What is Rai? Write a paragraph of at least 5 sentences.

Radioactive iodine (RAI) is treatment for overactive thyroid (hyperthyroidism) and certain types of thyroid cancer. The term “radioactive” may sound frightening, but it is a safe, generally well-tolerated, and reliable treatment that targets thyroid cells so there is little exposure to the rest of your body's cells. Some people may have a feeling of tightness or swelling in their neck for a few days after treatment. This is more common if you still had a large part of your thyroid gland when you have radioactive iodine treatment. Some people also feel flushed.