unmarked vans inside which poorly trained "agents" with GEDs fiddle with the controls of secret portable xray scanners.
I've no idea what a GED is, nor why you would fiddle with one. "GE Deathrays"?
You really haven't thought this through, have you? Electromagnetic radiation travels in straight lines (unless you've got a magnetic, electric, or gravitational field so strong that it would rip the iron atoms out of your haemoglobin), so your putative "secret portable X-ray scanner would need to take the form of a doorway, with source on one side and a detector on the other side. Yes, you could disguise such as, say, a doorway ; or hide it in a structure which poses as scaffolding that is part of building work. But that rather mitigates against the description of "secret" and "portable".
Back-scatter X-ray ... well, it's not impossible (I've done a little cathodoluminiscence work, which goes a fair way down into the UV) ; I can see that X-rays might backscatter sufficiently to provide useful surface composition data. But you'd need horribly high dose rates, and therefore a lot of batteries to power the thing (again, making it less than "portable", or "secret"). You'd do far better using millimetre to micrometre wavelength radio waves, which do scatter from organic materials quite well. But they don't significantly penetrate skin, so they're not X-rays in either a strict or a lax meaning of the term.