Department of Radiology, Haukeland University Hospital, Bergen, Norway.
Department of Clinical Medicine (K1), University of Bergen, Bergen, Norway.
J Magn Reson Imaging. 2017 Aug;46(2):421-430. doi: 10.1002/jmri.25588. Epub 2017 Feb 15.
The reproducibility of the MEGA-PRESS (MEshcher-GArwood Point RESolved Spectroscopy) MR spectroscopy sequence for the measurement of gamma- aminobutyric acid (GABA) is addressed, focusing on optimizing the number of repetitions at two voxel locations in the human brain and associated possibilities in analysis tools.
Two 20-min MEGA-PRESS acquisitions were run (echo time = 68 ms, repetition time = 1800 ms, repetitions = 328): one from a 21 mL volume in the anterior cingulate cortex (ACC) and one from a 22 mL volume in the left Broca's area in 21 healthy male volunteers (age 32 years ± 6[SD]). Subjects were scanned twice with identical protocols, 1 week apart. Data were acquired on a 3 Tesla GE Discovery 750 scanner using a 32-channel head coil. Spectroscopy data were partitioned into shorter epochs, numerically equivalent to scans of progressively increasing duration, and compared both within and between sessions. Three different analysis schemes were applied: (1) Vendor prototype preprocessor, with quantification by LCModel. (2) Pure Gannet pipeline. (3) Preprocessing with Gannet, and quantification with LCModel. The coefficient of variation (CV) were calculated as a measure of reproducibility.
Increasing the number of repetitions showed improvements for within- and between-session reproducibility up to around 218 repetitions. (CV ranging from 4 to 14%). Gannet combined with LCModel approach proved the best method. (CV = 4-5%). Measurements from the ACC area had higher CVs than the Broca area. (CV = 6-14% versus 4-7%).
Measurement in the Broca area yields better reproducibility than the ACC. With appropriate acquisition times and preprocessing tools, measurements from the ACC area are also reliable.
1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:421-430.
本研究旨在探讨 MEGA-PRESS（Meshcher-GArwood Point RESolved Spectroscopy）磁共振波谱序列在测量γ-氨基丁酸（GABA）方面的可重复性，重点优化在人脑两个体素位置的重复次数，并探讨相关分析工具的可能性。
本研究招募了 21 名健康男性志愿者（年龄 32 岁±6 岁），使用 3 特斯拉 GE Discovery 750 扫描仪，对其双侧额极（ACC）和左侧布罗卡区（Broca）分别进行了两次时长 20 分钟的 MEGA-PRESS 采集（回波时间=68ms，重复时间=1800ms，重复次数=328）。两次扫描间隔一周，扫描方案完全相同。使用 32 通道头部线圈采集数据。将光谱数据分成较短的时间窗，数值上相当于扫描时间逐渐延长的情况，并在同一和不同会话之间进行比较。采用三种不同的分析方案：（1）供应商原型预处理，采用 LCModel 进行定量分析；（2）纯 Gannet 流水线；（3）Gannet 预处理，采用 LCModel 进行定量分析。计算变异系数（CV）作为可重复性的衡量指标。
随着重复次数的增加，无论是在同一和不同会话之间，重复性都有所提高，直到重复次数达到约 218 次。（CV 范围为 4-14%）。采用 Gannet 结合 LCModel 的方法可获得最佳结果（CV=4-5%）。ACC 区的测量结果比 Broca 区的 CV 更高（CV=6-14%对 4-7%）。
Broca 区的测量结果比 ACC 区具有更高的可重复性。在适当的采集时间和预处理工具的帮助下，ACC 区的测量结果也具有可靠性。
1 技术功效：阶段 1 J. MAGN. RESON. IMAGING 2017；46：421-430。
