I had a head computer assisted tomography scan and want to know if radiation used?

Yes. It is true that ionizing radiation (x-rays) are used but the dose for a single ct of the head is low and should not have any effects.
CT scan. Ct scans use x-rays to obtain an image. Mri scans use magnetism & radio waves to get an image. Modern ct scanners should minimize radiation exposure by operating at faster speeds than older ones but some facilities' protocols result in higher exposure. Avg head ct is 2-10 millisieverts (msv) which is equivalent to one's yearly exposure from background radiation.