Benign focal liver lesions: discrimination from malignant mimickers

Focal lesions of the liver often have various imaging characteristics which may be interpreted as either benign or malignant. Understanding the underlying pathophysiology of these liver lesions may lead to characteristic imaging manifestations, which direct the radiologist to the diagnosis. Benign lesions include congenital hepatic cyst, autosomal dominant polycystic disease, hemangioma, focal nodular hyperplasia (FNH), hepatic adenoma, inflammatory pseudotumor, peliosis hepatis, focal fatty infiltration, hamartoma, and infectious processes such as hepatic abscess, echinococcal cyst, and candidiasis. Characteristic imaging features, clinical symptoms, and treatment/prognosis will be discussed. Emphasis will be placed on key reliable features of each disease to develop a method of discriminating these lesions from other benign and malignant disorders.     

MRI诊断含脂质肝脏肿瘤的价值

目的:评估MRI诊断含脂质肝脏肿瘤的价值.材料和方法:回顾性分析34例含脂质肝脏肿瘤的MRI表现和术前或穿刺前诊断,并与病理对照.结果:T1WI 32例呈高信号、2例低信号,T2WI 32例呈高信号、1例等信号、1例低信号.用脂肪抑制后,15例肝细胞癌(HCC)、7例血管平滑肌脂肪瘤(HAML)、1例肝腺瘤和1个局灶结节性增生(FNH)T1WI的高信号完全消失,1例不典型腺瘤样增生结节局灶癌变和1例HAML出血囊变T1WI 高信号大部分消失,6例肝腺瘤和1个FNH病灶T1WI高信号无变化 .26例血供丰富,4例血供不丰富.14例HCC、2例腺瘤、7例HAML和1例FNH诊断正确,2例HAML诊断为良性肿瘤.结论:MRI能显示含脂质肝脏肿瘤的特征性表现,并正确诊断多数这类肿瘤.     

肝海绵状血管瘤MRI动态增强表现

目的研究肝脏海绵状血管瘤MRI动态增强表现。材料与方法107例患者行MRI平扫及FL2D或SE序列动态增强扫描,分析其中的119个血管瘤的动态增强表现。结果41个血管瘤在增强早期(团注造影剂后1min内)表现为均一高信号增强,78个血管瘤表现为边缘结节状增强并逐渐向中间充填增强。SE序列扫描1.2％(1/84)的病灶延迟期呈等信号充填增强,FL2D扫描11.5％(4/35)的病灶延迟期呈等信号充填增强,余病灶均表现为高信号充填增强。结论肝血管瘤可归纳为两种增强类型快速充填型和边缘结节增强充填型。少部分血管瘤FL2D序列扫描时病灶可呈等信号充填增强。     

肝脏局灶性结节性增生2例报告及文献复习

目的通过分析肝脏局灶性结节增生的影像表现，提高其诊断准确性。方法2例经手术病理证实的肝脏局灶性结节增生患者均接受超声、CT和MRI检查，其影像表现结合文献复习进行了分析。结果超声显示了2例的肝右叶实性占位性病变。1例CT平扫肝右叶病灶显示不清，增强扫描后，肝右叶前段有一直径约3．1cm的类圆形病灶呈均匀强化。MR平扫见2例的肝内结节病灶均呈等T1、等T2信号，增强扫描动脉期病灶明显强化，门脉期和延迟期病灶的强化程度逐渐下降。结论腹部超声可提示本病的诊断，而CT和MRI，尤其是增强扫描，可清晰显示病灶的血供特点和强化特征，为定性诊断提供重要依据。     

Late results after resection of benign hepatic tumors: clinical and radiological findings

The purpose of our work was to provide data on the recurrence of resected benign hepatic lesions and to evaluate the value of follow-up examinations in this group of patients. From August to October 1993, 75 patients who had been admitted for liver surgery for benign tumors between 1975 and 1993 were controlled by physical examinations, serological tests, US, and, in the case of equivocal US findings, by CT. The histological diagnoses of the operative specimen included hydatidosis in 43 patients, focal nodular hyperplasia (FNH) in 12 patients, liver cell adenoma in 8 patients, cavernous hemangioma in 8 patients, and congenital cyst in 4 patients. Hepatic scars were observed in 36 of the 75 patients. Four cases of intrahepatic recurrence and 1 case of intraperitoneal spread were observed in the 42 patients with recent hydatosis. Long-term postoperative controls (specific serological tests, US) are necessary in the management of patients with hydatid disease. Follow-up examinations are not indicated in asymptomatic patients who have been operated on for FNH, hemangioma, or congenital cysts. Received 8 November 1995; Revision received 27 March 1996; Accepted 2 July 1996     

Telangiectatic focal nodular hyperplasia: US,CT, and MR imaging findings with histopathologic correlation in 13 cases

PURPOSE: To review the ultrasonographic (US), computed tomographic (CT), and magnetic resonance (MR) imaging findings in 13 patients with telangiectatic focal nodular hyperplasia (FNH) and to compare imaging features with histopathologic results from resected specimens. MATERIALS AND METHODS: US, helical multiphasic CT, and MR images in 13 patients with pathologically proven telangiectatic FNH were reviewed retrospectively. Two abdominal radiologists evaluated lesions for number, size, heterogeneity, surface characteristics, presence of a central scar, presence of a pseudocapsule, US appearance, attenuation at CT, signal intensity at MR imaging, and presence of associated lesions. Imaging and pathologic findings were compared. RESULTS: Sixty-one lesions (5-140 mm in diameter) were seen at imaging. Lesions were multiple in eight of 13 (62%) patients. Imaging characteristics were heterogeneity in 26 of 61 lesions (43%), well-defined margins in 43 of 61 (70%), lack of a central scar in 56 of 61 (92%), presence of a pseudocapsule in three of 61 (5%), hyperintensity on T1-weighted MR images in 17 of 32 (53%), strong hyperintensity on T2-weighted MR images in 24 of 54 (44%), and persistent enhancement on delayed contrast material-enhanced CT or T1-weighted MR images in 23 of 38 (61%). No specific US pattern was noted. Two patients had additional lesions: One had classic FNH, and the other had a cavernous hemangioma. Hyperintensity on T1-weighted MR images was due to sinusoidal dilatation. Hyperintensity on T2-weighted MR images correlated well with the presence of inflammation. CONCLUSION: Telangiectatic FNH differs from typical FNH at imaging: Atypical FNH features often observed with telangiectatic FNH are lack of a central scar, lesion heterogeneity, hyperintensity on T1-weighted MR images, strong hyperintensity on T2-weighted MR images, and persistent contrast enhancement on delayed contrast-enhanced CT or T1-weighted MR images.     

Benign hepatic tumors: MRI features before and after administration of superparamagnetic contrast media

PURPOSE: To assess the yield of superparamagnetic iron oxide (SPIO)-enhanced MR images in the detection and characterization of benign hepatic tumors and to evaluate the potential role and safety of SPIO administration in the diagnosis of these tumors. MATERIAL AND METHODS: Eighteen patients underwent MRI before and after administration of SPIO particles. Spin echo (SE) T1, DP, T2 and Gradient echo (GE) T2* images were acquired with a.5 T superconductive unit. MR diagnosis was bioptically proved in 12 patients. In the remaining six patients, who had hemangiomas only, diagnosis was confirmed by at least two imaging techniques-such as MR, CT, ultrasonography, radio-labeled red cells scintigraphy-and by both clinical and imaging follow-up. RESULTS: Thirthy-four tumors were detected on the MR images: 29/34 (85,3%) before and 33/34 (97%) after SPIO administration - 6 focal nodular hyperplasias (FNH), 6 adenomas and 22 hemangiomas. One small tumor (adenoma) was detected on the unenhanced MR images only, while 4 lesions (3 adenomas, 1 FNH) were detected after SPIO administration only. DISCUSSION: SPIO-enhanced MRI increased the detection rate of benign hepatic tumors compared to non-enhanced MRI. Iron oxide was also useful in the characterization of such lesions as it was able to demonstrate any heterogeneity resulting from the presence of central scars or septa. Nevertheless, in our experience it was useful to compare baseline with SPIO-enhanced MRI, even if time consuming. Indeed the uptake of iron oxide particles by well-differentiated lesions and normal hepatic parenchyma, is comparable, so that well-differentiated lesions appear isointense and therefore undetectable. CONCLUSIONS: In our experience, although numerically limited, SPIO-enhanced MRI was clinically safe and more effective than non-enhanced MRI in both the detection and characterization of benign hepatic tumors, providing useful clues for diagnosis.     

肝局灶性结节性增生的影像诊断及病理对照研究

目的探讨肝局灶性结节性增生(focal nodu lar hyperp lasia,FNH)的影像学表现特点。方法经手术切除病理证实为肝局灶性结节性增生17例病例,术前均行螺旋CT平扫及动态增强扫描,其中10例又行MR平扫及动态增强扫描,分别进行影像学及病理学对照分析。结果17例FNH病灶均呈孤立结节或分叶状肿块,多数直径2~5 cm。平扫呈等或略低密度及信号,T2W I为略高信号。动态增强扫描,动脉期病灶均为明显的均质的强化,静脉期及延迟期12例仍略高于肝实质,6例略低于或等于肝实质。11例病灶内显示瘢痕,其中8例呈延迟强化。4例静脉期出现包膜样强化。病理观察:17例FNH均无包膜,增生的肝细胞形成肝板被纤维间隔分割呈结节状,瘢痕区域由纤维结缔组织及厚壁畸形血管组成。结论典型的FNH影像学可明确诊断,不典型的FNH应与肝细胞腺瘤、肝细胞癌、肝血管瘤相鉴别。     

MR imaging of hepatic focal nodular hyperplasia: characterization and distinction from primary malignant hepatic tumors

Spin-echo MR imaging at 0.35 T was used to image hepatic focal nodular hyperplasia (FNH) and to attempt to distinguish it from primary malignant hepatic tumors. There were six FNH and 10 malignant tumors including seven hepatocellular carcinomas, two cholangiocarcinomas, and one hepatoblastoma. Our results show that FNH has a fairly consistent appearance, dissimilar from that of malignant primary hepatic tumors. Four of six FNH lesions were isointense (except for a central scar in three) and indistinguishable from normal hepatic parenchyma on all pulse sequences, whereas two of six were homogeneous but slightly hyperintense on T2-weighted sequences. Furthermore, a central hyperintense scar was seen in three of six lesions on T2-weighted sequences. In contrast, each of the malignant primary hepatic tumors was hyperintense on T2-weighted sequences and seven of 10 were hypointense on T1-weighted sequences; in nine of 10, heterogeneous areas of intensity were noted. In two fibrolamellar hepatocellular carcinomas a central scar was seen that was hypointense on all pulse sequences. By using quantitative data, the best characterization was obtained by using lesion/normal-liver intensity ratios from a T2-weighted sequence; all FNH had a ratio less than 1.33, while in nine of 10 primary malignant tumors it was greater than 1.41. We conclude that focal nodular hyperplasia may have a consistent appearance on spin-echo MR imaging and probably can be distinguished from primary malignant lesions in most instances.     

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.     

Accurate differentiation of focal nodular hyperplasia from hepatic adenoma at gadobenate dimeglumine-enhanced MR imaging: prospective study

PURPOSE: To prospectively determine the accuracy of differentiating benign focal nodular hyperplasia (FNH) from hepatic adenoma (HA) and liver adenomatosis (LA) by using gadobenate dimeglumine-enhanced magnetic resonance (MR) imaging. MATERIALS AND METHODS: The ethics committee at each center approved the study, and all patients provided informed consent. Seventy-three patients with confirmed FNH and 35 patients with confirmed HA (n = 27) or LA (n = 8) underwent MR imaging before (T2-weighted half-Fourier rapid acquisition with relaxation enhancement or T2-weighted fast spin-echo and T1-weighted gradient-echo [GRE] sequences) and at 25-30 seconds (arterial phase), 70-90 seconds (portal venous phase), 3-5 minutes (equilibrium phase), and 1-3 hours (delayed phase) after (T1-weighted GRE sequences only, with or without fat suppression) bolus administration of 0.1 mmol per kilogram of body weight gadobenate dimeglumine. The enhancement of 235 lesions (128 FNH, 32 HA, and 75 LA lesions) relative to the normal liver parenchyma was assessed. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy for the differentiation of FNH from HA and LA were determined. RESULTS: Hyper- and isointensity on T2-weighted and iso- and hypointensity on T1-weighted GRE images were noted for 177 (88.9%) of 199 lesions visible on unenhanced images. On dynamic phase images after contrast material administration, 231 (98.3%) of 235 lesions showed rapid strong enhancement during the arterial phase and appeared hyper- to isointense during portal venous and equilibrium phases. Accurate differentiation of FNH from HA and LA was not possible on the basis of precontrast or dynamic phase images alone. At 1-3 hours after contrast material enhancement, 124 (96.9%) of 128 FNHs appeared hyper- or isointense, while 107 (100%) HA and LA lesions appeared hypointense. The sensitivity, specificity, PPV, NPV, and overall accuracy for the differentiation of FNH from HA and LA were 96.9%, 100%, 100%, 96.4%, and 98.3%, respectively. CONCLUSION: Accurate differentiation of FNH from HA and LA is achievable on delayed T1-weighted GRE images after administration of gadobenate dimeglumine.     

泪腺良性混合瘤的CT和MRI诊断

目的 探讨CT和MRI对泪腺良性混合瘤的诊断价值. 资料与方法 回顾性分析45例经病理证实的泪腺良性混合瘤的临床和影像学资料,30例行CT检查,35例行MRI检查. 结果 45例中,起源于泪腺眶部43例,泪腺睑部2例.肿瘤呈椭圆形29例,圆形10例,不规则形6例;边缘光滑30例,边缘不规则呈分叶状或结节状15例.CT表现为等密度,大多数密度均匀.眶壁骨质受压、凹陷或缺损22例,骨质破坏伴眶壁硬化、肥厚6例,骨质增生硬化14例.MR T1WI上呈低信号25例,等信号10例,T2WI上呈高信号21例,等信号14例,增强后肿瘤呈中度至明显强化,大多数强化均匀. 结论 泪腺良性混合瘤的CT和MRI表现有一定特征,CT和MRI结合可以提高病变诊断的准确性.     

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。     

Hemangioma in the cirrhotic liver: diagnosis and natural history

PURPOSE: To investigate the natural history and diagnosis of cavernous hemangioma in the cirrhotic liver with computed tomography (CT) and magnetic resonance (MR) imaging. MATERIALS AND METHODS: Imaging and pathologic findings of 21 hemangiomas in 17 patients were retrospectively reviewed. CT of the liver was performed in all patients; MR imaging, in four. Cirrhosis was confirmed histologically in all patients, and the diagnosis of hemangioma was based on histopathologic findings (15 patients, 18 hemangiomas) or strict imaging criteria (two patients, three hemangiomas). Ten patients underwent imaging follow-up. The number, sizes, location, attenuation, pattern of enhancement, exophytic growth, presence of capsular retraction, and size stability were evaluated. RESULTS: Of the 21 hemangiomas, five were not detected at CT or MR imaging. Twelve (75%) of 16 hemangiomas were subcapsular, two (12%) of 16 demonstrated exophytic growth, 14 (87%) of 16 demonstrated nodular peripheral enhancement, and 16 (100%) of 16 were isoattenuating to blood vessels. At MR imaging, all five hemangiomas demonstrated nodular peripheral enhancement and hyperintensity on T2-weighted images. Seven lesions were smaller at follow-up, and five lesions developed retraction of the hepatic capsule. CONCLUSION: Even within the cirrhotic liver, larger hemangiomas can usually be diagnosed confidently with CT or MR imaging. With progressive cirrhosis, however, hemangiomas are likely to decrease in size, become more fibrotic, and are difficult to diagnose radiologically and pathologically.     

CT and MR imaging evaluation of hepatic adenoma

Hepatic adenoma is a rare benign epithelial tumor that is usually encountered in young women who use oral contraceptives. It is clinically significant because of the risk of hemorrhage and of its low-grade malignancy potential. Adenomas usually are mildly hypervascular at contrast-enhanced CT and MR imaging, and heterogeneous due to the presence of hemorrhage, necrosis, calcifications and fat. The objective of our study was to illustrate the CT and MR imaging findings of hepatic adenoma.     

CT and MR imaging of benign primary cardiac neoplasms with echocardiographic correlation.

Benign primary cardiac neoplasms are rare but may cause significant morbidity and mortality. However, they are usually treatable and can often be diagnosed with echocardiography, computed tomography (CT), or magnetic resonance (MR) imaging. Myxomas typically arise from the interatrial septum from a narrow base of attachment. Fibroelastomas are easily detected at echocardiography as small, mobile masses attached to valves by a short pedicle. Cardiac fibromas manifest as a large, noncontractile, solid mass in a ventricular wall at echocardiography and as a homogeneous mass with soft-tissue attenuation at CT. They are usually homogeneous and hypointense on T2-weighted MR images and isointense relative to muscle on T1-weighted images. Paragangliomas usually appear as large, echogenic left atrial masses at echocardiography and as circumscribed, heterogeneous masses with low attenuation at CT. These tumors are usually markedly hyperintense on T2-weighted MR images and iso- or hypointense relative to myocardium on T1-weighted images. Cardiac lipomas manifest at CT as homogeneous, low-attenuation masses in a cardiac chamber or in the pericardial space and demonstrate homogeneous increased signal intensity that decreases with fat-saturated sequences at T1-weighted MR imaging. Cardiac lymphangiomas manifest as cystic masses at echocardiography and typically demonstrate increased signal intensity at T1- and T2-weighted MR imaging. Familiarity with these imaging features and with the relative effectiveness of these modalities is essential for prompt diagnosis and effective treatment.     

平扫和动态增强MRI诊断肝脏局灶性结节增生

目的 探讨肝脏避灶性结节增生（ＦＮＨ）的平扫和动态增强的ＭＲＩ表现及诊断价值。方法 回顾分析２２例２２个手术病理证实的肝脏ＦＮＨ的平扫及动态增强ＭＲＩ资料。结果 病灶平均大小为４．０５ｃｍ,４个病灶在Ｔ１ＷＩ及Ｔ２ＷＩ上呈典型等信号肿块,１８个为不典型信号肿块。８个在平扫ＭＲ上显示中央瘢痕。２１个病灶的实质部分在增强后动脉期呈明显均匀强化,在门脉期及延迟期呈等强化或强于肝实质。２个病灶在门脉期和延     

肝局灶结节样增生MR、CT表现(附6例报告)

目的分析肝FNH的MR、CT表现,旨在提高对FNH认识。方法对6例肝FNH进行MR平扫及Gd-DTPA动态增强检查,其中3例CT平扫及动态增强,1例行CT平扫。结合文献分析其不典型表现。结果6例肝FNH不典型表现包括1例平扫呈明显长T1、长T2信号,动脉期弥漫不均匀强化,假包膜的存在及延迟强化;2例动脉期仅轻度强化;2例MR、CT动态增强各期表现不完全符合。结论MR、CT尤其是动态增强是诊断肝FNH的有效方法。对肝FNH的不典型表现需有足够的认识,以免误诊误治。     

Magnetization transfer contrast of hepatic lesions in breath-hold gradient-echo images of different T1 weighting

Seventeen patients with hepatic lesions [six metastases from colon, breast, and gallbladder carcinoma; one gallbladder carcinoma; five hepatocellular carcinoma; three focal nodular hyperplasia (FNH); one adenoma; and one cyst] were examined by MR breath-hold two-dimensional gradient-echo imaging to assess the potential of magnetization transfer contrast (MTC) for improved conspicuity and classification. Imaging sequences were applied with and without irradiation of off-resonant radiofrequency (RF) prepulses, but other parameters were unchanged. Therefore, quantitative assessment of MTC could be performed. In contrast to former examinations of other researchers, no significant difference of MTC was found between malignant liver lesions and benign lesions as FNH or adenoma. MTC might provide differentiation between hemangioma and cysts versus solid tumors, but MTC is not capable of distinguishing benign and malignant types of solid liver tumors. Effects of unchanged MTC prepulses on signal intensity of normal liver tissue and most lesions were more pronounced for nearly proton density-weighted fast low-angle shot (FLASH) images than for T1-weighted FLASH images, obtained by using higher excitation flip angles. Liver-to-lesion contrast could not be improved clearly by MTC prepulses. The contrast between liver and lesions in the gradient-echo breath-hold images was compared with standard T1- and T2-weighted spin-echo images. Liver-to-lesion contrast in the breath-hold images was found to be inferior to T2-weighted spin-echo images in 14 of 17 cases. Lesion conspicuity in regions near the diaphragm was better in breath-hold images, because problems with marked breathing motion (as in standard imaging) could be avoided.     

Intraoperative US in patients undergoing surgery for liver neoplasms: comparison with MR imaging

PURPOSE: To retrospectively compare intraoperative ultrasonography (US) and preoperative magnetic resonance (MR) imaging with contrast material enhancement for the depiction of liver lesions in patients undergoing hepatic resection. MATERIALS AND METHODS: A radiologist (D.V.S.) and a surgeon (K.K.T.) retrospectively identified 79 patients (36 female and 43 male patients; age range, 10-78 years; mean age, 57 years) who had undergone surgical resection for primary liver tumor or metastasis and had also undergone preoperative contrast-enhanced MR imaging within 6 weeks before surgery. MR imaging was performed with a 1.5-T system. Dedicated intraoperative US of the liver was performed or supervised by a gastrointestinal radiologist using a 7.5-MHz linear-array transducer, after adequate hepatic mobilization by the surgeon. Histopathologic evaluation of the 159 resected hepatic lesions served as the reference standard. The lesion distribution included colon cancer metastasis (n = 122), hepatocellular carcinoma (n = 23), cholangiocarcinoma (n = 6), cavernous hemangioma (n = 4), focal nodular hyperplasia (n = 2), hamartoma (n = 1), and metastatic embryonal sarcoma (n = 1). RESULTS: Of 159 lesions, 138 (86.7%) were identified at both MR imaging and intraoperative US. Twelve additional lesions (7.5%) in 10 patients were detected only at intraoperative US (eight metastases, one hepatocellular carcinoma, one cholangiocarcinoma, one hemangioma, and one biliary hamartoma). Both modalities failed to depict nine lesions (5.6%) (four metastases, four hepatocellular carcinomas, and one cholangiocarcinoma). The sensitivities of MR imaging and intraoperative US for liver lesion depiction were 86.7% and 94.3%, respectively. Surgical management was altered on the basis of the intraoperative US findings in only three of 10 patients (4%). CONCLUSION: Contrast-enhanced MR imaging is as sensitive as intraoperative US in depicting liver lesions before hepatic resection.