Establishment of the Mathematical Model for PMI Estimation Using FTIR Spectroscopy and Data Mining Method
WANG Lei1,2,3, QIN Xin-chao4, LIN Han-cheng5, DENG Kai-fei2, LUO Yi-wen2, SUN Qi-ran2, DU Qiu-xiang1, WANG Zhen-yuan5, TUO Ya3, SUN Jun-hong1
1. School of Forensic Medicine, Shanxi Medical University, Taiyuan 030001, China; 2. Shanghai Key Laboratory of Forensic Medicine, Shanghai Forensic Service Platform, Academy of Forensic Science, Shanghai 200063, China; 3. School of Basic Medical Science, Shanghai University of Medicine and Health Sciences, Shanghai 201318, China; 4. Linwei Branch of Weinan Public Security Bureau, Weinan 714000, China; 5. Department of Forensic Science, Health Science Center, Xi’an Jiaotong University, Xi’an 710061, China
Objective To analyse the relationship between Fourier transform infrared （FTIR） spectrum of rat’s spleen tissue and postmortem interval （PMI） for PMI estimation using FTIR spectroscopy combined with data mining method. Methods Rats were sacrificed by cervical dislocation, and the cadavers were placed at 20 ℃. The FTIR spectrum data of rats’ spleen tissues were taken and measured at different time points. After pretreatment, the data was analysed by data mining method. Results The absorption peak intensity of rat’s spleen tissue spectrum changed with the PMI, while the absorption peak position was unchanged. The results of principal component analysis （PCA） showed that the cumulative contribution rate of the first three principal components was 96%. There was an obvious clustering tendency for the spectrum sample at each time point. The methods of partial least squares discriminant analysis （PLS-DA） and support vector machine classification （SVMC） effectively divided the spectrum samples with different PMI into four categories （0-24 h, 48-72 h, 96-120 h and 144-168 h）. The determination coefficient （R2） of the PMI estimation model established by PLS regression analysis was 0.96, and the root mean square error of calibration （RMSEC） and root mean square error of cross validation （RMSECV） were 9.90 h and 11.39 h respectively. In prediction set, the R2 was 0.97, and the root mean square error of prediction （RMSEP） was 10.49 h. Conclusion The FTIR spectrum of the rat’s spleen tissue can be effectively analyzed qualitatively and quantitatively by the combination of FTIR spectroscopy and data mining method, and the classification and PLS regression models can be established for PMI estimation.