Quantitative characterization of speckle-based x-ray imaging setup for sub-resolution microstructure analysis using standardized samples

Chronic respiratory diseases are the third leading cause of death worldwide, affecting over 454.6 million people. Current diagnostic methods, such as imaging, often fail to detect early lung changes effectively. However, when x-rays are considered as electromagnetic waves, additional contrast mechanisms like diffraction, phase-shift, and small-angle scattering become accessible. X-ray scattering in healthy lung alveoli produce a strong dark-field signal, which decreases when alveolar integrity is compromised. This suggests dark-field imaging could be valuable for evaluating alveoli in vivo, although it remains unavailable for clinical and preclinical applications as many wave-optical imaging methods require complicated, shock-sensitive, and expensive hardware. Speckle-based dark-field imaging addresses this issue, generating dark-field contrast and transmission images using only a relatively simple diffuser material. We present a small animal lung imaging setup with a liquid-metal jet x-ray source operating at 50kV and a photon-counting detector. A sandpaper diffuser was used to create interference patterns, and polystyrene spheres (3 to100μm) were used to characterize the system. In vivo-like conditions were simulated with a single-shot technique and short acquisition times. We found that the contrast-to- noise ratio for dark-field images was significantly higher than transmission images. The results demonstrate that speckle-based dark-field imaging can detect structural changes in lung alveoli, showing a clear correlation between particle size and signal. This study underscores the potential of wave-optical methods for both preclinical and longitudinal assessment of pulmonary structures.