Fiber orientation estimation by constrained spherical deconvolution of the anisotropic edge illumination X-ray dark field signal

Abstract

Determining fiber orientations in a fiber reinforced material with X-ray CT is challenging because the width of the individual fibers is often much smaller than the spatial resolution of the X-ray images. However, the anisotropic X-ray scattering signal of the fibers yields information about the fiber direction without the need to individually resolve them. In this work, edge illumination phase contrast imaging is used to sample the anisotropic X-ray scattering in the object along different directions. The measured scatter is represented on a sphere by a set of spherical harmonics. Next, the orientation of the fibers is extracted from the scatter function by constrained spherical deconvolution. This approach is experimentally validated, for both parallel and crossing fiber distributions in a single voxel, using Monte Carlo simulations in GATE. The retrieved fiber orientations for parallel and crossing carbon fibers are presented as result.