Hi Cheryl,
In my case when I switched from the ENT to the ENT Oncologist after radiation (and 1 follow-up visit to the ENT) the oncologist was surprised I had not had a baseline CT done after radiation. He sent me for one.
I don't know how frequently he would have done scans since I've been sidetracked and haven't been back to him.
Sorry that's all I can contribute is my expereiene. There was an old post about follow-ups and what most people were doing but I can't seem to locate it.
Take care,
Dinah