Diagnostic value of diffusion-weighted MRI and conventional MRI in the differentiation of benign and malignant orbital lesions

Purpose: The aim of this study was to assess the role of diffusion-weighted imaging (DWI) and conventional magnetic resonance imaging (MRI) in the differentiation of benign and malignant orbital lesions. Materials and Methods: 43 patients (27 women and 16 men; mean age: 26.3 +/- 28.5) with orbital lesions were assessed with conventional MRI and DWI. The apparent diffusion coefficient (ADC) of the lesions was measured, and maximum ADC (ADC(max)), mean ADC (ADC(mean)), minimum ADC (ADC(min)), the ratio of ADC(mean) to cerebral white matter ADC (ADC(meanratio)), and the ratio of ADC(min) to cerebral white matter ADC (ADC(minratio)) were calculated. T1-weighted and T2-weighted imaging features and contrast enhancement patterns were determined. The diagnostic performances of ADC variables and conventional MRI features for the differentiation of benign and malignant orbital lesions were assessed. Results: ADC(mean), ADC(min), ADC(meanratio), and ADC(minratio) of the malignant lesions were significantly lower than those of the benign ones . ADC(meanratio) had the highest diagnostic performance with a sensitivity and specificity of 87.5% and 70.4% at a threshold of 1.27. Selecting a cut-off ADC(mean) of 0.97 X 10(-3) mm(2)/s for differentiating benign and malignant lesions revealed 75% sensitivity and 74% specificity. Conventional MRI features were not associated with the malignant diagnosis). Conclusion: ADC values obtained from DWI contribute to the differentiation of benign and malignant orbital lesions.