High-field MRI of brain cortical substructure based on signal phase
High-field MRI of brain cortical substructure based on signal phase
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DOI：
10.1073/pnas.0610821104
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发表时间：
2007-07-10
影响因子：
11.1
通讯作者：
Fukunaga, Masaki
中科院分区：
文献类型：
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作者：
Duyn, Jeff H.;van Gelderen, Peter;Fukunaga, Masaki
利用MRI检测脑解剖和病理生理的能力受到对比噪声比（CNR）的限制，该对比噪声比取决于所使用的对比机制和空间分辨率。在这项工作中，我们表明，在人脑的MRI中，大的改进，在高分辨率图像中的噪声相比，是可能的，通过利用MRI信号相位在高磁场强度。使用7.0特斯拉的梯度回波MRI和多通道探测器，实现了0.24 x 0.24 x 1.0 mm（3）（58 nl）的标称体素尺寸。在此分辨率下，观察到灰质（GM）和白质（WM）之间以及灰质（GM）和白质（WM）内部的强烈相位对比。在正常志愿者的梯度回波相位图像在这个高分辨率下，GM和WM之间的CNR范围从3：1到20：1的皮质。该CNR比不使用图像相位的传统MRI技术提高了近10倍，并且当包括来自高场和多通道检测的分辨率增益时，其提高了约100倍。在WM，相差似乎与主要的纤维束，而GM内的对比度是暗示的底层结构。所观察到的相位差是由于磁化率的局部变化，其中，至少部分，似乎起源于铁商店。在高场条件下，利用MRI相位衬度检测大脑皮层亚结构的能力有望极大地增强活体人脑解剖学的研究。
The ability to detect brain anatomy and pathophysiology with MRI is limited by the contrast-to-noise ratio (CNR), which depends on the contrast mechanism used and the spatial resolution. In this work, we show that in MRI of the human brain, large improvements in contrast to noise in high-resolution images are possible by exploiting the MRI signal phase at high magnetic field strength. Using gradient-echo MRI at 7.0 tesla and a multichannel detector, a nominal voxel size of 0.24 x 0.24 x 1.0 mm(3) (58 nl was achieved. At this resolution, a strong phase contrast was observed both between as well as within gray matter (GM) and white matter (WM). In gradient-echo phase images obtained on normal volunteers at this high resolution, the CNR between GM and WM ranged from 3:1 to 20:1 over the cortex. This CNR is an almost 10-fold improvement over conventional MRI techniques that do not use image phase, and it is an approximate to 100-fold improvement when including the gains in resolution from high-field and multichannel detection. Within WM, phase contrast appeared to be associated with the major fiber bundles, whereas contrast within GM was suggestive of the underlying layer structure. The observed phase contrast is attributed to local variations in magnetic susceptibility, which, at least in part, appeared to originate from iron stores. The ability to detect cortical substructure from MRI phase contrast at high field is expected to greatly enhance the study of human brain anatomy in vivo.