7T 下人脑白质半固态质子的光谱特征。
Spectral characteristics of semisolid protons in human brain white matter at 7 T.
机构信息
Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
出版信息
Magn Reson Med. 2017 Nov;78(5):1950-1958. doi: 10.1002/mrm.26594. Epub 2017 Feb 2.
PURPOSE
To inform the quantification of MRI magnetization transfer contrast at high field by measuring the spectral characteristics of H protons in semisolids in human brain at 7 T, while avoiding prohibitive radiofrequency (RF) tissue heating and confounding effects from chemical exchange.
METHODS
Saturation-recovery type experiments were performed using brief, frequency-specific RF pulses that saturate semisolid proton magnetization. Analysis of the subsequent recovery of water proton magnetization with a two-pool model of exchange allowed the study of spectral characteristics of semisolid protons.
RESULTS
We show that in white matter, the semisolid proton spectrum can be approximated with a symmetric, super-Lorentzian line at -2.58 ± 0.05 ppm from the water resonance and an average transverse relaxation time constant (T ) of 9.6 ± 0.6 μs.
CONCLUSIONS
These results are consistent with studies at lower field that have indicated a major contribution from methylene protons to magnetization transfer contrast, and will facilitate the design and quantification of magnetization transfer studies at 7 T. Magn Reson Med 78:1950-1958, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
目的
在 7T 场强下，通过测量人脑中半固体组织中 H 质子的光谱特征，实现 MRI 磁化转移对比的定量测量，同时避免射频（RF）组织加热和化学交换引起的干扰。
方法
采用短暂的、频率特异性 RF 脉冲进行饱和恢复型实验，使半固体质子磁化饱和。利用交换的双池模型分析随后水质子磁化的恢复，从而研究半固体质子的光谱特征。
结果
我们发现，在白质中，半固体质子谱可以用一个对称的、超洛伦兹线来近似，其中心频率在水共振频率的-2.58±0.05ppm 处，横向弛豫时间常数（T）的平均值为 9.6±0.6μs。
结论
这些结果与较低场强下的研究结果一致，表明亚甲基质子对半固体质子磁化转移对比有较大的贡献，这将有助于在 7T 场强下设计和定量磁化转移研究。磁共振医学杂志 78:1950-1958, 2017。© 2017 国际磁共振学会。
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