Am no expert, but ionizing radiation as a cause of AN's is considered in cases when large doses were received earlier in life as a form of treatment.
Roger Ebert, the film critic from Chicago, received large doses of X-rays as a child for chronic ear infections, and as a result may have developed cancer of the salivary glands which spread and caused the loss of his jaw and other problems before he recently died.
Others have received radiation to the face and head in the 1960's and 1970's for severe acne and chronic sinus inflammation which has caused a higher incidence of thyroid cancer.
The risk seems not from regular, occasional low dose exposure to x-rays, but from reaching some threshold of accumulated higher doses.
Since this is true in cases of cancer, it is suggested the same may be true in benign tumors like AN's. Just my opinion.