Magnetic resonance imaging differentiation of adrenal masses at 1.5 T: T2-weighted images, chemical shift imaging, and Gd-DTPA dynamic studies

The purpose of our study was to assess the potential role of spin-echo (SE), chemical shift, and gadolinium-enhanced magnetic resonance imaging (MRI) in the differentiation of adrenal masses. Seventy-two adrenal masses (26 nonhyperfunctioning adenomas, 16 aldosterone-secreting adenomas and 6 other different benign cortical masses, 18 pheochromocytomas, and 6 malignant masses) in 63 patients were evaluated with spin-echo sequences, chemical shift imaging (CSI) and gadolinium diethylenetriamine penta-acetic acid (Gd-DTPA) dynamic studies. Ratios and indices of signal intensity for all examined MRI methods were calculated and examined for significance of difference between different types of adrenal masses. Quantitative magnetic resonance evaluation of adrenal masses showed significant differences (at least alpha<0.01) between nonhyperfunctioning adenomas vs. pheochromocytomas or vs. malignant lesions or vs. aldosterone-secreting adenomas and between pheochromocytomas vs. malignant lesions. The most specific indicators of adrenal mass character proved to be the CSI ratio based on opposed-phase and in-phase two-dimensional fast low-angle shot (FLASH) images, reflecting lipid content in the lesion, and Gd-DTPA dynamic studies ratios reflecting contrast agent inflow and washout in the lesion: Wo(MAX/LAST) and Dyn(1.2-3.2). There was no overlap of CSI ratio between adenomas and pheochromocytomas. The overlap of ranges of CSI ratio between nonhyperfunctioning adenomas and aldosterone-secreting adenomas was only 18.5%. There was no overlap of Wo(MAX/LAST) ratio between adenomas and pheochromocytomas, or adenomas and malignant lesions. The overlap of ranges of Dyn(1.2-3.2) ratio between pheochromocytomas and malignant lesions was only 17.6%. MRI enables good visualization and specific characterization of adrenal masses. The optimal MRI protocol for the adrenal region is presented.