Parallel imaging in MR angiography

The recently developed techniques of parallel imaging with phased array coils are rapidly becoming accepted for magnetic resonance angiography (MRA) applications. This article reviews the various current parallel imaging techniques and their application to MRA. The increased scan efficiency provided by parallel imaging allows increased temporal or spatial resolution, and reduction of artifacts in contrast-enhanced MRA (CE-MRA). Increased temporal resolution in CE-MRA can be used to reduce the need for bolus timing and to provide hemodynamic information helpful for diagnosis. In addition, increased spatial resolution (or volume coverage) can be acquired in a breathhold (eg, in renal CE-MRA), or in otherwise limited clinically acceptable scan durations. The increased scan efficiency provided by parallel imaging has been successfully applied to CE-MRA as well as other MRA techniques such as inflow and phase contrast imaging. The large signal-to-noise ratio available in many MRA techniques lends these acquisitions to increased scan efficiency through parallel imaging.     

Multidetector row CT and MR imaging in diagnosing hepatocellular carcinoma

It is important to diagnose hepatocellular carcinoma (HCC) correctly and in early stage, because viral hepatitis and liver cirrhosis are often complicated by HCC. Noncontrast and enhanced CT and MRI are very useful to visualize and diagnose HCC objectively. Especially, CT and MR imaging with dynamic study is essential to diagnose HCC, because it is usually hypervascular. Dynamic CT and MR study also improve differential diagnosis in the characterization of the tumor. However, to perform useful dynamic study, it is necessary to use a CT unit which can make a helical scan, or a MR system with fast imaging technique available that can obtain more than 15 slices within a single breath hold. Tissue specific contrast medium, such as superparamagnetic iron oxide that is available only on MRI, is also useful for diagnosis of HCC.     

动态增强MR成像在肿瘤血管生成功能成像中的应用

通过静脉注射细胞外对比剂(Gd-DTPA)后,磁共振成像(MRI)可以描述肿瘤的血管特征.由于不同组织对造影剂药物动力学的影响不同,因而动态增强磁共振成像(DCE-MRI)具有展示组织内在差异的功能.大量研究结果表明,DCE-MRI数据结果与肿瘤血管生成免疫组织标记物间具有相关性,可以用于监测各种肿瘤治疗方法的效果,如:放疗、化疗、激素治疗以及新的抗血管生成治疗等.本文就DCE-MRI基本方法和数据处理方法作一简要回顾.     

SWI与MRI增强扫描诊断小肝癌的对比性研究

目的对磁敏感加权成像(SWI)与MRI动态增强扫描诊断小肝癌进行对比性研究,探索SWI对小肝癌的临床应用价值。材料与方法采用双盲法,对60例临床诊断为小肝癌的患者同时进行SWI和MRI动态增强扫描并由3名高年资放射诊断医生进行独立诊断,并对诊断结果进行对比统计分析。结果 60例小肝癌中,应用SWI扫描48例阳性,12例阴性,MRI增强50例阳性,10例阴性。统计学分析结果显示,两种扫描方法诊断小肝癌差异并无统计学意义(P0.05)。结论本研究发现MRI增强扫描诊断小肝癌是临床上常规应用且可靠性较高的诊断方法,SWI扫描可作为MRI增强扫描的补充序列。应用SWI对肝硬化结节信号改变进行动态追踪,对小肝癌的诊断有重要的临床价值,但诊断小肝癌MRI增强扫描仍然不可替代。     

磁共振关节内增强扫描评价膝关节骨质、半月板、韧带和关节软骨损伤的准确性:与常规磁共振扫描比较

背景:常规磁共振检查可较为全面地显示关节内软组织的结构,但由于其成像后对比度欠缺等因素,在诊断关节内病变和损伤时仍存在一定的局限性.为了提高诊断的准确率,磁共振的增强扫描已应用于肝脏、脑等其他部位,但有关膝关节增强扫描的报道较少.目的:评价磁共振关节内增强扫描对膝关节损伤诊断的临床应用价值.方法:选择21例膝关节损伤患者(22膝),采用美国GE公司生产的0.5T Signa Contour磁共振扫描仪先进行常规磁共振扫描.常规扫描完成后,向关节内注入增强剂,行关节内增强扫描.所有病例均由同一医师进行关节内增强操作,由两名副主任职称以上的医师进行阅片分析和对比.结果与结论:所有病例在平扫中均发现有不同程度的关节结构损伤,包括骨质、半月板、韧带和关节软骨等.在磁共振增强扫描后进一步证实,其损伤的程度和范围上得到了更清楚的显示.同时,有2例平扫中误诊的半月板损伤,在增强扫描后得到否定;有的损伤部位在平扫中未发现的病变信号,在关节内增强扫描中被发现和证实.说明增强后磁共振扫描膝关节损伤的阳性率高于常规扫描.其中,增强前后半月板损伤诊断准确率差异有显著性意义(P=0.035).提示,与常规扫描相比,磁共振关节内增强扫描可进一步提高膝关节损伤的诊断率.     

DCE-MRI定量渗透性参数联合ADC值在肺部良恶性病变中鉴别诊断价值

目的探讨利用动态增强磁共振成像(dynamic contrast-enhanced MRI,DCE-MRI)的血流动力学双室模型渗透性参数联合ADC值鉴别诊断肺部良恶性病变的应用价值。材料与方法搜集2014年7月至2015年3月在我院行肺部CT增强检查、常规MRI扫描、DWI成像及DCE-MRI扫描的患者共49例(恶性病变29例,良性病变20例),MRI动态增强扫描采用三维快速容积扫描技术,通过MRI后处理工作站计算病灶的ADC值,血流动力学定量分析软件Omni-Kinetics计算病灶的微血管渗透性参数Ktrans、Kep等。结果 CT联合ADC值、DCE-MRI定量渗透性参数鉴别诊断肺良恶性结节准确率为93.9%;CT联合ADC值鉴别诊断肺良恶性结节准确率为85.7%;CT鉴别肺良恶性结节准确率为75.5%,CT联合ADC值、DCE-MRI定量渗透性参数鉴别肺良恶性结节准确性与CT有显著性差异(P0.05)。结论 DCE-MRI定量分析微血管渗透性参数Ktrans、Kep联合ADC值对肺部良恶性病变诊断效能高于CT,而且真正实现定量分析鉴别诊断肺部结节良恶性,值得广泛应用于临床工作。     

Magnetic resonance imaging of the kidney.

High tissue contrast, multiplanar image capabilities, and tissue characterization render MR into an ideal imaging modality for effective evaluation of a wide range of renal disorders. It provides high details of anatomy and can suggest the composition of lesions. Improvements of MRI technology during the last years have made MRI increasingly attractive for body imaging. Fast imaging sequences and parallel imaging techniques have proved to be useful in minimizing artifacts from respiratory motion and magnetic susceptibility differences providing superior imaging quality. Additionally, the use of renally eliminated paramagnetic contrast agents permits assessment of parenchymal perfusion and visualization of the excretion of the contrast medium providing information on renal function.     

Gd—BOPTA增强60min再延迟扫描对小肝癌的诊断价值

目的探讨具有双相增强作用的磁共振对比剂钆贝葡胺（GO—BOPTA）,MRI增强后60min再延迟扫描对小肝癌（SHCC）的诊断价值。方法手术或穿刺病理证实为SHCC患者25例,采用Philips Intera 1．5T磁共振扫描仪。行SE序列T1WI、FSE序列T2WI及Gd—BOPTA快速动态增强多期扫描。Gd—BOPTA增强扫描采用静脉团注快速动态增强扫描,并在团注后20s、1min、5min及60min行THRIVE扫描。观察分析MRI平扫、Gd—BOPTA三期增强扫描及60min再延迟扫描病灶的信号改变,并进行统计学处理。结果25例患者,共发现SHCC病灶33个;对SHCC病灶的检出率,MRI平扫为75．8％（25／33）,Gd—BOPTA三期增强为81．8％（27／33）,Gd—BOPTA三期增强＋60min再延迟扫描为96．9％（32／33）。Gd—BOPTA三期增强联合60min再延迟扫描对SHCC病灶的检出率明显优于Gd—BOP—TA三期增强,两者之间有统计学差异。结论Gd—BOFrA增强后60min再延迟扫描对小肝癌、尤其是乏血供的小肝癌具有较好的诊断价值。     

垂体微腺瘤MRI动态增强扫描的表现

目的 探讨垂体微腺瘤MRI动态增强扫描的特征。方法 回顾分析临床确诊的35例垂体微腺瘤动态MRI增强扫描的表现，并进行讨论。结果 平扫示20例TWI为低信号影，动态增强扫描早期28例为低或稍低信号，与强化明显之正常垂体呈明显对比。后期微腺瘤强化程度越来越接近垂体信号。结论 在MRI平扫不明确而临床高度怀疑垂体微腺瘤时进行动态增强扫描对临床诊断的价值较大。     

Contrast-enhanced magnetic resonance imaging of central nervous system tumors: agents, mechanisms, and applications

Brain tumors are one of the most common neoplasms in young adults and are associated with a high mortality and disability rate. Magnetic resonance imaging (MRI) is widely accepted to be the most sensitive imaging modality in the assessment of cerebral neoplasms. Because the detection, characterization, and exact delineation of brain tumors require a high lesion contrast that depends on the signal of the lesion in relation to the surrounding tissue, contrast media is given routinely. Anatomical and functional, contrast agent-based MRI techniques allow for a better differential diagnosis, grading, and especially therapy decision, planing, and follow-up. In this article, the basics of contrast enhancement of brain tumors will be reviewed. The underlying pathology of a disrupted blood-brain barrier and drug influences will be discussed. An overview of the currently available contrast media and the influences of dosage, field strength, and application on the tumor tissue contrast will be given. Challenging, contrast-enhanced, functional imaging techniques, such as perfusion MRI and dynamic contrast-enhanced MRI, are presented both from the technical side and the clinical experience in the assessment of brain tumors. The advantages over conventional, anatomical MRI techniques will be discussed as well as possible pitfalls and drawbacks.     

MR动态增强扫描结合T2WI首过灌注成像诊断乳腺肿瘤的价值

目的评价乳腺MR T1WI动态增强扫描结合T2＊WI首过灌注成像对乳腺良恶性肿瘤的鉴别诊断价值。材料与方法对39例乳腺良、恶性肿瘤均行T2＊WI首过灌注成像及T1WI动态增强扫描,计算T2＊WI首过灌注成像的最大信号强度下降率及动态增强扫描的早期强化率,绘制T2＊WI首过灌注TIC及动态增强TIC。结果乳腺良恶性肿瘤的T2＊WI首过灌注最大信号强度下降率的差异有统计学意义,以最大信号强度下降率20%作为诊断恶性肿瘤的阈值,敏感度为91.7%,特异度为93.3%,准确度为92.3%。乳腺良恶性肿瘤T1WI动态增强早期强化率的差异无统计学意义,但动态增强曲线类型差异有统计学意义,以流出型作为诊断恶性的标准,诊断的敏感度为62.5%,特异度为93.3%,准确度为74.4%。T1WI动态增强TIC表现为平台型（Ⅱ型）的乳腺肿瘤,其T2＊WI灌注TIC类型的差异有统计学意义。结论 T1WI 动态增强扫描结合T2＊WI首过灌注成像有助于乳腺良恶性肿瘤的鉴别诊断,T2＊WI首过灌注成像能提高动态增强Ⅱ型曲线病灶定性诊断的准确率。     

开放式低场MRI动态增强扫描在上腹部疾病诊断中的应用

目的 评估低场MRI 动态增强检查在上腹部病变诊断中的应用价值.方法 收集行低场MRI 检查的上腹部病变患者90例,所有病例均做平扫及动态增强扫描,动态后即刻扫描T1WI/ SE得到普通增强扫描图像.将取得的MRI 平扫+普通增强形态学及MRI平扫+动态增强形态学+动态曲线在上腹部病变的定性影像诊断与病理结果的诊断符合率进行比较.结果 MRI平扫+动态增强+动态曲线在上腹部病变的定性影像诊断与病理诊断的符合率为89.7%,MRI 平扫+普通增强为75.8%.MRI 平扫+动态增强形态学+动态曲线对于检查上腹部病变的定性影像诊断的能力明显优于MRI 平扫+普通增强形态学,差异具有统计学意义(P=0.031).结论 低场MRI动态增强检查对于鉴别上腹部肿块的良恶性有突出显著的作用,对病变的定性、定位、划定边界优于常规自旋回波增强扫描.     

肺栓塞的MRI研究现状

肺栓塞是具有潜在生命威胁的疾病,需要及时正确的诊断和治疗。近年来,随着硬件和软件的快速发展,肺栓塞的MRI研究较为热门。作者将肺栓塞的MRI检查技术、常用扫描序列、对比剂以及诊断准确度作一综述,并预测将来可能的发展趋势。     

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。     

Basic concepts of MR imaging, diffusion MR imaging, and diffusion tensor imaging

MR image contrast is based on intrinsic tissue properties and specific pulse sequences and parameter adjustments. A growing number of MRI imaging applications are based on diffusion properties of water. To better understand MRI diffusion-weighted imaging, a brief overview of MR physics is presented in this article followed by physics of the evolving techniques of diffusion MR imaging and diffusion tensor imaging.     

Magnetic resonance imaging features of aortic diseases

The usefulness of magnetic resonance imaging (MRI) for aortic diseases is discussed, with special attention given to the MRI features of aortic dissection and Takayasu arteritis. Computed tomography (CT) and MRI provide excellent visualization of vessels and their relationship to surrounding structures; however, CT depicts the vessel lumen optimally only when contrast enhancement is used. MRI, with its inherent multiplanar imaging capability, is well suited for evaluation of the thoracic and abdominal aorta and can be used with or without contrast enhancement. Basic technical considerations in cardiac imaging, which include conventional spin-echo, fast spin-echo, cine gradient, and echo-planar imaging, with time-of-flight and phase-contrast methods, are discussed and applied to aortic aneurysm, aortic dissection, and Takayasu arteritis. The diagnostic capacity of spin-echo MRI in patients with suspected aortic dissection is enhanced when it is combined with cine MRI. Despite the ability of CT and MRI to demonstrate luminal and mural changes of aortic abnormalities, conventional angiography still may be necessary at first admission for selected patients in the late occlusive phase to provide additional information on the degree and extent of the arteritis. CT angiography and MR angiography are promising imaging techniques that will overcome difficulties in visualizing distal branch vessel lesions and obviate the need for conventional angiography in the near future.     

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.     

Parallel imaging of the abdomen

Parallel imaging holds great potential for improving the quality of diagnostic abdominal MRI. The increased imaging speed afforded by parallel imaging can be translated into the obvious benefits of reduced scan time with set resolution and coverage, improved spatial resolution with set imaging time and coverage, increased anatomic coverage for a set imaging time and resolution, or some combination of the above. Additionally, the reduction in scan time can also allow some sequences that normally require multiple breath-holds to be performed with only one, or simply make breath-hold imaging possible for more patients. The decreased echo-train length allows for truer T2-weighting, less magnetic susceptibility artifact, and less blurring with echo-train imaging. Dynamic contrast-enhanced sequences can be acquired with improved temporal or spatial resolution. All of these potential advantages come with the trade-off of decreased signal-to-noise ratio, but for many patients, the benefits far outweigh the drawbacks and can vastly improve the diagnostic quality of abdominal MRI.     

磁共振动态增强及弥散加权成像在肝脏占位性病变中的应用价值

目的探讨联合应用磁共振动态增强及弥散加权成像(DWI)对各种肝脏占位性病变的诊断及鉴别诊断价值。方法对78例肝脏占位病变行常规MRI平扫及动态增强和DWI,观察各种肝脏占位性病变的强化类型。结果本组27例(87.1%)肝细胞癌强化方式呈快进快出型,22例(84.6%)肝转移瘤呈边缘环形强化,10例(90.9%)肝脏海绵状血管瘤呈渐进性强化,10例肝囊肿动态增强病变未见强化;原发性肝细胞癌及肝脏转移瘤的表观扩散系数(ADC)值比较差异无统计学意义(P>0.05),两者与肝脏海绵状瘤、肝囊肿ADC值比较差异均具有统计学意义(P<0.05);肝脏海绵状血管瘤与肝囊肿ADC值比较差异有统计学意义(P<0.05)。MRI平扫及动态增强结合DWI检查对肝细胞癌、肝转移瘤、肝脏海绵状血管瘤和肝囊肿的诊断准确性分别为96.8%,96.1%,90.9%和100%。结论常规MRI平扫及动态增强扫描是诊断各种肝脏病变的基础,DWI对诊断良恶性病变有较高的价值。     

临床用肢端柔性表面线圈和相控阵线圈在小动物磁共振成像中的性能比较

目的对比肢端柔性线圈和相控阵线圈非并行采集及并行采集技术在小动物实验中对图像质量的影响。方法10只Wistar大鼠,分别用西门子标配的临床用正交柔性肢端线圈和相控阵肢端线圈在同一扫描参数的条件下用于头部信号采集,同时在肢端相控阵线圈采集中采用并行采集技术再获得相同的图像,然后对三组图像选择同一层面进行SNR的比较。结果正交柔性线圈和4通道肢端相控阵线圈采集的图像信噪比有明显的差异,正交柔性线圈能获得更高的图像信噪比,而肢端相控阵线圈非并行采集与并行采集技术(R=2)所获得的图像信噪比没有差异,但采用并行采集技术能极大地减少扫描时间。结论小动物实验在线圈的选用上,线圈的填充因数对图像质量的影响更大,但相控阵线圈与并行采集技术合用可以极大地减少成像时间。