Kim & Toby: even in the human world of medicine, diagnostic films belong to
the instition that took them.  Most will give you copies of them, however.
Your vets office might not own the equipment necessary to make copies so
they might not be able to offer that option to you.
 
If I were you, I'd ask for a copy of all his medical records to take to a
new vet anyway.  Just make sure there is a copy of the report (or some
written description of the doctor's actual reading of the x-ray) in the
file!
 
A picture is worth a thousand words - but in the absence of film, the
words may be enough to do the trick!
 
Hope this helps!
[Posted in FML issue 1490]