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

Jump to first page What is required when you order orbital MR studies? n 1.Surface coil (orbital or head coil) for better visualization of structures of the orbit n 2.Precontrast axial, coronal, and sagittal T1 -weighted images n 3.Axial, coronal T2-weighted images (fast spin-echo sequences) n 4.Postcontrast axial coronal T1 -weighted images with fat suppression techniques n 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 Diagnosis--Ca++ U/S +/- CT Scan n Extraocular ext. -- MRI orbits n 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 U/S n IVFA/ICG n MRI--fat suppression

Jump to first page What are paramagnetic agents? n shorten the intrinsic T1 and T2 relaxation times n increase the signal intensity n 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 1.Evaluation of orbital trauma n 2.Detection of foreign body n 3.Detection of calcification n 4.Evaluation of osseous, cartilaginous, and fibroosseous lesions n 5.Evaluation of orbital soft tissue lesion with suspicion of bony erosion or detection n 6.Contraindication to MRI

Jump to first page What are the indications for ordering MR orbital studies as a first choice? n 1.Acute proptosis n 2.Suspicion of optic nerve sheath complex lesion n 3.Intraocular tumor with extraocular extension n 4.Detection of wood foreign body n 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 1.Dermoid cyst n 2.Lymphangioma n 3.Rhabdomyosarcoma n 4.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 1.Cavernous hemangioma n 2.Neurofibroma n 3.Neurilemoma n 4.Fibrous histiocytoma n 5.Lymphoproliferative disorders

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

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

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

Jump to first page In which clinical situation are contrast- enhanced 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 MRI n Normal nerve does not demonstrate any enhancement n Optic nerve tumor or inflammation demonstrates central enhancement n Optic nerve sheath neoplasm or inflammation demonstrates peripheral enhancement n A cystic or hemorrhagic lesion does not enhance

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