*7.2.2 Dosing considerations*

The activity to be administered as fixed doses of about 15 mCi or calculated using the Quimby-Marinelli formula, or the modified version based on the 24-hour uptake values on RAIU scan. Estimation of total gland size can be done by physical examination or by ultrasound dimensions of the gland, and is particularly challenging in pediatric patients. In general, the total dose of I-131 should be atleast 150 μCi/g of thyroid tissue, resulting in hypothyroidism in >95% of cases. Increased doses of 200–300 μCi/g may be required in patients with large goitres and lower radioiodine uptake. There are no studies available to compare the two methods in children.

Radioiodine is retained in the thyroid for several days, and is also excreted in body fluids like saliva, tears, sweat, stool and urine. Appropriate local radiation safety precautions have to be observed by the patient and family members after RAI treatment [18, 22, 31, 36].
