HIFU Reapplication in Benign Nodules

Inclusion Criteria: * patients age older than 18 years, * a nodule that has previously been completely treated by single-session HIFU ablation but has not responded adequately (i.e. \<50% volume reduction from baseline after 6 months), * a benign nodule without signs of malignancy (e.g, nonsuspicious clinical and US appearance, benign results at cytologic examination performed in the last 6 months, normal serum calcitonin level), * a nodule measuring on US greater than or equal to 10 mm in three orthogonal dimensions, * less than 30% of the targeted nodule comprising cystic area, * HIFU accessibility of the targeted nodule (distance between the skin and the anterior surface of the nodule less than 17 mm, with no interference of the collarbone with HIFU unit movements) * normal thyrotropin concentration and * absence of vocal cord immobility at laryngoscopy. Exclusion Criteria: * head and/or neck disease preventing hyperextension of the neck, * history of thyroid cancer or other malignant tumors in the neck region, * history of neck irradiation, * intranodular macrocalcifications inducing a shadow substantial enough to preclude treatment with HIFU, * nodules next to the posterior margin of the thyroid lobe with anteroposterior diameter less than 15 mm, * pregnancy or lactation, * any contraindication related to intravenous moderate sedation in the first HIFU treatment.