A Functional Medical Imaging System for the Measurement of Oxygen Saturation in the Superficial Retina Vasculature

The retinal vasculature's oxygen saturation (SO2) is a valuable indicator of disease, in particular for patients with diabetic retinopathy (DR) who may experience changes in retinal oxygen saturation during their lifetime. Although numerous experimental systems aimed at measuring retinal SO2 have been developed in the last thirty years, a reliable, robust model for in vivo monitoring is still lacking.;This dissertation explores the feasibility of using Two Dimensional Spatial Fourier Domain Imaging (2D-SFDI) and its related physics-based models for observation of the human retina. Two dimensional SFDI is based on spatially modulated light in two perpendicular axes. The most significant benefit of the 2D-SFDI technique compared with the current SFDI technique is to decrease the number of snapshots to one. The proposed proof of concept instrument was one in which spatially modulated illumination was achieved using two dimensional sinusoidal mechanical patterns positioned at a conjugate plane of the patient's retina. In additional to implementing 2D-SFDI, this dissertation employs Extended Modified Beer-Lambert Law (EMBLL) to obtain the optical properties of a two-layered structure. EMBLL is a modified version of MBLL that is used to measure the optical properties of the top layer in a two-layered structure using an imaging technique. Thus, this dissertation is focused on the structure of the vessels on top of the optic disc. Since the goal is determining the optical properties and ultimately measuring the oxygen saturation of vessels on top of the optic disc, in this dissertation the ophthalmic system (fundus camera) was modified to implement the presented algorithm in the eye. The system was tested using optical phantoms of known optical properties as well as a cow's optical disc. In the end, the optical properties of the human optic disc and oxygen saturation of the vein and artery on top of the optic disc were obtained. The tests' results show less than 6% error for phantoms. Also, vascular results are comparable with other reports. In summary, the proposed concepts provide an algorithm that is capable of determining the optical properties of the top layer in a two-layered media, using a single snapshot.