Orbital computed tomography biomarkers for the assessment of activity of Thyroid Eye Disease

Objectives To investigate the relationship between orbital metrics obtained using computed tomography (CT) imaging and inflammatory activity in thyroid eye disease (TED). Methods This retrospective study analyzed the medical records and CT images of 85 patients with TED and 15 controls. Orbital segmentation was performed using commercially available software. The volumes and densities of the extraocular muscles (EOMs), intraorbital fat, and lacrimal gland were measured. CT parameters were compared among the control, active TED, and inactive TED groups. Patients were further classified into two subgroups based on disease severity: mild TED and moderate to severe TED, and CT parameters were compared in each severity subgroup. Results Patients with active TED showed significantly higher thyroid-stimulating immunoglobulin levels than patients with inactive TED (p < 0.001). Orbital CT analysis revealed that the EOM volume was significantly larger in the active TED than in the inactive TED and control groups (p < 0.001). Additionally, intraorbital fat density was higher in patients with active TED (p < 0.001), whereas intraorbital fat volume and EOM density showed no significant differences between the groups. Lacrimal gland parameters did not differ significantly between the groups. Subgroup analysis based on TED severity also indicated that EOM volumes were larger and intraorbital fat densities were higher in the active TED than in the inactive TED (all p < 0.05). Conclusions Orbital CT revealed significant differences in EOM volume and intraorbital fat density between patients with active and inactive TED. These findings suggest that quantitative CT analysis may be useful for assessing TED activity.