It sounds like your physio is doing everything right and that you should trust her.
You can have a Wikipedia reference-linkMRI - but it'll really be for your piece of mind. I don't truely believe you need it... MRI's are most commonly used by surgeons to assess whether surgery is required. In your case you appear to have enough evidence to be confident with continuing down a conservative treatment pathway for now with a good physio guiding you (which I believe you have).
Good luck