Simmons A, Smail M, Moore E, Williams S C
Department of Clinical Neurosciences, Institute of Psychiatry, London, UK.
Magn Reson Imaging. 1998 Apr;16(3):319-30. doi: 10.1016/s0730-725x(97)00280-4.
The precision of cerebral proton magnetic resonance spectroscopy (MRS) measurements is critical both in the clinical setting and for research purposes. Marshall et al. have recently concluded that "disappointing in vivo repeatability...is likely to limit" the ability of MRS to detect modest changes. We present here a comprehensive study of the precision of short- and long-term metabolite peak area ratios and water referenced metabolite peak areas for long echo time point resolved spectroscopy (PRESS) spectra (repetition time (TR) = 2000 ms, echo time (TE) = 136 ms) acquired from the occipital lobes of normal volunteers and a phantom using a conventional whole body 1.5 T MR system and conventional acquisition and analysis protocols. Short-term in vitro precision determined by five repeat scans on five occasions was excellent as measured by a mean coefficient of variation (NAA/Cho = 1.3%, NAA/Cr + PCr = 1.0%, Cho/Cr + PCr = 1.6%, NAA/H2O = 0.5%, Cho/H2O = 1.2%, Cr + PCr/H2O = 0.8%). Long term in vitro precision using 100 spectra acquired over 2 years was also very good (NAA/Cho = 2.7%, NAA/Cr + PCr = 1.4%, Cho/Cr + PCr = 2.2%, NAA/H2O = 1.5%, Cho/H2O = 2.4%, Cr + PCr/H2O = 1.5%). Short-term in vivo precision determined by five repeat scans in a single scanning session on eight subjects was also excellent (NAA/Cho = 5.2%, NAA/Cr + PCr = 3.0%, Cho/Cr + PCr = 6.6%, NAA/H2O = 1.4%, Cho/H2O = 4.9%, Cr + PCr/H2O = 2.7%) and only worsened slightly for long-term in vivo precision determined by five repeat scans on eight subjects over 3 months (NAA/Cho = 5.2%, NAA/Cr + PCr = 4.8%, Cho/Cr + PCr = 7.7%, NAA/H2O = 2.5%, Cho/H2O = 6.4%, Cr + PCr/H2O = 3.8%). We attribute the excellent precision reported here to the use of highly automated techniques for voxel shimming, water suppression and peak area measurements. These results allow us to repudiate Marshall's assertion regarding disappointing repeatability of in vivo MRS.
脑质子磁共振波谱（MRS）测量的精度在临床环境和研究目的中都至关重要。马歇尔等人最近得出结论，“体内重复性令人失望……可能会限制”MRS检测适度变化的能力。我们在此展示了一项关于短回波时间点分辨波谱（PRESS）谱（重复时间（TR）=2000毫秒，回波时间（TE）=136毫秒）的短期和长期代谢物峰面积比以及水参考代谢物峰面积精度的综合研究，这些波谱是使用传统全身1.5T MR系统以及传统采集和分析协议，从正常志愿者的枕叶和一个模体中获取的。通过在五个不同时间进行五次重复扫描测定的短期体外精度非常出色，平均变异系数测量结果如下（NAA/Cho = 1.3%，NAA/Cr + PCr = 1.0%，Cho/Cr + PCr = 1.6%，NAA/H2O = 0.5%，Cho/H2O = 1.2%，Cr + PCr/H2O = 0.8%）。使用在两年内采集的100个波谱测定的长期体外精度也非常好（NAA/Cho = 2.7%），NAA/Cr + PCr = 1.4%，Cho/Cr + PCr = 2.2%，NAA/H2O = 1.5%，Cho/H2O = 2.4%，Cr + PCr/H2O = 1.5%）。通过在一次扫描会话中对八名受试者进行五次重复扫描测定的短期体内精度也非常出色（NAA/Cho = 5.2%，NAA/Cr + PCr = 3.0%，Cho/Cr + PCr = 6.6%，NAA/H2O = 1.4%，Cho/H2O = 4.9%，Cr + PCr/H2O = 2.7%），并且在三个月内对八名受试者进行五次重复扫描测定的长期体内精度仅略有变差（NAA/Cho = 5.2%，NAA/Cr + PCr = 4.8%，Cho/Cr + PCr = 7.7%，NAA/H2O = 2.5%，Cho/H2O = 6.4%，Cr + PCr/H2O = 3.8%）。我们将此处报告的出色精度归因于使用了高度自动化的体素匀场技术、水抑制技术以及峰面积测量技术。这些结果使我们能够驳斥马歇尔关于体内MRS重复性令人失望的断言。
