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 (Ga-67) 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 Ga-67 scintigraphies of 8 patients without any history of ophthalmic, thyroid, or autoimmune disease were studied as controls. Ga-67 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 Ga-67 scintigraphy was repeated 6 months after the treatment. Quantitative analysis of mean orbital Ga-67 uptake demonstrated significant difference between active, inactive, and control groups (p = 0.0001). The orbital uptake of Ga-67 was significantly elevated in the active group compared to the inactive and control groups. A threshold orbital Ga-67 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 Ga-67 orbital uptake (r = 0.73, p = 0.0001). Clinical improvement and significant decrease in orbital Ga-67 uptake were achieved after immunosuppressive treatment (p = 0.0004). These preliminary results suggest that orbital Ga-67 scintigraphy may provide objective assessment of the disease activity in Graves' ophthalmopathy.