This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Keywords: Maxwell's equations, tissue optics, coherent backscattering, random media, early stage cancer detection, epithelial tissues, colon cancer Abstract: This project addresses the development of computational methodologies to model and analyze optical propagation within, and scattering by, biological tissues. The numerical investigation is based on two related algorithms: (1) the finite-difference time-domain (FDTD) method, which enables solving the full-vector Maxwells equations for optical interactions with biological tissues with nanometer spatial resolution; and (2) the pseudospectral time-domain (PSTD) technique, a recent technical advance of the FDTD method which allows spatial sampling approaching the Nyquist rate, and therefore enables modeling optical-tissue interactions at macroscopic scales. Our specific modeling efforts are aimed at understanding the physics of the recently observed phenomenon of low-coherence optical backscattering, which has significant promise for improving early-stage cancer detection in epithelial tissues, especially the colon. At present, approximate models involving photon diffusion and transport provide an inadequate physics basis because of their inability to treat near and evanescent fields and polarization. Establishment of a rigorous physical understanding of low-coherence optical backscattering by solving the underlying full-vector Maxwells equations could lead to the development of optimized clinical instruments and procedures capable of accelerated detection of precancerous conditions in epithelial tissues.
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