Long Zaiyang, Dyke Jonathan P, Ma Ruoyun, Huang Chaorui C, Louis Elan D, Dydak Ulrike
Department of Radiology, Mayo Clinic, Rochester, MN, USA.
Department of Radiology, Weill Cornell Medical College, New York, NY, USA.
NMR Biomed. 2015 Oct;28(10):1315-23. doi: 10.1002/nbm.3381. Epub 2015 Aug 28.
MRS provides a valuable tool for the non-invasive detection of brain γ-aminobutyric acid (GABA) in vivo. GABAergic dysfunction has been observed in the aging cerebellum. The study of cerebellar GABA changes is of considerable interest in understanding certain age-related motor disorders. However, little is known about the reproducibility of GABA MRS in an aged population. Therefore, this study aimed to explore the feasibility and reproducibility of GABA MRS in the aged cerebellum at 3.0 T and to examine the effect of differing tissue composition on GABA measurements. MRI and (1)H MRS examinations were performed on 10 healthy elderly volunteers (mean age, 75.2 ± 6.5 years) using a 3.0-T Siemens Tim Trio scanner. Among them, five subjects were scanned twice to assess the short-term reproducibility. The MEGA-PRESS (Mescher-Garwood point-resolved spectroscopy) J-editing sequence was used for GABA detection in two volumes of interest (VOIs) in the left and right cerebellar dentate. MRS data processing and quantification were performed with LCModel 6.3-0L using two separate basis sets, generated from density matrix simulations using published values for chemical shifts and J couplings. Raw metabolite levels from LCModel outputs were corrected for cerebrospinal fluid contamination and relaxation. GABA-edited spectra yielded robust and stable GABA measurements with averaged intra-individual coefficients of variation for corrected GABA+ between 4.0 ± 2.8% and 13.4 ± 6.3%, and inter-individual coefficients of variation between 12.6% and 24.2%. In addition, there was a significant correlation between GABA+ obtained with the two LCModel basis sets. Overall, our results demonstrated the feasibility and reproducibility of cerebellar GABA-edited MRS at 3.0 T in an elderly population. This information might be helpful for studies using this technique to study GABA changes in normal or diseased aging brain, e.g. for power calculations and the interpretation of longitudinal observations.
磁共振波谱（MRS）为体内无创检测脑γ-氨基丁酸（GABA）提供了一种有价值的工具。在衰老的小脑中已观察到GABA能功能障碍。研究小脑GABA变化对于理解某些与年龄相关的运动障碍具有重要意义。然而，关于老年人群中GABA MRS的可重复性知之甚少。因此，本研究旨在探讨3.0 T下老年小脑GABA MRS的可行性和可重复性，并研究不同组织成分对GABA测量的影响。使用3.0-T西门子Tim Trio扫描仪对10名健康老年志愿者（平均年龄75.2±6.5岁）进行了MRI和（1）H MRS检查。其中，5名受试者进行了两次扫描以评估短期可重复性。采用MEGA-PRESS（Mescher-Garwood点分辨波谱）J编辑序列在左右小脑齿状核的两个感兴趣体积（VOIs）中检测GABA。使用LCModel 6.3-0L，通过两个独立的基组进行MRS数据处理和定量，这两个基组是根据已发表的化学位移和J耦合值通过密度矩阵模拟生成的。对LCModel输出的原始代谢物水平进行脑脊液污染和弛豫校正。GABA编辑谱产生了可靠且稳定的GABA测量结果，校正后的GABA+个体内平均变异系数在4.0±2.8%至13.4±6.3%之间，个体间变异系数在12.6%至24.2%之间。此外，两个LCModel基组获得的GABA+之间存在显著相关性。总体而言，我们的结果证明了3.0 T下老年小脑GABA编辑MRS的可行性和可重复性。这些信息可能有助于使用该技术研究正常或患病衰老大脑中GABA变化的研究，例如用于功效计算和纵向观察结果的解释。
