Conventional x-ray machines, as invasive as they are, can leave a lot to be desired when it comes to telling what, exactly, is going on in there. For example, a block of chocolate is indistinguishable from some kinds of explosives on a conventional airplane conveyor belt X-Ray system.
It's for this reason (and to clear up images in the medical field, of course) that a group of Swiss scientists developed High Contrast x-rays using dark-field technology, an imaging technique that has conventionally been used in microscopes. The resulting images have higher contrast and can distinguish things like tiny cracks in bones by measuring how different surfaces scatter light. The system sounds fairly expensive— the new x-ray filter is made from silicon and gold— but it's worth it if it will keep me from getting stopped at security every time I come back from Europe with bags full of cheese and chocolate.