PET in the diagnostic evaluation of adrenal tumors

Early experience with positron emission tomography (PET) has provided exciting results in the evaluation of a broad spectrum of neoplasms, to include primary adrenal tumors, their metastases and metastatic disease to the adrenal glands. By virtue of the well-recognized propensity of malignancies to preferentially use glycolysis as an important energy source and the stimulation of mechanisms designed to absorb substrate glucose, the glucose analog, [18F]fluorodeoxyglucose, has become a successful radiopharmaceutical in the scintigraphic evaluation of adrenal tumors. Building upon prior experience gained with imaging the adrenal gland, other positron-labeled radiopharmaceuticals are finding their way into clinical use. The 11b-hydroxylase inhibitor, metomidate labeled with 11C has been used to scintigraphically identify tissues of adrenocortical origin, to accurately identify recurrent and metastatic adrenocortical carcinoma and may be useful in assessing the malignant potential of these tumors and predicting survival in afflicted patients. Adrenomedulla imaging with 11C- and 18F-labeled catecholamines and catecholamine analogs draws heavily from the experience gained from predecessor compounds, labeled with single photon emitting isotopes and, in some instances, single photon emission tomography, and has been shown to depict with high efficacy pheochromocytomas, neuroblastomas and other neoplasms of neural crest origin. Additional structural and functional information provided by computed tomography (CT), performed as part of hybrid PET/CT imaging directly complements PET and adds measurable diagnostic value in the evaluation of adrenal tumors.