الفهرس 
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Abstract
This thesis aims to highlight the diagnostic role of Diffusion–Weighted MRI that rapidly became established as the preferred imaging modality in detection and characterization and of pediatric musculoskeletal soft tissue tumors with distinction between the benign and the malignant masses. Conventional anatomic MRI sequences remain essential in the initial workup of a pediatric musculoskeletal mass, especially for the determination of tumor extent and depicting invasion of adjacent structures. However, for soft tissue mass characterization, conventional sequences are often deficient and rank second to functional techniques which provide information for characterizing lesions for malignancy. Importantly, DWI technique discussed here requires no intravenous contrast and adds only little time to an MRI protocol, making these sequences particularly worthwhile in the pediatric population. This study included 30 pediatric patients, 17 female (56.7%) & 13 male (43.3%) with mean age of 5.39 years. Complementary histopathological results yielded 26 patients had benign masses and 4 patients had malignant masses. Receiver Operating characteristic (ROC) curve analysis showed that the mean ADC value for the benign masses was (1.495 + 0.55) x10-3mm2/sec. which is significantly higher than that of the malignant soft tissue masses which was (0.449+0.27)x10-3mm2/sec. with a statistical difference between them (p= 0.001*) , 100.0% sensitivity , a specificity of 92.3% , based on a cut-off point of 0.88, positive predictive value of 66.7%, negative predictive value of 100.0% and overall diagnostic accuracy of 93.3%.