I found this, it may or may not be related. The gist is relatively recent research (2011) discussing using x-ray refraction rather than just attenuation and is

I found this, it may or may not be related. The gist is relatively recent research (2011) discussing using x-ray refraction rather than just attenuation and is capable of "creating precise images of the contours of all objects". A New Generation of X-ray Baggage Scanners Based on a Different Physical Principle www.mdpi.com/1996-1944/4/10/1846/pdf