Factors Affecting Chemical Exchange Saturation Transfer Imaging on 1.5 T Clinical MRI Scanners

本文探讨1.5 T磁共振化学交换饱和转移(Chemical Exchange Saturation; Transfer,CEST)成像的影响因素.通过试管模型和临床病例,采用GE Signa HDe 1.5 T磁共振成像(Magnetic; Resonance; Imaging,MRI)扫描仪分别进行不同矩阵、激励次数、翻转角、磁化传递翻转角的CEST成像对比分析,以及不同激励次数、磁化传递翻转角的Z谱分; 析,并从成像组织、成像设备、成像技术等方面对原始图信号、酰胺质子转移(Amide Proton Transfer,; APT)信号及Z谱进行分析研究.实验结果表明1.5 T; MRI扫描仪的CEST图像信噪比相对较低,且磁场稳定性及均匀度影响了CEST成像的效果.在其他参数不变的情况下,降低采集矩阵和增加激励次数与翻转; 角可以增加原始图像信噪比.磁化传递翻转角为105?时,CEST成像效果最好.激励次数为2、磁化传递翻转角为105?时,所得数据符合组织Z谱情况.; 模型Z谱在磁化传递频率为-294 ~ -194; Hz范围可显示30%谷氨酸(Glu)、碘剂(I_(320))、纯水(H_2O)、肌酸(Cr)的信号差异,与H_2O差异最大处在-244 ~; -214 Hz.原始图像信号30%; I_(320)明显高于Glu、H_2O、Cr,Cr略低于Glu,APT图Cr略低于Glu.25例脑肿瘤的APT图呈高信号、12例脑梗塞的APT图; 呈低信号,CEST原始图像均可区分病变区域.有12例因采集时间、患者配合情况、环境及室温等影响导致CEST成像的失败.由此得出1.5; T场强下,CEST技术受到成像组织、设备、技术等因素的影响,需要进行多方面优化.在保证磁场稳定性及均匀度的情况下,优化参数的CEST成像和Z谱成; 像可以区分代谢物及其浓度.Acquisition parameters for chemical exchange saturation transfer (CEST); imaging were optimized on a GE Signa HDe 1.5 T magnetic resonance; imaging (MRI) scanner with phantoms and clinical cases. The effects of; matrix size, number of averages (NEX) and flip angles on the quality of; CEST images were assessed. It was shown that the signal-to-noise ratio; (SNR) of the CEST images acquired on the 1.5 T scanner was relatively; low, and the stability and uniformity of the B0 field affected the; outcome significantly. Reducing matrix size and increasing NEX improved; the SNR of the CEST images. Optimal flip angle for magnetization; transfer was found to be 105?. With a NEX of 2, usable Z spectra could; be obtained. The Z spectra indicated that, with the saturation pulse; frequency centered at -294 ~ -194 Hz, signal differences could be; observed for 30% Glu, I_(320), H_2O, and Cr. Maximal signal differences; were observed when the saturation pulse applied at -244 ~ -214 Hz. Amide; proton transfer (APT) imaging on patients showed that 25 cases of brain; tumor had high CEST signals, 12 cases of cerebral infarction had low; CEST signals. It was therefore possible to differentiate brain tumor; from infarction with CEST imaging. There were also 12 cases which failed; due to long acquisition time, patient movements, and temperature changes; in the scanner room.厦门市科技局科技惠民计划资助项目; 卫生部福建省卫生教育联合攻关计划资助项

Research of chemical exchange saturation transfer in brain

化学交换饱和转移(chemical exchange saturation transfer,CEST)成像是在磁化传递及化学交换理论基础上发展起来的一种磁共振成像新方法,其扩展了磁共振分子影像新领域,但还处于研究阶段。其以细胞内物质为内源性对比剂,通过水信号间接检测代谢物信息,进行组织的酸碱度成像及其各种代谢物成像。本文主要探讨MRI领域中与水相关的化学交换饱和转移现象,阐述其原理、研究现状及其在不同场强磁共振仪上脑部疾病的应用。Chemical exchange saturation transfer(CEST) imaging is a new method for magnetic resonance imaging theory of exchange in the magnetization transfer and chemical, the expansion of the new field of molecular magnetic resonance imaging,but it's still in the research stage. The intracellular substances as an endogenous contrast agent, through the indirect detection of metabolite water signal information for tissue p H imaging and imaging of various metabolites. This paper mainly discusses the chemical and water exchange in the field of MRI saturation transfer phenomenon,expounds the principle, research status and the application in brain diseases used the different field strength clinical MRI scanner.2014年厦门市科技局科技惠民计划项目(编号:3502Z20144052)~

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