Retrobulbar 99mTc-Diethylenetriamine-Pentaacetic-Acid Uptake May Predict the Effectiveness of Immunosuppressive Therapy in Graves' Ophthalmopathy

Background: In Graves' ophthalmopathy (GO), only patients with immunologically active disease respond to immunosuppressive therapy. Previous studies and theoretical considerations suggest that elevated orbital 99mTc-diethylenetriamine-pentaacetic-acid (DTPA) single photon emission computed tomography (SPECT) reflects inflammatory disease activity. We studied whether corticosteroid treatment causes a substantial decrease in DTPA uptake in GO, a result consistent with successful immunosuppressive treatment of GO and referred to as a favorable treatment outcome. Methods: One hundred fourteen orbits in 57 patients with active GO (CAS ≥ 4) were entered into the study. All patients received corticosteroid treatment. Orbital DTPA uptakes were numerically quantified for the entire orbit as well as the anterior and posterior segments separately. DTPA SPECT was performed before, and 2 to 9 months after the initiation of immunosuppressive treatment. The normal range for DTPA uptake was established in 34 orbits of 17...