Orbital Gallium-67 Scintigraphy in Graves' Ophthalmopathy

Abstract

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