Adrenal Molecular Imaging

The major workload in the field of adrenal imaging comprises patients with adrenal tumors incidentally depicted by imaging performed for other reasons than adrenal disease. These so-called 'incidentalomas' are generally managed by CT and MRI, and molecular imaging techniques are required only for a few patients. PET/CT with 18F-fluorodeoxyglucose (18F-FDG) is useful for establishing whether an adrenal metastasis is the only lesion, and therefore is available for surgical resection, or if the disease is disseminated. 18F-FDG PET/CT may be applied to differ benign from malignant incidentalomas and can be helpful in the imaging of pheochromocytoma and adrenocortical cancer (ACC). 11C-metomidate PET/CT can differentiate adrenocortical from nonadrenocortical tumors and a suspected ACC may be characterized and staged before surgery. 11C-metomidate PET/CT is currently also used to help diagnose Conn's adenomas in primary aldosteronism, but further development is needed. Scintigraphy with 123I/131I-metaiodobenzylguanidine (MIBG) remains the mainstay for molecular imaging of pheochromocytoma and is mandatory in patients for whom 131I-MIBG therapy is considered. A PET tracer for the imaging of pheochromocytoma is the norepinephrine analogue (11)C-hydroxyephedrine that can be used to characterize equivocal lesions and for the follow-up and diagnosis of recurrent malignant disease. Other specialized PET tracers for the imaging of pheochromocytoma are 18F-fluorodihydroxyphenylalanine (18F-DOPA) and 18F-fluorodopamine.