Yup, doctors specialize. When a GP gets orders a scan, such as a CT or x-rays, it's typically another doctor that specializes in the imaging area who examines it and writes a report. I don't think many GPs would have much of a use for an ultrasound because they would prefer a specialist perform it.

A few caveats. One, telepresence. You can have the specialist basically be there with you as you operate the probe. Everything gets done in office and the patient doesn't have to travel which can be a big deal in rural communities. I find most urban GPs don't even have a second thought about sending patients off for a scan at some other office.

Following that would be very remote doctors, those that might be labeled as a GP, but basically have to have a ton of specialist knowledge because of the wide range of things they might need to do.

And of course vets, especially large animal vets. Who are already using cool devices such as head mounted displays to view the ultrasound as they generally have their arm all the all the way up an animals rear end.