局灶性结节增生与肝细胞癌MR扩散加权成像表现特征的比较

Comparison of imaging features between focal nodular hyperplasia and hepatocellular carcinoma on MR diffusion weighted imaging

目的探讨肝局灶性结节增生（FNH）和肝细胞癌在MRDWI上的表现特征。方法回顾性分析2008年8月至2010年11月间，有MR检查资料并经手术病理证实的FNH和小肝癌患者资料，共有24例26个FNH病灶和36例39个小肝癌病灶。行b值=500s／mm^2 DWI和常规动态增强扫描，对病灶DWI的信号特点进行记录和分析，对病灶的ADC值、病灶对周围肝实质ADC值比进行测量。对两组病灶信号特点分布行Fisher确切概率法检验，两组病灶ADC值及病灶与周围肝实质ADC值比采用独立样本t检验，并用ROC曲线评价ADC值和病灶与周围肝实质ADC值比对两种病灶的鉴别价值。结果多数（23／26）FNH病灶在DWI上表现为等或略高信号，多数（25／39）HCC病灶表现为高信号，两者信号特点分布差异有统计学意义（P=0．000）。FNH病灶的平均ADC值、病灶与周围肝实质ADC值比分别为（1．76±0．62）×10^-3mm^2／s和1．06±0．18，均高于HCC的平均值（1．26±0．46）×10^-3mm^2／s（P=0．001）和0．79±0．12（P=0．000）。ADC值和病灶与周围肝实质ADC值比的ROC曲线下面积（Az）分别为0．79±0．05和0．85±0．05，差异无统计学意义（P=0．270）；特异度分别为69．23％和97．44％，差异有统计学意义（P=0．001）。结论FNH在DWI上表现为等或略高信号，病灶ADC值和病灶与周围肝实质ADC值比高于HCC，应用ADC参数分析有助于FNH与HCC的鉴别。

Objective To investigate the imaging features of focal nodular hyperplasia and hepatocellular carcinoma on DWI. Methods The data of patients with histopathologically confirmed FNHs and HCCs between August 2008 and November 2010 were collected. A total of 24 patients with 26 FNH lesions and 36 patients with 39 HCC lesions were included in our study. All patients underwent breath-hold DWI with b = 500 s/mm2 and dynamic contrasted-enhanced （DCE） MRI. The imaging findings of FNHs and HCCs were retrospectively analyzed and compared. The signal intensity （SI） of the lesions on DWI were classified as iso-, slightly high, high SI and the distribution of SI between FNHs and HCCs was compared with Fisher exact test. ADC value and lesion-to-liver ADC ratio of FNHs and HCCs were measured and compared by using independent sample t test. ROC was performed to assess the diagnostic value of ADC value and lesion-liver ADC ratio in the characterization FNHs versus HCCs. Results Of 26 FNHs, 23 manifested as isointensity or slightly high SI on DWI, but most 25 out of 39 HCCs showed high SI. The distribution of SI between FNHs and HCCs had significant difference （ P = 0. 000 ）. The mean ADC value and lesion-liver ADC ratio for FNHs [ （ 1.76 ±0. 62） ×10^-3mm^2/s and 1.06 ±0. 18, respectively] were significantly higher （ P = 0. 001, P = 0. 000, respectively ） than those for HCCs [ （ 1.26 ±0. 46 ） ×10^-3mm^2/s and 0. 79 ±0. 12, respectively]. The area （Az） under the ROC for the ADC value and lesion- liver ADC ratio for the differentiation of FNHs versus HCCs were 0. 79 ± 0. 05 and 0. 85 ±0. 05, respectively, with no significant difference （P =0. 270）. The specificity of the two measures was 69.23% and 97.44% , respectively, with significant difference （P = 0. 001 ）. Conclusion FNH shows isointensity or slightly high SI with relatively higher ADC value and lesion-liver ADC ratio than those of HCCs on DWI, which is characteristic for its diagnosis and differentiation.