What imaging studies are available for evaluating adrenal pathology?
There are three main imaging techniques for the differentiation of malignant from benign adrenal tumors: CT, magnetic resonance imaging (MRI), and positron emission tomography with fluorodeoxyglucose (FDG-PET/CT). CT and MRI are mainly techniques to identify benign lesions and exclude adrenal malignancy. FDG-PET/CT is mainly used for detection of malignant disease.
Abdominal CT is the initial modality of choice. An adrenal protocol CT consists of thin-cut imaging through the adrenal glands first without IV contrast, and then with contrast, followed by delayed (usually 10–15 minutes) images to assess contrast washout.
MRI is considered essentially equivalent to CT for adrenal tumors and is a reasonable, although more expensive, alternative; MRI should be considered in patients with contrast allergy and in situations where radiation exposure should be limited (pregnancy, children, patients with known germline mutations). MRI is recommended in patients with known or suspected metastatic pheochromocytomas.
FDG-PET/CT standard uptake value (SUV) has been utilized to differentiate between benign and malignant adrenal lesions.
Meta-iodo-benzyl-guanidine (MIBG) nuclear medicine scans are best utilized for recurrent, familial, or extraadrenal pheochromocytomas.