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.
Highlights
X-ray phase contrast imaging has gained increasing attention over the last decades
Since X-ray phase is not directly measurable, several techniques have been developed for phase contrast, for example propagation-based imaging, analyzer-based imaging [2], Talbot interferometry [3], active pixel sensors [4] and speckle-based imaging [5]
Several wave-propagation mathematical models have been developed, in particular for phase retrieval imaging [8,9,10], but most methods are based on a linearization of the problem
Summary
X-ray phase contrast imaging has gained increasing attention over the last decades. Since X-ray phase is not directly measurable, several techniques have been developed for phase contrast, for example propagation-based imaging (or in-line holography [1]), analyzer-based imaging [2], Talbot interferometry [3], active pixel sensors [4] and speckle-based imaging [5]. Several wave-propagation mathematical models have been developed, in particular for phase retrieval imaging [8,9,10], but most methods are based on a linearization of the problem. The differences in their derivations come from the various assumptions that are made to derive the filter expression. Simpler approximations have been proposed when the detected diffraction has a Laplacian signature, i.e. for small propagation distances or for large detector point spread functions with respect to the diffraction patterns, using analytical approaches based on geometrical optics [13] or simplification of the transport of intensity equation [14,15]. The Wigner distribution formalism has been proposed to model phase effects more accurately in order to take into account the changes in spatial coherence and wave-front curvature of X-rays during the radiation propagation [17,18,19,20]
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