Robust Sample Information Retrieval in Dark-Field Computed Tomography
with a Vibrating Talbot-Lau Interferometer
Abstract
X-ray computed tomography (CT) is a crucial tool for non-invasive
medical diagnosis that uses differences in materials’ attenuation
coefficients to generate contrast and provide 3D information.
Grating-based phase- and dark-field-contrast X-ray imaging is an
innovative technique that utilizes refraction and small-angle scattering
to generate additional co-registered images with improved contrast and
microstructural information. While it is already possible to perform
human chest dark-field radiography, it is assumed that its diagnostic
value increases when performed in a tomographic setup. However, the
susceptibility of Talbot-Lau interferometers to mechanical vibrations
coupled with a need to minimize data acquisition times has hindered its
application in clinical routines and the combination of the two
techniques in the past.
In this work, we propose a processing pipeline to address this issue in
a human-sized clinical dark-field CT system. We present the corrective
measures that have to be applied in the employed processing and
reconstruction algorithms to mitigate the effects of vibrations and
deformations of the interferometer gratings. This is achieved by
identifying and mitigating spatially and temporally variable vibrations
in the interferometer. By exploiting correlations in the modular grating
setup, we can identify relevant fluctuation modes and separate the
fluctuation and sample information, enabling vibration-artifact free
sample reconstruction.