Application of second harmonic generation and auto-fluorescence lifetime imaging microscopy in imaging dental tissue

• Main Authors: Hong-Chou Lyu, 呂宏洲
• Other Authors: Fu-Jen Kao
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/n7wpag

碩士 === 國立陽明大學 === 生醫光電工程研究所 === 97 === In this thesis, we have developed a 2-channel TCSPC based microscopy platform for anisotropy imaging with fluorescence and second harmonic. Polarization measurements are conducted in both forward and backward directions. Dental tissues, purified collagen, and periodically poled lithium niobate (PPLN) are used as specimens to elucidate the importance and the role of anisotropy. A dental section is a highly mineralized tissue and is formed by the association of organic materials. In this study, we used second harmonic generation (SHG) and two-photon fluorescence lifetime imaging microscope (FLIM) to image the enamel and dentin sections. In the SH measurements, dental tissues and purified collagen exhibit excitation wavelength dependence. The SH intensity increases with the increment of excitation wavelength. For comparison, periodically poled lithium niobate (PPLN) does not show such dependence. The wavelength dependence may be caused by the competition between auto-fluorescence (AF) and SHG in collagen. In SH imaging, the tubular structure in dentin can be revealed while enamel does not exhibit any SH signal. Both dentin and enamel exhibit strong AF signals that can be used to reveal their unique morphological features, such as dentinal tubule and enamel rods. Additionally, the FLIM images show different auto-fluorescence lifetime distributions in dentin and enamel. AF lifetime in purified collagen is also measured as a comparison. The hollow tubular structures within dentin are visualized through the absence of organic materials. We have also performed the following measurements with our unique 2-channel TCSPC based microscopy platform: extinction ratio characterization, polarization of SH (PPLN), and polarization of collagen auto-fluorescence. It is interesting to note that in the auto-fluorescence measurement, fluorescence from different polarizations exhibits different lifetimes.