IR Spectroscopy and Linear Support Vector Machine Analysis of Colorectal Liver Metastasis.

The Colorectal Liver Metastasis (CLM) library contains 756,096 full range Fourier transform infrared (FTIR) microscope imaging spectra of 14 frozen tissue sections from 7 different consenting patients with liver metastasis of colorectal origin. A subset of 30 windows was defined in predominant tumor or nontumor regions for the training or testing of linear support vector machine (SVM) models. Since the number of consenting patients was small, the primary purpose of this work was to establish a physical chemistry perspective on the infrared (IR) spectroscopy of metastatic liver cancer using the large number of available spectra. The linear SVM model was trained with a Leave-One-Case-Out strategy to avoid case leakage, minimize overtraining, and offer simple feature selection. The primary result is the derivation and measurement of a spectral form for the average contribution to the tumor/nontumor decision at each spectral step, i.e., the "Decision Contribution Spectrum". Finally, the results are used toward the design of a fast mid-IR cancer probe for the operating room giving quick tumor decisions despite a reduced range of wavenumbers and an increased interval between wavenumber steps as compared to the FTIR input spectral data.