Adrenal imaging.

CT provides exquisite anatomic detail of normal and pathologic adrenal glands but little specificity as to the nature of adrenal masses. MR reliably distinguishes non-functioning and hyperfunctioning adenomas (adrenal mass/liver ratio less than 1.2) and pheochromocytomas (adrenal mass liver ratio greater than 2.5). Metastases to the adrenal gland and primary adrenocortical carcinomas lie in the intermediate range (adrenal mass/liver ratio 1.4-2.5). Particularly problematic are masses with ratios in the 1.2-1.4 range since some non-functioning adenomas and some metastases will have similar signal intensities and cannot be distinguished.