MRI criteria for adenoma

On MRI, the presence of intracellular lipid in adenomas is reliably identified with the use of chemical shift imaging with an accuracy >90%.[20] The signal loss on opposed-phase images related to intracellular lipid is based on phase cancellation of fat and water protons within the same voxel. The concept of chemical shift imaging is further described in the Appendix of this article. Signal loss ≥20% in an adrenal lesion on opposed-phase images relative to in-phase images is characteristic of an adenoma. This signal loss is usually apparent by visual inspection using the spleen or skeletal muscle as a reference standard (Figures 12 and 13). The liver is not a reliable reference standard because fatty infiltration of the liver is quite common and will cause the liver to lose signal intensity on out-of-phase images

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