Renal Angiomyolipoma with Minimal Fat: Differentiation from Other Neoplasms at Double-Echo Chemical Shift FLASH MR Imaging

Purpose: To prospectively evaluate the diagnostic performance of double-echo gradient-echo (GRE) chemical shift magnetic resonance (MR) imaging in the differentiation of angiomyolipoma (AML) with minimal fat from other renal neoplasms, with pathologic examination or follow-up data serving as the reference standard. Materials and Methods: Institutional review board approval and informed consent were obtained. Double-echo GRE chemical shift MR imaging was performed in 55 patients (29 men and 26 women; mean age, 49 years ± 14 [standard deviation]) with 55 renal tumors, including 37 (67%) pathologically proved tumors (23 renal cell carcinomas, nine AMLs, two oncocytomas, two lymphomas, and one reninoma) and 18 (33%) clinically diagnosed tumors (17 AMLs and one indeterminate malignancy). All tumors showed no intratumoral fat and had homogeneous enhancement and a prolonged or gradual enhancement pattern on biphasic helical computed tomographic scans. Signal intensity was measured in the renal tumor and spleen o...