الفهرس 
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Abstract
This thesis aimed at evaluation of the role of Diffusion-Weighted MRI in the characterization of the orbital masses and determining whether it is benign or malignant. The study included forty-five patients (22 female and 23 male). Of these 45 cases 18 were benign and 27 were malignant tumors. The globe was the seat of more than fifth of these lesions (22.2%) followed by extra-ocular muscles (17.8%) while the rest of the lesions located at the different orbital location. The DWI was obtained with b values including 0 and 800 mm2/sec. The Apparent Diffusion Coefficient (ADC) generated by measuring identical images at different b-values and represented as ADC map from which ADC value calculated. The diagnosis was confirmed after the MRI examination by histologic biopsy according to standard histopathological procedures in most of the cases. Our results revealed that the mean ADC value of benign and malignant orbital masses was 1.68 x 10-3 mm2/sec and 0.72 x 10-3 mm2/sec, respectively. There was a significant difference in the mean ADC value between benign and malignant orbital masses (P < 0.001). The mean ADC value of benign was significantly higher than that of malignant orbital masses, with considering ADC value of 0.90 x 10-3 mm2/sec is a cut off between benign & malignant orbital masses by sensitivity 81.5% and specificity 84%.
characterization of orbital masses and differentiation between benign and
malignant lesions.
ADC measurement coupled with MRI technique enables effective
characterization of pathological features of orbital masses with high
sensitivity and specificity leading to an increase in the overall accuracy of
MRI, hence reducing the number of unnecessary biopsies.