Dark ring sign: Finding in patients with fungal liver lesions and transfusional hemosiderosis undergoing treatment with antifungal antibiotics

Objective: To describe the MR appearance of necrotizing fungal granulomas occurring in the liver of leukemic patients with hepatosplenic fungal disease and transfusional hemosiderosis on antifungal antibiotics. Subjects and Methods: Four patients with acute myelogenous leukemia (n=2) or acute lymphocytic leukemia (n=2) who developed hepatosplenic fungal disease, and were treated with antifungal medication, underwent MRI examination on a 1.5 T MR imager. MR images were prospectively evaluated and correlated with liver biopsy (three patients), and clinical picture (one patient). Results: Multiple liver lesions measuring approximately 1 cm in diameter were identified in all patients, Lesions possessed a distinctive MR appearance: central mild hyperintensity with a peripheral ring of very low signal intensity on precontrast T-1- and T-2-weighted images. The central region of the lesions enhanced following gadolinium administration with the peripheral ring remaining low in signal intensity. Conclusion: Necrotizing fungal granulomas in the liver of patients with transfusional hemosiderosis on treatment with antifungal antibiotics have a distinctive appearance of moderate high signal intensity center on T-1- and T-2-weighted and postgadolinium MR images with a peripheral rim of low signal intensity, This appearance reflects the presence of iron-laden macrophages in the periphery of granulomas and may be expected in processes that initiate an immune response involving aggregation of macrophages in the liver of patients with transfusional iron overload.