Fluorescence Optical Imaging Research Based On The Diffusion Approximation Theory

The birth of the world’s first laser has been over half a century. In the past half century, Laser technology has been rapid development. At the same time, the laser technology has been widely used in many areas, such as communication, measurement technology, biological medicine, industrial material processing, national defense military, science and technology and many other fields. Optical imaging technology which uses near-infrared light to detect internal information of media has been rapid development. Fluorescence diffuse optical imaging with high contrast and strong selectivity has been got more and more attention and study. The measurement mode of fluorescent diffuse optical imaging technology mainly includes the steady state mode, the time domain mode and the frequency domain mode. Time-domain fluorescence diffuse optical imaging technology has certain advantages in the information data integrity and flexibility and the stability of the system compared with the steady-state fluorescence diffuse optical imaging technology and frequency-domain fluorescence diffuse optical imaging technology. Time-domain fluorescence diffuse light imaging technology has become the mainstream of current research.In this paper, the fluorescence optical imaging methods were studied systematically. The main content of this paper is the steady-state fluorescence diffuse optical imaging technology and time-domain fluorescence diffuse optical imaging technology research. Specific work includes the following aspects: 1. The forward model of fluorescence diffuse optical imaging technology was established to simulate the transmission of the incident laser and excited fluorescence in the medium. The finite difference method was used to solve the coupling diffusion equations to get the media surface emitted fluorescence analog signal. The effects of factors that the incident laser pulse width, optical parameters of background medium, the size and optical parameters of the heterogeneity on the exit surface fluorescence signal has been got detailed analysis. 2. For the reverse question, the conjugate gradient method was selected to media for medium internal fluorescence parameters inversion. Fluorescent light diffusion imaging technology based on the steady-state coupled diffusion equations has been studied. The maximum posterior probability estimation method was introduced in the reconstruction process in conjunction with the generalized Gauss- Markov random field to improve the quality of the reconstructed image. In addition, the effects of the size of the heterogeneity and inversion initial estimates on the fluorescence parameters reconstruction has been studied. 3. Fluorescent light diffusion imaging technology based on the time-domain coupled diffusion equations has been studied to simultaneously recover fluorescent yield and lifetime distributions of a two-dimensional rectangular inhomogeneous media. The effects of the contrast and measurement errors on the reconstructed image have been analyzed. On this basis, the use of time-domain fluorescence diffuse optical imaging technology has realized the simultaneously recovering of fluorescent yield and lifetime distributions within a two-dimensional inhomogeneous round media.