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 between benign, border line tumors and invasive ovarian cancers, in order to decide if 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 assessment with the development of recent technologies, new functional MRI sequences are being used. Of these, is the diffusion weighted images (DWI) and dynamic contrast enhanced MRI (DCE-MRI). 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 their hyper cellular 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.
DCE- MRI depends on the leakage of contrast agent from capillaries into the extravascular extracellular space, thus allowing quantitative analysis which reflects the blood flow and the vascular permeability. The early enhancement patterns of ovarian tumors on dynamic contrast-enhanced MR images can help distinguish among benign, borderline, and invasive tumors and were found to correlate with tumoral angiogenesis.