Orbital Gallium-67 Scintigraphy in Graves' Ophthalmopathy

Assessment of orbital disease activity in patients with Graves' ophthalmopathy is important in planning the therapeutic approach. In this study, orbital uptake of gallium-67 citrate ( 67 Ga) was evaluated in 46 consecutive patients demonstrating active or inactive Graves' ophthalmopathy. The disease activity with Graves' ophthalmopathy was evaluated by using clinical activity score (CAS). Orbital 67 Ga scintigraphies of 8 patients without any history of ophthalmic, thyroid, or autoimmune disease were studied as controls. 67 Ga scintigraphy was performed 48 hours after intravenous injection of 4 mCi (128 MBq) of radioactive complex. Single-photon emission computed tomography (SPECT) images were obtained with a gamma camera. Intravenous corticosteroid treatment was given to 8 selected patients demonstrating bilateral active orbital disease and 67 Ga scintigraphy was repeated 6 months after the treatment. Quantitative analysis of mean orbital 67 Ga uptake demonstrated significant difference between active, inactive, and control groups ( p = 0.0001). The orbital uptake of 67 Ga was significantly elevated in the active group compared to the inactive and control groups. A threshold orbital 67 Ga uptake value was calculated to differentiate active and inactive groups based on receiver operating characteristic (ROC) analysis. A significant correlation was found between the CAS and the 67 Ga orbital uptake ( r = 0.73, p = 0.0001). Clinical improvement and significant decrease in orbital 67 Ga uptake were achieved after immunosuppressive treatment ( p = 0.0004). These preliminary results suggest that orbital 67 Ga scintigraphy may provide objective assessment of the disease activity in Graves' ophthalmopathy.