A novel method to measure T1-relaxation times of macromolecules and quantification of the macromolecular resonances
A novel method to measure T1-relaxation times of macromolecules and quantification of the macromolecular resonances
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DOI：
10.1002/mrm.28484
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发表时间：
2020-08-30
影响因子：
3.3
通讯作者：
Henning, Anke
中科院分区：
文献类型：
--
作者：
Murali-Manohar, Saipavitra;Wright, Andrew Martin;Henning, Anke
目的代谢物光谱下的大分子峰影响代谢物的定量。因此，了解大分子(MMS)在代谢产物定量中的贡献程度是很重要的。然而，为了在光谱拟合中更准确地模拟MMS，必须考虑各个MM峰之间T(1)弛豫时间的差异。由于代谢物的最终贡献，使用单一反转恢复技术很难表征所有单个MM峰的T-1弛豫时间。相反，双重反转恢复(DIR)技术提供了灵活性，以最小的代谢物影响获得跨越一系列纵向磁化的MM光谱。因此，本文报道了一种确定单个MM峰T-1弛豫时间的新方法。方法广泛的Bloch模拟被用来确定DIR技术的反转时间组合，该技术可以产生足够的具有不同纵向磁化强度的MM信号，同时将代谢物的贡献降至最低。用DIR-代谢物-循环半激光序列获得MM光谱。将LC模型浓度与DIR信号方程进行拟合，计算T-1驰豫时间。结果9.4T时，灰质和白质丰富体素MMS的T-1弛豫时间分别为204~510ms和253~564ms。此外，还报告了13个MM峰的浓度。结论提出了一种新的计算人脑MMS T-1弛豫时间的DIR方法。在9.4T首次报道了富含灰质和白质的体素中的T-1驰豫时间和单个MMS的驰豫时间校正浓度。
Purpose Macromolecular peaks underlying metabolite spectra influence the quantification of metabolites. Therefore, it is important to understand the extent of contribution from macromolecules (MMs) in metabolite quantification. However, to model MMs more accurately in spectral fitting, differences in T(1)relaxation times among individual MM peaks must be considered. Characterization of T-1-relaxation times for all individual MM peaks using a single inversion recovery technique is difficult due to eventual contributions from metabolites. On the contrary, a double inversion recovery (DIR) technique provided flexibility to acquire MM spectra spanning a range of longitudinal magnetizations with minimal metabolite influence. Thus, a novel method to determine T-1-relaxation times of individual MM peaks is reported in this work. Methods Extensive Bloch simulations were performed to determine inversion time combinations for a DIR technique that yielded adequate MM signal with varying longitudinal magnetizations while minimizing metabolite contributions. MM spectra were acquired using DIR-metabolite-cycled semi-LASER sequence. LCModel concentrations were fitted to the DIR signal equation to calculate T-1-relaxation times. Results T-1-relaxation times of MMs range from 204 to 510 ms and 253 to 564 ms in gray- and white-matter rich voxels respectively at 9.4T. Additionally, concentrations of 13 MM peaks are reported. Conclusion A novel DIR method is reported in this work to calculate T-1-relaxation times of MMs in the human brain. T-1-relaxation times and relaxation time corrected concentrations of individual MMs are reported in gray- and white-matter rich voxels for the first time at 9.4T.