The Single-integrating-sphere Technique For Determining The Optical Properties Of Bio-tissue

In order to determine the optimum wavelength and irradiated power density of excited light in the photodynamic diagnosis and localization of early nasopharyngeal carcinoma, the optical and fluorescent properties of the bio-tissue are studied respectively in this thesis based on the theory of light transportation in bio-tissue.Firstly, both the optical transportation models and the measurement methods for the optical properties of tissue are discussed, which provide the theoretical foundation for the application of preclinical and clinical trials.Secondly, the advantages and disadvantages between single-integrating sphere system and double-integrating sphere system for the measurement of optical properties of biological tissues are analyzed in detail by using the integrating sphere theory. The reflectance and transmittance of porcine tissue with or without photosensitizer of HMME, as well as the collimated transmission with a extremely thin sample are measured by a single-integrating sphere system. Measurements are also carried out in various distances by moving detector to determine the collimated transmission using very thick sample based on the scattered transmission of tissue is isotropically distributed over all angles. The optical properties of porcine tissue under the irradiation of Ar+ laser are derived using the Kubelka-Munk theory and Inverse adding-double theory, and the results are almost identical with those deduced from Monte Carlo simulation combining with the diffusion theory.Finally, the investigation for the sensitivity and the image contrast of fluorescence imaging for diagnosis and localization of early nasopharyngeal carcinoma are carried out at the wavelength of 488nm and 514.5nm, respectively. The results show the contrast of fluorescence imaging excited by 488nm is better than that of 514.5nm under the irradiation with same power density.