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An experimental approach to optimising refraction sensitivity for lab-based edge illumination phase contrast set-ups

Kallon, GK; Vittoria, FA; Buchanan, I; Endrizzi, M; Olivo, A; (2020) An experimental approach to optimising refraction sensitivity for lab-based edge illumination phase contrast set-ups. Journal of Physics D: Applied Physics , 53 (19) , Article 195404. 10.1088/1361-6463/ab747c. Green open access

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Abstract

Refraction sensitivity can be optimised for differential x-ray phase contrast (XPC) imaging methods by modifying the set-up. Often, modifications involve changing source/detector parameters, propagation distances, or the design of optical components, i.e. parameters that are not readily changed without non-trivial time investment, replacing components, or performing high-precision recalibrations. The edge illumination (EI) XPC method provides a method of optimising the refraction sensitivity, by exploiting micrometric translations of its periodic masks, that bypasses the constraints listed above. These translations can be performed on-the-fly and allow optimising the refraction signal for specific applications without making significant changes to the set-up. The method can prove advantageous for lab-based systems that make use of larger sources but with limited available set-up space. In this paper, we study how refraction sensitivity varies as a function of illuminated pixel fraction (IPF) under two commonly encountered experimental conditions: (1) at approximately constant detected counts, and (2) at equal exposure time. We compare the standard deviation in the background of reconstructed refraction images at different IPFs and find that refraction sensitivity is optimal at 25% IPF under both conditions. Finally, we demonstrate that refraction sensitivity affects the visibility of weakly refracting features on an insect leg. The results suggest that IPFs lower than 50% can actually be preferable, especially in the case where the statistics is kept constant, and provide experimental validation that phase sensitivity in EI is not fixed once the system parameters are defined.

Type: Article
Title: An experimental approach to optimising refraction sensitivity for lab-based edge illumination phase contrast set-ups
Open access status: An open access version is available from UCL Discovery
DOI: 10.1088/1361-6463/ab747c
Publisher version: https://doi.org/10.1088/1361-6463/ab747c
Language: English
Additional information: Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/10090852
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