MR imaging of benign focal liver lesions

MRI has become the most important imaging modality for detecting and characterizing focal liver lesions. The introduction of high-field-strengths, such as 3 Tesla MR imaging, in combination with the parallel imaging technique, has led to significant improvements in spatial and temporal resolution and has established this technique as a valuable asset in daily clinical practice. New techniques, such as diffusion-weighted imaging, may improve MR imaging sensitivity and specificity in the diagnostic workup of focal liver lesions. The tailored administration of various nonspecific and liver-specific contrast agents enables clinicians to increase the detection rate and improve the characterization of the different focal liver lesions. This article describes the usefulness of these imaging techniques in detecting and characterizing the most common benign focal liver lesions.     

A Pictorial Review of the MRI Appearances of Focal Liver Lesions

The role of magnetic resonance imaging (MRI) in evaluating benign and malignant liver lesions has undergone significant expansion in recent years with the evolution and optimization of imaging sequences and contrast enhanced techniques. The aim of this article is first to summarize the various imaging sequences employed in the evaluation of liver pathology, with reference to the recent literature on the subject and second, to illustrate through pictorial review, the MRI characteristics of a number of benign and malignant lesions both in the normal liver and in those with chronic liver disease. We highlight the importance of availability of adequate clinical history in the interpretation of focal liver lesions on MRI, including the presence or absence of chronic liver disease, known history of primary malignancy and if applicable, serum alpha fetoprotein levels. In conclusion, MRI is the optimum imaging modality in the evaluation of focal liver lesions. Pattern recognition and knowledge of patient history enables characterization of the majority of liver lesions without the use of ionizing radiation.     

磁共振全身弥散成像对胃肠道恶性肿瘤的术后随访价值

目的探讨3.0 T全身磁共振成像的技术对于胃肠道恶性肿瘤性疾病的术后随访价值。材料与方法对19例术后随访的胃肠道恶性肿瘤患者行WBMRI(DWI+T2WI),后处理平台为GE ADW4.6工作站。Functool工具拼接横断面弥散图像,得到HD-MIP图像、黑白反转图像(类"PET"图像)及伪彩色图像;Pasting工具拼接冠状面T2加权图像,得到全身冠状面T2加权图像,再经图像融合得到类"PET-MR"图像。结果 19例患者(其中胃弥漫性大B细胞淋巴瘤2例,胃癌8例,结肠癌7例,直肠癌2例)均获得图像质量良好的全身磁共振图像。发现恶性转移性病例6例,阳性率约32%。结论使用头颈联合线圈及体线圈接收方法可以改善中心频率漂移现象,得到符合诊断需要的全身弥散图像。3.0T MR全身弥散成像可清晰显示胃肠道恶性肿瘤的转移灶,对胃肠道恶性肿瘤的术后随访和辅助诊断具有重要价值。     

Liver metastases in cancer: detection with contrast-enhanced ultrasonography

In patients with known or suspected malignancy, ultrasonography (US) is often the first choice for liver imaging because of its widespread availability and low cost. Compared with contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI), the sensitivity of conventional US for detecting hepatic metastases is relatively poor. The advent of microbubble contrast agents changed this situation. Sensitivity and specificity increased substantially with the use of these contrast agents and contrast-specific imaging modes in recent years. Currently, numerous US imaging methods exist, based on Doppler techniques or harmonic imaging. They exploit the complex nonlinear behavior of microbubbles in a sound field to achieve marked augmentation of the US signal. Although microbubble contrast agents are essentially blood pool agents, some have a hepatosplenic specific late phase. Imaging during this late phase is particularly useful for improving the detection of malignant liver lesions and allows US to perform similarly to spiral CT as shown by recent studies. In addition, this late phase imaging is very helpful for lesion characterization. Low mechanical index imaging with the newer perfluor agents permits real-time imaging of the dynamic contrast behavior during the arterial, portal venous, and late phases and is particularly helpful for lesion characterization. The use of US for hemodynamic studies of the liver transit time may detect blood flow changes induced by micrometastases even before they become visible on imaging. In this field of functional imaging, further research is required to achieve conclusive results, which are not yet available.     

Solid focal liver lesions indeterminate by contrast-enhanced CT or MR imaging: the added diagnostic value of contrast-enhanced ultrasound

The main clinically recognized application of contrast-enhanced US (CEUS) with microbubble contrast agents is the characterization of incidental focal liver lesions. CEUS with low transmit power insonation allows the real-time assessment of contrast enhancement in a focal liver lesion after microbubble contrast agent injection, during the arterial (10-25 s), portal venous (from 35 s up to 2 min) and late phase (4-6 min after microbubble injection). During the portal venous and late phase benign lesions appear hyper or iso-enhancing in comparison to the adjacent liver parenchyma, while malignant lesions prevalently present contrast washout with hypo-enhancing appearance. CEUS may provide an added diagnostic value in those incidental focal liver lesions in which contrast-enhanced CT or MR imaging are not conclusive. In particular, CEUS may provide an added diagnostic value in those focal liver lesions appearing indeterminate on single-phase CT scan, or on CT scans performed by an incorrect delay time or also after injection of a low dose of iodinated contrast agent, or also in those focal liver lesions revealing equivocal enhancement patterns on contrast-enhanced CT or MR imaging. CEUS may have an added diagnostic value also in hepatocellular nodules in a cirrhotic liver and can be considered a complementary imaging technique to CT.     

超声造影剂Sonazoid与SonoVue的物理特征及临床特点比较

目的 CEUS技术应用于肝脏的研究已近30年,近10年来随着其在临床应用的普及,其对肝脏病灶的检出率及诊断的准确率也显著提高。造影剂及造影技术的不断改进使CEUS在临床中占据较为重要的地位。本综述旨在分析Sonazoid与SonoVue这两种造影剂的物理学特征及临床特点,以期为鉴别肝脏占位性病变的良恶性提供更多重要的信息。     

腹部磁共振增强扫描结合弥散加权成像对肝脏良恶性肿瘤的鉴别诊断价值

目的探讨腹部MRI动态增强扫描（DCEI）结合弥散加权成像（DWI）技术对肝脏良恶性肿瘤的鉴别诊断价值。方法回顾性分析2019年3月~2020年3月我放射科核磁室同北京大学第一医院核磁室合作检查64例（91个病灶）肝肿瘤患者的临床资料,经手术病理证实为恶性病灶61个、良性病灶30个。患者均行MRI DCEI及DWI检查,观察肝脏病灶在上述序列上的表现特征,评估MRI DCEI联合DWI对肝脏良恶性肿瘤的鉴别诊断价值。结果恶性病灶中DCEI表现为快进快出、DWI呈高信号者占比大于良性病灶（P < 0.05）。DCEI联合DWI诊断灵敏度、准确度高于DCEI、DWI单独诊断（P < 0.05）;特异度与DCEI诊断差异无统计学意义（P>0.05）,但高于DWI（P < 0.05）。结论良性、恶性肝肿瘤DCEI、DWI表现特征具有差异,DCEI联合DWI诊断肝肿瘤可显著提高诊断准确度和灵敏度,对肝肿瘤良恶性鉴别诊断有重要价值。      

实时导航超声造影在小肝癌诊断中的应用研究

目的探讨超声造影（CEUS）联合磁共振成像（MRI）实时导航技术在小肝癌诊断中的应用。 方法收集2008年1月至2015年6月复旦大学附属中山医院门诊及住院的临床疑诊为小肝癌（直径小于20 mm）的患者50例,共50个病灶,所有患者在常规超声检查未发现病灶,而增强MRI均提示有小肝癌。采用GE公司LOGIQ E9超声诊断仪,配备超声造影与MRI导航技术。超声造影采用低机械指数下实时灰阶超声造影（MI 0.05~0.12）,每次造影经肘静脉团注1.5~2.4 ml造影剂SonoVue。 结果所有病灶均经手术、活检或其他影像学检查证实为肝癌,其中原发性肝癌45个,转移性肝癌5个。实时导航超声造影时,50例患者均成功完成图像融合,融合成功率100%,平均融合时间为（9.1±0.5）min。在50个病灶中,常规超声造影发现15个病灶（30%,15/50）,实时导航超声造影检出48个病灶（96%,48/50）,两者比较差异具有统计学意义（Z=1.73,P<0.05）。在实时导航超声造影中,46个（92.0%,46/50）病灶表现为动脉期快速增强,4个病灶（8%,4/50）呈同步增强;28个病灶在门脉期呈等回声（56%,28/50）,超声造影联合MRI实时导航成像技术检出48个病灶（96%,48/50）,2个未能显示的病灶经人工胸水后再次实时导航顺利检出。实时导航超声造影对本组小肝癌的检出率及诊断准确性为100%。 结论实时导航超声造影可显著提高小肝癌检出率和诊断准确性。     

Ultrasound of focal liver masses

Detecting and characterizing focal liver lesions is one of the most difficult challenges in imaging today. All standard noninvasive imaging modalities are less sensitive than generally perceived, and characterization is imperfect. Liver sonography's main strengths are its ability to definitively characterize common benign lesions (eg, cysts and hemangiomas), safety, low cost, and its ability to guide biopsy. Sonography's weaknesses include its inability to image the entire liver in many patients and its inferiority to CT as a means of detecting extrahepatic malignant disease. Sonography is less sensitive than CT or MRI in detecting focal lesions. Ultrasound contrast agents will certainly improve liver lesion detection and characterization, but their impact is not yet clear.Typical findings in common focal liver lesions are discussed, and some hints to improve sonographic diagnosis are presented. Increased color Doppler flow should bring the possibility of hepatocellular carcinoma and focal nodular hyperplasia to mind, but Doppler diagnosis is ultimately not highly specific. Sonography, including Doppler analysis, is useful to assess the resectability of malignant masses. Intraoperative ultrasound is the most sensitive imaging modality in detecting focal liver lesions.     

MRI在乳腺良恶性病变诊断中的应用研究

目的;探讨MRI对乳腺良、恶性病变的诊断价值。方法;对65例76处乳腺病灶进行MRI平扫和增强检查,分析乳腺病灶MRI平扫和增强图像表现以及动态增强时间－信号强度曲线,并以B超,钼靶及病理结果对照。结果：MRI平扫加增强扫描对乳腺良、恶性病灶的诊断准确率为93．3％,优于B超和钼靶摄片。结论：乳腺MRI增强扫描能提高对乳腺病灶的鉴别诊断价值。     

MR imaging in chronic hepatitis and cirrhosis.

The role of magnetic resonance imaging (MRI) in the evaluation of diffuse parenchymal abnormalities of the liver has been expanded by recent technical advances of MR systems as well as the evolution of intravenous contrast media. Currently, MR is undoubtedly the most useful imaging modality for detecting the presence of chronic liver disease. Tailored sequences allow acurate depiction of specific disorders, including steatohepatitis and iron-overload states. Morphologic changes and signal intensity effects not only facilitate the diagnosis of chronic liver disease with MRI but they also help to distinguish between different etiologies, and they assist in staging the histologic severity of certain chronic conditions. Moreover, the faster MRI scanning techniques presently available permit the dynamic assessment of contrast enhancement, which permits improved characterization of focal hepatic lesions, including regenerative nodules, dysplastic nodules, and hepatocellular carcinoma (HCC). Although overlap in MRI findings still may exist among different types of chronic liver disease and among focal liver lesions, familiarity with certain specific imaging features may be diagnostic in the proper clinical setting. Finally, comprehensive MRI examination, including MR angiography and MR cholangiography, is the most sensitive and cost-effective technique for detecting extrahepatic disease, diagnosing vascular disorders, and evaluating the patient before or after liver transplantation. This article focuses on the current role of MR imaging in patients with chronic liver disease. The subjects covered include the detection and characterization of chronic hepatitis and cirrhosis, specific findings seen in steatohepatitis and certain metabolic diseases, the evaluation of extrahepatic vascular complications of cirrhosis, and patient assessment before and after liver transplantation. The characterization of hepatic masses is also included briefly. This subject is covered in greater depth elsewhere in this issue.     

乳腺DCE-MRI环形强化病变的研究现状及展望

乳腺疾病是女性的常见病,乳腺磁共振动态对比增强检查在临床诊断中占有举足轻重的地位.在乳腺动态对比增强磁共振成像检查中,环形强化作为一种常见的强化方式,既可见于良性病变,又可见于恶性病变,其病理类型广泛,临床上容易误诊.目前,国内外对乳腺MRI上环形强化病变的诊断及鉴别诊断缺乏系统性认识.本文从形态学、血流动力学及扩散加...     

磁共振成像与多层CT对肝脏局灶性病变定性的比较研究

目的比较综合MRI（1.5T或3T）多种序列与MSCT（16或64层）动态增强扫描对肝脏局灶性病变定性的价值。方法回顾性分析行腹部MSCT与MRI检查（两种检查间隔时间不超过1个月）且发现肝脏局灶性病变的41例患者（75个病灶）的诊断结果。结果MSCT鉴别诊断良恶性病灶的敏感度为80.77%（21/26）,特异度为68.42%（26/38）。MRI鉴别诊断良恶性病灶的敏感度为93.33%（28/30）,特异度为97.56%（40/41）。两者敏感度之间的差异无统计学意义（P=0.311）,MRI的特异度高于MSCT（P〈0.001）。对于具体的各类病灶,MRI的总体诊断准确率（86.36%,57/66）高于（P=0.004）MSCT（64.41%,38/59）。结论MRI对肝脏局灶性病变的定性能力优于MSCT。     

磁共振成像及对比剂在细胞移植中的研究进展

随着细胞移植研究的不断深入,细胞移植在临床治疗中的应用逐渐增多.但不论是在科研工作还是临床治疗中进行细胞移植,都需要监测移植后细胞的命运.磁共振成像技术具有无创伤性、时间连续性等优点,是在活体上对移植细胞进行连续多时间点监测的理想方法之一.应用磁共振对比剂在体外标记细胞后将细胞移植入动物体内,可通过磁共振成像追踪移植细...     

Is iron oxide a tissue-specific contrast medium in diagnostic ultrasound? A case report

We present a patient with Hodgkin's disease in whom computed tomography suggested focal lesions in the liver. As no lesions were detected by diagnostic ultrasound, magnetic resonance imaging (MRI) with iron oxide as contrast medium was performed for verification. MRI confirmed at least 3 small lesions. The ultrasound study performed immediately after this MRI scan easily detected these lesions. A biopsy was taken and histology showed infiltrates of Hodgkin's disease. The change in echogenicity of the liver and/or the lymphomatous tissue may be an effect of iron oxide. This observation has not been reported before.     

声弹性成像半定量参数诊断乳腺实性肿块的现状

声弹性成像是近年来发展的新技术之一,能客观评价乳腺肿块的相对弹性硬度。本文系统回顾了近年来乳腺弹性应变比、面积比和直径比等在区分良恶性肿块方面的文献,就声弹性成像半定量参数的诊断现状进行综述。     

MRI for Traumatic Knee Injury: A Review

Magnetic resonance imaging (MRI) is a well-established technique for detecting internal derangements of the knee joint with high diagnostic accuracy. It is an effective tool to select patients for targeted therapeutic arthroscopy. In this article, indications for knee MRI and most commonly used MRI techniques are outlined, followed by an overview of the most frequently encountered traumatic knee derangements in daily practice and their appearance and grading system on MRI. Lesions discussed include fractures, osteochondral lesions, bone bruise, cruciate and collateral ligament lesions, and meniscal tears. Finally, common pitfalls and recent developments in knee MRI are addressed.     

MR imaging in the evaluation of hepatic metastases

Optimal detection of focal hepatic lesions in patients with metastases can alter patient management and result in significant cost savings by reducing the number of unnecessary laparotomies for unresectable disease. Liver-specific MR imaging contrast agents (reticuloendothelial and hepatobiliary agents) offer greater lesion-to-liver contrast than the conventional extracellular fluid space MR imaging contrast agents (gadolinium chelates), which have a nonspecific distribution. For the detection of hepatic metastases, although the work of Seneterre et al suggests that the accuracy of ferumoxide-enhanced MR imaging is equivalent to that of CTAP, other studies find CTAP to be superior. Comparisons of reticuloendothelial agents and hepatobiliary agents for imaging liver metastases are lacking in the literature. Further studies comparing MR imaging enhanced with liver-specific contrast agents to CTAP are needed to determine if hepatic MR imaging can replace CTAP for the preoperative evaluation of hepatic metastases. For the characterization of focal liver lesions, MnDPDP and ferumoxides have been added to the small list of FDA-approved contrast agents, and both can help to increase diagnostic specificity. Two of the hepatobiliary agents which are not yet approved, Gd-BOPTA and Gd-EOB-DTPA, have the potential of characterizing liver lesions during dynamic contrast enhancement (similar to Gd-DTPA) and during the hepatocyte phase (similar to MnDPDP), and may increase the detection of focal liver lesions.     

State-of-the-art magnetic resonance imaging of pancreatic cancer

Technical advances of magnetic resonance imaging (MRI), including ultrahigh-field magnetic resonance at 3.0 T, parallel imaging techniques, and multichannel receive coils of the abdomen, have promoted MRI of the pancreas. For adenocarcinoma, which is the most common malignant pancreatic tumor, helical CT has been most often used for detection and staging, but it has limitations in the detection of small cancers 2 cm in diameter or less (sensitivity, 63%). Moreover, it is not very accurate in determining nonresectability, because small liver metastases, peritoneal carcinomatosis, and subtle signs of vascular infiltration may be missed. At ultrahigh field at 3.0 T, gadolinium-enhanced MRI using volume-interpolated 3-dimensional gradient-recalled echo pulse sequences with near-isotropic voxels are very useful for detection of subtle abnormalities. Mangafodipir-enhanced MRI reveals a very high tumor-pancreas contrast, which helps to diagnose small cancers. Contrast-enhanced MRI is a problem-solving tool in case of equivocal CT: it helps to differentiate between cancer and focal pancreatitis. Neuroendocrine carcinoma may present with a spectrum of appearances at MRI, but the primary tumor and liver metastases are hypervascular in approximately 70%. In this article, pancreas imaging protocols for 1.5 and 3.0 T are explained. We present the imaging features of pancreatic cancer and the important questions in staging, which should be addressed by the radiologist.     

Characterization of Focal Liver Lesions with Contrast-Enhanced Ultrasound

The introduction of second generation microbubble ultrasound (US) contrast agents, such as SonoVue (Bracco, Milan, Italy), has considerably improved the diagnostic yield of US imaging for the evaluation of focal hepatic lesions in recent years because of its ability to very sensitively depict tumoral vascularity. In addition, contrast-enhanced US (CEUS) has the advantage of the absence of ionizing radiation, the widespread availability, even at the bedside, and the possibility to characterize a lesion as soon as detected on conventional B-mode US, commonly used as the first technique for exploration of the liver. The present review focuses on the basic principles of the technique and the various patterns of benign and malignant hepatic lesions at CEUS, contributing to their characterization. Understanding of these enhancement features at CEUS according to the type of tumors enables to make more accurate characterization of focal liver lesions as well as give better advice to oncologists, hepatologists or other clinicians in case of suspected liver tumors. (E-mail: fabio.piscaglia@unibo.it)