Role of Diffusion Weighted MR imaging in the Evaluation of Uterine and Ovarian malignant neoplastic lesions

Abstract

MRI examination is a useful modality for staging and evaluation of gynecologic malignancy in ovarian and uterine malignancy. The DW-MRI method has been introduced to cancer diagnostics in the recent years, and this has widened the diagnostic capabilities of MRI. Conventional MRI findings in conjunction with DWI and quantitative measurement of the Apparent Diffusion Coefficient (ADC) are effective methods in the diagnosis and staging of gynecological cancer. DWI can provide excellent tissue contrast and may be able to demonstrate malignant tumors. ADC values may be valuable in distinguishing between malignant and benign lesions. Future work should be directed by the potential of DWI in assessment of degree of differentiation of malignant gynecologic tumors which significantly affects the post-therapeutic outcome and overall survival. Additional advantages of DWI include its completely non invasive nature and its cost effectiveness. DWI does not involve radiation exposure, the oral or intravenous administration of contrast material, and does not elicit patient discomfort. DWI can be easily added to MR study protocols and loses no time to the injection of contrast material. DWI may play an important role in the diagnosis and follow-up of patients with gynecological cancer diseases. DW imaging is a sensitive tool in detection of Endometrial cancer. Malignant endometrium appear hyperintense on DW imaging in majority of patients with fallacies induced by the secretory/hyperplastic/ histologic variants of the malignancy but the ADC value of endometrial cancer is significantly lower than that of normal endometrium. Therefore, the measurement of ADC value has a potential role in differentiating normal from cancerous endometrium. The application of a mean ADC threshold less than 1.2x10-3mm2/s gives 84.4% accuracy in predicting the presence of endometrial cancer rather than benign endometrial pathology, which is particularly relevant in those patients for whom it is difficult to obtain pre-operative histology. Uterine cervical cancer is one of the most common gynecological tumors diagnosed in women worldwide and is the second most common cause of cancer-related deaths in women living in developing countries. Clinical applications of DWI for uterine cervical cancer predominantly focused on tumor detection, staging of disease, differentiating between metastatic and non metastatic lymph nodes, and treatment evaluation. However, little information is available for capturing some histopathological features of uterine cervical cancer by using DWI. 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. Finally, Diffusion-weighted MR imaging enables noninvasive characterization of biological tissues based on the properties of water diffusion. Because of its ability to provide functional and morphological information, there is a growing interest in DWI applications in cancer management. In several malignancies, DWI has been shown to be useful in the discrimination between benign and malignant lesions and in capturing some histopathological features, like tumor pathological subtypes and tumor differentiation.