Benign adrenocortical masses: diagnosis with chemical shift MR imaging

Benign adrenocortical masses often contain lipid; metastases and pheochromocytomas do not. Standard and lipid-sensitive (chemical shift) magnetic resonance (MR) images of the adrenal glands in 31 patients with 45 adrenal masses were reviewed to determine if simple visual analysis of these images would increase diagnostic specificity. Lipid was considered present if signal intensity of the adrenal mass relative to other tissues decreased on chemical shift images relative to comparable standard images. Both myelolipomas and 26 of 27 benign cortical masses displayed a loss of signal intensity on at least one chemical shift image; all 12 metastases, the three hemorrhages, and a cyst did not. Opposed-phase images were slightly more sensitive than fat-suppressed images in depicting lipid within benign cortical masses. All masses had higher signal intensity than that of the liver on standard T2-weighted MR images. Chemical shift MR imaging can demonstrate lipid within benign adrenocortical masses and thus increase specificity, potentially obviating biopsy and aggressive follow-up.