MR imaging of adrenal masses

Signal intensity (SI) ratios and T2 values of 23 adrenal masses were analyzed using 1. 5 tesla MR imaging system to evaluate these capabilities for tissue characterization. They included 11 nonhyperfunctioning adenomas, 4 hyperfunctioning adenomas, 1 nodular hyperplasia, 3 metastatic tumors, and 4 pheochromocytomas. SI ratios of adrenal/fat, adrenal/liver, and adrenal/muscle on both T1-weighted images (WI) and T2-WI were obtained in each adrenal mass. The T2 values of adrenal masses were calculated with two echo sequences. In results, SI ratios on both T1-WI and T2-WI were not useful in the differentiation of metastatic tumors from adenomas. The calculated T2 value was more relaible. All 14 masses with a T2 value less than 60 msec were adenomas, and 4 masses with a T2 value of 60 msec or more included one adenoma and 3 metastatic tumors. The T2 value of 1 nodular hyperplasia was 58 msec and the T2 values of all 4 pheochromocytomas were over 70 msec. There were no significant differences in SI ratios and T2 value between nonhyperfunctioning and hyperfunctioning adenomas. Therefore, the T2 value is more accurate than SI ratios for tissue characterization of adrenal masses at 1. 5 tesla. Although the T2 value correlated well with the size of mass, whether it depends on mass size or tissue character remains controversial. (author)