ultrasonography vs imaging

ultrasonography and imaging both are nouns.

Word	Noun	Adjective	Verb	Adverb
ultrasonography	Yes	No	No	No
imaging	Yes	No	No	No

As nouns, imaging is a hypernym of ultrasonography; that is, imaging is a word with a broader meaning than ultrasonography:

ultrasonography: using the reflections of high-frequency sound waves to construct an image of a body organ (a sonogram); commonly used to observe fetal growth or study bodily organs
imaging: (medicine) obtaining pictures of the interior of the body

Other hypernyms of ultrasonography include prenatal diagnosis, tomography.

ultrasonography (noun)	imaging (noun)
using the reflections of high-frequency sound waves to construct an image of a body organ (a sonogram); commonly used to observe fetal growth or study bodily organs	(medicine) obtaining pictures of the interior of the body
	the ability to form mental images of things or events