肝细胞腺瘤与局灶性结节增生:钆塞酸MRI增强扫描的鉴别诊断价值

目的回顾性分析钆塞酸MRI增强扫描对于肝细胞腺瘤(HCA)和局灶性结节增生(FNH)的鉴别诊断价值。材料与方法本研究已通过机构伦理审查委员会审查,免除知情同意书。研究对象为82例病人(FNH58例,HCA24例),共111     

肝脏局灶性结节增生的MRI与病理对照性分析

目的:研究肝脏局灶性结节增生(FNH)的MRI表现和病理学表现及其它们的相关性。方法:回顾性分析9例经手术病理证实的FNH的MRI表现及其病理学表现。结果:FNH平扫T1WI 5例为等信号,4例为稍低信号;T2WI 3例为等信号,6例为稍高信号。7例病灶中心或偏心有瘢痕。动态增强扫描9例病灶在动脉期均呈明显均匀强化;门脉期和延迟期为轻度增强或等信号;7例病灶在延迟期出现瘢痕强化。FNH是多血供实质性肿块,肿瘤内部结构均匀,出血和坏死少见,镜下可见典型的星状瘢痕。结论:MRI平扫和动态增强扫描能够显示FNH的特征性表现,反映FNH的病理特点,提高FNH的确诊率。     

肝细胞腺瘤在钆塞酸增强MR成像上的表现

摘要目的使用钆塞酸作为肝细胞特异性MRI对比剂,评估肝细胞腺瘤(HCA)的MRI增强表现。方法对组织病理学证实为HCA的24例病人进行回顾性分析。MR成像包括T1WI、T2WI以及饱和脂肪抑制序列(FS)、多相动态T1WI、肝实质期T1WI的FS序列。以手术切除(19例)或活检(5例)作为参照标准。影像学分析包括形态学和强化形式[包括测量与增强前基线相比标准化的T1WI上的信号强度(SI)]。     

Appearance of hepatocellular adenomas on gadoxetic acid-enhanced MRI

Objective

The purpose of this study was to evaluate enhancement characteristics of hepatocellular adenomas (HCAs) using gadoxetic acid as a hepatocyte-specific MR contrast agent.

Methods

Twenty-four patients with histopathologically proven HCAs were retrospectively identified. MRI consisted of T1- and T2-weighted (w) sequences with and without fat saturation (fs), multiphase dynamic T1-w images, and fs?T1-w images during the hepatobiliary phase. Standard of reference was surgical resection (n?=?19) or biopsy (n?=?5). Images were analysed for morphology and contrast behaviour including signal intensity (SI) measurement on T1-w images normalised to the pre-contrast base line.

Results

In total 34 HCAs were evaluated. All HCAs showed enhancement in the arterial phase; 38?% of HCAs showed reduced contrast enhancement (“wash-out”) in the venous phase. All HCAs showed enhancement (SI increase, 56 ± 53?%; P <0.001) in the hepatobiliary phase, although liver uptake was stronger (96 ± 58?%). Thus, 31 of all HCAs (91?%) appeared hypointense to the surrounding liver in the hepatobiliary phase, while 3 out of 34 lesions were iso-/hyperintense.

Conclusions

Gadoxetic acid accumulates in HCAs in the hepatobiliary phase, although significantly less than in surrounding liver. Thus, HCA appears in the vast majority of cases as a hypointense lesion on hepatobiliary phase images.

Key Points

? Magnetic resonance-specific contrast agents are now available for hepatic imaging. ? Hepatocellular adenomas enhance with gadoxetic acid as in previous CT/MRI experience. ? Enhancement during the hepatobiliary phase is less in HCAs than in liver. ? Typical HCAs appear as hypointense lesions on T1-w hepatobiliary phase images. ? True hyperintense HCA enhancement can occasionally occur during the hepatobiliary phase.     

Focal nodular hyperplasia: natural course observed with CT and MRI

PURPOSE: The purpose of this work was to assess the natural course of biopsy-proven focal nodular hyperplasia (FNH). METHOD: Eighteen biopsy-proven FNHs in 14 patients (12 women and 2 men) who were followed for at least 6 months with CT and/or MRI were included in the study. The volume of the lesions was calculated twice by two observers using the summation of areas method. Intra- and interobserver variability was assessed by intraclass correlation coefficients. Longitudinal data analysis was performed with generalized estimating equations. RESULTS: The volume of FNH was stable in 6 cases, decreased in 10 cases, and increased in 2 cases. Intra- and interobserver variability in size measurements was 5-10%. Intraclass correlation coefficients were >0.992. Longitudinal data analysis showed that there was a general trend of lesion regression. CONCLUSION: Long-term follow-up and objective measurements performed in patients with biopsy-proven lesions show that the natural course of FNH is variable. In particular, lesion regression is not rare.     

Focal nodular hyperplasia

Focal nodular hyperplasia is the second most common benign liver tumor after hemangioma and occurs predominantly in young women. Imaging techniques are crucial in the diagnosis of this lesion. In this article, we will present the imaging findings of the classic and non-classic FNHs. The role of percutaneous biopsy will also be detailed.     

Diagnostic efficacy of gadoxetic acid-enhanced MRI for the detection and characterisation of liver metastases: comparison with multidetector-row CT

Objectives

We compared the diagnostic performance of gadoxetic acid-enhanced MRI and 16-slice multidetector CT (MDCT) with respect to their abilities to detect hepatic metastases and differentiate hepatic metastases from hepatic cysts and haemangiomas.

Methods

67 patients with 110 liver metastases (size 0.3–2.5 cm), 33 haemangiomas (size 0.5–1.5 cm) and 17 cysts (size 0.3–1.0 cm) underwent 4-phase MDCT and gadoxetic acid-enhanced MRI, including early dynamic phases, post-contrast T₂ weighted turbo spin echo sequences and 20 min hepatocyte-selective phases. Two observers independently analysed each image in random order. Sensitivity and diagnostic accuracy for lesion detection and differentiation for MDCT and gadoxetic acid-enhanced MRI were calculated using receiver operating characteristic analysis.

Results

For both observers, the Az values of gadoxetic acid-enhanced MRI (mean, 0.982 and 0.981) were significantly higher than the Az values of MDCT (mean, 0.839 and 0.892) (p<0.05) for the detection of metastases and for the differentiation of metastases from haemangiomas and cysts. Sensitivities of gadoxetic acid-enhanced MRI with regard to the detection and characterisation of liver metastases (mean, 96.9% and 96.0%) were significantly higher than those of MDCT (mean, 78.7% and 75.0%) (p<0.05).

Conclusion

Gadoxetic acid-enhanced MRI showed higher diagnostic accuracy and sensitivity than did MDCT for the detection of hepatic metastases and for the differentiation between hepatic metastases and hepatic haemangiomas or cysts.The early detection and precise characterisation of liver metastases are crucial factors in liver imaging because the success of surgery and ablation therapy depends on the knowledge of the precise number and locations of metastatic lesions [144]. Multidetector-row CT (MDCT) has been widely used as a primary imaging modality for evaluating liver metastases because of its wide availability. However, there has been some concern that MDCT images may not accurately characterise small hepatic nodules that are “too small to characterise”, and may not sufficiently differentiate small hepatic metastases from small hepatic cysts or haemangiomas, which are the most frequently encountered causes of focal liver lesions on CT [5-7]. Furthermore, MDCT is less able to detect liver metastases than MRI using liver-targeted agents, such as superparamagnetic iron oxide [8-13]. Thus, with the advent of new MR contrast agents for liver imaging, considerable attention has been focused on the ability of MR contrast agents to detect and characterise small focal liver lesions relative to the conventional imaging modality or previously existing MR contrast agents.Gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA, gadoxetic acid disodium, Primovist®; Bayer HealthCare, Berlin, Germany) is a recently introduced dual-acting MR contrast agent that combines the properties of an extracellular space contrast (ECS) agent and a liver-specific agent [14-19]. The combination of these properties enables the acquisition of the early vascular-interstitial phase, which provides haemodynamic information, and the hepatocyte phase, which detects liver malignancies. Thus, gadoxetic acid has a potency to fulfil the dual requirements for early detection and accurate characterisation of focal liver lesions. To the best our knowledge, no previous study has evaluated the diagnostic capability of gadoxetic acid-enhanced MRI to detect and characterise liver metastases compared with MDCT. In this study, we retrospectively compared the diagnostic performance of gadoxetic acid-enhanced MRI and 16-slice MDCT in detecting small hepatic metastases and in differentiating hepatic metastases from hepatic haemangiomas and cysts, using alternative free-response receiver operating characteristic (ROC) analysis.     

Focal nodular hyperplasia: imaging findings

Focal nodular hyperplasia is an uncommon benign hepatic tumor that continues to pose diagnostic dilemmas. Imaging techniques are of great value in diagnosis of this tumor. In this article we present the US, CT, MR imaging, scintigraphy, and angiography findings. The demonstration of a central vascular scar is very helpful. Although the radiologic features may be diagnostic, many atypical cases must be differentiated from other benign or malignant hepatic tumors. In these cases excisional biopsy and histopathologic examination are necessary to determine a definite diagnosis. Received: 7 March 2000/Revised: 13 June 2000/Accepted: 15 June 2000     

肝局灶性结节增生的MRI诊断价值与CT征象比较

目的:评价肝局灶性结节增生(FNH)的MRI诊断价值。方法:经手术或穿刺活检病理证实的FNH19例,共21个病灶。全部病例进行了CT和MRI检查,CT检查常规行平扫和双期增强扫描;MRI平扫序列如下:用快速恢复快速自旋回波序列(FRFSE)采集压脂T2W图像,用快速扰相梯度回波序列(FSPGR)采集压脂T1W图像,用真稳态进动梯度回波序列(FIESTA)采集T2/T1比值加权图像,用FSPGR序列同时采集无脂肪抑制的反相位和同相位T1W图像。所有病例均行Gd-DTPA动态增强扫描,其中3例进行细胞特异性对比增强扫描。结果:17个FNH在平扫T2WI fs为等信号或略高信号,在T1WI fs上呈等信号或略低信号。MRI平扫共见中心瘢痕12个、中央粗大血管3条、假包膜数2个,均多于CT平扫所见。Gd-DTPA动态增强扫描时,21个FNH于动脉期均明显强化,16个FNH于门脉期或延迟期的信号强度与肝组织接近,中心瘢痕和假包膜延迟强化。行细胞特异性对比增强扫描的3个FNH实质均明显强化,中心瘢痕无强化。结论:绝大多数FNH在MRI上有特征性的征象,MRI可以明确诊断,MRI对FNH的诊断价值高于CT。     

Characterization of hepatic adenoma and focal nodular hyperplasia with gadoxetic acid

Purpose:

To characterize imaging features of histologically proven hepatic adenoma (HA) as well as histologically and/or radiologically proven focal nodular hyperplasia (FNH) using delayed hepatobiliary MR imaging with 0.05 mmol/kg gadoxetic acid.

Materials and Methods:

Five patients with six HAs with histological correlation were retrospectively identified on liver MRI studies performed with gadoxetic acid, and T1‐weighted imaging acquired during the delayed hepatobiliary phase. Additionally, 23 patients with 34 radiologically diagnosed FNH lesions (interpreted without consideration of delayed imaging) were identified, two of which also had histological confirmation. Signal intensity ratios relative to adjacent liver were measured on selected imaging sequences.

Results:

All six hepatic adenomas (100%), which had histological confirmation, demonstrated hypointensity relative to adjacent liver on delayed imaging. Furthermore, all of the FNH (including 34 radiologically proven, 2 of which were also histologically proven) were either hyperintense (23/34, 68%) or isointense (11/34, 32%) relative to the adjacent liver on delayed imaging. None of the FNHs were hypointense relative to liver.

Conclusion:

Distinct imaging characteristics of HA versus FNH on delayed gadoxetic acid‐enhanced MRI, with adenomas being hypointense and FNH being iso‐ or hyperintense on delayed imaging may improve specificity for characterization, and aid in the differentiation of these two lesions. J. Magn. Reson. Imaging 2012;36:686–696. © 2012 Wiley Periodicals, Inc.