Which of the following has more anti-thyroid action

Radioactive Iodine (I131) Therapy I131 is an effective agent for delivering high radiation doses to thyroid tissue It emits mainly beta radiation (90%), which penetrates only 0.5mm of the tissues & allow therapeutic effects on thyroid without any damage to the surrounding structures, paicularly parathyroid Mechanism of action I131 emits beta paicles and g-rays Beta rays are utilized for their destructive effects on thyroid cells X-rays are useful for tracer studies Indications in carcinoma thyroid Contraindications of I131 Therapy Distant metastasis at diagnosis Incomplete tumor resection Patients at high risk for Moality or recurrence Childhood Pregnancy Lactation Ref : schwaz's principle of surgery 10th edition Pgno : 897