I don't think it should be an accredited doctor. As you can only get them from hospitals.
I reckon that the more recent the x-ray is, the better...
At Immigration they don't usually check them, but from time to time someone will be asked to show it, and in the absence of one, the x-ray will be done at the airport, adding to more wasted time and stress for the traveller.
After such a long trip, being asked to wait God knows how long can be quite harrowing and stressful.![]()