Author: Jonthomas Michael Box, Isaac B. Rutel 👨🔬
Affiliation: University of Oklahoma Health Sciences Center 🌍
Purpose: This study assesses the feasibility of using speckle images and a modified phase retrieval algorithm to reconstruct the point spread function (PSF) of a diagnostic x-ray system. While speckle-based PSF reconstruction has primarily been demonstrated in lower-energy x-ray microscopy, our work explores its application in a clinical diagnostic setting.
Methods: Speckle images were obtained from a single diagnostic x-ray system utilizing sandpaper of various grit sizes, and under varying exposure conditions. A phase retrieval algorithm, modified for this context, was then employed to reconstruct the system’s PSF. The reconstructed focal spot sizes were compared to the manufacturers listed focal spot size, as well as a calculated focal spot size, measured using a star pattern phantom.
Results: Focal spot size was quantified by measuring the full width at half maximum in both the x and y directions. For small and large focal spots, the reconstructed sizes were comparable to the manufacturer’s nominal values of 0.6 mm and 1.2 mm, respectively, and closely matched the star pattern phantom measurements (0.74 mm and 1.91 mm).
Conclusion: This work indicates the potential for speckle image- based point spread function reconstruction in diagnostic x-ray systems, which has previously only been demonstrated in lower energy x-ray microscopy systems. Accurate PSF reconstruction provides an additional method for focal spot size determination, as well as unlocking the ability to perform PSF deconvolution on subsequent images taken on the x-ray system, which has been shown to improve image quality.