title: Application of Monte Carlo simulation-based photon migration for enhanced understanding of near-infrared (NIR) diffuse reflectance. Part II: Photon radial diffusion in NIR chemical images.
abstract: This is the second of a series of articles applying Monte Carlo simulation-based photon migration as a means of enhancing understanding of near-infrared (NIR) diffuse reflectance in pharmaceutical analysis. This work utilizes Monte Carlo simulation to explore photon movement along the radial direction, as a means of investigating the potential 2-D spatial distortion in NIR chemical images caused by photon radial diffusion. Simulations indicate that the physical sample represented by an observed pixel in an image contributes 17% of the spectral information, while the remaining contribution comes from a radial area around the observed pixel about 500 microm wide. Empirical measurements on a two-medium sample (i.e., Teflon films with different thicknesses laid on the top of a pure theophylline compact) were used to confirm the effect of photon radial movement on a physical feature in an NIR chemical image, that is, edge blurring. As a means of edge clarification, a preliminary Monte Carlo simulation-based deconvolution filter was developed and tested for its efficacy on sharpening the physical feature and maintaining the original chemical information in a measured NIR chemical image. The initial success of the deconvolution filter highlights the potential to develop a filter for practical applications.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282, USA.
authors.forename: Zhenqi
authors.initials: Z
authors.lastname: Shi
authors.forename: Carl A
authors.initials: CA
authors.lastname: Anderson
mesh_terms: D036262:Empirical Research; D009010:Monte Carlo Method; D017785:Photons; D019265:Spectroscopy, Near-Infrared; D013806:Theophylline / Q000737:chemistry
chemical_list: D013806:Theophylline