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Indeterminate orbital masses: restricted diffusion at MR imaging with echo-planar diffusion-weighted imaging predicts malignancy Sepahdari AR; Aakalu VK; Setabutr P; Shiehmorteza M; Naheedy JH; Mafee MFRadiology 2010[Aug]; 256 (2): 554-64PURPOSE: To determine whether magnetic resonance (MR) imaging with diffusion-weighted (DW) imaging can help discriminate between radiologically indeterminate benign and malignant orbital masses and to identify optimal apparent diffusion coefficient (ADC) thresholds for such discrimination. MATERIALS AND METHODS: Informed consent was waived for this HIPAA-compliant institutional review board-approved retrospective study. Forty-seven orbital masses imaged with echo-planar DW imaging were identified in 47 patients (25 female patients, 22 male patients; average age, 35 years). A fellowship-trained orbital surgeon determined reference-standard diagnoses on the basis of chart review, and a neuroradiology fellow and senior neuroradiologist who were blinded to the diagnoses selected a region of interest for each lesion by consensus. ADC was calculated from signal intensity on DW images obtained with b = 1000 and b = 0 sec/mm(2). Lesion ADC was also compared with that of normal-appearing white matter (ADC ratio). The Student t test was used to compare groups. Receiver operating characteristic analysis was performed. Intraobserver agreement was assessed with a repeat data collection. RESULTS: Malignant lesions had lower ADCs than benign lesions, irrespective of patient age (P < .02) and in adults specifically (P < .05). Lymphomas had lower ADCs than pseudotumors (P < .001). An ADC of less than 1.0 x 10(-3) mm(2)/sec and an ADC ratio of less than 1.2 were optimal for predicting malignancy (sensitivity, 63% for both; specificity, 84% and 90%, respectively; and accuracy, 77% and 81%, respectively). Lymphoma was differentiated from pseudotumor with 100% accuracy (in 16 of 16 cases) by using these values. Infiltrative lesions that were hypointense on T2-weighted images were better characterized with DW imaging than lesions that were hyperintense or well defined. CONCLUSION: Echo-planar DW MR imaging can help characterize indeterminate orbital masses.|*Subtraction Technique[MESH]|Adolescent[MESH]|Adult[MESH]|Aged[MESH]|Aged, 80 and over[MESH]|Child[MESH]|Child, Preschool[MESH]|Diffusion Magnetic Resonance Imaging/*methods[MESH]|Echo-Planar Imaging/*methods[MESH]|Female[MESH]|Humans[MESH]|Infant[MESH]|Infant, Newborn[MESH]|Male[MESH]|Middle Aged[MESH]|Orbital Neoplasms/*diagnosis[MESH]|Reproducibility of Results[MESH]|Sensitivity and Specificity[MESH]|Young Adult[MESH] |