Department of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
Anal Chim Acta. 2010 Dec 17;683(1):1-11. doi: 10.1016/j.aca.2010.09.026. Epub 2010 Sep 24.
The peaks of magnetic resonance (MR) spectra can be shifted due to variations in physiological and experimental conditions, and correcting for misaligned peaks is an important part of data processing prior to multivariate analysis. In this paper, five warping algorithms (icoshift, COW, fastpa, VPdtw and PTW) are compared for their feasibility in aligning spectral peaks in three sets of high resolution magic angle spinning (HR-MAS) MR spectra with different degrees of misalignments, and their merits are discussed. In addition, extraction of information that might be present in the shifts is examined, both for simulated data and the real MR spectra. The generic evaluation methodology employs a number of frequently used quality criteria for evaluation of the alignments, together with PLS-DA to assess the influence of alignment on the classification outcome. Peak alignment greatly improved the internal similarity of the data sets. Especially icoshift and COW seem suitable for aligning HR-MAS MR spectra, possibly because they perform alignment segment-wise. The choice of reference spectrum can influence the alignment result, and it is advisable to test several references. Information from the peak shifts was extracted, and in one case cancer samples were successfully discriminated from normal tissue based on shift information only. Based on these findings, general recommendations for alignment of HR-MAS MRS data are presented. Where possible, observations are generalized to other data types (e.g. chromatographic data).
磁共振（MR）光谱的峰值可能会因生理和实验条件的变化而发生偏移，因此在进行多元分析之前，对峰位进行校正对齐是数据处理的重要环节。本文比较了五种变形算法（icoshift、COW、fastpa、VPdtw 和 PTW）在对齐三个具有不同程度偏移的高分辨魔角旋转（HR-MAS）MR 光谱的光谱峰的可行性，并讨论了它们的优缺点。此外，还研究了在偏移中提取信息的可能性，既包括模拟数据，也包括真实的 MR 光谱。通用评估方法采用了许多常用的质量标准来评估对齐，同时使用 PLS-DA 评估对齐对分类结果的影响。峰对齐极大地提高了数据集的内部相似性。特别是 icoshift 和 COW 似乎适合对齐 HR-MAS MR 光谱，可能是因为它们分段进行对齐。参考光谱的选择会影响对齐结果，因此建议测试几个参考。从峰偏移中提取了信息，在一种情况下，仅基于偏移信息就成功区分了癌症样本和正常组织。基于这些发现，提出了对齐 HR-MAS MRS 数据的一般建议。在可能的情况下，将观察结果推广到其他数据类型（例如色谱数据）。
