الفهرس 
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Abstract
Ovarian tumors; are the second most common gynecological tumor and is the fifth commonest tumor in women.
Although the final diagnosis of an ovarian tumor is based on the histological examination, it is desirable to preoperatively differentiate benign, BOTs and invasive ovarian cancers in order to decide whether surgery is required, and which type of surgery is appropriate. Thus, it can help avoiding unnecessary surgery especially in postmenopausal women and help deciding for conservative surgery for young ones wishing to preserve childbearing potential.
TVUS is the first imaging modality that can be used for detection of adnexal mass lesion. However,lesion characterization is done with the help of MRI. Conventional MRI provides soft tissue characterization based on different signal intensities and contrast uptake in post contrast images.
Being a cost effective choice, and in addition to its ability for accurate diagnosis, it can replace computed tomography (CT) in preoperative pelvic assessment.
With the development of recent technologies, new functional MRI sequences are being used. Of these, is the diffusion weighted images (DWI). DWI is used in the abdomen and pelvis after it has been established as a useful functional imaging tool in neurologic applications for a number of years.
DWI depends on the fact that water molecules can diffuse freely in low cellular environment, while tissue hyper cellularity causes its restriction, a phenomenon called ‛Brownian motion’. As a result, malignant ovarian tumors due to its hypercellular nature show restriction of diffusion, unlike most benign tumors. So it implies a noninvasive technique which can be used especially if contrast intake is avoided as in pregnancy.
Our study which was conducted on twenty ovarian tumors showed that addition of DWI to the conventional MRI increased the specificity, PPV, NPV and accuracy of the examination.
In conclusion, the combination of DWI to conventional MRI implies:
• Using a completely noninvasive technique with no radiation exposure.
• DWI might be an alternative for contrast administration especially for those were contrast intake is better avoided as during pregnancy.
• Cost effective technique (no additional cost to MRI examination), easily added to the MR study protocols with no marked lengthening of examination time.
• It improves the specificity of MRI and thus increasing the radiologist’s confidence in image interpretation which will finally reflect on the patients’ outcome and prognosis.
Limitations:
- DWI interpretation should in conjunction with other morphological criteria in conventional MRI sequences.