Ditto what Robert stated. The use of X-rays in the US is regulated strictly under the US Nuclear Regulatory Commission and In Canada with the Atomic Energy Commission. I am certain there are similar rules and regulations in Europe. These rules and regulations cover the use and registration of equipment that contain nuclear isotopes for the production of x-rays. I'm pretty sure the language in the regs state that use is for medical and scientific purposes only. It covers the sale of this equipment as well, so I highly doubt you can just buy a used one from a hospital or dentist through above board channels (ie you need a lisence). This doesn't mean that you could not get an one time exemption lisence with conditions attached, but the paperwork filing would probably drown you in beaurocracy. I would caution you against this. X-ray over exposure can lead to some serious cancers.
Then again, there's always e-bay...you never know!