Contrast enhancement in second harmonic imaging: Discriminating between muscle and collagen

摘要

In this study, polarization second harmonic generation (SHG) imaging is used and data analysis is developed to gain contrast and to discriminate with pixel resolution, in the same image, SHG source architectures. We use mammalian tissue in which both skeletal muscle and fibrilar collagen can be found. The images are fitted point by point using an algorithm based on a biophysical model, where the coefficient of determination is utilized as a filtering mechanism. For the whole image we retrieve for every pixel, the effective orientation, θ_e, of the SHG active structures. As a result a new image is formed which its contrast depends on the values of θ_e. Collagen presented in the forward direction for a predefined region of interest (ROI), peak distribution of angles θ_e centered in the region of ～45°, while muscle in the region of ~65°. Consequently, collagen and muscle are represented in different colors in the same image. Thus, here we show that it is possible to gain contrast and to discriminate between collagen and muscle without the use of any exogenous labeling or any co-localization with fluorescence imaging.