MAGNETIC-RESONANCE-IMAGING OF ORBITAL LYMPHANGIOMA WITH AND WITHOUT GADOLINIUM CONTRAST ENHANCEMENT

Background. Lymphangioma is a vascular tumor of the orbit with a propensity for recurrent hemorrhage. These tumors may be difficult to diagnose in young patients who present with sudden proptosis due to hemorrhage into a previously unrecognized lesion. Magnetic resonance imaging (MRI) should be ideally suited for evaluating lymphangioma due to the unique ability of MRI to characterize hemorrhage because of the paramagnetic qualities of hemoglobin. Methods: The authors performed T1-, T2-, and proton density-weighted MRI on 12 patients with orbital lymphangioma. Six patients underwent MRI with gadolinium-DTPA contrast enhancement. The MRI studies were performed using a 1.5 Tesla super-conducting magnetic resonance unit, except for 3 early studies performed with a 0.5 Tesla unit. All studies were performed with orbital surface coil imaging. Computed tomography (CT) was performed in 10 patients. Results: Tumor was visible on MRI in all 12 patients. Magnetic resonance imaging delineated clearly the internal structure of subacute and chronic hemorrhagic cysts, and differentiated between these tumors because of the different paramagnetic qualities of subacute hemorrhage compared to chronic hemorrhage. In two patients, MRI detected large tumor feeding vessels by the flow void phenomenon unique to MRI. Computed tomography did not detect these vessels. Gadolinium-contrasted T1-weighted MRI did not further delineate or characterize the tumor. Conclusion: Magnetic resonance imaging is the modality of choice for imaging orbital lymphangioma because of its unequalled differentiation of hemorrhagic cysts, and its unique ability to detect tumor feeding vessels by the flow void phenomenon.