1H/31P双核并行磁共振成像线圈的研究与设计

本文通过对鸟笼线圈原理和阵列线圈去耦原理的分析,提出了一种适用于自主研发的多核并行磁共振成像（MRI）系统的双核并行成像线圈设计方案,并在电感去耦的基础上提出LC并联trap去耦法,提高了去耦方法的可适性．依据设计方案制作了¹H/³¹P双核并行成像线圈,并将其应用于4.7 T磁体系统,利用自主研发的多核并行MRI系统进行了并行成像实验测试,成功获得了¹H和³¹P的并行磁共振图像,验证了设计方案的可行性．     

多通道磁共振成像仪控制台数据传输模块设计

当前临床高场磁共振成像（MRI）系统要求成像仪控制台支持16个甚至32个接收通道,可以频繁和高速地进行数据传输并支持快速成像．基于此要求,本文研发了一个基于PowerPC处理器的数据传输模块,将其集成于自行研发的MRI成像仪控制台中,用于成像过程中控制台与计算机之间数据的高速传输．该模块以飞思卡尔公司的高性能PowerPC处理器—MPC8270为核心,运行嵌入式Linux操作系统．处理器与用户计算机之间通过百兆以太网连接,使用局部总线连接控制台的序列运行模块和数据采集模块（数量可扩展）．处理器响应数据采集模块发来的中断请求以快速读取和上传数据．本设计通过驱动程序的设计以保障响应的速度与可靠性．成像实验表明此设计方案能够满足多个接收通道数据快速获取与传输的需求．     

Asymmetric MRI Magnet Design Using a Hybrid Numerical Method

This paper describes a hybrid numerical method for the design of asymmetric magnetic resonance imaging magnet systems. The problem is formulated as a field synthesis and the desired current density on the surface of a cylinder is first calculated by solving a Fredholm equation of the first kind. Nonlinear optimization methods are then invoked to fit practical magnet coils to the desired current density. The field calculations are performed using a semi-analytical method. A new type of asymmetric magnet is proposed in this work. The asymmetric MRI magnet allows the diameter spherical imaging volume to be positioned close to one end of the magnet. The main advantages of making the magnet asymmetric include the potential to reduce the perception of claustrophobia for the patient, better access to the patient by attending physicians, and the potential for reduced peripheral nerve stimulation due to the gradient coil configuration. The results highlight that the method can be used to obtain an asymmetric MRI magnet structure and a very homogeneous magnetic field over the central imaging volume in clinical systems of approximately 1.2 m in length. Unshielded designs are the focus of this work. This method is flexible and may be applied to magnets of other geometries.     

H double-quantum filtered MR imaging of joints tissues: bound water specific imaging of tendons, ligaments and cartilage

The ¹H double-quantum filtered (DQF) NMR and DQF MRI is applied to the joint tissues of rabbits for selective visualization of tendons, menisci and articular cartilage. The ¹H DQF NMR selectively filters double-quantum coherence arising from the ¹H dipolar interaction of the “bound” water in these tissues. The double-quantum creation time dependency of the DQF signal intensity is determined by the molecular environment of the “bound” water. Therefore, each tissue has a unique creation time at which the DQF signal reaches its maximum intensity, τ_max (Achilles tendon: 0.46 ± 0.02 ms, patella: 0.55 ± 0.8 ms, anterior cruciate ligament: 0.60 ± 0.05 ms, meniscus: 0.78 ± 0.02 ms, skin: 0.81 ± 0.07 ms). We have presented the creation-time-contrasted DQF images of the meniscus, patella, foot, and knee joint. Compared with conventional T₂*-weighted gradient-echo (GRE) MR images, tendons, ligaments, menisci, and articular cartilage were more clearly seen in the DQF MR images. All these tissues were distinctly discriminated from each other by their creation times. DQF MR images of foot and knee joints can selectively demonstrated tendons, ligaments, and cartilage, which make it easier to understand the complicated anatomic structure of joints. Because the DQF NMR signal intensity and τ_max are sensitive to the order structure of the “bound” water, it might be possible to introduce the creation-time dependent-contrast of ¹H DQF MR images as a new tool for analyzing the changes in the ordered structure of the tissue.     

基于MRI的绝经后女性腰椎退行性病变程度与骨质疏松的相关性研究

本研究探讨基于磁共振成像(MRI)的绝经后女性腰椎退行性病变程度与骨质疏松的关系。选取经骨密度检查确诊的骨质疏松绝经后女性患者50例为骨质疏松组、非骨质疏松症绝经后妇女50例作为对照组,两组妇女均接受MRI检查。结果显示,骨质疏松组的L1/L2、L2/L3、L3/L4、L4/L5、L1~S1椎间盘Pfirrmann分级评分均高于对照组,差异均具有统计学意义(P<0.05);骨质疏松组患者的腰椎L1/L2、L2/L3、L3/L4、L4/L5、L1~S1之间的BMD与椎间盘Pfirrmann分级评分呈显著的正相关关系(P<0.05);多元线性回归模型结果显示:绝经时间、年龄、腰椎BMD值与患者椎间盘Pfirrmann分级评分呈显著的正相关关系(P<0.05)。绝经后女性采用MRI检查评估的腰椎退行性病变程度Pfirrmann分级评分与骨质疏松程度有关,同时与患者的年龄、绝经时间长度有关。     

DTPA双酯Gd (Ⅲ)配合物的合成及其弛豫率

二乙三胺五乙酸双酐与甘醇单醚反应,得到含多氨基多羧基双酯配体,配体与GdCl₃·6H₂O反应生成非离子配合物.配体及配合物用IR、¹H NMR和元素分析进行了表征,并测试了配合物的驰豫率,其中3种配合物的弛豫率比已用于临床诊断的Gd (DTPA)强,     

Dual surface coil with high-B1 homogeneity for deep organ MR imaging

The theory and construction of a dual surface coil which provides good B₁ homogeneity and sensitivity in a defined volume of interest is described. The probe comprises two coaxial rings, of different diameters and in different planes, which carry opposing currents of different values. Current in the second ring compensates for the roll-off of the B₁ field associated with a single surface coil. Coupling between the rings and a third matching ring is by mutual inductance only. A comparison to a traditional surface coil with practical application to pig brain imaging at a field strength of 7 Tesla is shown.     

脉冲形状对定域谱中水峰抑制作用的影响

报道了用MRI中STEAM方法获得定域谱(MRS)的实验结果,用相位正交、时间一长一短的二个特形脉冲对水峰进行预饱和照射,得到抑制水峰的MRS.这种方法抑制水峰的效果比用梯度散相压水峰的效果好。对于三种常见的特形脉冲,用GAUSS脉冲得到效果最好的实验结果。     

磁共振成象数据在486微机上的处理

把BRUKER磁共振成象(MRI)数据传输到486高档微机上后,经过一系列适当的编程处理,可在微计算机上进行数据压缩和文件格式转换,借助当前的通用图象处理软件系统,可进行图象的校正、增强、编辑、合成等处理,非常有效地扩展一般NMR成象谱仪图象处理软硬件的系统功能.另外,本方法也可用于其它类似谱仪的处理,使普通NMR谱仪用户的添加成象设备后所面临的计算机软硬件系统图象处理功能不足的问题得到解决.     

Undisclosed and undetected foreign bodies during MRI screening resulting in a potentially serious outcome

The risks associated with performing magnetic resonance imaging (MRI) examinations in patients with ferromagnetic foreign bodies are well known. Accordingly, screening procedures are implemented to identify items that may pose hazards to patients and other individuals before allowing them to enter the MRI system room. This report describes a patient who, despite undergoing proper MRI screening procedures, did not disclose the presence of ferromagnetic foreign bodies, which resulted in a potentially serious outcome.