Formalism, simulation and application of inter- and intra- molecular multiple quantum coherences

分子间多量子相干(intermolecularMultipleQuantumCoherence，iMQC)自1990年被发现以来，便引起核磁共振(NMR)研究者极大的兴趣，并在许多方面得到广泛的应用。实验与理论研究均表明iMQC是由远程偶极相互作用引起的。由于非局域化的远程偶极场具有复杂的非线性特性，与其它效应的联合作用可能导致复杂多样的现象，因此，模拟研究包含远程偶极场的效应具有重要的意义。本论文通过提出新的模拟算法研究复杂多自旋体系在各种效应特别是在远程偶极场和分子内标量耦合作用下的演化行为，并在此基础上编写了高效的NMR模拟软件――POM软件。本论文主要研究成果有：1、研究了传统单量子相...Since the discovery of intermolecular multiple quantum coherences (iMQCs) in 1990s, iMQCs have triggered much interest in NMR research community and found many applications. In the subsequent deliberate research, iMQC phenomena were referred to be resulted from intermolecular dipole-dipole interactions. Because the non-localized dipolar field is non-linear and complex, its joint action with other ...学位：理学博士院系专业：物理与机电工程学院物理学系_凝聚态物理学号：B20012400

THEORETICAL EXPRESSION AND MONTE CARLO SIMULATION OF DIFFUSION BEHAVIORS IN NMR WITH NONLINEAR FIELD GRADIENTS

利用传播子方法研究了在一般非线性场梯度下NMR信号的扩散衰减 .在自由扩散和平板间的限制扩散情况下获得了扩散衰减因子的理论表达式 .该表达式适用范围宽 ,且具有较简单的数学形式和明确的物理意义 .文中还将理论预测与蒙特卡罗模拟结果进行了比较 .结果表明 :文中所采用的理论方法适合于表述自由扩散和短脉冲近似下的受限扩散 ;蒙特卡罗模拟提供了一种定性研究MRI和NMR中非均匀场梯度扩散衰减的方法A propagator method was used to calculate diffusion attenuation of the NMR signal under general nonlinear field gradients. Theoretical expressions of the attenuation factor were obtained for free and restricted diffusion between two plates. Monte Carlo simulation was performed and the results were compared with the theory. It shows that the theoretical method is appropriate for the free diffusion, as well as the restricted diffusion under the short gradient pulse approximation. Monte Carlo simulation provides an alternate way to quantify the effects of inhomogeneous field gradients used in MRI and NMR.ProjectSupportedbytheNationalNaturalScienceFoundationofChina( 1 0 0 0 5 0 0 6,1 0 1 0 40 1 1and1 0 2 3 40 70

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

Theoretical Expression and Computer Simulation of Diffusion Behaviors in Multiple-Quantum Coherence NMR

改进了Warren所提出的CRAZED脉冲序列以研究分子间多量子相干的扩散过程 ,讨论了利用核磁共振测量分子内和分子间多量子相干表观自扩散系数的理论表述 ,采用粒子的随机行走模型模拟其扩散行为 .在短脉冲近似和长脉冲梯度场两种实验条件下 ,分别获得了因扩散引起的不同相干阶数的相对信号衰减强度随梯度场脉冲间隔时间的变化曲线 ,由此得到分子内多量子相干和分子间多量子相干的表观扩散率与溶液分子扩散系数的关系 .还将计算机模拟结果与理论预测进行分析和比较 ,发现二者能很好地吻合 .研究结果表明 ,分子间多量子相干的表观扩散率与常规的分子内多量子相干的表观扩散率明显不同 ,因此 ,分子间多量子相干的表观扩散率可能提供一种新的核磁共振成像的对比度机理Self-diffusion is one of the most fundamental motions of particles in liquid. Nuclear magnetic resonance (NMR) provides a convenient and noninvasive means for accurately measuring the self-diffusion coefficient of molecules in solution. The theoretical expressions of apparent diffusion rates of MQCs are given and computer simulation based on the method to measure the self-diffusion coefficient by NMR was discussed and the random walk model of particles is used to simulate the apparent diffusion behaviors of intra-molecular and inter-molecular multiple-quantum coherences (MQCs). The results of computer simulation agree well with theoretical predictions.ProjectsupportedbytheNationalNaturalScienceFoundationofChina (10 2 340 70and 10 10 4 0 11)andtheNaturalScienceFoundationofFujianprovince (A0 2 10 0 0 3

WxSPROM-an Efficient Software for NMR/MRI Simulations under Inter-molecular Multiple Quantum Coherences

WXSPrOM是一款用于模拟核磁共振谱和磁共振成像的软件。结合积算符矩阵和非线性blOCH方程,该软件可以同时高效模拟经典理论和量子效应下的标量耦合、远程偶极耦合、扩散、化学位移、辐射阻尼、横向弛豫以及纵向弛豫等效应。这一款软件支持在模拟中进行基于图形界面的复杂脉冲序列的设计,并在模拟中支持各种自定义形状的脉冲、梯度。它采用JAVA语言编码,基于EClIPSE rCP插件模式开发,提供良好的用户体验和极强的可扩展性。WXSPrOM还可以与小组开发的WXnMr磁共振仪控制软件进行无缝连接,极大的拓展了后者的功能。WxSPROM can be used to simulate nuclear magnetic resonance(NMR) spectra and magnetic resonance imaging(MRI).Com bining the product operator matrix with the non-linear Bloch equations,the software can be used to simulate the classical and quantum ef fects such as,scalar coupling,long-rang dipolar coupling,diffusion,chemical shift,radiation damping,transverse relaxation and longitudinal relaxation efficiently.WxSPROM supports the design of complex pulse sequence based on GUI and a variety of custom shapes for pulse/ gradient in the simulation.The software,written in Java,based on Eclipse RCP plug-in frame,provides a good user experience and has strong scalability.WxSPROM can be seamlessly connected with WxNMR,which developed for magnetic resonance instrument by our team,greatly expanded the functions of latter

Automated measurement system for temperature controllable LED electrical parameter based on LabVIEW

基于nI公司的lAbVIEW8.2设计了一套可控温功率lEd电参数自动测试系统,解决了仪器手动操作测量既繁琐费时又容易出错的问题,可自动测量样品在不同温度下的伏安特性,并同步显示测量数据和曲线。利用PId运算调节温度控制的精度,提高了测量结果的准确性和可靠性。并利用本系统对lEd的正向电压与温度的关系进行了实验研究,发现在恒定电流下,温度较高时正向电压与温度成反比关系,温度较低时正向电压随温度减小而突然急剧增大。A temperature controllable automated measurement system for the electrical parameter of power LED based on Labview 8.2 of National Instruments is designed.It solved the problems of the inconvenient and fallible procedure of instrument manual measurement,this system can Automatic measure the voltage-current characteristic of sample at different temperature.Using PID operation to adjust the precision of attemperation and improve the accuracy and reliability of measurement result.And experimental investigation was carried out on the relationship between the forward voltage and temperature in LEDs by this system.It is discovered that at a constant current,in the high temperature region a linear inverse relationship exists between the forward voltage and temperature;while in low temperature region,forward voltage increases drastically as the temperature decreases.福建省半导体照明工程技术研究中心开放课

Hadamard技术在不均匀场中获取高分辨核磁共振谱的应用

核磁共振(NMR)谱广泛应用于化学,生物和材料科学等领域。分子间多量子相干技术(iMQCs)可以有效地在不均匀磁场中获得高分辨NMR谱,但是该方法获取高分辨谱通常需要较长的数据采集时间,在很大程度上限制了它的应用。Hadamard技术具有时间短和信噪比高的特点,该技术可以较大地缩短不均匀场下采集高分辨NMR谱的时间,因而扩展并增强iMQCs方法在不均匀场下获取高分辨谱的实用性。总结了近几年Hadamard技术结合iMQCs方法在不均匀磁场中获取高分辨NMR谱的基本原理和应用,并对其优缺点做了详细的分析和讨论

磁共振成像中背景不均匀场去除方法研究

磁敏感加权成像(susceptibility weighted imaging,SWI)是近年来新开发的磁共振成像技术,最早由E.Mack Haacke等于1997发明[1],并最初被称作"高分辨率血氧水平依赖静脉成像"(high resolution blood oxygenation level dependent venographic imaging)。中央高校基本科研业务费专项资金(2010121101);国家自然科学基金(81171331

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)~

定量磁化率成像重建方法及其应用

磁共振成像(MRI)中,相位图像包含丰富的组织磁化率变化信息,获取相位图像不需要额外的扫描时间.组织中的顺磁性物质会影响组织磁化率差异,从而导致局部磁场不均匀.对组织内顺磁性物质的定量有利于许多脑血管疾病和神经系统疾病的诊断,但利用局部相位信息重建组织磁化率分布是一个不适定逆问题,目前仍然有许多问题亟待解决.该文着重介绍定量磁化率成像(QSM)的原理、重建方法及其在MRI中的应用.国家自然科学基金资助项目(81171331,11174239);中央高校基本业务费资助项目(2010121101