Iodine 131 therapy, or internal radiation therapy with the isotope iodine 131. After being absorbed by the thyroid gland through oral iodine 131, it can release gamma and beta rays in the body, which in turn kill the diseased cells of the thyroid gland. Clinically, iodine 131 therapy is usually used as a treatment option for hyperthyroidism where conservative treatment with internal medicine has failed, and for certain patients who need further treatment after surgery for differentiated thyroid cancer, such as papillary thyroid cancer with relatively large tumors, or lymph node metastasis or elemental metastasis. After performing iodine 131 treatment, a better therapeutic effect can be obtained.