Because this is involving the human body you are going to need a whole cabinet full of paperwork, approvals for whatever method you come up with etc. to be able to use it.
I would have thought that if there was a simple way, the medical fraternity would already be using it.
MRI machine cost millions, ultrasonics cost far less, xrays are dangerous, all require certification.
My reccomendation is - if its for a one off just see if you can get into your local hospital and get them to look, if your wanting to design a product then you need to be doing a lot more research than asking on an internet forum.