Purpose: To retrospectively compare the accuracy of delayed ehanced computed tomography (CT) and chemical shift magnetic resonance (MR) imaging for characterizing hy-perattenuating adrenal masses at CT, with either follow-up imaging or pathologic review as the reference standard.
Methods:The institutional review board approved this retrospective study with a waiver of patient informed consent. Forty-three hyperattenuating adrenal masses (>10 HU) on unen-hanced CT images were found in 34 patients (23 men and 11 women; mean age, 52.7 years) by reviewing radiologic reports. These lesions were retrospectively analyzed with delayed enhanced CT and chemical shift MR. The diagnos-tic accuracy of CT by using absolute percentage loss of enhancement (PLE) and relative PLE and of chemical shift MR by using adrenal-to-spleen ratio (ASR) or signal inten-sity index (SII) were obtained to determine which modality was more accurate for lipid-poor adenoma. For CT, an adenoma was diagnosed if a mass had an absolute PLE greater than 60% and a relative PLE greater than 40%. For MR, an adenoma was diagnosed if a mass had an ASR of 0.71 or an SII greater than 16.5%. McNemar test was used to compare diagnostic performance of CT and MR.
Results: Hyperattenuating adrenal masses included 37 adenomas and six nonadenomas. The sensitivity, specificity, and ac-curacy for adenoma at CT were 97% (36 of 37), 100% (six of six), and 98% (42 of 43), respectively, and at MR wen 86% (32 of 37), 50% (three of six), and 49% (21 of 43), respectively. CT helped confirm five more adenomas and three more metastatic tumors than did MR. However, there was no significant difference for diagnostic accuracy between these two imaging modalities (P > .05)
Conclusion: Delayed enhanced CT can characterize additional hyperat-tenuating adrenal masses that cannot be characterized with chemical shift MR.