I didn't think she was speaking of X-ray but radiation treatment of the thyroid, which my niece had a similar occurrence. See below:
http://www.endocrineweb.com/thyroidca.html
About 4-6 weeks after the thyroid has been removed, the patient will undergo radioactive iodine treatment. This is very simple and consists of taking a single pill. The pill will contain the radioactive iodine in the dose that has been calculated for that individual. The patient goes home, avoids contact with other people for a couple of days (so they are not exposed to the radioactive materials), and that's it.