<s>[INST] context: Iodine scintigraphy with I 123 and I 131 is used to evaluate the functional status of the gland. Advantages of scanning with I 123 include a low dose of radiation and sho half-life. I 123 is a good choice for evaluating suspected lingual thyroids or substernal goiters. I 131 has a longer half-life and emits higher levels of b-radiation. I 131 is optimal for imaging thyroid carcinoma and is the screening modality of choice for the evaluation of distant metastasis. RAI (I 131 ) has several paicular purposes in the treatment of DTC after thyroidectomy, including Ablation of remnant thyroid tissue to facilitate detection of later disease recurrence by imaging and Tg assay, Adjuvant therapy with the intention of targeting occult metastatic disease, and Primary treatment of known persistent disease Technetium 99m peechnetate (99mTc) is taken up rapidly by the normal activity of follicular cells. 99mTc has a sho half-life and low radiation dose. Its rapid absorption allows quick evaluation of increased uptake ("hot") or hypofunctioning ("cold") areas of the thyroid . Malignancy is present in 15% to 20% of cold nodules and in less than 5% of hot nodules. [/INST] question: Which of the following is used in the treatment of well differentiated thyroid carcinoma | options: A: I131 B: 99m Tc C: 32p D: MIBG | answer: A </s>