Diffuse Reflectance Spectroscopy: Using a Monte Carlo method to determine chromophore compositions of tissue

Abstract: In this work, inverse diffusion equation and Monte Carlo methods are used in conjunction with diffuse reflectance spectroscopy to develop a protocol for evaluating the chromophore compositions of tissue mimicking liquid phantoms. A novel two spectrometer system is used which provides real time calibration of any intensity fluctuations of the light source. The calibration of this setup is investigated in detail. In order to analyse the limitations of the two theoretical models (diffusion equation and Monte Carlo), two optical probes with source-detector separations of 0.5 and 2 mm are used. The final evaluated fittings of whole blood, deoxygenated haemoglobin, oxygenated haemoglobin concentrations and scattering coefficient values are relatively good. Possible approaches for improving the experimental data are discussed. The Monte Carlo method is shown to give better results than the diffusion equation for short probe designs, as expected from theory. However, for longer probe designs, the diffusion theory evaluates the data better. This is likely due to worse planar fitting of the Monte Carlo look-up table at long source-detector separations. In general however, the results are promising and indicate good prospects for using this system on real biological systems.