An investigation on annular cartilage samples for post-mortem interval estimation using Fourier transform infrared spect
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ORIGINAL ARTICLE
An investigation on annular cartilage samples for post-mortem interval estimation using Fourier transform infrared spectroscopy Zhouru Li 1,2 & Jiao Huang 2 & Zhenyuan Wang 1 & Ji Zhang 3 & Ping Huang 3 Accepted: 8 July 2019 # Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract Many attempts have been made to estimate the post-mortem interval (PMI) using bioanalytical methods based on multiple biological samples. Cartilage tissues could be used as an alternative for this purpose because their rate of degradation is slower than that of other soft tissue or biofluid samples. In this study, we applied Fourier transform infrared (FTIR) spectroscopy to acquire bioinformation from human annular cartilages within 30 days post-mortem. Principal component analysis (PCA) showed that sex and causes of death have almost no impact on the overall spectral variations caused by post-mortem changes. With preprocessing approaches, several predicted models were established using a conventional machine learning method, known as the partial least square (PLS) regression. The best model achieved a satisfactory prediction with a low error of 1.49 days using the second derivative transform of 3-point smoothing and extended multiplicative scatter correction (EMSC), and the spectral regions from proteins and carbohydrates contributed greatly to the PMI prediction. This study demonstrates the feasibility of cartilage-based FTIR analysis for PMI estimation. Further work will introduce advanced algorithms for more accurate and precise PMI prediction. Keywords Post-mortem interval . Fourier transform infrared spectroscopy . Annular cartilage . Partial least square regression
Introduction Post-mortem interval (PMI), also known as the time since death, refers to the period between death and the beginning of autopsy [1–3]. As the first step of criminal investigations, PMI estimation is helpful for providing clues in caseworks, narrowing the
Zhouru Li and Jiao Huang contributed equally to this work. * Zhenyuan Wang [email protected] * Ji Zhang [email protected] * Ping Huang [email protected] 1
Department of Forensic Pathology, Xi’an Jiaotong University, Xi’an 710061, Shaanxi, China
2
Department of Forensic Medicine, Xuzhou Medical University, Xuzhou 221000, Jiangsu, China
3
Shanghai Key Laboratory of Forensic Medicine, Shanghai Forensic Service Platform, Academy of Forensic Science, Shanghai 200063, China
scope of investigation and targeting potential suspects [4, 5]. In some countries, PMI estimation is also essential in civil cases such as insurance claims and property inheritance [4]. Coroners or medical examiners conduct a practical rough PMI evaluation based on post-mortem signs, including livor mortis, rigor mortis and supravital reaction. Nevertheless, this approach often leads to a large margin of predicted error because it is highly dependent upon subjective judgement and experience. Moreover, PMI is most difficult to evaluate at later phases (>24 h post-mortem), as most post-mortem signs can
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