Our experience was just the opposite. The radiation oncologist was the one that ordered the scans, not the ENT. My husband had his first post treatment CT scan 3 months after treatment ended.
Can you call the radiation oncologist and ask him when he will want to do the first scan? Our RO was great about answering any questions. I had his email address and I would send him questions and he would respond with very detailed replies.
Congratulations on beign almost through with the radiation - that is a great milestone.
Anita