There is a nifty online tool that I use from time to time: NIST XCOM Photon Cross Sections Database. You can plug in any mixture or compound and a range of incident photon energies, and it will give you a plot and text-based spreadsheet of the photon attenuation, optionally broken down by physical process. Folks interested in this thread might be interested in playing with this tool.
Here is an example graph for water covering energies from 1 keV to 10 MeV. You can see that as you move through the energies, the physical processes that dominate vary. For medical imaging x-rays, Compton scattering (labeled “incoherent scattering” in the graph) and photoelectric absorption are the dominant processes.
For kicks, here’s calcium, showing one of its K edges.
