Comparison DW-MRI vs FDG PET/CT in the Detection of Early Recurrence of Cervical Well-differentiated Thyroid Carcinoma

Inclusion Criteria: * Male or female, * Subjects must be 18 years of age or older, * Histologically confirmed papillary or follicular differentiated thyroid carcinoma with partial response or complete response, defined by * Thyroglobulin \> 2 μg/L under thyrotrophin stimulation, four months after at least two 131-I based treatments (3,7 GBq/100mCi or more if optimal conditions), * Negative extension assessment (total body bone scan, (3,7 GBq/100 mCi or more)), echography, CT scan ( neck, thorax, abdomen): no findings.. * Patient's Informed Consent form signed. Exclusion Criteria: * History of previous cancer within the least three years, * Performance Status \> 2, * Protected adults * Any medical, psychological, social or disabling conditions that could interfere or jeopardize the patient's participation * History of allergy to radio-iodine, * Estimated GFR \< 45 ml/min /m² (MDRD method), * Women of childbearing potential without contraceptive method, * Uncontrolled diabetes mellitus, * Hypersensitivity to FDG or to any radio-tracers, * Contraindication to administration of Thyrogen® 0.9mg * Intraocular foreign bodies or any metallic foreign bodies that contraindicates the MRI. * Vascular clips, any object or implanted device that could interact with the ferromagnetic field, * Coronary and peripheral clips, aortic stent grafts, prosthetic heart valves, annuloplasty rings, vena cava filters, cardiac pacemaker, implantable cardiovascular defibrillators...., * Implanted insulin infuser * Neurostimulator device * Claustrophobia * Agitation or psychological trouble