The open-source X-ray imaging simulatorXRaySim is a free, open-source simulation package for use in Industrial Non-Destructive testing and medical imaging applications. It is currently available for Microsoft Windows, and (technically) for Linux. Pre-compiled binaries are distributed for Windows only, though the code is platform-independent and should compile on most Linux distributions. Learn more about XRaySim or check out the documentation to understand what it can do and gauge its capabilities.
XRaySim is being actively developed and maintained by Koushik Viswanathan It includes several custom modules,including a GPU accelerated simulation and complete image reconstruction framework.
The latest release of XRaySim is v 0.7. Due to its beta status, the package is not completely stable yet (though it is being used extensively right now). All of the code is written using C++ only, while the material system uses a customized script interface (using the Boost.Spirit parser framework). Older releases are also available on the Sourceforge project page. These are predominantly alpha releases and are are deprecated. The current release also adds significant functionality. Check the features page for more information.
The links page contains more information about X-rays, radiography, tomography and imaging systems in general. These should serve to provide a good overview to the technology behind X-ray imaging and the motivation for simulations. If you are new to Non-Destructive testing and evaluation in general, you might want to check out some introductory slides on the Documentation page.