Towards Monte Carlo simulation of X-ray phase contrast using GATE

Abstract

We describe the first developments towards a Monte Carlo X-ray phase contrast imaging simulator for the medical imaging and radiotherapy simulation software GATE. Phase contrast imaging is an imaging modality taking advantage of the phase shift of X-rays. This modality produces images with a higher sensitivity than conventional, attenuation based imaging. As the first developments towards Monte Carlo phase contrast simulation, we implemented a Monte Carlo process for the refraction and total reflection of X-rays, as well as an analytical wave optics approach for generating Fresnel diffraction patterns. The implementation is validated against data acquired using a laboratory X-ray tomography system. The overall agreement between the simulations and the data is encouraging, which motivates further development of Monte Carlo based simulation of X-ray phase contrast imaging. These developments have been released in GATE version 8.2.

Characterization of internal fatigue cracks in aluminum alloys by simulation of phase contrast tomography

“…A method 20 developed by Langer et al was used to simulate phase contrast tomography. The first step consists in using a ray casting procedure in the voxellized object, from which the integral of the refractive index after passing through the object can be obtained.…”

“…refraction and scattering) have been implemented in Gate 18 and in Geant-4 19 . In this work, we focused on phase contrast (Fresnel diffraction), therefore, a method proposed by Langer et al 20 using a ray casting procedure to obtain integral of the refractive index, as well as an analytical wave optics approach for generating Fresnel diffraction patterns is used to simulate phase contrast tomography. The implementation is in the GATE software (version 8.2 and later).…”

Evaluation of simulators for x-ray speckle-based phase contrast imaging

“…Refractive indices are calculated using Xraylib (Schoonjans et al, 2011), integrated in GATE for this purpose (Langer et al, 2020). X-ray particles propagation is step-bystep in the usual Monte Carlo way.…”

“…Contrary to the wave optics approach, Monte Carlo simulation is based on particle tracking and can correctly simulate attenuation, refraction, and scattering (Bottigli et al, 2004;Peter et al, 2014;Langer et al, 2020). Some methods to include phase contrast and coherent effects in Monte Carlo simulations have been proposed.…”

Computational simulations and assessment of two approaches for x-ray phase contrast imaging

“…There is a limited number of computational studies in the field of phase-contrast grating imaging reported in the literature [19][20][21][22][23][24]. All these studies are based on the use of simple objects, such as spheres and cylinders, and aim at proof of concept and optimisation of dose and imaging parameters.…”