Phase contrast simulator on VIP

Phase contrast imaging
During the past twenty years, there has been a growing interest in X-ray phase contrast imaging (PCI). In PCI, the
transmission of coherent X-rays properties through matter can be described in terms of the complex refractive
index n. The real (1-δ) and imaginary (β) parts of n are respectively related to the phase-shift and the absorption.
Unlike conventional absorption-based imaging, which is only sensitive to the attenuation of the incoming X-ray
beam, PCI also relies on the phase shift of X-rays occurring when they pass through a medium. This modality
offers a better sensitivity than conventional radiology, since for hard X-rays (10-100 keV) and low-Z materials
(such as soft tissues), refraction is at least two or three orders of magnitude higher than absorption at typical
imaging energies 1.

Monte Carlo simulation
In medical physics, Monte-Carlo simulations have been widely used to model the transport of particles (photons,
electrons) in matter. The type of the interaction (Compton, Photoelectric, Rayleigh) is stochastic, conditioning
the interactions of the particle with matter. Given the model of the considered media and the source of the
particle beam, we can determine the evolution of every particle (energy, direction) after each interaction using a
Monte Carlo simulation. This simulation modality has been considered as a powerful and accurate tool, to
calculate, for example, the energy deposit in every position of a medium (radiation therapy planning treatment)
or the amount of scattered radiation (radiology, CT). Moreover, it can handle complex geometries such as the
anatomy of a patient.

Monte Carlo simulator for phase contrast
Recently, a few Monte Carlo simulators have been developed for particular PCI set-ups 2,3. The purpose of this
project is to develop a MC code to model propagation-based phase contrast tomography. A MC simulation of the
stochastic process for attenuation imaging will be combined with an analytical model for phase shift. This
solution will be implemented on VIP (Virtual Imaging Platform) developed at Créatis (Villeurbanne, France)4.

Candidate profile
The candidate should have a solid background in programming with experience in C++, i.e. be enrolled in a
computer engineering, electrical engineering, computer science, engineering physics or similar program, and a
strong interest in medical and biomedical imaging, image analysis, simulation, microscopy or related fields.
1.
2.
3.
4.
Momose, A., Takeda, T., Itai, Y. & Hirano, K. Phase–contrast X–ray computed tomography for observing
biological soft tissues. Nat. Med.2, 473–475 (1996).
Wang, Z., Huang, Z., Zhang, L., Chen, Z. & Kang, K. Implement X-ray refraction effect in Geant4 for phase
contrast imaging. in 2009 IEEE Nucl. Sci. Symp. Conf. Rec. 2395–2398 (IEEE, 2009).
Khromova, A. N. et al. Monte Carlo Simulation of X-ray Multiple Refractive Scattering from Fine Structure
Objects imaged with the DEI Technique. in IEEE Symp. Conf. Rec. Nucl. Sci. 2004.6, 4014–4018 (IEEE, 2010).
Glatard, T. et al. A virtual imaging platform for multi-modality medical imaging simulation. IEEE (2012).