MRI评估肝硬化再生结节和退变结节

MRI features of regenerative and dysplastic nodules in cirrhotic liver

目的:研究肝硬化再生结节和退变结节的MRI特点并以此鉴别二者及肝细胞癌(HCC).方法:前瞻性地研究了26例肝硬化再生结节和退变结节的MRI表现.对26例临床疑为肝硬化的患者做了平扫MRI,其中18例还做了Gd-DTPA增强MRI,10例同时做了超顺磁性氧化铁(菲立磁,Feridex)增强MRI.所有患者经穿刺或手术病及临床影像追踪观察证实.并将MRI表现与病理对照分析.结果:26例中再生结节(RN)12例,病灶直径在0.3-1cm:退变结节(DN)14例,其中8例病灶在1-3cm,6例病灶大于3cm.MRI表现:12例RN均在T1WI呈等稍高信号和T2WI等低信号,Gd-DTPA和菲立磁增强与正常肝实质呈同步强化.14例DN的MRI表现:5例1-3cm结节在T1WI呈高信号和T2WI低信号,Gd-DTPA和菲立磁增强与正常肝实质呈同步强化;另3例1-3cm结节病灶在T1WI呈等信号,T2WI呈高信号,在Gd-DTPA增强MRI上,早期呈明显强化,延迟扫描可见环行强化带,在菲立磁增强呈高信号提示恶变,病理上可见肝癌细胞.6例大于3cm的结节中2例在T1WI、T2WI均呈等高信号,菲立磁增强MRI呈高信号,Gd-DTPA增强MRI示巨大结节较周邻正常肝组织信号高,其中1例还可见“结中结”征,病理上呈分化较好的HCC;另4例大于3cm的结节在T1WI呈高信号,T2WI呈低信号,菲立磁强化呈低信号,Gd-DTPA增强巨大结节无强化,较周邻正常肝组织信号低,有时可见血管经过巨大结节表面.此外,Gd-DTPA增强的时间信号强度曲线显示:RN和良性DN与周邻正常肝组织表型近似,呈缓进缓出;DN恶变时,呈快进快出表型,与正常肝组织不同.结论:肝硬化再生结节(RN)在MRI上能较好地与HCC鉴别,但较难区别于良性退变结节(DN).良性退变结节在T2WI不呈高信号,以此区别HCC.此外,退变结节在Gd-DTPA增强上出现环行包膜强化,时间信号强度曲线呈快进快出表型,菲立磁增强上T2WI呈高信号,提示有恶变.

AIM: To study MR features of the regenerative nodule (RN) and dysplastic nodule (DN) in the cirrhotic liver. METHODS: MRI was performed in 26 cases of suspected cirrhotic liver with RN and DN. Additional enhanced MRI with administration of Gd-DTPA on T1WI was performed in 18 of 26 cases. Meanwhile in 10 of 18 both Gd-DTPA and SPIO (Feridex) enhancement were underwent one day apart. All patients were confirmed by aspiration biopsy or histopathology. MRI was compared to the pathological findings. RESULTS: In 26 cases, there were 12 cases of regenerative nodules measuring 0.3-1cm in size, and 14 dysplastic nodules including 8 nodules measuring ≥1 cm and <3 cm in size, and 6 nodules measuring ≥3 cm. Their MR appearances were as followings: nodules with <1 cm in size showed isointensity on T1WI and hypointensity on T2WI, of which the intensity was as isointense as the surrounding hepatic parenchyma on enhanced MRI with administration of Gd-DTPA or SPIO. In 8 cases with nodules measuring 1-3 cm in size, 5 cases appeared hyperintense on T1WI and hypointense on T2WI as well as the enhancement as that of nodules with <1 cm in size; the other 3 cases appeared hypointense on T1WI and hyperintense on T2WI, and were enhanced after administration of Gd-DTPA but hyperintense on SPIO enhancing MRI, which indicated malignant transformation of dysplastic nodule into hepa-tocellular carcinoma (HCC) arising from hepatic nodule on histopathology. In 6 cases of nodules measuring >3 cm in size, 2 cases appeared hyperintense compared to the surrounding hepatic parenchyma on T1,T2WI and enhanced MRI, one of which was documented 'nodule within a nodule' on T2WI. The 2 cases were demonstrated well-differentiated HCC. The other 4 cases showed hyperintense on T1WI, and hypointense on T2WI and enhanced MRI. Sometimes, normal vessels were seen to pass through the surface of macroregenerative nodule. Additionally, RN and DN had the same pattern of the time-signal intensity course as the normal surrounding hepatic parenchyma, but malignant transformation of DN appeared fast wash-in and wash-out. CONCLUSION: RN of cirrhosis has features on MRI that usually allow distinction from HCC but not always from DN. A helpful distinction between HCC and DN is that the latter is almost never hyperintense on T2WI. Additionally, the followings indicate malignant transformation of DN when DN appears a ring like enhancement after injection of Gd-DTPA, and fast wash-in and wash-out as well as hyperintensity on SPIO enhanced MRI.