I'm confused. When I had piriformis syndrome, the treatments were PT, walking & x-ray guided steroid injection. As far as I can see, everywhere I look, that is still the recommendation.
---- https://www.spine-health.com/conditions/sciatica/symptoms-and-diagnosis-piriformis-syndrome

In over 5 years of struggling, none of these therapies was successful for more than a few weeks for me because the underlying cause was a hip badly deteriorated by severe osteoarthritis. At 54, the surgeon said I had the hips of an 85 year old. The problem was that the unstable hip was causing the piriformis to repeatedly press on the sciatic nerve. The solution was hip replacement, and 17 years later I have not had a recurrence of the piriformis issue.

I think you mentioned in another discussion that your ortho diagnosed osteoarthritis in your hip, and suggests it is the cause of your pain. The doctor should be able to show you the x-rays that show the damage, and compare them to a normal joint.

What exactly makes you question the arthritis diagnosis? Where did you learn about a specific MRI to diagnose piriformis syndrome?

I understand reluctance to undergo unnecessary surgery, but if you have exhausted the "usual" treatments without success, maybe it is time to consider the joint replacement. Has this been recommended by more than one of the orthopedists you saw?
Sue