The first 131I focal clearance treatment should be performed at least 3 months after 131I nail clearance. The 131I dose for a single focal clearance treatment is controversial. The empirical dose is 3.7-7.4 GBq (100-200 mCi). There are two other methods of determining the treatment dose: calculation of the dose based on the upper limit of radiation tolerance of the blood and the whole body, and calculation of the dose based on the amount of radiation required for the tumor lesion [83]. There are no prospective studies on which of these three methods is the best. The management of the perifocal treatment period is essentially the same as for nail clearing treatment.131 Rx-WBS is performed 2-10 days after focal clearing treatment to predict the treatment effect and the need for subsequent focal clearing treatment. After 6 months of focal clearance treatment, efficacy assessment can be performed. If the treatment is effective (sustained decrease in serum Tg and reduction of metastases on imaging), focal clearance treatment can be repeated with an interval of 4-8 months between focal clearance treatments. If serum Tg continues to rise after focal clearance treatment, or if imaging shows an increase in metastases, or if 18F-FDG PET reveals additional hypermetabolic lesions, this suggests that the treatment has no significant effect and termination of 131I treatment should be considered.