Orbit and Visual Pathways
Computed tomography (CT) and magnetic resonance imaging (MRI) are excellent imaging modalities that have significantly enhanced orbital imaging in the diagnosis of ocular and orbital lesions. CT is excellent in the evaluation of the bony orbit and is the imaging modality of choice for most trauma situations. One of the most important roles played by CT is in the detection of calcification, which is crucial in the diagnosis of retinoblastoma. It is also the first choice in suspected orbital infection, especially from sinus disease. Also, orbital metallic foreign bodies are a contraindication to MRI. Rapid scanning allows for motion-free imaging and avoids the need for sedation in pediatric patients. However, it is also important to remember that CT imaging results in a radiation dose of 50 mGy to the lens. Most orbital lesions can be evaluated by CT; however, the increased spatial resolution of MRI allows better depiction of the globe, optic nerve, and orbital apex, and improved evaluation of the intracranial extension of disease. MRI differentiates among the various tissues based on signal characteristics and thus aids in differential diagnosis.
KeywordsOptic Nerve Optic Neuritis Uveal Melanoma Cavernous Hemangioma Noonan Syndrome
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