The purpose of this research study is to explore novel imaging methodologies using advanced polarimetric principles in conjunction with molecular contrast agents and biomarkers for early detection of tissue abnormalities. The novelty of this work consists in the use of optically active polar molecules, proteins and enzymes as innovative biomolecular contrast agents to extract biochemical and structural information contained within the optical signatures emitted by the tissue upon light interrogation. A preclinical phantom with multiple refractive-index variations was designed for the study and the experiments were conducted in two phases.
The first phase of experiments was performed using a Near-Infrared (NIR) Laser source by combining Rotating Retarder Polarimeter Method and Polarimetric Measurement Matrix reduction techniques. L-Phenylalanine and Insulin Glargine were chosen as molecular contrast agents for this study. The resulting Degree of Linear Polarization (DOLP) images were analyzed for contrast differences and the image quality was assessed by computing Signal-to-Background Ratios (SBRs) for every concentration of molecular contrast agent added to the surrounding medium of the target.
The second phase of experiments involved a broadband visible light source (655nm) and a microscopic objective lens system to interrogate the target utilizing Polarization Discrimination Methodologies. Isopropyl Alcohol, Glucose solution and Insulin Glargine were chosen as the molecular contrast agents for this study. The resulting co-polarized and cross-polarized images were processed to obtain DOLP images which were subsequently analyzed for contrast variations for every concentration of molecular contrast agent added. The quality of images obtained was assessed by implementing edge detection techniques on the DOLP images and tracing the changes in number of pixels detected as edges for varying concentrations of molecular contrast agents.
Experimental results from both the studies indicate clearly that the molecular contrast agents used in this study were successful in improving the image contrast of the DOLP images obtained through (NIR) polarimetric imaging as well as broadband visible light polarimetric imaging techniques. Specifically, the results of this study indicate that the DOLP images were more sensitive to the variations in concentrations of the molecular contrast agents added to the surrounding medium of target compared to nonpolarimetric (S0) images, leading to a net enhancement of the image contrast. Overall, the contributions of this study suggest that the presented optical principles can be successfully applied to the diagnosis and assessment of cancer in early stages utilizing molecular contrast agents in conjunction to polarimetry concepts.