Monte Carlo simulation of scattering in X-ray phase contrast imaging
Recrutement en cours/passé: 
Recrutement en cours
Max Langer : Jean Michel Letang : Simon Rit :

X-ray phase contrast imaging permits to reach nanometric resolution in tomographic imaging with several orders of magnitude higher sensitivity than using the attenuation. The main drawback is that it needs an additional reconstruction step, known as phase retrieval, to yield quantitative images. A common problem with phase retrieval is the presence of low frequency noise in the reconstructions. The sensitivity to noise in the low spatial frequency range is due to low transfer of contrast by the imaging system. The origin of the noise is not known, however. One hypothesis is that it originates from the scattering by the imaged object. Therefore, the aim of this project is to combine simulation of phase contrast with simulation of scattering. Phase contrast is usually modelled from a wave perspective using the Fourier transform, while scattering is usually modelled from a particle perspective using e.g. Monte Carlo simulation. The main challenge of this project is therefore to combine the two perspectives. In a previous Master project, we developed tools to simulate refraction using MC simulation in Geant4 [1] as well as an analytical phase contrast simulator in GATE [2] and VIP [3]. These tools will be combined to study the possibilities of combining the two signals, either by directly summing the two, or first calculating the exit wave-field and phase contrast analytically and calculating the MC probability for position and momentum of the corresponding particles by sampling the Wigner transform of the wave-field. These images will then be used to reconstruct the phase to compare the resulting artifacts with experimental data acquired at the ESRF.

[1] S. Agostinelli et al., Nuclear Instruments and Methods A 506 (2003) 250-303

[2] G Santin et al. IEEE Trans. Nucl. Sci. 50 (2003) 1516-1521

[3] T. Glatard et al., IEEE Transactions on Medical Imaging, 32 (2013) 10-118.