磁共振成像原理与应用介绍

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Travelling-Wave MRI: Without head coil
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(a) Traditional resonant probes form a standing radiofrequency wave within the sample. (b) new approach, an antenna probe interacts with the sample through a travelling wave. (c) In a wide-bore, high-field magnet, such waves can be guided by a conductive lining, permitting remote NMR excitation and detection with an antenna at the end of the magnet.
isocenter
Gradient Coils
MRI system
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RF coil Gradient system shimming coil B0 超导电磁场, 液He
梯度系统
RF线圈 磁场的空间分布
梯度系统： x/y/zBiblioteka Baidu向的空间分辨率 由梯度系统决定
Head Coils
Coils (transmitter / receiver)
GE 3T Phillips 0.6T Open Scanner
FONAR Upright multi-position MRI
二级水冷系统 工业空调系统
UPS电源
网络设备
MRI system
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The uniform field ～ 50 cm The precision of B0 is good to 2ppm
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讲座提纲
磁共振成像发展简介 磁共振成像系统 MR常用的成像序列、成像方法 脑功能成像、脑扩散成像 在认知神经科学方面的应用举例 图像质量, 研究的可重复性
磁共振成像技术及其 在认知神经科学方面的应用
黄瑞旺 （Email: ruiwang.huang@gmail.com) 华南师范大学 心理学院, 脑成像中心
MRI = Magnetic Resonance Imaging
磁共振成像系统 Ø 核磁共振Ø
MRI 是利用原子核在磁场内所产生的 信号经重建成像的一种影像技术
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MRI system
我们研究中使用 的是1.5T、3T… 磁场～超导线圈 0.6T
Magnex-9.4T animal scanner Siemens 3T Phillips 3T Scanner
初期的MRI技术
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MRI system
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M
Induction Apparatus & Display
R
头部线圈
March, 1977. The first attempt to take a human MR scan. Dr. Raymond Damadian, using MRI as a tool for medical diagnosis. He filed his idea with the U.S. Patent Office, entitled "Apparatus and method for detecting cancer in tissue." A patent was granted in 1974, it was the world's first patent issued in the field of MRI
100% O2
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The 1st BOLD EPI fMRI
Flickering Checkerboard
OFF (60 s) - ON (60 s) -OFF (60 s) - ON (60 s) - OFF (60 s)
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～blood glucose levels ≥20 mg/dl
BOLD对比度的变化 Effect of blood CO2 level on BOLD contrast Effect of insulininduced hypoglycemia on BOLD contrast
大脑结构
PET show different patterns of glucose metabolism related to various tasks.
18F-FDG
器官或组织的代 谢状态, 进而间 接得到相应部位 的生理生化信息
Parallel imagining
Parallel coil and image reconstruction
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动物实验用的MRI系统
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7T-MR
9.4T-MR
Birdcage 4T
Solenoid 7T
Surface / Ring 9.4T
Butterfly 9.4T
Double-Tuned 9.4T Surface 4T
Courtesy of Avdo Celik, Juelich
3.0T MR-PET
IN-PLANE SLICE
3 mm
Matrix Size e.g., 64 x 64 Field of View (FOV) e.g., 19.2 cm
MRI技术发展简介
快速发展的MRI技术 技术发展
1971年 Damadian (纽约卅立大学)发现恶性组织的T1 延长(NMR方法) Science, 171(1971)1151 -115 1973, Paul C Lauterbur 获得第一幅 MR 图像 1976, Peter Mansfield的EPI成像技术 1977, Raymond V Damadian和他同事制造第1台全身MRI装置 1993年第一代3T MRI （长磁体, 颅脑专用） 1998年第二代3T MRI （长磁体, 颅脑、体部） 2003年第三代3T MRI（短磁体、双梯度线圈设计, 颅脑、体部） 现在：高场强、短长度、开放舒适、高性能、并行发射技术 术中磁共振成像系统
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the 1st in-vivo BOLDcontrast Image 重水：分子式D2O, (氘) 普通的水, H2O, (氢)
Lauterbur, P.C. (1973). Image formation by induced local interaction: Examples employing nuclear magnetic resonance. Nature, 242, 190-191.
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Terminology of MRI
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Slice Thickness e.g., 3 mm
VOXEL (Volumetric Pixel)
In-plane resolution e.g., 192 mm / 64 = 3 mm
3 mm 6 mm
BOLD-fMRI, 磁共振血氧水平依赖 脑功能成像 rs-fMRI：resting state fMRI DTI：diffusion-tensor imaging DWI：diffusion-weighted imaging MRS：magnetic resonance spectroscopy
New method
less distortions
Without PAT With PAT 7T
DO Brunner, J Paska, J Froehlich, Klaas Pruessmann. Nature 457, 994-998 (2009) doi:10.1038/nature07752
Sagittal sinus
90% O2 + 10% CO2
Seiji Ogawa, et al. , 1990 "Brain magnetic resonance imaging with contrast dependent on blood oxygenation." PNAS 87: 9868-9872.
Terminology of MRI
EPI GE SE fMRI BOLD Echo Planer Imaging gradient echo spin echo functional MRI blood oxygenation level dependent, 血氧水平依赖 - 大脑的解剖结构 GM gray matter WM white matter CSF cerebrospinal fluid - MR image session, runs, volume, slice voxel, data matrix partial volume effect SNR, signal-to-noise ratio CNR, contrast-to-noise ratio
The 1st MR image
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BOLD-fMRI
Seiji Ogawa, Magn Reson Med., 1990 - Oxyhemoglobin is diamagnetic (抗磁性). - Deoxyhemoglobin (dHb, 去氧血红蛋白) is paramagnetic (顺磁性) increase transverse relaxation rate (R2) of water protons, induce susceptibility effect around dHb Breathing air Breathing 100% O2 BOLD = BloodOxygen-Level Dependent Proton拉莫频 率： 42.7 MHz/T
1.5T ～blood glucose levels <<20 mg/dl GE scanner ROI:60mm^2 8Hz
Kwong, K. K., J. W. Belliveau, et al. "Dynamic magnetic resonance imaging of human brain activity during primary sensory stimulation.". PANS, 1992 89(12): 5675-5679
Seiji Ogawa, et al. , PANS, 1990
Mouse brain images at 360 MHz
The 1st in-vivo BOLD-contrast Image
- Sprague-Dawley rats, - anesthetized - 7T horizontal magnet （300MHz) - Surface coil: D20-25mm - Voxel: 117*117*500μm^3 -Scanning time: 9mins
Inhalant gas: 50% O2, 50% N2
What can we scan? (human)
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Comparisons to other imaging techniques
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特点： 无射线辐射, 组织对比分辨率 空间分辨率 时间分辨率
射频线圈(radiofrequency coil)
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MRI技术发展简介
The Nobel Prize in Physiology or Medicine 2003 Prize motivation: "for their discoveries concerning MRI"
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应用
成本： 1 Tesla ～ 1百万美元 1981-82 临床应用 1982年 MRI商品化 1983-84 美国FDA获准进入市场 2003, 美国FDA获准3T之下的磁共振系统用于临床
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MRI system
按键反应盒 视觉-听觉刺激系统 3D数字视觉刺激系统（goggle system） 同步脑电记录系统（EEG） 生理多导仪 经颅磁刺激系统（TMS） 近红外光学成像系统（NIRS） 数据存储阵列（10TBB） 服务器
磁共振辅助设备 （射频、梯度系统）
服务器与存储阵列 3T Siemens TIM Trio
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9.4T-MR-PET
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MR - PET
Siemens 3T MR-PET Siemens 9.4T MR-PET
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要求：
PET- Positron Emission Tomography
control-zone (放射性原因) ＰＥＴ－插件非铁磁性, 对ＭＲ的影响要小； ＰＥＴ－插件的空间限制