How is MRI used to differentiate adrenal masses?

Adenomas have the same signal intensity as adrenal tissue on T1- and T2-weighted images and show a drop in signal on opposed-phase gradient echo sequences compared with in-phase sequences. 
Metastases have a higher signal intensity than adenomas on T2-weighted images. 
Pheochromocytomas have a very high signal intensity on T2-weighted images.