[Distinction between adrenal adenomas and metastases using 0.5 Telsa MR imaging: diagnosis with out-of-phase...

The purpose of this study was to investigate the ability of MR imaging with a 0.5-T apparatus to distinguish adrenal adenomas from adrenal metastases. The series included 23 adrenal adenomas (18 non-hyperfunctioning adenomas, 5 hyperfunctioning) and 23 adrenal metastases (14 from lung, 5 liver, 3 colon, and 1 stomach cancer). The signal intensity (SI) ratio (adrenal tumor/liver) on T1-, T2-, and T2*-weighted MR images was calculated for adrenal tissue characterization. Adrenal adenomas were more precisely distinguished from adrenal metastases on T2*-weighted images (21/23, 91%) than on T2-weighted images (15/23, 65%). In conclusion, T2*-weighted images were better than routine T2-weighted images in distinguishing adrenal adenomas from adrenal metastases. The reason could be that the total signal intensity of adrenal adenomas which contained some fat components decreased on T2*-weighted images due to an out-of-phase effect.