@debra54 A PET scan, CT scan, or MRI- any of these can show the interior of the uterus. Which scan a physician orders would depend on what they want to see and what they are looking for. I'm going to tag @val64 as she is very good at providing scientific explanations.

I do know that some insurance companies (BC/BS, for instance) refuse to pay for a PET scan (more expensive and involved) until a CT has been done. This has happened to a few people I know. The reason is that the insurance company wants to pay for the less expensive scan that might show what the physician is looking for and then order a PET scan because of what the CT did or did not show.

--Positron Emission Tomography (PET) Scan
https://www.mayoclinic.org/tests-procedures/pet-scan/about/pac-20385078
Does this help?