1 - Adrenal Lesions: Role of Computed Tomography, Magnetic Resonance Imaging, 18F-Fluorodeoxyglucose-Positron Emission Tomography, and Positron Emission Tomography/Computed To

Abstract

The imaging techniques such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) have played an important role in defining physiological and pathological conditions of the adrenal glands. Various imaging modalities can be broadly divided into structural, functional, and structural and functional. Integrated information obtained from anatomic and functional imaging is essential for characterization of adrenal disease. CT is the primary imaging modality for adrenal imaging. Widespread use of CT in clinical practice makes it an ideal noninvasive technique for evaluating adrenal gland morphology owing to its widespread availability, the speed with which examinations can be performed, its superior spatial resolution, and quantification of contrast washout patterns. MRI has become another imaging modality to aid the characterization of indeterminate adrenal masses. With the introduction of higher field strength magnets, chemical shift imaging, and dynamic gadolinium-enhanced imaging, MRI has shown promising results with adrenal gland lesion characterization. F-18-fluorodeoxyglucose-PET (18F-FDG-PET) permits acquisition of functional information and, when fused with CT imaging, results in accurate localization and metabolic characterization of adrenal lesions. Cytology from a specimen obtained by needle aspiration biopsy (FNA) cannot distinguish a benign adrenal lesion from adrenal carcinoma, but it can differentiate an adrenal tumor and a metastatic tumor. Thus, FNA may be indicated when there is a suspicion for metastatic lesion in the adrenal gland. Adrenal cysts, adrenal hemorrhage, and myelolipoma are usually easily characterized in noncontrast CT because of their distinctive imaging characteristics and do not require any further investigation.