Easy particle propagation (Epp) is a Monte Carlo simulation EGSnrc user code that we have developed for dose
calculation in a voxelized volume, and to generate images of an arbitrary geometry irradiated by a particle source.
The dose calculation aspect is a reimplementation of the function of DOSXYZnrc with new features added and
some restrictions removed. Epp is designed for x-ray application, but can be readily extended to trace other
kinds of particles.
Epp is based on the EGSnrc C++ class library (egspp) which makes modeling particle sources and simulation
geometries simpler than in DOSXYZnrc and other BEAM user codes based on EGSnrc code system. With Epp
geometries can be modeled analytically or voxelized geometries, such as those in DOSXYZnrc, can be used.
Compared to DOSXYZnrc (slightly modified from the official version for saving phase space information of
photons leaving the geometry), Epp is at least two times faster. Photon propagation to the image plane is
integrated into Epp (other particles possible with minor extension to the current code) with an ideal detector
defined. When only the resultant images are needed, there is no need to save the particle data. This results in
significant savings of data storage space, network load, and time for file I/O.
Epp was validated against DOSXYZnrc for imaging and dose calculation by comparing simulation results
with the same input. Epp can be used as a Monte Carlo simulation tool for faster imaging and radiation dose
It has been shown that coherently scattered x-rays can be used to discriminate and identify specific components in a mixture of materials. To assess the feasibility of using coherent x-ray scatter (CXS) to characterize the material components within tissue scaffolds, we studied the CXS properties of the bio-compatible materials of polymers (polypropylene fumarate, polycaprolactone, epoxy, etc.), sugar and salt solutions at different concentration, and
complex materials consisting of more than one polymer. We also investigated the effects of x-ray spectra on the CXS functions of polymers by measuring them with different x-ray source anodes.
It is shown that the synthesized polymers with different portions of base polymers can be characterized with CXS. The polymerization process does not significantly change the CXS characteristics of the measured polymers. When protein is denatured, no substantial change in scatter was detected. Solutions of different concentration
can be characterized and quantified by the CXS features corresponding to the solutes. The difference among CXS of solutions of different concentration makes it possible to image and trace fluids and their concentration changes in tissues or scaffolds. Our results show that CXS of complex specimens can be decomposed with the scatter functions of the component materials. By simulating a tissue scaffold with a phantom with several bio-compatible materials, we demonstrated that significant contrast can be achieved at proper scatter angles by
measuring the coherent x-ray scatter, despite the low attenuation-based contrast between them. We conclude that use of x-ray scatter makes it possible to track and map the fate (e.g., its breakdown and/or removal) of specific components within tissue scaffolds.