Correlation between computed tomography and magnetic resonance imaging in Graves' orbitopathy.

Radiologic examination of patients with severe Graves' disease with possible optic neuropathy has routinely been done with computed tomography (CT). With the more widespread use of magnetic resonance imaging (MRI), its potential use in Graves' disease must be considered. We compared these two imaging techniques for use in severe Graves' orbitopathy. Thirty-nine orbits of 20 consecutive patients with severe Graves' disease (19 with optic neuropathy and 20 without optic neuropathy) were examined clinically. CT and MRI were performed, and the radiologic images were assessed for five measures chosen to illustrate overall muscular changes, tissue plane changes of the orbital apex, optic nerve changes and proptosis. The MR images were significantly more reliable than the CT scans for two measures in particular: degree of fat effacement (a measure of optic nerve compression) and minimal optic nerve index (a measure of optic nerve thickness), both of which involve the orbital apex. We conclude that MRI is a better technique than CT for imaging the apex in Graves' optic neuropathy.