Barton Sinead J, Hennelly Bryan M
1 Department of Electronic Engineering, Maynooth University, Kildare, Ireland.
2 Department of Computer Science, Maynooth University, Kildare, Ireland.
Appl Spectrosc. 2019 Aug;73(8):893-901. doi: 10.1177/0003702819839098. Epub 2019 Apr 22.
Cosmic ray artifacts may be present in all photo-electric readout systems. In spectroscopy, they present as random unidirectional sharp spikes that distort spectra and may have an affect on post-processing, possibly affecting the results of multivariate statistical classification. A number of methods have previously been proposed to remove cosmic ray artifacts from spectra but the goal of removing the artifacts while making no other change to the underlying spectrum is challenging. One of the most successful and commonly applied methods for the removal of comic ray artifacts involves the capture of two sequential spectra that are compared in order to identify spikes. The disadvantage of this approach is that at least two recordings are necessary, which may be problematic for dynamically changing spectra, and which can reduce the signal-to-noise (S/N) ratio when compared with a single recording of equivalent duration due to the inclusion of two instances of read noise. In this paper, a cosmic ray artefact removal algorithm is proposed that works in a similar way to the double acquisition method but requires only a single capture, so long as a data set of similar spectra is available. The method employs normalized covariance in order to identify a similar spectrum in the data set, from which a direct comparison reveals the presence of cosmic ray artifacts, which are then replaced with the corresponding values from the matching spectrum. The advantage of the proposed method over the double acquisition method is investigated in the context of the S/N ratio and is applied to various data sets of Raman spectra recorded from biological cells.
宇宙射线伪影可能存在于所有光电读出系统中。在光谱学中，它们表现为随机的单向尖峰，这些尖峰会扭曲光谱，并可能对后处理产生影响，从而可能影响多元统计分类的结果。此前已经提出了许多方法来从光谱中去除宇宙射线伪影，但在不对基础光谱进行其他更改的情况下去除伪影这一目标具有挑战性。最成功且常用的去除宇宙射线伪影的方法之一是捕获两个连续光谱并进行比较，以识别尖峰。这种方法的缺点是至少需要两次记录，这对于动态变化的光谱可能存在问题，并且与等效持续时间的单次记录相比，由于包含了两次读出噪声，会降低信噪比（S/N）。在本文中，提出了一种宇宙射线伪影去除算法，该算法的工作方式与双采集方法类似，但只要有相似光谱的数据集，仅需单次捕获。该方法采用归一化协方差来在数据集中识别相似光谱，通过直接比较可揭示宇宙射线伪影的存在，然后用匹配光谱中的相应值替换这些伪影。在信噪比的背景下研究了所提出的方法相对于双采集方法的优势，并将其应用于从生物细胞记录的各种拉曼光谱数据集。
