Spatially Resolved IR Hyperspectral Imaging for Malignant Cell Detection

To systematically investigate the IR spectral alterations associated with carcinogenesis and tumor progression, we initiated a research program to spatially resolve chemistry from IR hyperspectral imaging of individual cells. When an instrument measures the missing light at the detector, the generated IR spectrum is a consequence of both absorbances and scattering of the particle. This phenomenon often manifests as intense baseline profiles, fringes, band distortion, and peak position and intensity changes. Consequently, a recorded spectrum hardly reflects the pure absorbance that carries the molecular composition of the cell. Instead, the obtained IR spectrum is a superposition of the pure absorbance of the molecules and signals from scattering as well as other optical phenomena that are dependent on the geometric cross-section of the sample and the wave nature of light. Since the goal is to determine the internal structure of cells, we want to ensure that the scattering contribution to the measured absorbance is removed so that only the pure absorbance of the functional groups is recovered. It then becomes necessary to find ways to extract the space-dependent complex index of refraction from the measured absorbance spectra and, by extension, solve an inverse scattering problem.