الفهرس 
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Abstract
The incidental identification of an indeterminate complex ovarian mass during radiological examination is one of the most common clinical problems today, Conventional imaging is not always sufficient to define nature of ovarian masses. Sometimes surgical approach is chosen which in many cases proved unnecessary by the subsequent histological examination Ultrasonography ,Usually with transvaginal approach is the first line diagnostic tool ,however ,because of its major limitations in the term of spatial resolution and more importantly, contrast resolution , is unable to differentiate between benign and malignant masses .Magnetic resonance imaging (MRI) is characterized by a higher information content compared to transvaginal ultrasonography.MRI can be used also in assessment and in the pre-operative planning in cases of advanced ovarian cancer where pelvic spread is suspected or in cases of pelvic recurrence. It is the best method for detection of spread to the uterus, bladder, rectum or pelvic sidewall. MRI is indicated in patients who are allergic to iodinated contrast media, pregnant or in cases where the CT findings are inconclusive. It is also indicated if there is a significant rise in the CA-125 while the CT findings are negative.Adding diffusion weighted to magnetic resonance imaging can help in differentiation of benign ovarian tumors from malignant.DWI depend on the fact that water molecules can diffuse freely in low cellular environment while tissue hyper cellularity causes its restriction .As a result malignant ovarian tumors due to its hyper cellular nature show restriction of diffusion unlike most benign tumors
DWI is a non-invasive modality that helps in discrimination between benign and malignant lesions, increases the contrast between lesions and surrounding tissues, and improves the detection and delineation of peritoneal implants at both initial staging and follow-upMoreover, diffusion-weighted imaging provides quantitative information about tissue cellularity that may be used to distinguish viable tumors from treatment-related changes. Because When diffusion-weighted MR imaging is used in gynecologic applications, cancers have shown lower ADC (apparent diffusion coefficient) values.
Increasing ADC values is noted in carcinomas responding to radiation therapy, so it can be used as a biomarker for treatment response and the evaluation of recurrence and multifocality.
In conclusion combination with conventional MRI,DWI and ADC findings :
•Provide additional information in patients with ovarian tumors and identified additional sites of pelvic tumors.
•Improve the radiologist’s confidence in image interpretation
So DWI may play an important role in diagnosis and follow up of patients with ovarian tumors.