化学交换饱和转移在心脏磁共振中的研究进展

化学交换饱和转移（chemical exchange saturation transfer，CEST）MRI成像是一种新兴的基于饱和质子与周围水中质子化学交换的体内分子成像技术，将传统的解剖成像扩展到组织酸碱度成像及体内多种生化代谢成像，且具有无辐射、非侵入性等显著优势，成为时下研究一大热点。目前CEST在心血管磁共振成像的应用研究刚刚起步，本文主要对其原理及其在心脏磁共振的临床应用价值研究进展予以详细阐述。     

酰胺质子转移成像在泌尿生殖系统疾病中的研究进展

酰胺质子转移成像是一种新型磁共振分子成像技术.它是化学交换饱和转移成像的一个分支,通过检测组织内源性蛋白质或多肽中的酰胺质子-水质子交换速率反映细胞内蛋白质浓度及pH值变化.本文拟对酰胺质子转移成像在泌尿生殖系统疾病中的应用进展做一综述.     

化学交换饱和转移在心脏MRI中的研究进展

化学交换饱和转移（CEST）MRI是一种新兴的基于饱和质子与周围水中质子化学交换的体内分子成像技术，将传统解剖成像扩展到组织酸碱度成像及体内多种生化代谢成像，具有无辐射、非侵入性等显著优势。目前CEST在心血管MRI的应用研究刚刚起步。本文主要对其原理及其在心脏MRI的临床应用研究进展进行综述。     

化学交换饱和转移效应量化方法的应用进展

化学交换饱和转移(chemical exchange saturation transfer,CEST)是一种新兴的分子成像技术,通过分子间化学交换现象间接获得代谢物浓度信息,进行疾病诊断、预后评估等.然而得到的CEST信号并不是单纯来自化学交换,而混杂了诸如传统磁化转移效应(magnetization transfer,MT)、直接饱和效应(direct water saturation,DS)、核奥氏效应(nuclear overhauser enhancement,NOE)等效应.去除或利用这些效应以提高量化的准确度和成像质量是向临床转化的关键.     

磁共振分子影像学研究进展

磁共振分子影像是分子影像学的重要分支,具有其他成像技术不可比拟的优越性和广阔的发展前景.近年来,新型磁共振靶向探针及成像序列的研发取得了一系列进展,包括可激活探针、19F成像、超极化成像以及化学交换饱和转移成像等方面,进一步拓展了磁共振分子影像的应用范围.此外,磁共振分子成像在多系统疾病的早期诊断、代谢成像、细胞示踪及基因分析等方面也发挥着巨大优势.尽管磁共振分子成像距离临床转化还存在着一定差距,随着成像技术的日新月异,其在临床疾病诊治中必将发挥重要价值.     

定量磁共振成像技术原理及研究进展

定量磁共振成像技术近年来已广泛用于各个疾病的研究之中，最佳定量磁共振成像技术的应用将会对疾病的早期诊断和治疗产生更好的帮助。本文从成像原理出发对目前常见定量技术进行分类，介绍了化学交换饱和转移技术、化学位移同反相位技术、磁共振波谱、定量磁敏感图、弛豫率成像等技术的原理以及研究进展，最后对各个技术进行汇总分析。结果表明磁共振定量技术种类繁多，定量物质种类广泛。且部分定量磁共振成像技术之间存在交叉，一种技术可定量多种物质，多种技术可用于一种与疾病相关的物质定量研究。尽管目前有相关研究对定量同一物质的多种技术进行比较，但比较结果仍需进一步探索。本文的分析结果便于了解常见定量磁共振成像技术及其研究进展，可为临床诊疗研究提供可借鉴的依据。      

磁共振氨基质子转移成像的临床应用

磁共振氨基质子转移(amide proton transfer,APT)成像是一种基于化学交换饱和转移技术且可反映生物组织中内源性游离蛋白和肽类含量以及氨基质子交换速率的无创性分子磁共振成像方法。APT加权图像是通过对Z谱中水频率两侧±3.5 ppm处的非对称性磁化转移率进行计算得到的。近年来,APT磁共振成像(magnetic resonance imaging,MRI)已被越来越多地应用于疾病诊断中。本文针对目前APT MRI在临床应用和科学研究方面的进展予以综述。     

7.0 T MR γ-氨基丁酸化学交换饱和转移成像的新技术研究

目的γ-氨基丁酸是大脑内最主要的抑制性神经递质,作者运用一种基于化学交换饱和转移(CEST)的MRI新方法对γ-氨基丁酸进行成像。材料与方法实验在安捷伦7.0 T动物MR扫描仪上完成,配制不同浓度γ-氨基丁酸及其他代谢物溶液(谷氨酸、肌醇、肌酸及胆碱)的试管模型,在温度与酸碱度统一的情况下,分别获得γ-氨基丁酸及其他代谢物Z谱图,并通过收集CEST图研究γ-氨基丁酸的CEST效应与浓度的关系及其他代谢物对γ-氨基丁酸CEST效应的潜在贡献。结果通过谱线分析,在偏离水峰2.75 ppm处可以明显地观察到γ-氨基丁酸的CEST效应。改变B1值后获得的Z谱非对称曲线显示γ-氨基丁酸的CEST效应随着B1值的增大而增加,在6.0μT(255 Hz)下达到最大值。体外试管CEST成像显示γ-氨基丁酸的图像信号随其浓度升高而升高,在2.75 ppm处获得的大脑中其他代谢物CEST图示除谷氨酸外其他代谢物几乎不显影。结论实现了γ-氨基丁酸的特异性成像,在本实验条件下获得了最优预饱和能量B1值为6μT,提供了一种无创、无放射性及高时空分辨率的成像方法,有望获得在体的γ-氨基丁酸浓度分布结构图。     

氨基质子转移成像用于缺血性脑卒中进展

缺血性脑卒中是致残率及致死率均较高的脑血管疾病。影像学检查对于精准诊疗缺血性脑卒中具有重要作用。氨基质子转移(APT)成像是一种新型化学交换饱和转移(CEST)成像技术,可反映组织pH值变化,在评估缺血性脑卒中组织代谢微环境、指导治疗及评估预后等方面展现出巨大潜能。本文对APT成像技术的基本原理及其在缺血性脑卒中的研究及应用进展进行综述。     

化学交换饱和转移成像技术在肌肉骨骼系统的研究进展

化学交换饱和转移成像(chemical exchange saturation transfer,CEST)技术是一种新型磁共振成像技术,它可利用磁化传输比不对称(magnetization transfer ratio asymmetry,MTRasym)分析产生半定量的结果,对肌骨系统相关疾病的早期诊断和手术决策具有重要意义.传统MRI只能反映病变的形态学差异,很难为疾病的早期诊断提供帮助.CEST技术具有无侵入性和定量检测的优势,已应用于骨关节炎的早期诊断、椎间盘变性及软骨修复手术术后评估等.作者重点总结了CEST的原理、信号测定及其在肌肉骨骼系统的临床应用.     

A review of optimization and quantification techniques for chemical exchange saturation transfer MRI toward sensitive in vivo imaging

Chemical exchange saturation transfer (CEST) MRI is a versatile imaging method that probes the chemical exchange between bulk water and exchangeable protons. CEST imaging indirectly detects dilute labile protons via bulk water signal changes following selective saturation of exchangeable protons, which offers substantial sensitivity enhancement and has sparked numerous biomedical applications. Over the past decade, CEST imaging techniques have rapidly evolved owing to contributions from multiple domains, including the development of CEST mathematical models, innovative contrast agent designs, sensitive data acquisition schemes, efficient field inhomogeneity correction algorithms, and quantitative CEST (qCEST) analysis. The CEST system that underlies the apparent CEST‐weighted effect, however, is complex. The experimentally measurable CEST effect depends not only on parameters such as CEST agent concentration, pH and temperature, but also on relaxation rate, magnetic field strength and more importantly, experimental parameters including repetition time, RF irradiation amplitude and scheme, and image readout. Thorough understanding of the underlying CEST system using qCEST analysis may augment the diagnostic capability of conventional imaging. In this review, we provide a concise explanation of CEST acquisition methods and processing algorithms, including their advantages and limitations, for optimization and quantification of CEST MRI experiments. Copyright © 2015 John Wiley & Sons, Ltd.     

Developing imidazoles as CEST MRI pH sensors

A series of intra‐molecular hydrogen bonded imidazoles and related heterocyclic compounds were screened for their N–H chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) contrast properties. Of the compounds, imidazole‐4,5‐dicarboxamides (I45DCs) were found to provide the strongest contrast, with the contrast produced at a large chemical shift from water (7.8 ppm) and strongly dependent on pH. We have tested several probes based on this scaffold, and demonstrated that these probes could be applied for in vivo detection of kidney pH after intravenous administration. Copyright © 2016 John Wiley & Sons, Ltd.     

多模态磁共振技术预测脑胶质瘤MGMT启动子甲基化状态的研究进展

胶质瘤是最常见的原发性中枢神经系统恶性肿瘤。O6-甲基鸟嘌呤-DNA甲基转移酶（MGMT）启动子甲基化是胶质瘤一个重要的分子特征,与烷化剂化疗敏感性、预后、风险分层、肿瘤复发等密切相关。当前仅使用手术标本通过基因检测分析来确定MGMT启动子甲基化状态,这一过程有局限性。MRI是目前应用最广泛的脑肿瘤非侵入性检查方法,近年来已有多种先进磁共振成像技术被用于术前无创性评估MGMT甲基化状态,这将有助于预测治疗反应和预后。本文就近几年化学交换饱和转移成像和酰胺质子转移成像、灌注加权成像（动态磁敏感对比增强成像、动态对比增强灌注成像、动脉自旋标记、基于流入的血管空间占位）、扩散成像（扩散张量成像、扩散峰度成像、体素内不相干运动、限制光谱成像）、磁敏感加权成像、波谱成像等磁共振成像技术预测MGMT甲基化状态的研究进展及MGMT甲基化临床意义进行综述,以期为患者个体化治疗方案的制定提供术前依据。      

多参数乳腺MRI技术的研究现状及潜力

磁共振成像(magnetic resonance imaging,MRI)是乳腺疾病诊断中必不可少的工具,尤其是乳腺功能成像在鉴别良恶性乳腺肿块中发挥重要价值.动态对比增强MRI可以提供乳腺肿瘤组织灌注等相关功能信息,提高了乳腺癌诊断的敏感度.扩散加权成像可以反映水分子的运动情况,研究表明扩散功能图如表观扩散系数、体素...     

Classification and basic properties of contrast agents for magnetic resonance imaging

A comprehensive classification of contrast agents currently used or under development for magnetic resonance imaging (MRI) is presented. Agents based on small chelates, macromolecular systems, iron oxides and other nanosystems, as well as responsive, chemical exchange saturation transfer (CEST) and hyperpolarization agents are covered in order to discuss the various possibilities of using MRI as a molecular imaging technique. The classification includes composition, magnetic properties, biodistribution and imaging applications. Chemical compositions of various classes of MRI contrast agents are tabulated, and their magnetic status including diamagnetic, paramagnetic and superparamagnetic are outlined. Classification according to biodistribution covers all types of MRI contrast agents including, among others, extracellular, blood pool, polymeric, particulate, responsive, oral, and organ specific (hepatobiliary, RES, lymph nodes, bone marrow and brain). Various targeting strategies of molecular, macromolecular and particulate carriers are also illustrated. Copyright © 2009 John Wiley & Sons, Ltd.     

化学交换饱和转移MRI中B0场不均匀性校正的研究进展

化学交换饱和转移（CEST）MRI数据采集过程中主磁场B0的不均匀部分会导致空间编码错误,扭曲CEST成像,产生伪影并严重影响定量分析的准确性,因此需要对MRI进行匀场校正。近年来,研究者对B0场不均匀性的校正问题进行了一系列研究,通过优化线性拟合算法、改进采集序列等手段,可以在一定程度上降低B0场不均匀性带来的伪影,减少扫描时间并且提高对比噪声比。本文旨在对B0场不均匀性校正的研究进行综述。     

Molecular MRI of Inflammation in Atherosclerosis

Inflammatory activity in atherosclerotic plaque is a risk factor for plaque rupture and atherothrombosis and may direct interventional therapy. Inflammatory activity can be evaluated at the (sub)cellular level using in vivo molecular MRI. This paper reviews recent progress in contrast-enhanced molecular MRI to visualize atherosclerotic plaque inflammation. Various MRI contrast agents, among others ultra-small particles of iron oxide, low-molecular-weight Gd-chelates, micelles, liposomes, and perfluorocarbon emulsions, have been used for in vivo visualization of various inflammation-related targets, such as macrophages, oxidized LDL, endothelial cell expression, plaque neovasculature, MMPs, apoptosis, and activated platelets/thrombus. An enzyme-activatable magnetic resonance contrast agent has been developed to study myeloperoxidase activity in inflamed plaques. Agents creating contrast based on the chemical exchange saturation transfer mechanism were used for thrombus imaging. Transfer of these molecular MRI techniques to the clinic will critically depend on the safety profiles of these newly developed magnetic resonance contrast agents.