Estimating the stretching characteristics of fiber bundles in microscopic images

Collagen fiber bundles are important constituent parts of biological soft tissues, such as tendons, blood vessels and skin. The single collagen fibers within a bundle have a certain crimp that determines the bundle´s stretching characteristic, which is of particular interest in mechanobiology. A thorough understanding of the complex interrelations between mechanical factors and the associated biological responses may help to improve diagnostics, which allow disease and injury to be treated earlier. We present a method to obtain the relative stretching characteristics (RSC) of collagen (fibrous) bundles based on the analysis of microscopic tissue images. We show, how the orientation statistics of local orientations in a bundle can be directly related to the RSC. The von Mises distribution (VMD) - a circular probability distribution is used to describe the 2D orientation statistics. The k parameter of the VMD is used to obtain the mean stretching and the probability density function (PDF) of the bundles´ RSC is identified.