Benign versus malignant hepatic nodules: MR imaging findings with pathologic correlation.

According to the currently used nomenclature, there are only two types of hepatocellular nodular lesions: regenerative lesions and dysplastic or neoplastic lesions. Regenerative nodules include monoacinar regenerative nodules, multiacinar regenerative nodules, cirrhotic nodules, segmental or lobar hyperplasia, and focal nodular hyperplasia. Dysplastic or neoplastic nodules include hepatocellular adenoma, dysplastic foci, dysplastic nodules, and hepatocellular carcinoma (HCC). Many of these types of hepatic nodules play a role in the de novo and stepwise carcinogenesis of HCC, which comprises the following steps: regenerative nodule, low-grade dysplastic nodule, high-grade dysplastic nodule, small HCC, and large HCC. State-of-the-art magnetic resonance (MR) imaging facilitates detection and characterization in most cases of hepatic nodules. State-of-the-art MR imaging includes single-shot fast spin-echo imaging, in-phase and opposed-phase T1-weighted gradient-echo imaging, T2-weighted fast spin-echo imaging with fat saturation, and two-dimensional or three-dimensional dynamic multiphase contrast material-enhanced imaging.     

Atypical focal nodular hyperplasia of the liver: imaging features of nonspecific and liver-specific MR contrast agents

OBJECTIVE: The objective of our study was to describe the functional and differential uptake features of atypical focal nodular hyperplasia using different MR contrast agents and to evaluate their potential role in the diagnosis and characterization of focal nodular hyperplasia. MATERIALS AND METHODS: Contrast-enhanced MR images of 45 patients with 85 focal nodular hyperplasia lesions were retrospectively reviewed. In these patients, sonographic findings were nonspecific (n = 37), or CT features were inconclusive (n = 8). Non-liver specific gadolinium chelates were used in 18 patients (48 lesions) suspected of having either focal nodular hyperplasia or hemangioma. The following liver-specific agents were used in patients with suspected focal nodular hyperplasia or metastases: mangafodipir trisodium, 30 patients (55 lesions); ferumoxides, six patients (16 lesions); and SHU 555 A, six patients (six lesions). Individual lesions were quantified by signal intensity and assessed qualitatively by homogeneity, contrast enhancement, and presence of a central scar. RESULTS: At unenhanced MR imaging, the triad of homogeneity, isointensity, and central scar was found in 22% of the focal nodular hyperplasia lesions. On mangafodipir trisodium-enhanced T1-weighted images, all focal nodular hyperplasia lesions showed contrast uptake: in 64% of the lesions, uptake was equal to parenchyma; 25%, greater than the parenchyma; and 11%, less than the parenchyma. On iron oxide-enhanced T2-weighted images, all focal nodular hyperplasia lesions showed uptake of the contrast agent, but contrast uptake in the lesions was less than in the surrounding parenchyma. Dynamic gadolinium chelate-enhanced MR imaging showed early and vigorous enhancement of focal nodular hyperplasia lesions with rapid washout in 88%. Atypical imaging features of the lesions included hyperintensity on T1-weighted images, necrosis and hemorrhage, and inhomogeneous or only minimal contrast uptake. CONCLUSION: For patients in whom the diagnosis of focal nodular hyperplasia cannot be established on unenhanced or gadolinium-enhanced MR imaging, homogeneous uptake of liver-specific contrast agent with better delineation of central scar may help to make a confident diagnosis of focal nodular hyperplasia.     

Characterization of focal hepatic lesions with ferumoxides-enhanced T2-weighted MR imaging

OBJECTIVE: The purpose of this study was to evaluate whether ferumoxides-enhanced MR imaging of focal hepatic lesions provides distinctive signal intensity and lesion-to-liver contrast changes for benign and malignant lesions, helping to further characterize and differentiate these lesions. MATERIALS AND METHODS: Data analysis was performed on 70 patients, with previously identified focal hepatic lesions, who underwent MR imaging of the liver before and after IV administration of ferumoxides (10 micromol Fe/kg). Lesions analyzed with pathologically proven diagnoses included metastases (n = 40), hepatocellular carcinoma (n = 11), cholangiocarcinoma (n = 6), hemangioma (n = 4), focal nodular hyperplasia (n = 6), and hepatocellular adenoma (n = 3). Response variables measured and statistically compared included the percentage of signal-intensity change and lesion-to-liver contrast. RESULTS: Focal nodular hyperplasia showed significant signal intensity loss on ferumoxides-enhanced T2-weighted images (mean, -43%+/-6.7%, p < 0.01). All other lesion groups showed no statistically significant change in signal intensity on ferumoxides-enhanced T2-weighted images, although signal intensity loss was seen in some individual hepatocellular adenomas (mean, -6.6%+/-24.0%) and hepatocellular carcinomas (mean, -3.3%+/-10.3%). All lesions, with the exception of hepatocellular carcinoma, had a marked increase in lesion-to-liver contrast on ferumoxides-enhanced T2-weighted images, which was statistically significant for metastases and hemangioma (p < 0.02). CONCLUSION: Focal nodular hyperplasia shows significant decrease in signal intensity on ferumoxides-enhanced T2-weighted images, which may aid in the differentiation of focal nodular hyperplasia from other focal hepatic lesions. Other lesions, namely, hepatocellular adenoma and carcinoma, can have reticuloendothelial uptake, but usually to a lesser degree than that of focal nodular hyperplasia.     

Fat in the liver: diagnosis and characterization

The purpose of this article is to provide an update on imaging techniques useful for detection and characterization of fat in the liver. Imaging findings of liver steatosis, both diffuse steatosis and focal fatty change, as well as focal fatty sparing, are presented. In addition, we will review computed tomography (CT) and magnetic resonance (MR) findings of focal liver lesions with fatty metamorphosis, including hepatocellular carcinoma, hepatocellular adenoma, focal nodular hyperplasia, angiomyolipoma, lipoma, and metastases.     

Focal lesions in cirrhotic liver: what else beyond hepatocellular carcinoma?

Detection and characterization of focal lesions in the cirrhotic liver may pose a diagnostic dilemma. Several benign and malignant lesions may be found in a cirrhotic liver along with hepatocellular carcinoma (HCC), and may exhibit typical or atypical imaging features. In this pictorial essay, we illustrate computed tomography and magnetic resonance imaging findings of lesions such as simple bile duct cysts, hemangioma, focal nodular hyperplasia-like nodules, peribiliary cysts, intrahepatic cholangiocarcinoma, lymphoma, and metastases, all of which occur in cirrhotic livers with varying prevalences. Pseudolesions, such as perfusion anomalies, focal confluent fibrosis, and segmental hyperplasia, will also be discussed. Imaging characterization of non-HCC lesions in cirrhosis is important in formulating an accurate diagnosis and triaging the patient towards the most appropriate management.The detection and characterization of focal lesions in a cirrhotic liver on computed tomography (CT) and magnetic resonance imaging (MRI) is a challenging task due to the marked changes in the organ architecture. Although hepatocellular carcinoma (HCC) is the most frequent primary tumor arising in a cirrhotic liver, several other benign and malignant lesions may be encountered in this setting (1, 2). It is thus not surprising that CT and MRI have limited specificity for the diagnosis of HCC in cirrhosis.Imaging characterization of focal lesions in cirrhosis is of the utmost importance for appropriate patient management. The radiologist’s primary task is to maximize tumor detection (i.e., minimize false negatives), because missing the diagnosis of HCC may preclude potentially curative therapies, such as hepatic resection, percutaneous ablation procedures, and, in selected patients, liver transplantation. However, it is equally important to avoid the misdiagnosis of benign liver lesions as HCC (i.e., minimize false positives) because this diagnostic interpretation may incorrectly increase the tumor burden. This may also result in the ineligibility of the patient for potentially curative treatments or the inappropriate assignment of increased priority scores for patients on the waiting list for liver transplantation. In this paper, we discuss and illustrate CT and MRI features of both common and uncommon non-HCC liver lesions occurring in cirrhotic patients.     

Enhancement of focal liver lesions at gadoxetic acid-enhanced MR imaging: correlation with histopathologic findings and spiral CT--initial observations

PURPOSE: To detect hepatocyte-selective enhancement of focal lesions with gadoxetic acid at magnetic resonance (MR) imaging and to correlate enhancement in hepatocyte-selective phases with histopathologic findings and in arterial and portal venous phases with biphasic computed tomographic (CT) findings. MATERIALS AND METHODS: Study was supported by local ethics committee; all patients gave written informed consent. In 19 men and 14 women recruited in three clinical studies, histopathologic correlation and CT scans of 41 focal lesions (13 primary malignant lesions, 21 metastases, three adenomas, three cases of focal nodular hyperplasia [FNH], and one cystadenoma) and ultrasonographic confirmation of five cysts were available. MR was performed before and during arterial and portal venous phases and in hepatocyte-selective phases 10 and 20 minutes after injection of gadoxetic acid. Enhancement was evaluated in consensus by two observers. Enhancement pattern and morphologic features during arterial and portal venous phases were correlated between gadoxetic acid-enhanced MR and CT images by means of adjusted chi(2) test. RESULTS: Hepatocyte-selective uptake was observed 10 and 20 minutes after injection in FNH (three of three), adenoma (two of three), cystadenoma (one of one), and highly differentiated hepatocellular carcinoma (HCC [grade G1], two of four). Uptake was not detected in metastases (21 of 21), cholangiocarcinoma (three of three), combined hepatocellular cholangiocarcinoma (one of one), undifferentiated carcinoma (one of one), moderately or poorly differentiated HCC (grade G2-G3) (four of four), HCC (grade G1, two of four), adenoma with atypia (one of three), or cysts (five of five). During arterial and portal venous phases, there was high overall agreement rate of 0.963 between gadoxetic acid-enhanced MR and CT (simultaneous 95% confidence interval: 0.945, 0.981). CONCLUSION: Liver-specific enhancement of focal lesions is hepatocyte selective and correlates with various histopathologic diagnoses regarding presence of certain hepatocytic functions. Arterial and portal venous MR images obtained with gadoxetic acid are comparable to those of CT.     

MRI对比噪声比对肝占位性病变微血管评估的价值

目的:研究肝良恶性病变微血管密度(MVD)与动态增强MRI对比噪声比(CNR)之间的联系,以建立通过MRl评估微血管分布的理论基础,为临床诊断治疗HCC提供依据.方法:115例肝细胞癌(HCC),6例肝细胞胆管细胞混合癌,14例胆管细胞癌,3例局灶性结节增生(FNH),2例肝腺瘤,4例坏死肝癌,3例慢性肝脓肿,3例凝固坏死,4例腺瘤样增生,2例血管平滑肌脂肪瘤,6例炎性假瘤,1例纤维炎性坏死结节,1例嗜酸性肉芽肿及1例神经纤维瘤.MRI检查后手术切除全部病灶,切除标本经CD34单克隆抗体免疫组化染色,计数MVD.测量痛灶信号强度SI灶,肝实质信号强度SI肝和背景噪声信号强度SI噪,分别计算各时相CNR=(SI灶-SI肝)/SI噪.按病灶直径＜3cm,＞3cm分组分别计算动态增强各时相病灶的对比噪声比(CNR),按病理诊断分组分别对动脉期、门脉期和平衡期CNR与病灶MVD计数行Pearson相关分析.HCC组按病灶最大径＜3cm和＞3cm分为两组.结果:两组HCC各时相CNR与MVD计数均有显著相关性(P＜0.05),但其余病变未显示明显相关.结论:MRI对比噪声比可用于评估HCC微血管密度,动态增强MRI对于显示HCC病灶具有重要作用.     

Radiology disease of rare liver tumors (author's transl)

The past decade has shown an increase in the number of rare primary hepatic tumors, such as focal nodular hyperplasia (FNH), and hepatocellular adenoma and carcinoma. Some examples serve to demonstrate the value of scintigraphy, ultrasound, angiography and CT in the diagnosis of these lesions. Furthermore, the value of the radiographic finding for treatment and follow-up studies is pointed out--in conservative as well as surgical treatment.     

The dynamic magnetic resonance study of focal liver lesions by FLASH sequences with bolus intravenous gadolinium-DTPA]

Thirty-five patients with hepatic hemangioma (n = 12), metastasis (n = 10), hepatocellular carcinoma (HCC) (n = 10) and focal nodular hyperplasia (n = 3) were examined with the fast low-angle shot (FLASH) technique and an intravenous bolus injection of Gd-DTPA. In order to differentiate the lesions, the following criteria were used: a) pre Gd-DTPA intensity of lesions; b) post Gd-DTPA patterns of contrast enhancement. On the basis of these criteria, an unquestionable differential diagnosis could be made. Hemangiomas were characterized by an hypointense mass before Gd-DTPA, by peripheral contrast enhancement and by subsequent continuous hyperintense fill-in; thus, hemangiomas were visualized as hyperintense lesion during the late phase. Before contrast administration hypovascular metastases appeared as hypointense; they were characterized by delayed uptake of contrast agent. HCCs were hyperintense lesions before contrast administrations; then, quick contrast enhancement and rapid decrease in signal intensity were observed with visualization of a hyperintense ring due to the capsule. Finally, focal nodular hyperplasia appeared isointense or hypointense relative to normal liver on precontrast scans; the lesions were enhanced transiently with subsequent quick dismission of contrast agent. This initial experience suggests dynamic contrast-enhanced MR imaging as an effective method to improve the differential diagnosis among hepatic tumors when precontrast T2-weighted images are equivocal.     

Focal nodular hyperplasia-like nodules in alcoholic liver cirrhosis: radiologic-pathologic correlation

OBJECTIVE: The purpose of this study was to describe our experience with three patients who had pathologically proven focal nodular hyperplasia (FNH)-like nodules that radiologically mimicked hepatocellular carcinoma (HCC). CONCLUSION: FNH-like nodules may radiologically mimic HCC, appearing as hypervascular masses on contrast-enhanced CT images and as high-signal-intensity masses on superparamagnetic iron oxide-enhanced MR images. Pathologically, there is the presence of a high number of unpaired arteries and sinusoidal capillarization, which may mimic HCC. Thus, it is important to differentiate FNH-like nodules radiologically, pathologically, and clinically from HCC.     

肝硬化结节与小肝癌的CT、MRI诊断

在肝硬化结节及小肝癌的早期诊断方面,CT、MRI仍是目前临床工作中最重要的方法,本文阐述肝硬化结节演变为肝癌过程中的几个重要环节的CT、MRI表现及国内、外对此的研究现状,这几个环节包括肝硬化再生结节、发育不良性结节(低、中、高级)、小肝癌及肝癌,它们在CT、MRI表现上各有特征,但相互间也有影像学表现上的重叠,故多数较典型者可以通过CT密度值、MRI信号值及增强表现判断其性质,少部分诊断有困难的病灶可以通过双动脉期扫描、MR菲立磁增强及灌注成像等方法提供更多的诊断信息。     

Hepatocellular carcinoma in the cirrhotic liver with helical CT and MRI: imaging spectrum and pitfalls of cirrhosis-related nodules

OBJECTIVE: This article reviews the imaging spectrum of cirrhosis-related nodules on CT and MRI and differentiates between hepatocellular carcinoma (HCC) and common focal lesions that can simulate HCC in the cirrhotic liver. CONCLUSION: Knowledge of cirrhotic nodules and focal lesions and how they mimic HCC will improve the diagnosis and characterization of focal lesions in cirrhotic liver on CT and MRI.     

Primary hepatocellular lesions: imaging findings on state-of-the-art magnetic resonance imaging, with pathologic correlation

Magnetic resonance imaging is routinely used for the workup of patients with focal or diffuse liver disease, including primary hepatocellular lesions, storage diseases, metastatic liver disease, and diseases of the hepatobiliary tree. The most important magnetic resonance imaging sequences used for diagnostic imaging of the liver consist of T1-weighted sequences, T2-weighted sequences, and at least the arterial and delayed phases of dynamic gadolinium-enhanced imaging. This article provides an overview of magnetic resonance imaging of primary hepatocellular lesions and will describe the following: (1) the classification and etiology of primary hepatocellular lesions, including focal nodular hyperplasia, hepatocellular adenoma, and hepatocellular carcinoma; (2) the stepwise carcinogenesis of hepatocellular carcinoma in cirrhosis on magnetic resonance imaging; and (3) the typical imaging findings of primary hepatocellular lesions on magnetic resonance imaging, with differential diagnoses.     

Focal nodular hyperplasia and hepatocellular adenoma of the liver: differentiation with multiphasic helical CT

OBJECTIVE: Differences of attenuation and enhancement patterns in focal nodular hyperplasia and hepatocellular adenoma were evaluated and quantified using triphasic single-slice helical CT. MATERIALS AND METHODS: Forty-five histologically proven focal nodular hyperplasias in 27 patients and 18 hepatocellular adenomas in six patients were examined with helical CT. Quantitative evaluation included the following: attenuation of lesions, scar, and liver parenchyma during unenhanced, arterial (20 sec after injection), and portal venous phases (70 sec after injection); relative enhancement of lesions and liver (the ratio between attenuation in arterial phase and portal venous phase, respectively, and attenuation in unenhanced phase); and the prevalence of scar and its central vessel in focal nodular hyperplasia. RESULTS: The study showed no significant difference between mean attenuation values of focal nodular hyperplasia (mean +/- SD, 51.2 +/- 5.9 H) and hepatocellular adenoma (mean +/- SD, 56.3 +/- 7.8 H) in the unenhanced phase. In the arterial phase attenuation values were significantly higher in focal nodular hyperplasia (mean +/- SD, 117.9 +/- 15.1 H) than in hepatocellular adenoma (mean +/- SD, 80.1 +/- 10.5 H). In the portal venous phase no significant differences in attenuation values were detected between focal nodular hyperplasia (mean +/- SD, 112.1 +/- 20.4 H) and hepatocellular adenoma (mean +/- SD, 110.2 +/- 12.9 H). For enhancement parameter thresholds separating focal nodular hyperplasia from hepatocellular adenoma, the following were found: the relative enhancement was higher in 100% of the focal nodular hyperplasias and lower than or equal to 1.6 (accuracy, 96%) in 87% of the hepatocellular adenomas. CONCLUSION: Triphasic helical CT combined with quantitative evaluation of liver lesions offers the possibility of detecting differences in liver lesions that are visually similar on CT. The attenuation and relative enhancement in the arterial phase show significant differences that make accurate differentiation between focal nodular hyperplasia and hepatocellular adenoma possible.     

Magnetic resonance imaging of hepatocellular carcinoma mimicking focal nodular hyperplasia: a potential pitfall in patients with cirrhosis?

The magnetic resonance imaging findings in 2 cases of pathologically proven hepatocellular carcinoma that mimicked focal nodular hyperplasia are presented. Both cases were found in patients with cirrhosis, a condition in which focal nodular hyperplasia is unlikely to occur. Recognition that hepatocellular carcinoma may mimic focal nodular hyperplasia in patients with cirrhosis may prevent misdiagnosis and allow for earlier intervention.     

微小肝细胞结节性病变CTHA及CTAP的诊断价值

目的:分析肝细胞结节性病变在CTHA 和CTAP 上的不同表现,评价其对早期肝细胞癌的诊断价值。方法:对32例肝细胞结节性病变患者行CTHA、CTAP和组织学检查。结果:18 个中、低分化型肝细胞癌结节均显示为CTHA高密度、CTAP低密度;7个再生性结节和腺瘤样增生中有4个结节CTHA和CTAP均呈等密度;其余21 个结节根据恶性程度的不同,显示为由高分化到低分化不同类型的CTHA和CTAP表现。结论:CTHA和CTAP可提高早期肝细胞癌的检出率,且可用以推测肝细胞结节性病变的恶性程度,指导临床治疗。     

Radiologic features of focal nodular hyperplasia. Comparison with hepatocellular carcinoma by angiography and CT scan]

Radiographic features of eight focal nodular hyperplasia (FNH) of livers of 6 patients were described in comparison with those of 72 hepatocellular carcinoma (HCC). In arterial angiograms, 3 of the examined 4 FNH showed a large tumor vessel entering the center of the lesion. However, 1 of the examined HCC (1/39) had such a vessel. Tumor vessels in all of the examined FNH (4/4) were mainly curvilinear, without an encased and obstructive appearance. These angiographic features were not found in the examined HCC (0/39). Spoke-wheel patterns of tumor vessels were observed in 2 FNH (2/4) and in 3 HCC (3/39). In CT scan without contrast imaging, 5 HCC (5/39) and 3 FNH (3/5) were isodense. One of HCC (1/50) and 3 FNH (3/5) were isodense in the late phases of dynamic CT images. 4 HCC (4/50) and 4 FNH (4/5) had an irregular margin in the lesions. 5 HCC (5/50) and 4 FNH (4/5) demonstrated central low density areas in lesions in the early phases of dynamic CT imaging. In the late phases of the image, central high density areas in lesions were found in 2 HCC (2/50) and 3 FNH (3/5). Based on the above radiographic features such as a large tumor vessel having a curvilineal appearance, irregular margin of the lesions in FNH, we conclude that it is possible to make a differential diagnosis between FNH and HCC clinically.     

动态增强容积内插序列在肝脏占位性病变的临床应用价值

目的:评价MRI三维动态增强容积内插序列在肝脏局灶性病变的临床应用价值.方法:91例肝脏占位性病变患者进行常规MR T1WI和T2WI扫描后,采用三维扰相梯度序列行屏气全肝3期动态增强扫描并进行图像重组,观察病灶的增强特点,并对肝动脉的显示程度进行分级.结果:91例中原发性肝癌17例,肝血管瘤24例,肝转移性肿瘤16例,局灶性结节增生2例,肝脓肿11例,肝囊肿21例.肝动脉显示为2级86例94.5%,1级3例3.3%,0级2例2.2%.结论:MR 动态增强容积内插技术可以获得高质量的图像(尤其是动脉期),有利于肝脏局灶性病变的定性、定位诊断和指导临床治疗.     

Diagnosis of small hepatocellular carcinoma: correlation of MR imaging and tumor histologic studies

Magnetic resonance (MR) images of the liver were used to study 43 patients with relatively small hepatocellular carcinomas (HCCs) and 36 with other hepatic mass lesions. In 27 HCC patients, histologic findings were available. All focal lesions detectable by CT without contrast media were delineated with greater contrast by MR imaging. The rate of detection depended on tumor size, being 97.5% for HCCs greater than 2 cm in the longest axis and 33.3% for those less than 2 cm. MR imaging demonstrated the ring sign characteristic of encapsulated HCC twice as frequently as CT scans. Inversion recovery (IR) images depicted the internal structure of the HCC better than T2-weighted spin-echo images. Lesions were classified into four patterns of intensity: low, iso, high, and mixed. The latter three were relatively characteristic of HCC and related closely with steatosis of cancer tissue. HCCs with fibrosis tended to have long T1 values; those with steatosis had short T1 values. T1 and T2 relaxation times were useful in the differential diagnosis.     

探讨双b值对比法在肝脏局灶性病变诊断中的作用

目的：探讨双b值对比法在肝脏局灶性病变诊断中的价值.方法：回顾性分析108例行肝脏MRI平扫及动态增强扫描患者的病例（肝癌44例.转移瘤4例,血管瘤40例,囊肿18例,局灶性结节增生2例）,分为良恶性两组（恶性组48例,A组;良性组60例,B组）.均行b值为500和800 s/mm2的DWI扫描,测量肝脏病变的信号强度值,计算相对信号比R500、R800（R=病灶信号/背景信号）,观察不同b值时病变的信号变化情况△R（△R=R800-R500）.采用X2检验分析采用△R值诊断良恶性病变与病理结果的一致性.结果：△R≥0.25有42例（PA组）,△R〈0.25（PB组）有66例,其中PA中有4个为良性病变（均为血管瘤）,PB中有10个为恶性病变（2个转移瘤,8个肝癌）,差异无统计学意义（X2=1.786,P〉0.05）.结论：双b值对比法在肝脏局灶性病变的定性诊断中具有可行性.