title: Imaging of adrenal incidentalomas with PET using (11)C-metomidate and (18)F-FDG.
abstract: Our aim was to evaluate the use of PET with (11)C-metomidate and (18)F-FDG for the diagnosis of adrenal incidentalomas.
  
  
  METHODS
  Twenty-one patients underwent hormonal screening before dynamic imaging of the upper abdomen with (11)C-metomidate, and for 19 of these 21 patients, static (18)F-FDG imaging followed. Uptake of (11)C-metomidate and (18)F-FDG in incidentalomas was quantified and correlated with the hormonal work-up and the mass size on CT (median, 2.5 cm; range, 2-10 cm).
  
  
  RESULTS
  The final diagnoses were hormonally active adenoma (n = 7), nonsecretory adenoma (n = 5), adrenocortical carcinoma (n = 1), pheochromocytoma (n = 2), benign noncortical tumor (n = 2), normal adrenal (n = 1), and malignant noncortical tumor (n = 3). Diagnosis was established at surgery (n = 9), percutaneous biopsy (n = 4), or follow-up (n = 8). The highest uptake of (11)C-metomidate, expressed as standardized uptake value (SUV), was found in adrenocortical carcinoma (SUV = 28.0), followed by active adenomas (median SUV = 12.7), nonsecretory adenomas (median SUV = 12.2), and noncortical tumors (median SUV = 5.7). Patients with adenomas had significantly higher tumor-to-normal-adrenal (11)C-metomidate SUV ratios than did patients with noncortical tumors. (18)F-FDG detected 2 of 3 noncortical malignancies but failed to detect adrenal metastases from renal cell carcinoma. All inactive and most active adenomas were difficult to detect with (18)F-FDG against background activity, whereas both pheochromocytomas and adrenocortical carcinoma showed slightly increased uptake of (18)F-FDG. There was no correlation between uptake of (11)C-metomidate or (18)F-FDG and mass size.
  
  
  CONCLUSIONS
  (11)C-Metomidate is a promising PET tracer to identify incidentalomas of adrenocortical origin. (18)F-FDG should be reserved for patients with a moderate to high likelihood of neoplastic disease.
authors.affiliation: Turku PET Centre, University of Turku, Turku, Finland. heikki.minn@utu.fi
authors.forename: Heikki
authors.initials: H
authors.lastname: Minn
authors.forename: Anna
authors.initials: A
authors.lastname: Salonen
authors.forename: Johan
authors.initials: J
authors.lastname: Friberg
authors.forename: Anne
authors.initials: A
authors.lastname: Roivainen
authors.forename: Tapio
authors.initials: T
authors.lastname: Viljanen
authors.forename: Jaakko
authors.initials: J
authors.lastname: Långsjö
authors.forename: Jorma
authors.initials: J
authors.lastname: Salmi
authors.forename: Matti
authors.initials: M
authors.lastname: Välimäki
authors.forename: Kjell
authors.initials: K
authors.lastname: Någren
authors.forename: Pirjo
authors.initials: P
authors.lastname: Nuutila
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000097:blood / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000378:metabolism*; D000328:Adult; D000368:Aged; D002250:Carbon Radioisotopes / Q000097:blood; D005045:Etomidate / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000097:blood / Q000493:pharmacokinetics*; D006801:Humans; D033162:Incidental Findings; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014055:Tomography, Emission-Computed / Q000379:methods*
chemical_list: D002250:Carbon Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; C084586:metomidate; D005045:Etomidate