The application of polarized light to biomedical diagnostics and monitoring.

摘要

The application of polarized light to biomedical diagnostics and monitoring offers several fascinating possibilities for the eventual design of noninvasive sensors applied to such areas as diagnosis of cancerous lesions and glucose monitoring. In this dissertation, two separate investigations are reported on and discussed. The first study involves the theoretical modeling of polarized light transport in a turbid medium. The Monte Carlo method is then applied to numerically solve the two-dimensional backscattering Mueller matrix of a polystyrene sphere suspension. Experimental measurements wire also performed and found to be in excellent agreement both qualitatively and quantitatively. In addition, theoretical and experimental cross-polarized backscattered images were obtained for phantoms of different concentration. The variations observed between the phantoms provide a foundation to better understand why the differences between normal and cancerous cell suspensions observed by other groups occur. The second investigation involves the application of polarized light toward the development of an in vivo glucose monitor. In this study, results are presented that measure the time lag between blood and aqueous humor glucose levels to be between 5 to 10 minutes in New Zealand White rabbits. In addition, a novel multispectral (532 nm and 635 nm) laser-based polarimeter was designed and constructed. This polarimeter was first evaluated in vitro to demonstrate the application of multiple wavelengths to minimize glucose prediction error in the presence of multiple optically active component solutions. The solutions used for this investigation were composed of varying physiological concentrations of glucose and albumin. A novel contact lens was then constructed to couple a polarized light signal through the anterior chamber of a rabbit eye. This device was used in conjunction with the designed polarimeter for in vivo polarimetric glucose measurements. It was determined that motion artifact due to respiration coupled with corneal birefringence were the main limiting factors hindering long-term physiologic glucose measurements through the eye. Lastly, in vitro/ in vivo glucose measurements were acquired to demonstrate that the current polarimetric sensor has enough sensitivity to measure short-term physiologic glucose levels.