Orbital Imaging Mounir Bashour M D C M

Orbital Imaging Mounir Bashour, M. D. , C. M. Jump to first page

What is required when you order orbital MR studies? n n n 1. Surface coil (orbital or head coil) for better visualization of structures of the orbit 2. Precontrast axial, coronal, and sagittal T 1 -weighted images 3. Axial, coronal T 2 -weighted images (fast spin-echo sequences) 4. Postcontrast axial coronal T 1 -weighted images with fat suppression techniques 5. Sedation in children Jump to first page

What is the strategy in ordering imaging studies in a child with the diagnosis of retinoblastoma? n n n Diagnosis--Ca++ U/S +/- CT Scan Extraocular ext. -- MRI orbits Familial/Bilat --> MRI brain (pinealoblastoma) Jump to first page

What is the strategy in ordering imaging studies in an adult with the diagnosis of intraocular neoplasm? n n n U/S IVFA/ICG MRI--fat suppression Jump to first page

What are paramagnetic agents? n n n shorten the intrinsic T 1 and T 2 relaxation times increase the signal intensity Melanin, methemoglobin, protein, and gadolinium Jump to first page

In which clinical situations are contrast -enhanced MR studies most helpful in the evaluation of a child with leukocoria? n To differentiate retinoblastoma from Coats' disease. Jump to first page

In which clinical situations are contrast -enhanced MR studies most helpful in the eval-uation of an adult with vitreous hemorrhage? n To differentiate a malignant melanoma of the choroid from a hemorrhagic retinal detachment in age-related macular/extramacular degeneration. Jump to first page

What are the indications for ordering CT orbital studies as a first choice? n n n 1. Evaluation of orbital trauma 2. Detection of foreign body 3. Detection of calcification 4. Evaluation of osseous, cartilaginous, and fibroosseous lesions 5. Evaluation of orbital soft tissue lesion with suspicion of bony erosion or detection 6. Contraindication to MRI Jump to first page

What are the indications for ordering MR orbital studies as a first choice? n n n 1. Acute proptosis 2. Suspicion of optic nerve sheath complex lesion 3. Intraocular tumor with extraocular extension 4. Detection of wood foreign body 5. Contraindications to CT Jump to first page

Name the most common orbital lesions showing a well-circumscribed and sharply delineated appearance on CT and MRI in kids n n 1. 2. 3. 4. Dermoid cyst Lymphangioma Rhabdomyosarcoma Optic nerve glioma Jump to first page

Name the most common orbital lesions showing a well-circumscribed and sharply delineated appearance on CT and MRI in adults n n n 1. 2. 3. 4. 5. Cavernous hemangioma Neurofibroma Neurilemoma Fibrous histiocytoma Lymphoproliferative disorders Jump to first page

Name the most common orbital lesions showing an ill defined appearance on CT and MRI in children n n 1. 2. 3. 4. 5. Capillary hemangioma Idiopathic orbital inflammation Plexiform neurofibroma Leukemic infiltrate Eosinophilic granuloma Jump to first page

Name the most common orbital lesions showing an ill defined appearance on CT and MRI in adults n n n 1. 2. 3. 4. 5. Idiopathic orbital inflammation Metastasis Leukemic infiltrate Primary malignant tumor Lymphoproliferative disorders Jump to first page

Which are the ocular and orbital tissues that do not normally enhance on postcontrast MR studies? n n n 1. 2. 3. 4. 5. Lens Vitreous Sclera Orbital fat Optic nerve sheath complex Jump to first page

In which clinical situation are contrastenhanced MR studies most helpful in the evaluation of a patient with proptosis? n Well circumscribed lesions Jump to first page

What are the indications for MR angiography and carotid angiography when imaging orbital lesions? n None Jump to first page

How can you differentiate optic nerve from optic nerve sheath lesions with CT and MR studies? n n n MRI Normal nerve does not demonstrate any enhancement Optic nerve tumor or inflammation demonstrates central enhancement Optic nerve sheath neoplasm or inflammation demonstrates peripheral enhancement A cystic or hemorrhagic lesion does not enhance Jump to first page

MR Features of Normal Ocular and Orbital Tissues Jump to first page