Instrumental Analysis

Computer Research And Technology

Investigators

Linked publications & trials

Abstract

Two main topics constituted the main thrust of the optical imaging project. Because photons suffer significant scattering by cell components it is necessary to determine physical properties of photon trajectories in terms of some form of diffusion, random walk, or transport theory. Up till about the year 2000 the standard assumption was that optical tissue parameters were isotropic with respect to cell geometry. Since that time it has become more and more evident that this assumption is violated in a significant number of cases. This has impelled our research on the effects of optical parameter anisotropy on techniques used to detect differences between normal and abnormal tissues as well as to track the tissue interrogated by photons involved in optical measurements. A mathematical formalism, based on random walk theory, originally developed by members of MSCL to incorporate optical anisotropy has been used to produce a simple measure of the degree to which contrast due to the presence of an abnormal inclusion in a tissue is affected by the presence of optical anisotropy. A further project along these lines is that of determining how anisotropic optical parameters affects the amount of penetration of photons into a tissue as a measure of how much of the tissue is investigated in different types of imaging experiments. [unreadable] A presently popular technique in optical imaging related to cancer diagnostics and related animal models is based on fluorophore-conjugated probes. We have recently developed a model based on the continuous-time lattice random walk which considerably extends previous theoretical work on fluorescence lifetime imaging by removing rather severe restrictions imposed on the basic theoretical formalism previously described in the literature.[unreadable] Recent experimental advances known as various single-molecule techniques, have permitted physical chemists to investigate kinetics on an atomic level. To allow these to work effectively it is necessary to have a theoretical description of the process. Together with members of NIDDK we have developed such a theory based on Kramers' theory of diffusive barrier crossing. The resulting theory can be applied to interpret data from a number of experimental methods, e.g., atomic force microscopy, laser optical tweezers, and so forth.