MRI versus CT in Orbit imaging

MRI: There is no exposure of ionizing radiation, it provides excellent soft tissue resolution of orbital content and is ideal for entire course of optic nerve and pituitary gland as cortical bone appears as hypo intense dark area as there is no water content in bone. Therefore, the entire optic nerve is imaged without any bony shadow interference. MRI can identify age of hematoma. Bone marrow lesions have better resolution. MRI uses safer contrast agent.

CT: It is relatively economical and ideal for boney pathologies, fractures and calcification in tumor mass. It is especially indicated in intraocular foreign bodies. It is ideal for unstable patients as the test duration is very short.

Disadvantages

MRI: It is costly, prolonged examination, not suitable for unstable patients who cannot lie still for long time. It is not possible for obese and claustrophobic patients. Test duration is long. Fat saturation can cause hindrance in interpretation. MRI is contraindicated with ferromagnetic intraocular foreign body. Air and bone, both gives picture of signal void hence difficult to interpret and not suitable for bony lesions and fractures.

CT: Exposure of ionizing radiation and lesser sensitive than MRI in imaging intracanalicular and intracranial optic nerve, cavernous sinus and diseases of white matter such as disseminated sclerosis. Also, the bony orbital wall can sometimes interfere with the interpretation of soft tissue orbital content.