High-intensity focused ultrasound (HIFU) is a noninvasive procedure that involves application of a focused high-energy ultrasound beam for thermal tissue ablation inside the targeted zone, with minimal effect on the surrounding tissue. This method has been applied for treatment of a variety of medical conditions such as uterine fibroids and prostate, breast, pancreatic, and liver tumors. A favorable outcome also has been observed in patients with primary or secondary hyperparathyroidism. HIFU has also been proposed for thyroid nodule ablation . In a human feasibility study, 25 patients were treated 2 weeks before a scheduled thyroidectomy. Pathologic analysis demonstrated targeted tissue destruction of 2%-80% without any damage to neighboring structures. To the investigators knowledge, studies of follow-up after HIFU ablation of Graves' disease have not been published, except for one report where two patients received a combination of microwave ablation and RAI. Thus, the purpose of this prospective study is to assess the short-term efficacy and safety of US-guided HIFU ablation for the treatment of relapsed Graves' disease.