Optical characterization of biological tissues and rare earth nanoparticles

The ubiquitous use of lasers as both a diagnostic and therapeutic tool for medical applications (e.g. laser surgery, photoacoustic imaging, photodynamic therapy etc.), had rendered the understanding of optical properties of a biological medium critically important. The development of biomedical devices for the purposes of imaging or treatment requires a detailed investigation of these properties. Indeed, diagnostic monitoring of blood in vivo depends on knowledge of the distribution of light due to scattering in a blood medium. In addition, many optical properties of tissues have not been investigated experimentally at many clinically relevant wavelengths. The quantification of the scattering and absorptive behavior of tissue and its interaction with electromagnetic radiation is still at the core of predicting the outcome of a desired clinical effect. Therefore, the first portion of this Dissertation is a thorough characterization of ocular tissues in vitro using reflectance and transmittance spectroscopic techniques and computational models to extract and enlist a systematic study at wavelengths in the visible spectral region. The Kubelka-Munk (KM), Inverse Adding Doubling (IAD), and Inverse Monte Carlo (IMC) methods were used to determine the absorption and scattering coefficients and contrasted. The second portion of this Dissertation is an investigation of the optical and spectroscopic properties of novel rare earth Y₂O₃ and Nd3+:Y₂O₃nanoparticles in a blood medium. Reflectance and transmittance measurements were performed and the absorption and scattering properties for the nanoparticle/blood samples were determined by computational methods and compared. Absorption and emission of Y₂O₃ and Nd3+:Y₂O₃nanoparticle/blood medium revealed their utility as biomarkers.