Quantitative CT of the orbit in Graves' disease

In order to determine the value of quantitative CT of the orbit in patients with Graves' disease, we clinically examined 174 orbits of 87 patients wit h Graves' disease and evaluated them by CT in respect to the density and si ze of the extraocular muscles, the globe position and the width of the opti c nerve-sheath complex. We also determined the normal ranges for density of extraocular muscles in 200 normal orbits of 100 patients for comparison. N ormal ranges for the density of extraocular muscles were (mean +/- 2 SD) me dial rectus, 28-63 HU; lateral rectus, 24-78 HU; inferior rectus, 20-64 HU; superior muscle group, 28-62 HU. 51 of 77 (66%) patients with Graves' dise ase had extraocular muscle density changes. Some extraocular muscles showed fatty infiltration on CT. 50 of 87 (57%) patients had at least one enlarge d extraocular muscle, 47 (54%) patients had exophthalmos and 59 (68%) patie nts had either exophthalmos and/or extraocular muscle enlargement. A diagno sis of Graves' ophthalmopathy was made in 69 of 87 (79%) patients using CT and in 50 (57%) patients by clinical examination. We conclude that quantita tive CT imaging of the orbit with evaluation of the size and density values of extraocular muscles and the globe position may be very helpful in detec ting ophthalmopathy in patients with Graves' disease.