There have been previous reports of using High-intensity focused ultrasound (HIFU) as a feasible thermal ablative treatment for relapsed Graves' disease. In recent years, radiofrequency ablation (RFA) has become another promising alternative for thermal ablation of benign thyroid nodules. RFA has the advantage of avoiding a surgical scar, organ preservation and being an ambulatory procedure. It utilizes a small caliber radiofrequency electrode, which is inserted into the thyroid gland percutaneously. The active tip of the RF electrode would induce frictional heat in the surrounding tissue, causing a thermal ablative effect. The direct application of energy of RFA to tissue is different from that in HIFU, in which energy is transmitted through the skin of the participants from the transducer.

Studies of follow-up after RFA of Graves' disease have not been published. Given the previous successful experience with HIFU, the investigators would like to explore the feasibility, safety and efficacy of RFA as an alternative thermal ablation option for relapsed Graves' disease. Thus, the purpose of this prospective study is to assess the efficacy and safety of US-guided RFA for the treatment of relapsed Graves' disease.

Inclusion Criteria:

• (a) age older than 18 years,
• (b) relapsed Graves' disease despite an adequate ATD treatment for 18 months or more and
• (c) absence of vocal cord immobility.

Exclusion Criteria:

• (a) patients who prefer or indicated for surgery,
• (b) head and/or neck disease preventing hyperextension of the neck,
• (c) history of thyroid cancer or other malignant tumors in the neck region,
• (d) history of neck irradiation,
• (e) moderate to severe Graves' ophthalmopatty,
• (f) large compressive goiter
• (g) pregnancy or lactation, and
• (h) any contraindication related to intravenous moderate sedation.