In treatment of papillary carcinoma thyroid, radioiodine destroys the neoplastic cells predominantly by

RADIOACTIVE IODINE (I131) THERAPY: I131 is an effective agent for delivering high radiation doses to the thyroid tissue It emits mainly beta radiation (90%), which penetrates only 0.5 mm of the tissue and thus allow therapeutic effects on the thyroid without any damage to the surrounding structures, particularly the parathyroids. Mechanism of Action: I131 emits beta particles and X-rays. Beta rays are utilized for their destructive effects on thyroid cells. X-rays are useful for tracer studies.