肝脏局灶性病变MRI表现与病理学的相关性研究

肝脏局灶性病变的MRI信号强度受许多病理因素的影响。病变的组织学特征:细胞构成、血液供应、间质构成和肿瘤内的坏死或者出血等,都会使病变的T1及T2弛豫时间发生显著变化。细胞内的某些内容物:糖原、脂肪、黑色素、铁和铜,在决定MRI信号表现方面起着重要的作用。MRI与病理学之间联系的研究对于诊断局灶性病变非常有帮助。     

Computed tomographic and ultrasound appearances of focal spared areas in fatty infiltration of the liver

Computed tomography (CT) and ultrasound (US) appearances of diffuse and focal fatty infiltration of the liver (FIL) are well recognized. We have recently seen 10 cases with "fat spared" areas in FIL presenting as pseudo tumours of the liver. Characteristic appearances of fat free areas in FIL which help differentiate these areas from other focal liver lesions include (i) location in the medial segment of the left lobe of the liver, (ii) absence of mass effect on surrounding vessels and liver tissue, and (iii) presence of typical changes of FIL elsewhere in the liver on CT or US examination.     

Steatosis hepatis – eine Herausforderung?

CLINICAL/METHODICAL ISSUE: With the increasing use of cross-sectional imaging techniques both diffuse and focal fat accumulations in the liver are frequent incidental findings. Focal fatty changes in particular, such as localized distribution disorders in steatohepatitis or focal fat deposition of the liver, can lead to difficulties in the correct diagnosis of patients with a history of malignant disease. STANDARD RADIOLOGICAL METHODS: Ultrasound is used as the first imaging modality in most cases but has a relatively low sensitivity and specificity. In most cases a further diagnosis of diffuse fatty liver accumulations is possible with non-contrast computed tomography (CT) scanning and chemical shift imaging in magnetic resonance imaging (MRI) enabling an even further differential diagnostic distinction of fatty disorders of the liver. PERFORMANCE: For the detection of generalized fatty liver disease ultrasound has a sensitivity and specificity of 60-100% and 77-95%, respectively. Non-contrast CT of the liver attains a sensitivity of between 43% and 95% with a specificity of 90%. Sensitivity and specificity for chemical shift imaging of MRI are 81% and 100%, respectively. PRACTICAL RECOMMENDATIONS: For advanced differential diagnostic distinction of the different forms of fatty liver disorders and for the correct diagnosis of benign and malignant liver lesions the leading imaging modality is chemical shift imaging of MRI (in-phase and opposed-phase).     

Liver cancer imaging: the need for accurate detection of intrahepatic disease spread

The last ten years have seen dramatic changes in the therapeutic approach to both primary (i.e., hepatocellular carcinoma: HCC) and secondary (i.e., metastatic lesions) focal liver malignancies. This has been due to the increasing proliferation of new modalities, including percutaneous ablative therapies (ethanol injection: PEI; radiofrequency: RF; laser; microwaves), angiographic therapies (segmental chemoembolization; hypoxic perfusion) and liver transplantation (OLT), in addition to a greater acceptance of pre-existing modalities (resection; systemic chemotherapy). Thus, a main aim of current medical management is to select for each patient the therapeutic modality which will provide the highest success rate, fewest risks and lowest costs for each given situation. However, in order to decide on the appropriate therapeutic choice, the accurate diagnosis of neoplastic lesions by means of one or more imaging modalities (ultrasound: US; computed tomography: CT; magnetic resonance: MR) is mandatory. This imaging work-up can be viewed as having three purposes: lesion detection, lesion characterization, intrahepatic and extrahepatic cancer staging. The present paper is concerned primarily with the imaging approach to liver lesion detection.     

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.     

Chemical shift: the artifact and clinical tool revisited.

The chemical shift phenomenon refers to the signal intensity alterations seen in magnetic resonance (MR) imaging that result from the inherent differences in the resonant frequencies of precessing protons. Chemical shift was first recognized as a misregistration artifact of image data. More recently, however, chemical shift has been recognized as a useful diagnostic tool. By exploiting inherent differences in resonant frequencies of lipid and water, fatty elements within tissue can be confirmed with dedicated chemical shift MR pulse sequences. Alternatively, the recognition of chemical shift on images obtained with standard MR pulse sequences may corroborate the diagnosis of lesions with substantial fatty elements. Chemical shift can aid in the diagnosis of lipid-containing lesions of the brain (lipoma, dermoid, and teratoma) or the body (adrenal adenoma, focal fat within the liver, and angiomyolipoma). In addition, chemical shift can be implemented to accentuate visceral margins (e.g., kidney and liver).     

Incidentalomas

A liver incidentaloma corresponds to a liver lesion detected during work-up of for unrelated pathology. The frequency of incidentalomas is directly related to the incidence of liver tumors in the general population. After detection of an incidental liver lesion, the goal is to assess if diagnosis can be made based on imaging features alone or if biopsy is required. As such, radiologists must be familiar with the imaging features of different types of liver lesions, irrespective of the imaging modality. US is useful to determine the number of lesions (single versus multiple) and the cystic or solid nature of each lesion. Cystic lesions are usually benign. Incidental solid liver lesions are typically benign, but detection of a malignant lesion, hepatocellular carcinoma and metastases, is possible. The most frequent benign incidental solid liver lesions are hemangioma, focal nodular hyperplasia and liver cell adenoma. Accurate imaging diagnosis may not always be achievable, and biopsy, percutaneous or surgical, may be required.     

胆囊穿孔的CT诊断及鉴别诊断(附12例分析)

目的 探讨胆囊穿孔的CT诊断及鉴别诊断.方法 12例经临床手术病理证实的胆囊穿孔患者的CT表现征象进行回顾性分析.结果 胆囊穿孔CT表现包括胆囊壁的改变、胆囊周围和右上腹腔的异常、肝脏内的异常密度.胆囊壁的特征性改变表现为连续性中断或局限性缺损、膨出.胆囊周围和有上腹的异常包括胆囊窝积液及右上腹包裹性积液,肌囊周围脂肪间隙密度增高或条索状影,胆囊邻近器官的改变.肝脏内异常灶表现为肝脓肿形成,胆囊与肝脓肿之间有通道.结论 螺旋CT能显示穿孔的胆囊壁连续性中断或局限性缺损,以及胆囊穿孔周围病变特征,为临床诊断和治疗提供可靠的影像学依据.     

Infarcted regenerative nodules in cirrhosis: CT and MR imaging findings with pathologic correlation

OBJECTIVE. The purpose of this article is to present the imaging findings and correlative pathologic findings of infarcted regenerative nodules in the cirrhotic liver. CONCLUSION. Infarcted regenerative nodules exhibit a spectrum of imaging appearances in the cirrhotic liver and can resemble hypovascular hepatocellular carcinoma or other neoplasms on CT and MR imaging. Although uncommon, this abnormality must be included in the differential diagnosis of focal liver lesions in patients with cirrhosis, particularly in patients with a history of substantial gastrointestinal bleeding. Serial imaging may help differentiate these lesions from malignant tumors.     

MRI findings of focal eosinophilic liver diseases

OBJECTIVE: The purpose of this study was to describe the MRI findings of focal eosinophilic infiltration and eosinophilic abscess of the liver. CONCLUSION: MRI shows characteristic findings of focal eosinophilic liver disease that can be helpful in differentiating lesions of focal eosinophilic liver disease from other focal liver lesions. In addition, eosinophilic abscess and focal eosinophilic infiltration showed different MRI findings from each other.     

实时超声造影在肝脏局灶性病变诊断中的应用

目的:评价实时超声造影技术在肝脏局灶性病变诊断中的作用及意义.方法:采用实时超声造影技术,对我院269例肝脏局灶性病变进行超声造影检查.结果:92.4%恶性病变动脉相呈现回声增强.病灶动脉相呈现高增强或等增强、延迟相消退为低增强或无增强,在良性病变中占13.8%(19/138),恶性病变中为94.7%(124/131);实时超声造影诊断肝脏局限性病灶的敏感度89.6%,特异度97.5%,诊断符合率93.2%.结论:实时超声造影可显示肝局灶性病变的血流灌注特点,对肝局灶性病变的分类诊断有重要的应用价值.     

Focal liver lesions: MR imaging-pathologic correlation

Magnetic resonance signal intensity of focal liver lesions is affected by numerous pathologic factors. Lesion histologic features, such as cellularity, vascularity, stromal component, and intratumoral necrosis or hemorrhage, strongly affect T1 and T2 relaxation times. Additionally, intracellular content of certain substances, such as glycogen, fat, melanin, iron, and copper, may also have a substantial role in determining MR signal behavior. In this review we discuss the correlations between MR imaging features and pathologic findings in benign and malignant focal liver lesions. Knowledge of imaging-pathology correlations greatly assist in charac terizing focal lesions. Moreover, in certain tumor histotypes, such as hepatocellular carcinoma, careful analysis of lesion signal intensity may help predict the degree of tumor differentiation.     

Fat attenuation lesions of the mediastinum.

The identification of fat within a focal or diffuse mediastinal lesion significantly narrows the differential diagnosis. In many cases, a specific diagnosis can be suggested on the basis of CT findings. In this article, we illustrate and review the characteristic CT features of common and uncommon fat attenuation lesions of the mediastinum, including focal masses and diffuse abnormalities.     

腹膜假性黏液瘤的CT诊断

目的:认识和提高腹膜假性黏液瘤的CT表现及诊断.方法:回顾性分析16例经病理或细胞学检查证实的腹膜假性黏液瘤的CT和临床表现.结果:腹膜假性黏液瘤是以黏液性腹水为特征,临床主要表现为腹胀、腹块等.依据CT表现不同可分为弥漫性和局限性两种类型,主要CT表现包括腹水内密度不均匀8例,肝脾表面黏液样结节10例,多发分隔的囊性病变5例和网膜增厚或"网膜饼"征6例.结论:典型的CT表现可以诊断腹膜假性黏液瘤,CT检查可为临床治疗的选择和改善预后提供有价值的信息.     

Focal liver lesions in multiple myeloma: ecography, computed tomography, and magnetic resonance findings. A case report

According to autopsy data, diffuse hepatic infiltration occurs in up to 50% of cases with multiple myeloma. However, focal infiltration (single or multiple), although exceptional, is also possible. Therefore, multiple myeloma should be included in the extensive differential diagnosis of space-occupying liver lesions. We present the case of a 71-year-old man diagnosed with multiple myeloma with multiple focal lesions in the liver and spleen studied by different imaging techniques (ultrasound, multi-phase computed tomography and magnetic resonance). The definitive diagnosis was made by immunohistochemical analysis of material obtained by US-guided fine needle aspiration. We review the imaging findings reported in the literature for focal liver lesions in multiple myeloma and in extramedullary plasmacytoma of the liver.     

Primary benign liver lesions

Benign focal liver lesions can origin from all kind of liver cells: hepatocytes, mesenchymal and cholangiocellular line. Their features at imaging may sometimes pose difficulties in differential diagnosis with malignant primary and secondary lesions. In particular, the use of MDCT and MRI with extracellular and hepatobiliary Contrast Agents may non invasively help in correct interpretation and definition of hepatocellular or mesenchymal and inflammatory nature, allowing to choose the best treatment option. The peculiarities of main benign liver lesions at US, CT and MRI are described, with special attention to differential diagnosis and diagnostic clues.     

快速扰相梯度回波同相或反相位成像技术在含脂病变检查中的应用

目的:探讨快速扰相梯度回波同相或反相位成像(FSPGR IP/OP)技术在含脂病变中的应用价值。方法:搜集46例含脂病变(其中脂肪肝12例、肝细胞癌合并脂肪变性7例、肾上腺腺瘤9例、肾血管平滑肌脂肪瘤16例、脂肪肉瘤2例),全部病例均作快速扰相梯度回波同/反相位(FSPGR IP/OP)成像,分析病变在IP/OP像上的信号变化。结果:46例含脂病变OP像与IP像比较,呈全部或部分信号衰减。结论:FSPGR IP/OP技术可敏感地检测病变中的脂质成分,有助于病变的定性诊断。     

Lesion/fat intensity ratio in MR characterization of hepatic masses.

On T2-weighted spin echo images, lesion/liver intensity ratios can be used to accurately distinguish hepatic cavernous hemangioma from malignant lesions. However, since patients with focal liver lesions may present diffuse liver disease, this relationship can be inaccurate. We studied 91 hepatic lesions to compare the value of lesion/liver and lesion/fat ratios in the differential diagnosis of liver lesions. In doubtful cases the use of lesion/fat intensity ratio can be used to improve accuracy in the diagnosis of liver lesions. The combination of both ratios into a single diagnostic index gave a correct classification of malignant versus hemangioma in 92.3% of the cases.     

MR findings in eosinophilic infiltration of the liver

OBJECTIVE: This study describes the findings of magnetic resonance imaging (MRI) of focal eosinophilic infiltration of the liver. METHODS: Contrast-enhanced MR images of 8 patients with focal hepatic eosinophilic infiltration were reviewed retrospectively. We evaluated the signal intensity of focal lesions in T1-weighted and T2-weighted images and the pattern of enhancement in a dynamic contrast study. RESULTS: A total 22 focal hepatic lesions were observed; the lesions were isointense (55%) or hypointense (45%) on T1-weighted images and isointense (14%) or hyperintense (86%) on T2-weighted images. The arterial phase of the contrast study revealed 11 hyperintense lesions (50%). During the portal and delayed phases, 18 (82%) and 17 lesions (77%) were hyperintense, respectively. CONCLUSION: The focal eosinophilic infiltrations showed homogeneous enhancement in the portal and delayed phases in the dynamic contrast MR study. These findings should help to distinguish focal eosinophilic infiltration, especially from metastasis in patients with malignancy.     

肝脏不典型腺瘤样增生结节的综合影像诊断

研究肝脏不典型腺瘤样增生结节的ＵＳ、ＣＴ和ＭＲＩ表现与诊断。方法回顾性分析经病理证实的７例（手术切除３例,ＵＳ引导下肝穿刺活检４例）肝脏不典型腺瘤样增生结节的ＵＳ、ＣＴ和ＭＲＩ表现,以及术前或穿刺前诊断情况,并与病理对照。结果５例诊断为癌前病变,２例误诊为小肝癌。ＵＳ显示稍低或等回声６例,稍强回声１例。