Axial and Lateral Resolution in Optical Coherence Tomography as a Function of System and Tissue Optical Properties

Abstract

This thesis presents the results of a study investigating the effects on the axial and lateral resolution of a time-domain optical coherence tomography (OCT) system, as a function of tissue optical properties and system numerical aperture. In theory, the equations governing the axial and lateral resolution of OCT are well characterized and defined. However, empirical evidence from previous studies performed by Dr. Jennifer Barton and her colleagues have seemed to indicate that these equations do not fully describe the trends observed when using OCT in the presence of multiply scattered photons due to imaging through highly scattering media. This study aimed to further investigate these observations by performing OCT on a series of tissue phantoms with varying parameters and with varying system parameters in order to identify what trends may exist between the axial and lateral resolutions of the resulting images, the scattering and absorption characteristics of the tissue phantoms, and the numerical aperture of the OCT system itself. Over the course of this study, it was concluded that the optical properties of the tissue being analyzed by OCT do not seem to impact either the axial resolution or the lateral resolution of the results (at least over the range of parameters covered), with the axial resolution being purely a function of the source and the lateral resolution being a function of the optics present in the system. These findings support the theoretical equations governing OCT and suggest that the empirically observed apparent decrease in resolution in highly scattering media may be an artifact due to errors in operation or alignment of the system, or simply not apparent with our setup of a highly reflective object placed at focus.