imaging vs X-radiation

imaging and X-radiation both are nouns.

Word	Noun	Adjective	Verb	Adverb
imaging	Yes	No	No	No
X-radiation	Yes	No	No	No

As nouns, X-radiation is a hyponym of imaging; that is, X-radiation is a word with a more specific, narrower meaning than imaging:

imaging (noun)	X-radiation (noun)
(medicine) obtaining pictures of the interior of the body	obtaining images by the use of X rays
the ability to form mental images of things or events	electromagnetic radiation of short wavelength produced when high-speed electrons strike a solid target