Thickness dependences of anisotropic tissues on polarized second harmonic imaging

• Main Authors: Shuai-Yan Chen, 陳帥彥
• Other Authors: Guan-Yu Zhuo
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/248k48

碩士 === 國立中山大學 === 醫學科技研究所 === 106 === Second-harmonic generation (SHG) microscopy is a very useful technique for investigating the three-dimensional (3D) organization of anisotropic biological tissues, such as dermis, tendon and blood vessels. These are mainly composed of type-I collagen, which is structurally birefringent and of non-centrosymmetric structure, which can induce strong SHG signal. Therefore, this approach is suitable for clinical study as a non-invasive prediagnosis. However, large number of scattering events occurs between incident light and scattering particles in the tissue, hence it reduces the penetration depth of tissue and limits the application of SHG. It has been reported that the degree of polarization of circular polarized light maintains initial polarization state for deeper penetration depth than the linearly or elliptically polarized light, which has been stimulated with a polarization-sensitive Moten Carlo model; however, this work was only obtained by programing simulation. Therefore, related estimations need to be confirmed by optical microscopy experiments. In this work, we used a Ti:sapphire laser, providing the wavelength at around 810 nm to define three kinds of polarizations of incident beam, which are circular, elliptical and linear polarization. The forward SHG signal was obtained by PMT from pig’s tendon (30, 60, 100μm) and pig’s leather tissue (300, 600 and 700μm). It is confirmed that the longest to shortest penetration depth is in the sequence of circular (150μm), elliptical (143μm) and linear (121μm) polarization when penetrating into thick sample. The percentage of polarization deterioration of circular, elliptical and linear polarization in different thick sample: the change of linear polarization is the most significant (-99%), second is elliptical polarization (-75%), the change in circular polarization is 55% that is the lowest. Keyword: SHG, birefringent, non-central symmetric, polarized light, penetration depth