| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 102 === Nowadays the need of biomedical imaging is growing so fast, researchers try to develop better technologies to provide noninvasive methods in disease detection and treatment. It follows by development of optical tomography to reconstruct transmitted and scattered light into an object inside a media. This research concentrate on lesion imaging on normal tissues using optical properties of tissues and lesion. We modified diffusion theory into a convolution function of coherence condition of light. Convolution can be applied to calculate the reflectance for arbitrary sources on transmission or reflection process in tissues.
The discrete ordinates method is developed to study transient radiative transfer in three-dimensional scattering, absorbing, and emitting media subject to Fresnel boundary condition. The Fresnel boundary effect with diffuse reflection at the tissues and lesion is investigated. The reflectance and transmittance of radiative flux inside the tissues in the slab medium. The adequate incorporation of Fresnel’s reflection is very important.
A light beam in a Gaussian format is used in the simulation for the reason of the closest waveform of laser. There are some steps of simulation in this research. First, diffraction by thin lens takes place. Second, the simulation of diffraction is caused by certain optical systems. Third, the simulation of light propagation into tissues and lesion is determined by the correlation function of the transmission and reflection of light in the phantom tissues and lesion.
From the simulation, we found that only the beam waist and curvature are altered when a gaussian beam with a certain parameter transmit into thin lens. And for the second simulation, when gaussian beam transmitting into optical system to examine cornea, the distribution of diffraction pattern transmitted out from cornea is found. In the simulation of the transmitted and reflected beams at tissues and lesion, it can be seen there are some different patterns between light transmitted in normal tissues and lesion. In normal tissues, the pattern appears more uniformly. But when there is a lesion inside the tissues, the reflection and/or transmission pattern appears more irregular.
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