Spectra were acquired in 33 healthy volunteers (50.1 years, SD = 17.19, 18 females) on a 3 T Philipps MR system using a point-resolved spectroscopy (PRESS) sequence optimized with very selective saturation pulses (OVERPRESS) and voxel-based flip angle calibration (effective volume of interest size: 8.8 × 10.2 × 12.2 mm3 ). Spectra were fitted using LCModel and SNR, NAA peak linewidths and Cramér-Rao lower bounds (CRLBs) were measured after spectral registration and after minimal frequency alignment.
Spectral registration improved SNR by 5% (p = 0.026, median value post-correction: 18.0) and spectral linewidth by 23% (p < 0.001, 4.3 Hz), and reduced the metabolites\' CRLBs by 1% to 15% (p < 0.026). Correlational analyses revealed smaller SNR improvements with greater head motion (p = 0.010) recorded using a markerless motion tracking system. Higher metabolite concentrations were detected using individual-based compared to literature-based water relaxation times (p < 0.001).
This study demonstrates high-quality 1 H-MRS acquisition in the PAG using spectral registration. This shows promise for future 1 H-MRS studies in the PAG and possibly other clinically relevant brain regions with similar methodological challenges.
方法:对33名健康志愿者(50.1岁,SD=17.19,18雌性)在3TPhilippsMR系统上使用点分辨光谱(PRESS)序列,该序列经过非常选择性的饱和脉冲(OVERPRESS)和基于体素的翻转角校准(有效感兴趣体积大小:8.8×10.2×12.2mm3)。使用LCModel和SNR拟合光谱,在光谱配准和最小频率对齐后,测量了NAA峰线宽和Cramér-Rao下界(CRLB)。
结果:光谱配准将SNR提高了5%(p=0.026,校正后中值:18.0),光谱线宽提高了23%(p<0.001,4.3Hz),并将代谢物CRLB降低1%至15%(p<0.026)。相关分析显示,使用无标记运动跟踪系统记录的头部运动(p=0.010)的SNR改善较小。与基于文献的水弛豫时间相比,使用基于个体的水弛豫时间检测到更高的代谢物浓度(p<0.001)。
结论:这项研究证明了使用光谱配准在PAG中进行高质量的1H-MRS采集。这显示了在PAG和其他可能具有类似方法学挑战的临床相关脑区域中的未来1H-MRS研究的希望。