Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan.
Magn Reson Med. 2009 Dec;62(6):1394-403. doi: 10.1002/mrm.22119.
Intrascan subject movement in clinical MR spectroscopic examinations may result in inconsistent water suppression that distorts the metabolite signals, frame-to-frame variations in spectral phase and frequency, and consequent reductions in the signal-to-noise ratio due to destructive averaging. Frame-to-frame phase/frequency corrections, although reported to be successful in achieving constructive averaging, rely on consistent water suppression, which may be difficult in the presence of intrascan motion. In this study, motion correction using non-water-suppressed data acquisition is proposed to overcome the above difficulties. The time-domain matrix-pencil postprocessing method was used to extract water signals from the non-water-suppressed spectroscopic data, followed by phase and frequency corrections of the metabolite signals based on information obtained from the water signals. From in vivo experiments on seven healthy subjects at 3.0 T, quantification of metabolites using the unsuppressed water signal as a reference showed improved correlation with water-suppressed data acquired in the absence of motion (R(2) = 0.9669; slope = 0.94). The metabolite concentrations derived using the proposed approach were in good agreement with literature values. Computer simulations under various degrees of frequency and phase variations further demonstrated robust performance of the time-domain postprocessing approach.
临床磁共振波谱检查中的扫描内受试者运动可能导致水抑制不一致，从而扭曲代谢物信号、谱相位和频率的帧间变化，以及由于破坏性平均导致的信噪比降低。尽管报道了帧间相位/频率校正方法在实现建设性平均方面是成功的，但它依赖于一致的水抑制，而在存在扫描内运动的情况下，这可能很困难。在这项研究中，提出了使用非水抑制数据采集进行运动校正，以克服上述困难。时域矩阵铅笔后处理方法用于从非水抑制波谱数据中提取水信号，然后根据水信号获得的信息对代谢物信号进行相位和频率校正。在 3.0T 下对 7 名健康受试者进行的体内实验中，使用未抑制的水信号进行代谢物定量显示与无运动时获得的水抑制数据具有更好的相关性（R²=0.9669；斜率=0.94）。使用所提出的方法得出的代谢物浓度与文献值吻合良好。在不同频率和相位变化程度下的计算机模拟进一步证明了时域后处理方法的稳健性能。
