TY - JOUR T1 - Imaging of Adrenal Incidentalomas with PET Using <sup>11</sup>C-Metomidate and <sup>18</sup>F-FDG JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 972 LP - 979 VL - 45 IS - 6 AU - Heikki Minn AU - Anna Salonen AU - Johan Friberg AU - Anne Roivainen AU - Tapio Viljanen AU - Jaakko Långsjö AU - Jorma Salmi AU - Matti Välimäki AU - Kjell Någren AU - Pirjo Nuutila Y1 - 2004/06/01 UR - http://jnm.snmjournals.org/content/45/6/972.abstract N2 - Our aim was to evaluate the use of PET with 11C-metomidate and 18F-FDG for the diagnosis of adrenal incidentalomas. Methods: Twenty-one patients underwent hormonal screening before dynamic imaging of the upper abdomen with 11C-metomidate, and for 19 of these 21 patients, static 18F-FDG imaging followed. Uptake of 11C-metomidate and 18F-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 11C-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 11C-metomidate SUV ratios than did patients with noncortical tumors. 18F-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 18F-FDG against background activity, whereas both pheochromocytomas and adrenocortical carcinoma showed slightly increased uptake of 18F-FDG. There was no correlation between uptake of 11C-metomidate or 18F-FDG and mass size. Conclusion: 11C-Metomidate is a promising PET tracer to identify incidentalomas of adrenocortical origin. 18F-FDG should be reserved for patients with a moderate to high likelihood of neoplastic disease. ER -