Patients undergoing MRI examination for evaluating an ovarian mass must fast for 3-4 hours and receive an antispasmodic drug, intramuscularly, 10 minutes before MRI, in order to reduce bowel peristalsis, also to improve visualization of the adnexa and peritoneal surfaces. For an adequate pelvic MRI evaluation, images must be obtained minimum in two planes. T1-weighted spin-echo images in the axial plane and T2-weighted fast spin-echo images obtained in the axial, sagittal, and coronal planes are usually employed to evaluate uterus, adjacent organs, pelvic floor, and broad ligaments, providing panoramic “morphological” view of the pelvis. Acquisition of T1- and T2-weighted images is fundamental for pelvic anatomy and tissue characterization .
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Several types of tissue and fluid characterizing an ovarian mass can be distinguished at MRI on the basis of their signal intensity . Cystic lesions demonstrate low signal intensity on T1-weighted images and very high signal intensity on T2-weighted images. Solid portions are characterized by relative high hyperintensity on T2-weighted images. Fat, hemorrhage, and some high-viscosity, mucin-containing lesions have high signal intensity on T1-weighted MRI. Fibrosis or smooth muscle has low or intermediate signal intensity on T1-weighted MRI and low signal intensity on T2-weighted images
T1-weighted images with a selective chemical fat-suppression technique in the axial plane are useful to identify blood and fat tissue . T2-weighted images with a selective chemical fat-suppression technique can be usefully employed to better identify inflammation changes or edema. 3D fat-saturated T1-weighted Spoiled Gradient Echo (SPGR) images after intravenous contrast material help detection of solid components into the mass, also improving detection of peritoneal and omental implants . The use of small fields of view (20 cm), high-resolution matrixes (256 × 256), and thin sections (4 mm) improves the delineation of papillary projections into cystic lesions. A body axial T2-weighted sequence for evaluating retroperitoneal space can also be used to complete the pelvis evaluation [8].
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