ROLE OF MRI DIFFUSION IN MEDIASTINAL MASSES

Abstract

Mediastinal masses span a wide histopathological and radiological spectrum, primary thymic neoplasms, thyroid masses and lymphomas are the most common in adults. Conventional radiography has a limited role in assessment of mediastinal masses. CT provides better contrast resolution and depicts the exact site, size, shape, number, contour and tissue characterization of mediastinal masses. PET/CT: It combines the functional information of PET with the benefit of detailed anatomic data from CT. However, it is expensive, relatively unavailable with the disadvantage of exposure to ionizing radiation and radioactive material. Magnetic Resonance Imaging advantages are lack of ionizing radiation, confirm cystic nature of mediastinal cystic masses, superior soft tissue contrast in assessment of mediastinal masses and chest wall invasion by a tumor. Diffusion describes the microscopically visualized random motion of water molecules as they diffuse through extracellular space. regions of high mobility ' rapid diffusion' is dark signal, regions of low mobility ' restricted diffusion' is bright signal.