Functional magnetic resonance imaging of amphetamine craving

The aim of this study is to identify the brain activity associated with amphetamine craving for understanding the neurobiology of addiction by watching pictures of happy, sad or amphetamine. Brain activity was measured in 12 amphetamine addicts and 12 healthy subjects by fMRI while the subjects watched pictures designed to elicit happy feelings, sad feelings, or the desire to use amphetamine. The result demonstrated that amphetamine cues led to abnormally high cingulate and low frontal lobe activation in amphetamine addicts, who showed abnormalities in affect-related brain activation.     

磁纳米分子影像探针研究热点与挑战

 近年来,磁纳米材料在分子影像领域的应用得到科研人员的广泛关注。常用的磁性纳米探针是超顺磁性氧化铁颗粒（SPION）,它具有较好的水质子横向弛豫时间（T₂）弥散加权核磁共振成像造影剂的性能。通过对SPION制备及表面修饰进行改进,使纳米颗粒具有磁共振造影功能和干细胞标记、药物/基因递送的功能。综述了SPION兼具影像探针和磁共振成像可视化治疗方面的功能。虽然已有多种磁纳米材料进入临床研究,但结合当前研究瓶颈以及纳米药物制备方法的发展,制备造影效果较好、药物生物相容性较高、具有靶向性及临床转换潜力较强的SPION是新一代磁纳米探针研究亟需解决的问题。     

基于正则化的SPACE-RIP并行磁共振成像重建算法

采用并行磁共振成像可以提高成像速度和图像分辨率,但这是以牺牲重建图像的信噪比为代价的。为此,该文提出了一种基于正则化的并行磁共振成像重建算法,降低由于阵列线圈的几何相关而造成的信噪比损失。以预扫描图像作为最后重建图像的先验信息,用L曲线方法求解最佳正则化参数。实验表明,该方法能较大限度地减弱噪声对重建结果的影响,当SPACE-RIP并行成像技术的加速因子达到4时,仍可得到高质量的高分辨率重建影像。重建后的图像质量良好,对临床诊断具有较高实用价值。     

稀土元素Gd、Ho和Dy在磁共振成像应用的研究进展

Gd、Ho和Dy因其独特的光学和磁学性质而在生物成像等方面有着广泛的应用.在镧系元素中,Gd~(3+)具有7个不成对的电子,可以提供高的弛豫度,已被广泛地用于磁共振成像(MRI)造影剂,而Ho~(3+)和Dy~(3+)具有最短的电子弛豫时间和最高的有效磁矩,因此有良好的高场T_2弛豫效果.介绍了基于这3种稀土元素的纳米材料在MRI方面的应用.     

稀土纳米粒子作为磁共振成像造影剂的研究进展

镧系元素拥有独特的4f外层电子结构,从而使其具有独特的光学和磁学性质.利用具有磁学性质的镧系元素合成的稀土纳米粒子被广泛用作磁共振成像造影剂.主要总结了近年来磁性稀土纳米粒子的种类、合成方法及不同系列(T_1,T_2)的磁共振成像造影剂的应用现状,并展望了其前景.     

Research progress of magnetic resonance imaging contrast agents

Magnetic resonance imaging (MRI) is a clinical diagnostic modality, which has become popular in hospitals around the world. Approximately 30% of MRI exams include the use of contrast agents. The research progress of the paramagnetic resonance imaging contrast agents was described briefly. Three important approaches in the soluble paramagnetic resonance imaging contrast agents design including nonionic, tissue-specific and macromolecular contrast agents were investigated. In addition, the problems in the research and development in future were discussed.     

The design of the robot assisted magnetic resonance imaging guidance for minimally invasive surgery system

assisted Minimally lnvasive Surgery (MIS) is one of the rapidest developing directiorls in the current surgical reahn. Magnetic Resonance Imaging (MRI) is an optimal imaging modality which was applied in MIS in recent years. By combination of precise positioning to the target by intra-operative MRI guided surgery and dexterous motion by the robot, safe and smooth operation is expected to be peffurmed.An overview of the MR I-guided robotic system for MIS is offered. The design of the intra-operative MR scalmer system is described. The MR-compatible robotic system is carefully desigaled for safety and sterilization issues. This system unifies image information from open MRI, an optical endoscope and conventional vital-sign detectors. It helps and guides the surgeon and other medical staffs so they can make the right decisions. The high-performance manipulator can mimic the movement of the surgeon‘ s hand precisely. And the analysis for active and passive interventional surgical instrument tracking is provided.     

关于磁共振图像质量评价方法的探讨

磁共振信号得到的人体断层图像,不仅可以反映形态学的信息,还可以从图像中得到与病理有关的信息,其图像质量的好坏将直接影响着医护人员对病人的诊断结果.目前对磁共振图像质量评价的重要指标是信号强度均匀度.但在信号强度几乎相同的条件下,这一评价指标的有效性较低.为了对磁共振图像质量作更加有效的评判,可采用比较信噪比的最大与最小区域的信号强度标准差的方法,其评价的有效性较高.     

Amphiphilic dextran/magnetite nanocomposites as magnetic resonance imaging probes

Superparamagnetic iron oxide （SPIO） nanoparticles are effective contrast agents for enhancement of magnetic resonance imaging at the tissue, cellular or even molecular levels. High quality SPIO nanoparticles can be synthesized in the organic phase but need to be transferred into water before any biomedical applications. In this study, amphiphilic poly（ε-caprolactone） grafted dextran （Dex-g-PCL） was used as carriers for particle encapsulation and stabilization in the aqueous phase. Multiple SPIO nanoparticles were self-assembled together with the help of Dex-g-PCL during phase transfer from chloroform to water, and diameters of Dex-g-PCL/SPIO nanocomposites were （64 ± 22） nm through dynamic light scattering measurement. These nanocomposites were superparamagnetic at 300 K with saturated magnetization of 88 emu/g Fe. In the magnetic field of 1.5 T, Dex-g-PCL/SPIO nanocomposites had a T2 relaxivity of 363 Fe mL·mol-1·s-1. This unique nanocomposite brought significant mouse liver contrast with signal intensity changes of -60% at 5 min after intravenous administration. However, uptake of Dex-g-PCL/SPIO nanocomposites in liver reticuloendothelial cells （Kupffer cells） did not immediately happen at shorter time points （〈4 h） as verified by histology studies, and it was evident that more iron staining would be located in Kupffer cells 24 h after contrast agent administration. After 24 h and 10 d, the signal intensities （SI） gradually recovered, and SI changes were -44% and -31%, respectively. From our observation, the time window for enhanced-MRI could last at least 12 days and totally recovered after 16 days. This novel sensitive MRI contrast agent may find potential applications in discovering small liver lesions such as early tumor diagnosis.     

基于核磁共振成像技术的堆浸细观渗流速度场特性

采用核磁共振成像技术对柱浸渗流过程进行非接触、无损探测,得到溶液静止和流动时的核磁共振图像.通过对速度值分布的分析,评价了速度场均匀性,得到了均匀性指数与喷淋强度的关系,进而研究了细观渗流速度场分布特性和孔隙内速度场演化规律.研究表明：流速分布具有明显的不均匀性,流速值与孔隙大小并不严格一致;不同喷淋强度下速度值分布趋势相似,最大流速与喷淋强度正相关;通过分析速度场均匀性与喷淋强度间关系可得到喷淋强度阈值,实验中0.7 L· cm -2·h -1为此粒级级配的喷淋强度阈值.现场应用动态喷淋强度可明显改善堆场的渗透性,提高铜的浸出率.     

The preparation and application of microbubble contrast agent combining ultrasound imaging and magnetic resonance imaging

Encapsulated gas microbubbles are well known as ultrasound contrast agents （UCAs） for medical ultrasound （US） imaging. With the development of shell materials and preparation technologies, the application of microbubbles has been enormously popular in molecular imaging, drug delivery and targeted therapy, etc. The objective of this study is to develop Fe3O4 nanoparticle-inclusion microbubble construct. The in vitro US imaging experiment indicates that the Fe3O4 nanoparticle-inclusion microbubbles have higher US enhancement than those without Fe3O4 nanoparticle-inclusion. According to the microbubble dynamic theory, the acoustic scattering properties can be quantified by scattering cross-section of the shell. The scattering study on Fe3O4 nanoparticle-inclusion microbubbles of different concentration shows that within a certain range of concentration, the scattering cross-section of microbubble increases with the addition of Fe3O4 nanoparticles. When exceeding the concentration range, the ultrasonic characteristic of microbubbles is damped. On the other hand, since Fe3O4 nanoparticles can also serve as the Magnetic Resonance Imaging （MRI） contrast agent, they can be potentially used as contrast agents for the double-modality （MRI and US） clinical studies. However, it is important to control the concentration of Fe3O4 nanoparticles in the shell in order to realize the combined functions of US and MRI.     

基于磁共振影像的乳腺癌计算机辅助检测方法综述

β钛合金具有良好的力学性能、高耐蚀性以及优异的生物相容性,在生物医用材料领域备受关注。β钛合金的超弹性归因于应力诱发的β→α马氏体相变及其逆转变。阐述了影响β钛合金超弹性的因素,归纳了提高合金超弹性的方法。通过添加合金元素调整相变温度和滑移临界应力使得应力诱发马氏体相变更易发生,延迟β相塑性变形的发生,能够获得更大的相变应变和超弹性回复。通过优化热处理工艺和加工方法调控合金的相组成、晶粒尺寸、位错密度和织构等,也可提高合金的可回复应变,增强合金的超弹性。     

化学交换饱和传递磁共振成像建模与仿真

为解决化学交换饱和传递(CEST)磁共振成像(MRI)脉冲序列参数优化设计困难的问题,提出基于脉冲序列模型的仿真方法.依据CEST的基本原理和饱和脉冲序列的特点,建立脉冲CEST MRI数学模型.通过仿真CEST MRI与脉冲序列各参数定量关系,得到CEST MRI与化学交换律存在单调关系的扫描序列参数,实现在给定实验条件下快速获得序列优化参数的方法.     

稀土纳米粒子磁共振成像造影剂的研究进展

镧系元素(Ln)独特的磁学性质主要来源于其4f外层电子结构.利用Ln磁学性质合成的无机稀土纳米粒子被广泛用作磁共振成像(MRI)造影剂(CAs).总结了近年来磁性无机稀土纳米粒子在不同系列(T_1,T_2以及T_1-T_2) MRI CAs的应用现状及发展前景.     

基于任务态和静息态功能核磁共振信号的抑郁症识别

为了提高抑郁症识别的准确率,将功能核磁共振成像的任务态数据和静息态数据相结合,建立基于数据驱动的模型以提取识别特征.在没有任何先验知识的条件下,采用独立成分分析法提取任务态数据和静息态数据的独立成分;然后,利用相关遍历分析法获取功能信号集,利用频谱分析法识别并获取功能信号成分;最后,将功能信号成分作为贝叶斯分类器的特征...     

AD-rfMRI图像的基于改进EDC的独立分量数目估计

阿尔茨海默病(Alzheimers disease,AD)在老年人中的患病人数逐年升高,而静息态功能磁共振成像(rfMRI)功能连接变化是研究AD发病机制的重要手段.为了有效地提取静息态功能磁共振成像图像感兴趣区域并进行功能连接变化分析,需要分离独立分量.而独立分量的分离实现,必须预先估计需要分离的独立分量的数目.在独立分量数目估计方法中,信息理论准则中的有效检测准则(effective detection criteria,EDC)具有灵活的惩罚函数,估计结果鲁棒性高,但存在过估计问题,影响独立分量分离结果的准确性.本文将对数函数引入惩罚函数的第2种表示(EDC₂)对其进行改进,并结合黄金分割法确定惩罚函数项的最优值,称为OIEDC₂(optimizing and improving effective detection criteria).实验结果表明,OIEDC₂与EDC₂相比提升了独立分量数目估计的合理性和准确性.     

光泵磁共振实验中测量gF值多种方法的探讨

光泵磁共振法是用光抽运方法和光探测法对弱磁场信号进行检测。恒定水平磁场换向测gF值,恒定频率换向测gF值,以及由最小二乘法求出直线的斜率计算gF值。阐述了前2种方法下如何区分。87Rb和85Rb出共振谱线。3种方法测量gF值其结果是一致。     

磁性纳米颗粒系统的铁磁共振和共振线宽分析

 对非相互作用磁性纳米颗粒系统的FMR线型模型进行了研究,以铁磁体从应用场中获得自由能F为例,导出磁性颗粒在较小各向异性时,共振场H_r与有效各向异性场H_A^eff的关系,这个结果与Raikher和Stepanou的结果一致.继而还对共振场线宽进行了分析,并与Smit和Beljers模型进行了比较,其结论说明:在超顺磁区域有效各向异性场H_A^eff对塞曼(Zeeman)相互作用和附加应用场H是不确定的.尤其是这种情况在H_A^eff较小、高温(高温区域),且H_A^eff≈H时,变得更显著.为此提出了随机颗粒阵列及参数特征对这个结果的影响机制.     

Imaging mechanical shear waves induced by piezoelectric ceramics in magnetic resonance elastography

MRI is a noninvasive medical imaging modality for stimulating the development of medical diagnosis tech-nology. Scientists and engineers are now trying to extend the use of traditional MRI scanner to a wider field. The magnetic resonance elastography (MRE…     

静息态人脑功能网络的小世界特性

研究了静息态下健康人脑的功能连接模式有助于理解人脑在正常或疾病状态下的功能活动规律.利用小波变换从健康志愿者静息态的功能磁共振成像中提取时间序列,计算90个脑区的相关性,设定阈值建立脑功能网络的无向简单图,然后计算特征路径长度和聚类系数,并对度分布进行拟合.结果显示:脑功能网络具有规则网络的大聚集系数又具有随机网络的小特征路径长度,度的拟合显示具有指数截断幂律分布,即脑功能网络具有小世界特性.