Cushing's disease is characterized by the existence of a benign pituitary tumor developed from corticotropic cells responsible for excessive ACTH secretion. This results in hypercorticism causing high morbidity and mortality and severely impairing quality of life. The etiological diagnosis is based on Magnetic Resonance Imaging (MRI). However, pituitary MRI revealed a pituitary tumor in only 60% of patients. The diagnostic procedure is complicated by the existence of extra pituitary tumors responsible for ACTH ectopic secretion. This rare etiology imposes, in the absence of typical pituitary image, the realization of catheterization of the lower petrosal sinuses. Treatment of Cushing's disease is based on transsphenoidal surgical management, even in the absence of a formal MRI image, if pituitary origin is confirmed by the catheterization. Although pituitary surgery without identified target is part of French recommendations, this surgery is associated with a high risk of failure and morbidity. Optimization of the management of patients' with Cushing's disease thus requires the improvement of the diagnostic methods.

Hypothesis of our study is that [11C] MET MRI-PET may be performed as a first-line MRI for suspected Cushing's disease and may limit indications for catheterization of lower petrosal sinuses. Its localizing value should also make it possible to improve the surgical results with a better identification of the adenoma

Inclusion Criteria:

• Aged 18 years old or over
• Patient with a diagnosed Cushing's disease according to the French "protocole national de diagnostic et de soins (PNDS)"
• Patient who underwent a MRI pituitary for diagnostic purposes
• Patient who have undergone catheterization of the lower petrosal sinuses (if MRI does not detect pituitary adenoma) and have a result in favor of a central secretion of ACTH
• Patient having an indication of surgical excision of the adenoma
• Patient with a micro-adenoma (less than 1 cm in diameter) if the tumor is visualized on MRI
• Patient for which informed and written consent to participate has been obtained.

Exclusion Criteria:

• - Patient participating in another study
• Patient with a pituitary macro-adenoma with visual impairment
• Patient with ACTH-dependent Cushing's syndrome secondary to ectopic ACTH secretion
• Patient with recurrence and / or history of pituitary adenoma excision
• Patient with a contraindication to pituitary surgery or general anesthesia
• Pregnant woman, breastfeeding or old enough to have children but without effective recognized contraception
• Contra-indication to the realization of an MRI: permanently fixed metal parts (pacemaker, cerebral clip, cephalic end piercing, cochlear implant, pin or screw for recent bone fracture, dental equipment, metal splinters), claustrophobia