Coherent x-ray scatter projection imaging using an array of monoenergetic pencil beams

Abstract

Traditional projection x-ray imaging utilizes only the information from the primary photons. Low-angle coherent scatter images can be made simultaneous to the primary images and provide additional information. To speed up acquisition time for coherent scatter projection imaging, we developed disentangling algorithms for the overlapping scatter patterns generated by multi pencil-beam geometries. A system at the Canadian Light Source synchrotron was configured which utilizes a custom collimator designed to convert a 33.17 keV monoenergetic fan beam from a Laue monochromator into multiple pencil beams by using 3 mm thick tungsten alloy stoppers. The pencil beams then travel through the sample and are absorbed by a tungsten bar. A digital flat panel detector records the superimposed scatter patterns from the beams. The sample is scanned through the beams using an automated step-and-shoot setup. The pixel value of the coherent scatter image is generated by integrating the radial profile (scatter intensity versus scattering angle) over an angular range. An MLEM-based iterative method and a least-squares method were developed to disentangle the scatter patterns. Although past work has primarily been applied to medicine, other applications include non-destructive testing and security.