Speaker
Description
Speckle-based X-ray imaging (SBXI) [1, 2] is a technique that utilises random speckle modulations imprinted into an X-ray wavefront to retrieve multimodal sample information. Here, the term “multimodal” is used in the sense that SBXI can recover information regarding a sample’s X-ray attenuation, refraction, and diffusion information – three complementary signals. Requiring only a piece of sandpaper in the experimental set-up as a mask, SBXI is an appealing technique for use in a broad range of applications. Furthermore, the signal-retrieving algorithm we have developed—Multimodal Intrinsic Speckle-Tracking (MIST) [3]—makes SXBI even more appealing as it is computationally rapid yet still capable of retrieving high-quality images of the sample. Transverse speckle shifts and speckle blurring are associated with the recovered phase-shift and diffuse dark-field (DDF) signals, respectively. MIST analyses these speckle changes by considering local energy conservation for each speckle in the SBXI regime, wherein, the Fokker-Planck equation for paraxial X-ray imaging [4, 5] is combined with the geometric flow formalism for SBXI [6]. There are various iterations of the MIST algorithm [3, 7, 8, 9], with each increasing in generality by reducing the number of sample requirements. In all the published MIST approaches, the multimodal inverse problem is solved by linearising the associated Fokker-Planck equation and deriving analytical or least-square solutions for the multimodal signals. Within this presentation, a general overview of the currently published MIST approaches will be provided. This will cover the mathematical techniques utilised in solving the Fokker-Planck inverse problem, as well as the underlying assumptions. Retrieved signals from various samples imaged using a synchrotron SBXI technique will be shown. The closing section of the presentation will discuss ongoing research avenues.
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[2] Morgan, K.S. et al. Appl. Phys. Lett. 100(12), 124102 (2012)
[3] Pavlov, K.M. et al. J. Opt. 22(12), 125604 (2020)
[4] Paganin, D.M and Morgan, K.S. Sci. Rep. 9(1), 17537 (2019)
[5] Morgan, K.S. and Paganin, D.M. Sci. Rep. 9(1), 17465 (2019)
[6] Paganin, D.M. et al. Phys. Rev. A, 98(5), 053813 (2018)
[7] Alloo, S.J. et al. J. Med. Imaging 9(3), 031502 (2022)
[8] Pavlov, K.M. et al. Phys. Rev. A, 104(5), 053505 (2021)
[9] Alloo, S.J. et al. Sci. Rep. 13(1), 5424 (2023)
