The main objective of the study is to show that the addition of ultrasonography to the dual tracer scintigraphy MIBI-Tc99m/Iodine-123 will increase (at least +5%) the negative predictive value compared to the dual tracer scintigraphy alone in detection of malignancy in thyroid nodules ≥15 mm classified as Bethesda III-IV on cytology.

Inclusion Criteria:

• Any patient over 18 years with a thyroid nodule ≥15 mm (maximal diameter measured on US) with a Bethesda class III or IV (FNA less than 6 months before the surgery).
• Given signed, written informed consent
• Affiliation to a social security system.
• Neither-pregnant nor breast-feeding women.
• Use of efficient contraception for patient with pregnancy potential (if needed).

Exclusion Criteria:

• Underage and adults under guardianship.
• Pregnant, without efficient contraception (if needed) or breast feeding women.
• Administration of iodinated contrast in the previous 3 weeks.
• Contraindication to scintigraphy or to Iodine123/ MIBI 99Tc administration
• Treatment containing iodine (i.e. : Amiodarone)
• Hypo or hyperthyroidism treated or not.
• Nodules inferior 15 mm.
• Refusal to sign the consent.
• Refusal of surgical treatment or contraindication for surgery or anesthesia
• Morbid obesity (BMI Superior 40 kg/m2).
• Hyperparathyroidism.
• History of cervicotomy.