磁共振成像技术的物理学原理

磁共振成像技术利用病人体内或样品里的核自旋属性成像,同其他成像技术相比拥有独特的优势,因此在现代医疗和脑科学研究中起着越来越重要的作用,文章从物理学的角度出发,介绍了磁共振成像的条件,基本原理和成像的过程．并在此基础上介绍了这种技术的优点和缺点.     

Gadobutrol at different injection rates for dynamic supra-aortic imaging by contrast-enhanced magnetic resonance angiography

The aim of this study was to compare differences in imaging quality at different injection rates of gadobutrol(Gadovist? 1.0M) for dynamic supra-aortic imaging by contrast-enhanced magnetic resonance angiography(CEM RA). In 6 healthy volunteers,dynamic CEM RA examinations were performed twice at a 7 d interval with a gadobutrol dose of 0.1 mmol given to 1 kg body mass. For the two examinations,the contrast medium was injected at rates of 1.5 mL/s and 2.0 mL/s,followed by 20 mL normal saline injected at the same rate. Using a GE Signa 3.0T M R apparatus and the time-resolved imaging of contrast kinetics(TRICKS) technique,scanning was performed continuously for 15 phases at a time resolution of about 2.4 s. Vascular reconstruction was undertaken by multiplane reconstruction and maximum intensity projection techniques. Two radiologists experienced in CEM RA diagnosis subjectively evaluated the contrast effect,vascular detail,and pseudo-shadow of all images,and graded them via a 5-point scale. With the two drug injection rates,the image quality,peak signal-to-noise ratio(SNR) and contrast-to-noise ratio(CNR) were compared for imaging of the infra-aortic arch,brachiocephalic trunk,subclavian artery(left/right),common carotid artery(left/right),internal carotid artery(left/right),and external carotid artery(left/right). Characteristics of the time-signal-intensity(T-S-I) curves were also analyzed at the two injection rates. All studies were performed successfully,without any complications. There was good image quality with both gadobutrol injection rates of 1.5 mL/s and 2.0 mL/s,and subjective scores for image quality,SNR and CNR were not significantly different between the two rates(P 0.05). The time-to-peak(TTP) from the hand dorsal vein injection site to the carotid artery ranged from 16.0 s to 27.1 s(mean 21.7 s ±3.4 s) in the 6 subjects,and was also not significantly different between the two drug injection rates(P 0.05). We conclude that dynamic CEM RA examination of the supra-aortic arch with gadobutrol injection at a rate of 1.5 mL/s was feasible,and satisfactorily reflected vascular shape and dynamic blood flow information.     

Electron paramagnetic resonance imaging

In this part we shall outline the challenges one faces while developing time-domain radiofrequency (RF) EPR imaging spectrometer for in vivo studies. Time-domain or FT-EPR is quite a different animal compared to the CW modality. The evolution of FT-EPR instrumentation at the National Cancer Institute, NIH, USA and representative examples of application in cancer research are outlined in this article.     

核磁共振波谱检测平台建设

针对核磁共振波谱检测平台,详细叙述了核磁共振波谱仪的组成及特点,根据探头类型,介绍了用该中心的核磁共振波谱仪可以进行的实验项目,同时对测试要求做了详尽的论述.     

影响磁共振的几个外部因素

目的:探讨影响磁共振成像设备性能的外部因素。方法:根据磁共振成像设备的特点,分别分析了对磁共振成像有影响的外部因素,包括设备周边环境、射频屏蔽、空调、冷水机等。结果:外部因素会影响磁共振成像设备性能的发挥,会影响图像的质量,会导致设备故障。结论:处理好对磁共振成像设备有影响的外部因素,是有效发挥磁共振成像设备性能、获得高质量图像的保证。     

光磁共振实验中数据处理

大学物理实验室中测量铷的朗德g 因数时,测得多个共振频率.这些频率是在扫场和地磁场下作用的结果.该文提出的数据处理方法可以消除地磁场和扫场的干扰,得到了很好的结果.     

The value of neurosurgical and intraoperative magnetic resonance imaging and diffusion tensor imaging tractography in clinically integrated neuroanatomy modules: A cross‐sectional study

Neuroanatomy is considered to be one of the most difficult anatomical subjects for students. To provide motivation and improve learning outcomes in this area, clinical cases and neurosurgical images from diffusion tensor imaging (DTI) tractographies produced using an intraoperative magnetic resonance imaging apparatus (MRI/DTI) were presented and discussed during integrated second‐year neuroanatomy, neuroradiology, and neurosurgery lectures over the 2008–2011 period. Anonymous questionnaires, evaluated according to the Likert scale, demonstrated that students appreciated this teaching procedure. Academic performance (examination grades for neuroanatomy) of the students who attended all integrated lectures of neuroanatomy, was slightly though significantly higher compared to that of students who attended these lectures only occasionally or not at all (P=0.04). Significantly better results were obtained during the national progress test (focusing on morphology) by students who attended the MRI/DTI‐assisted lectures, compared to those who did so only in part or not at all, compared to the average student participating in the national test. These results were obtained by students attending the second, third and, in particular, the fourth year (P≤0.0001) courses during the three academic years mentioned earlier. This integrated neuroanatomy model can positively direct students in the direction of their future professional careers without any extra expense to the university. In conclusion, interactive learning tools, such as lectures integrated with intraoperative MRI/DTI images, motivate students to study and enhance their neuroanatomy education. Anat Sci Educ 6: 294–306. © 2013 American Association of Anatomists.     

Relationships among magnetic resonance imaging, histological findings, and IGF-I in steroid-induced osteonecrosis of the femoral head in rabbits

Objective: To study the relationships among magnetic resonance imaging (MRI), histological findings, and insulin-like growth factor-I (IGF-I) in steroid-induced osteonecrosis of the femoral head in rabbits. Methods: Thirty rabbits were randomly divided into experimental Group A (n=15) and control Group B (n=15). The 7.5 mg/kg (2 ml) ofdexamethasone (DEX)and physiological saline (2 ml) were injected into the fight gluteus medius muscle twice at one-week intervals in animals of Groups A and B, respectively. At 4, 8 and 16 weeks after obtaining an MRI, the rabbits were sacrificed and the femoral head from one side was removed for histological study of lacunae empty of osteocytes, subchondral vessels, and size of fat cells under microscopy, and the femoral head from the other side was removed for enzyme-linked immunoadsorbent assay (ELISA) for IGF-I.Results: At 4, 8 and 16 weeks after treatment, no necrotic lesions were detected in Group B, while they were detected in Group A.Light microscopy revealed that the fat cells of the marrow cavity were enlarged, subchondral vessels were evidently decreased,and empty bone lacunae were clearly increased. The IGF-I levels in Group A were significantly higher than those in Group B. At 8 weeks after the DEX injection, the MRI of all 20 femora showed an inhomogeneous, low signal intensity area in the femoral head,and at 16 weeks, the findings of all 10 femora showed a specific "line-like sign". The MRI findings of all femora in Group B were normal. Conclusion: MRI is a highly sensitive means of diagnosing early experimental osteonecrosis of the femoral head. However, the abnormal marrow tissues appeared later than 4 weeks when the expression of IGF-I increased. This reparative factor has an early and important role in response to steroid-induced osteonecrosis of the femoral head, and provides a theoretical foundation for understanding the pathology and designing new therapies.     

结构基因组学与蛋白质核磁共振(NMR)光谱

阐述了核磁共振光谱在蛋白质结构基因组学研究中的重要作用,包括核磁共振光谱在结构基因组学研究中的优点和缺点,研究技术进展和展望。     

光泵磁共振实验评述

对光磁共振实验的主要内容进行了系统的评述，包括实验中水平方向的磁场、光抽运信号的变化、光泵磁共振信号观察时光抽运信号混杂出现和谐波共振的情况、gF因数的测量方法，以及用光磁共振和光抽运信号测地磁场的方法。     

Investigation of reinforcement of the modified carbon black from wasted tires by nuclear magnetic resonance

INTRODUCTION Waste tires cannot degrade in the short term; they may cause accidental fire and emit poisonous gases rich in dioxins. How to recycle and utilize them effectively, and prevent secondary pollution to the environment has become a new issue that the reuse of resources is faced with. Pyrolysis is an environ-ment-friendly process for recycling of used tires. Three products are typically obtained from the pyrolysis of waste tires: gas, oil and char (Gonzalez etal., 2001). Pyrolyt…     

从对比中去理解--对练习使用示波器实验的释疑

示波器是一种能够直接观察信号随时间变化情况的仪器,在电子技术和科学研究中有着广泛的应用。但是由于原理的复杂性,绝大多数同学按书本操作步骤做完后,反应还是不能很好掌握,尤其是判断在示波器的屏幕上会出现怎样的图形及为什么会出现这样的图形不能很好的作出判断和进行分析。为了很好解决该问题,我们与单摆一节中沙摆实验作一比较。在高中物理单摆一节中,为了讨论单摆的振动图像而引入了沙摆实验[见人教版全日制普通高级中学教科书(必修加选修)第九章第四节],我们若把玻璃板拖动方向定为XX′方向,沙摆的振动方向定为YY′方向,把它与…     

一种磁耦合谐振线圈结构阻抗测量装置设计

提出了一种基于矢量伏安法测量原理的便携式阻抗测量装置,并分析了磁耦合谐振式无线电能传输中耦合线圈结构阻抗测量电路的设计原理,通过单片机系统控制AD5933阻抗转换器测量待测谐振耦合结构的阻抗,利用串口通讯协议实现LabVIEW软件和单片机系统的相互通讯。实验结果表明,耦合线圈工作在谐振态下,阻抗测量值与理论阻抗值相对误差为2%,成本较低,便于携带,能够满足大部分耦合线圈设计需求。     

光磁共振实验中干扰峰的分析及利用

本文分析了在光磁共振实验中用扫场法测量铷原子的因子时所产生干扰峰的形成原因,并且巧妙地利用干扰峰来计算地磁场的水平分量.