A simulation tool for x-ray phase-contrast micro-CT featuring a small-pixel photon-counting detector

Abstract X-ray micro-CT ( µ CT) is an important tool for high-resolution, non-destructive inspection of samples with numerous applications ranging from preclinical imaging to materials science. µ CT imaging capabilities can be expanded through the use of small-pixel ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>&lt;</mml:mo> </mml:mrow> </mml:math> 100 µ m) photon-counting detectors (PCDs) which increase image contrast, reduce image noise, and provide additional insights into material composition through the collected spectral information. Along the same lines, phase-contrast x-ray imaging is increasingly being adopted in laboratory µ CT imaging setups to improve the visualization of low-attenuation contrast samples. Along with these technological improvements comes the need for improved modeling and simulation. However, no laboratory µ CT simulation tool currently exists that includes a small-pixel PCD. PEPIsim addresses this need, providing a simulation resource that produces photon-counting, spectral, and phase-contrast µ CT reconstructions, accurately modelling the response of the small-pixel PCD in addition to incorporating phase-contrast effects. PEPIsim has been benchmarked against experimental images of a custom plastic phantom acquired with a µ CT setup featuring a PCD and a micro-focus x-ray tube. Results show that the simulation reproduces the system spectral response (average NMRSE of 2.7%) across a wide range of tube voltages (45–100 kVp). Moreover, good accuracy in terms of measured x-ray attenuation (average relative error (RE) of 1.5%) and SNR (average RE of 6.5%) has been found. Similarly, after phase-retrieval, the simulated images’ SNR is found to be in agreement with experimental images (average RE of 5.5%). Finally, the simulation can also reproduce the fringe visibility due to the edge-enhancement effect (average RE of 5.2%) across a range of magnifications (from 1.3 to 3.7) and source to detector distances (from 40 to 133 cm). Due to its modular structure, PEPIsim can be adapted to any experimental µ CT imaging setup, provided that accurate detector and x-ray tube models exist.