MR RELAXATION-TIME MEASUREMENTS WITH AND WITHOUT FAT-SATURATION (SPIR) IN GRAVES OPHTHALMOPATHY

Purpose: To determine the value and utility of relaxation time measure ments with magnetic resonance (MR) imaging in patients with Graves' op hthalmopathy (G.O.). Materials and methods: 20 orbits were studied in control subjects and 58 orbits in patients with G.O. T-2 relaxation ti mes of extraocular muscles and retrobulbar fat tissue were calculated. The thickness of the eye muscles was correlated with the calculated T -2 times. 18 orbits were measured before and after retroorbital radiat ion therapy. Results: Upper limits of determined normal T-2 values wer e 60 ms in extraocular eye muscles and 40 ms in retrobulbar fat tissue . 89% (17/19) Of the patients with G.O. had prolonged T-2 times in ext raocular eye muscles. The retrobulbar fat tissue in 5 of 38 orbits rev ealed minimal edema with the use of fat saturated sequences. T-2 relax ation times decreased significantly (p < 10(-4)) after 10 Gy radiation therapy. No correlation was found between enlargement and T-2 relaxat ion times in extraocular eye muscles (r = 0.44 in patients before radi ation therapy). Conclusion: In patients with G.O. the determination of the enlargement of extraocular eye muscles in computed tomography is not a sufficient parameter for an antiinflammatory therapy, since CT c annot visualise eye muscle edema. T-2 relaxation time measurements wit h MR imaging allow differentiation between edematous and fibrotic chan ges. This is the diagnostic method of choice in patients with Graves' ophthalmopathy.