New Advances in Magnetic Resonance Imaging of Ovarian Tumors

Abstract

Ovarian tumors; are the second most common gynecological tumor and is the fifth commonest tumor in women.

TVUS is the first imaging modality that can be used for detection of adnexal mass lesion. Sonographically indeterminate adnexal masses of uncertain origin and solid or complex cystic content benefit from further evaluation with MRI, which is highly accurate for identifying the origin of a mass and characterizing its tissue content, obviating surgery in many cases. (Pegah et al., 2012). 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 (Füttereretal,2011). 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. (Thomassin-Naggara et al, 2013). Dissemination of tumor to lymph nodes is one of the principal routes of metastatic disease. The presence or absence of nodal disease is an important prognostic factor in gynecologic malignancies. Current imaging techniques such as CT & MR imaging have limitations because they rely almost exclusively on size criteria. MR lymphography uses a lymph node–specific contrast agent (ferumoxtran-10), Allows differentiation benign from malignant nodes on the basis of alterations in signal intensity. (Narayanan et al., 2009). Magnetic resonance spectroscopy is a non-invasive technique can provide important in vivo metabolic information, complementing morphological findings from conventional MRI in the clinical setting. This technique is an extremely valuable tool in solving difficult cases and increase confidence in diagnosis, which plays an important role in the characterization of ovarian tumors by differentiating between them whether being benign or malignant and reducing the possibility of unnecessary radical surgery for younger women with genuinely benign disease who wish to conserve fertility. (Stanwell et al., 2010) In conclusion, Functional MRI has played important roles in ovarian tumors, for tumor detection, primary staging, treatment planning, prediction of prognosis, as well as response evaluation. Emerging imaging technologies will continuously improve our practice. Such development will aid decision-making in personalized medicine and precisely guide radiation treatment plan or real-time surgical interventions, which will directly impact on patient survival. Finally there is no single imaging tool will universally apply in different tumor types.