AJR:203, July 2014 99 come the mainstay for assessing adrenal tu- mors, differentiating adenomas from metasta- ses on the basis that adenomas usually contain substantial intracytoplasmic lipid whereas other adrenal masses do not [12, 15, 16]. How- ever, it is recognized that up to 15–20% of ad- renal adenomas are lipid-poor lesions, with low lipid-to-water proton ratio and therefore cannot be characterized by CSI because their signal intensity (SI) is unchanged on out-of- phase images. These lesions are considered indeterminate on the basis of CSI [17, 18]. However, other benign and malignant lesions exhibit high lipid content that might mimic lipid-rich adenomas [19, 20]. Previous studies have shown the impor- tance of early dynamic serial gadolinium-en- hanced evaluation. Many adrenal adenomas, irrespective of their lipid content, display an immediate homogeneous capillary blush and rapid fading [11, 17], as opposed to the major- ity of malignant lesions. We hypothesize that Combined Chemical Shift Imaging With Early Dynamic Serial Gadolinium-Enhanced MRI in the Characterization of Adrenal Lesions Karina Rodacki 1 Miguel Ramalho 1 Brian M. Dale 2 Sofia Battisti 1 Rafael O. P. de Campos 1 Antonello Giardino 1 Richard C. Semelka 1 Rodacki K, Ramalho M, Dale BM, et al. 1 Department of Radiology, University of North Carolina at Chapel Hill, CB# 7510, 101 Manning Dr, Chapel Hill, NC 27599-7510. Address correspondence to R. C. Semelka (richsem@med.unc.edu). 2 Siemens Healthcare, Cary, NC. Genitourinary Imaging • Original Research AJR 2014; 203:99–106 0361–803X/14/2031–99 © American Roentgen Ray Society A drenal lesions are relatively fre- quent and their detection has in- creased with the growing use of cross-sectional imaging, ob- served in 6% of patients undergoing imaging studies [1, 2]. The incidence of an adrenal nodule further increases to 9–13% in pa- tients imaged for a known malignancy [3, 4], but only 26–36% of such lesions are meta- static [3, 5]. Most adrenal masses are adeno- mas, even in patients with a known ex- traadrenal malignancy [5–7]. Differentiation between benign and malignant lesions is im- portant to predict prognosis of the primary disease, to assess staging and direct therapy, and to preclude the need for both percutane- ous biopsy and follow-up imaging in these patients [8]. The accuracy of MRI in the differentia- tion between benign and malignant adrenal tumors has been extensively reported [1, 2, 9–14]. Chemical shift imaging (CSI) has be- Keywords: adrenal adenomas, adrenal gland, adrenal metastases, contrast-enhanced MRI DOI:10.2214/AJR.13.11731 Received August 5, 2013; accepted after revision October 8, 2013. OBJECTIVE. The purpose of this study was to retrospectively evaluate early dynamic se- rial gadolinium-enhanced and chemical-shift imaging (CSI) MRI to distinguish benign from malignant adrenal tumors. MATERIALS AND METHODS. Between July 2007 and December 2011, 205 patients with 239 adrenal lesions (177 adenomas, 54 metastases, 5 pheochromocytomas, and 3 ad- renal cortical carcinomas) underwent early dynamic serial gadolinium-enhanced MRI and CSI. CSI was assessed qualitatively and by calculating the adrenal index, and enhancement patterns were evaluated qualitatively and quantitatively. Statistical analyses were performed. RESULTS. Most adenomas exhibited either an arterial blush or homogeneous enhance- ment, whereas most metastases showed early peripheral or heterogeneous enhancement. Vi- sualization of higher enhancement on arterial and venous phases enabled differentiation of adenomas from metastases in most cases. Moderate to high signal intensity drop on CSI was seen in 95.4% of adenomas and 14.8% of metastases. In lesions with this level of signal in- tensity drop, 87 of 88 lesions with a capillary blush were adenomas. Early dynamic serial imaging alone was a significant ( p < 0.0001) indicator of nonadenoma (area under the curve [AUC], 0.912) with optimal sensitivity of 81% and specificity of 93% for differentiating ad- enomas from nonadenomas. Combined analysis (CSI and early dynamic serial imaging) was also significant ( p < 0.0001 and p= 0.0014, respectively) for diagnosing nonadenomas (AUC, 0.983) with optimal sensitivity of 94% and specificity of 98%. CONCLUSION. Early dynamic serial gadolinium-enhanced MRI aids in characterization of adrenal tumors, especially lesions that are categorized as indeterminate on the basis of CSI. Rodacki et al. MRI of Adrenal Lesions Genitourinary Imaging Original Research Downloaded from www.ajronline.org by 52.73.204.196 on 05/16/22 from IP address 52.73.204.196. Copyright ARRS. For personal use only; all rights reserved