X-rays are usually only needed in forensic genealogy or archaeology.

I am not aware of any standard genealogical use for X-rays.

Forensic genealogy is usually the process of finding living relatives for an inheritance. It could also play into police cases, usually missing persons, or murder victims, in an effort to locate next of kin.

The only other topic I could think of was eXamine your data and sources, but I have covered those topics adequately elsewhere.