Development and characterization of fiber-based systems for biomedical imaging

Abstract

This thesis focuses on the instrumentation aspect of biomedical imaging with the use of optical fiber probes across three different disciplines. This includes the design and development of novel fiber optic based techniques and instruments in fields of optical coherence tomography (OCT), bioremediation and optical mapping of cardiac action potentials. Although the mechanism behind the imaging techniques of fluorescence and OCT are fundamentally different, the fact that both techniques permit the use of fiber probes gives rise to the possibility of a combined fluorescence-OCT probe. For example, the OCT and fluorescence portions of the integrated system are optically distinct, except for the final optics of the fluorescence-OCT fiber probe. Analog processing electronics for the subsystems can also be distinct, but for the purpose of synchronization and simultaneous data acquisition, both should be controlled by a central computer. Tumlinson and co-workers [140] have already demonstrated the development of such a system for simultaneous optical coherence tomography and laser-induced fluorescence measurement. We begin by demonstrating the feasibility of using the novel source, supercontinuum, in an OCT system. Its capabilities and limitations are also discussed. A prototype all-fiber OCT system was subsequently constructed to meet the design requirements of combined fluorescence-OCT probes. Current bioremediation methods are hindered by the lack of reliable, non-destructive, and in situ monitoring techniques. We investigate the feasibility of developing a novel spectroscopic technique that can monitor bacterial species in situ. A fluorescence spectroscopy system that meets the design criteria is subsequently built. Its capabilities and limitations were demonstrated through a series of laboratory controlled experiments which showed promising preliminary results. Optical mapping of cardiac action potential have proved to be indispensable in the study of arrhythmia. Although optical recordings using optical fibers have already been demonstrated with convincing results, none of which were spectrally resolved. We have constructed a fluorescence setup to make spectroscopic measurement of cardiac action potentials. This has offered more insights into the complex process of spectral modulation which is usually associated with membrane potential and mechanical activity.