7T多核磁共振波谱学的应用
Applications of multi-nuclear magnetic resonance spectroscopy at 7T.
作者信息
Stephenson Mary C, Gunner Frances, Napolitano Antonio, Greenhaff Paul L, Macdonald Ian A, Saeed Nadeem, Vennart William, Francis Susan T, Morris Peter G
机构信息
Mary C Stephenson, Susan T Francis, Peter G Morris, The Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
出版信息
World J Radiol. 2011 Apr 28;3(4):105-13. doi: 10.4329/wjr.v3.i4.105.
AIM
To discuss the advantages of ultra-high field (7T) for (1)H and (13)C magnetic resonance spectroscopy (MRS) studies of metabolism.
METHODS
Measurements of brain metabolites were made at both 3 and 7T using (1)H MRS. Measurements of glycogen and lipids in muscle were measured using (13)C and (1)H MRS respectively.
RESULTS
In the brain, increased signal-to-noise ratio (SNR) and dispersion allows spectral separation of the amino-acids glutamate, glutamine and γ-aminobutyric acid (GABA), without the need for sophisticated editing sequences. Improved quantification of these metabolites is demonstrated at 7T relative to 3T. SNR was 36% higher, and measurement repeatability (% coefficients of variation) was 4%, 10% and 10% at 7T, vs 8%, 29% and 21% at 3T for glutamate, glutamine and GABA respectively. Measurements at 7T were used to compare metabolite levels in the anterior cingulate cortex (ACC) and insula. Creatine and glutamate levels were found to be significantly higher in the insula compared to the ACC (P < 0.05). In muscle, the increased SNR and spectral resolution at 7T enables interleaved studies of glycogen ((13)C) and intra-myocellular lipid (IMCL) and extra-myocellular lipid (EMCL) ((1)H) following exercise and re-feeding. Glycogen levels were significantly decreased following exercise (-28% at 50% VO(2) max; -58% at 75% VO(2) max). Interestingly, levels of glycogen in the hamstrings followed those in the quadriceps, despite reduce exercise loading. No changes in IMCL and EMCL were found in the study.
CONCLUSION
The demonstrated improvements in brain and muscle MRS measurements at 7T will increase the potential for use in investigating human metabolism and changes due to pathologies.
目的
探讨超高场（7T）在氢（¹H）和碳-13（¹³C）磁共振波谱（MRS）代谢研究中的优势。
方法
使用¹H MRS在3T和7T场强下测量脑代谢物。分别使用¹³C和¹H MRS测量肌肉中的糖原和脂质。
结果
在脑部，信噪比（SNR）的提高和谱线展宽使得无需复杂的编辑序列就能对氨基酸谷氨酸、谷氨酰胺和γ-氨基丁酸（GABA）进行光谱分离。相对于3T，7T场强下这些代谢物的定量分析得到了改善。7T场强下的SNR比3T场强时高36%，谷氨酸、谷氨酰胺和GABA的测量重复性（变异系数百分比）在7T场强下分别为4%、10%和10%，而在3T场强下分别为8%、29%和21%。7T场强下的测量用于比较前扣带回皮质（ACC）和脑岛中的代谢物水平。发现脑岛中的肌酸和谷氨酸水平显著高于ACC（P < 0.05）。在肌肉中，7T场强下SNR的提高和光谱分辨率的提升使得能够在运动和重新进食后对糖原（¹³C）以及肌内脂质（IMCL）和肌外脂质（EMCL）（¹H）进行交错研究。运动后糖原水平显著降低（在50%最大摄氧量时降低28%；在75%最大摄氧量时降低58%）。有趣的是，尽管运动负荷降低，但腘绳肌中的糖原水平与股四头肌中的糖原水平变化趋势一致。在该研究中未发现IMCL和EMCL有变化。
结论
7T场强下脑和肌肉MRS测量的显著改善将增加其在研究人类代谢及病理状态下代谢变化方面的应用潜力。
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