Imaging of hyperfunctioning adrenal masses

Area of Science:

• Radiology
• Nuclear Medicine
• Endocrinology

Background:

• Adrenal masses require imaging for diagnosis of clinical syndromes and malignancy.
• Computed tomography (CT), MRI, and ultrasound detect adrenal masses but lack specificity for malignancy.
• Size alone is insufficient to differentiate benign from malignant adrenal lesions.

Purpose of the Study:

• To review current imaging modalities for adrenal masses.
• To highlight methods for differentiating benign from malignant adrenal lesions.
• To discuss the role of functional nuclear medicine in adrenal imaging.

Main Methods:

• Review of CT, MRI, and ultrasound for adrenal mass detection.
• Analysis of CT attenuation and contrast washout characteristics.
• Evaluation of MRI chemical-shift imaging.
• Application of functional nuclear medicine imaging with specific and unspecific tracers.

Main Results:

• CT, MRI, and ultrasound show high sensitivity for adrenal mass detection.
• CT and MRI techniques like attenuation values, contrast washout, and chemical-shift imaging aid in differentiating adenomas.
• Functional nuclear medicine, using agents like ¹³¹I-6-iodomethyl-norcholesterol and ¹²³I-meta-iodobenzylguanidine, offers specific lesion characterization.
• ¹⁸F-fluorodeoxyglucose (FDG) PET is valuable for distinguishing malignant from benign adrenal tumors.

Conclusions:

• A combination of imaging techniques is crucial for comprehensive adrenal mass evaluation.
• Functional nuclear medicine imaging significantly enhances the characterization of adrenal lesions, particularly when CT and MRI are equivocal.
• ¹⁸F-FDG PET is a key tool for differentiating malignant from benign adrenal tumors, guiding clinical management.