Number of subjects required in common study designs for functional GABA magnetic resonance spectroscopy in the human brain at 3 Tesla.
Number of subjects required in common study designs for functional GABA magnetic resonance spectroscopy in the human brain at 3 Tesla.
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人脑功能性 GABA 磁共振波谱在 3 特斯拉的常见研究设计中所需的受试者数量。
DOI：
10.1111/ejn.14618
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
Sanaei Nezhad F
中科院分区：
文献类型：
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作者：
Sanaei Nezhad F
磁共振波谱（MRS）是一种测量大脑中γ -氨基丁酸（GABA）和谷氨酸等代谢物浓度的研究工具。由于低生理GABA浓度，因此信号低，MEGA - PRESS一直是GABA测量的首选脉冲序列。为了弥补这一点，研究人员考虑了较长的获取时间（7-10分钟），这使得对这种代谢物的功能测量具有挑战性。在这里，使用MEGA - PRESS在3 T时检测GABA特定浓度变化所需的采集时间和样本量分别用于组间和组内研究设计。在休息时，使用MEGA - PRESS从41名健康志愿者的6个不同脑区获得75个光谱，体素大小在13至22 cm3之间。计算不同获取持续时间的组间和会话内方差，并进行功率计算以确定检测GABA/NAA信号比给定百分比变化所需的受试者数量。受试者内部的可变性是通过对单个采集的不同部分取样来评估的。功率计算表明，使用2分钟采集和27 cm3体素大小（取决于区域）来检测15%的GABA变化，需要使用会话内设计的8到93名受试者。组间设计通常需要更多的参与者来检测相同的差异。在不理想的脑区，受试者数量可高达4倍以上。在本研究中检查的大脑区域收集超过4分钟的数据被认为是不必要的，因为信号的方差在更长的持续时间内并没有进一步减少。
Magnetic resonance spectroscopy (MRS) is a research tool for measuring the concentration of metabolites such as γ‐aminobutyric acid (GABA) and glutamate in the brain. MEGA‐PRESS has been the preferred pulse sequence for GABA measurements due to low physiological GABA concentrations, hence low signal. To compensate, researchers incorporate long acquisition durations (7–10 min) making functional measurements of this metabolite challenging. Here, the acquisition duration and sample sizes required to detect specific concentration changes in GABA using MEGA‐PRESS at 3 T are presented for both between‐groups and within‐session study designs. 75 spectra were acquired during rest using MEGA‐PRESS from 41 healthy volunteers in 6 different brain regions at 3 T with voxel sizes between 13 and 22 cm3. Between‐group and within‐session variance was calculated for different acquisition durations and power calculations were performed to determine the number of subjects required to detect a given percentage change in GABA/NAA signal ratio. Within‐subject variability was assessed by sampling different segments of a single acquisition. Power calculations suggest that detecting a 15% change in GABA using a 2 min acquisition and a 27 cm3voxel size, depending on the region, requires between 8 and 93 subjects using a within‐session design. A between‐group design typically requires more participants to detect the same difference. In brain regions with suboptimal shimming, the subject numbers can be up to 4‐fold more. Collecting data for longer than 4 min in brain regions examined in this study is deemed unnecessary, as variance in the signal did not reduce further for longer durations.