Surface coil magnetic resonance imaging of the orbit at 1.5T

MRI of the orbit at 1.5-Tesla was performed in 5 healthy volunteers and 30 patients with a variety of pathological intraocular or intraconal conditions. Major advantages of MRI over CT include higher spatial resolution, higher tissue contrast, possibility of direct multiplanar imaging, absence of bony and dental artifacts, and of ionising radiation. Specific indications of MRI in orbital pathology concern differentiation of uveal melanoma from subretinal haemorrhage, identification of lesions of the orbital apex, the orbital fissure or the optic canal, differentiation of inflammatory pseudotumour from malignant lesions, determination of the posterior extension of lesions of the optic nerve, and detection of abnormal flow in normal or hypertrophic intraorbital vessels. Limitations are due to motion artifacts on T2 weighted sequences, less accurate visualisation of calcification, poor specificity of some findings, and absence of signal from cortical bone.