Hess Aaron T, van der Kouwe André J W, Mbugua Kenneth K, Laughton Barbara, Meintjes Ernesta M
Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom.
J Magn Reson Imaging. 2014 Oct;40(4):958-65. doi: 10.1002/jmri.24436. Epub 2013 Nov 4.
To evaluate B0 shim and motion navigated single voxel spectroscopy in children. Assess the repeatability of metabolite concentrations in three regions: medial frontal grey matter, peritrigonal white matter, and basal ganglia. Determine the extent of intra- and interacquisition movement in this population.
Linewidth and signal to noise ratio were calculated to assess spectral quality of 186 spectra at 3 Tesla. Repeatability was assessed on 31 repeat scans. Navigator images were used to assess localization errors, while navigator motion and shim logs were used to demonstrate the efficacy of correction needed during the scans.
Average linewidths ± standard deviations of N-acetyl aspartate are 3.8 ± 0.6 Hz, 4.4 ± 0.5 Hz, and 4.7 ± 0.8 Hz in each region, respectively. Scan-to-scan measurement variance in metabolite concentrations closely resembled the expected variance. A total of 73% and 32% of children moved before and during the acquisition, causing a voxel shift of more than 10% of the voxel volume, 1.5 mm. The predominant movement directions were sliding out of the coil and nodding (up-down rotation). First-order B0 corrections were significant (>10 μT/m) in 18 % of acquisitions.
Prospective motion and B0 correction provides high quality repeatable spectra. The study found that most children moved between acquisitions and a substantial number moved during acquisitions.
评估儿童的B0匀场和运动导航单体素磁共振波谱技术。评估三个区域（额内侧灰质、三角区周围白质和基底神经节）代谢物浓度的可重复性。确定该人群中采集内和采集间运动的程度。
计算线宽和信噪比，以评估3特斯拉场强下186个波谱的谱质量。对31次重复扫描进行可重复性评估。使用导航图像评估定位误差，同时使用导航运动和匀场日志来证明扫描期间所需校正的效果。
每个区域中N-乙酰天门冬氨酸的平均线宽±标准差分别为3.8±0.6Hz、4.4±0.5Hz和4.7±0.8Hz。代谢物浓度的逐次扫描测量方差与预期方差非常相似。共有73%和32%的儿童在采集前和采集期间发生移动，导致体素移位超过体素体积的10%，即1.5毫米。主要的移动方向是滑出线圈和点头（上下旋转）。18%的采集过程中一阶B0校正显著（>10μT/m）。
前瞻性运动和B0校正可提供高质量的可重复波谱。研究发现，大多数儿童在采集之间发生移动，且相当数量的儿童在采集期间发生移动。
