The selection of target areas for orbital imaging, as well as the application of diethylenetriaminepentaacetic acid orbital imaging, clinical factors, alkaline phosphatase, and thyrotropin receptor antibodies in the staging and grading of thyroid-associated ophthalmopathy, are subjects of research
Authors: Yuan Min , Feng Yiren , Guo Lin , Li Ping , Liu Yuting , Wang Yao , Chen Yusong , Jin Gang 
Published: November 2024

Purpose
This study aimed to investigate whether patients with thyroid-associated ophthalmopathy (TAO) are in the active phase and explore their correlations with various clinical factors, serological tests, and orbital imaging parameters studied. It also aimed to evaluate the diagnostic value of different target areas in orbital imaging for assessing TAO inflammatory activity according to the American NOSPECS classification. Patients were stratified based on their NOSPECS grade to determine statistical differences among different stages. Receiver-operating characteristic (ROC) curves were used to assess the diagnostic efficacy of statistically significant data. Patients identified as active by orbital imaging were recommended for treatment to observe therapeutic outcomes.

Methods
A total of 45 patients with thyroid-related eye disease who underwent 99mTc-diethylenetriaminepentaacetic acid single-photon emission computed tomography/computed tomography (CT) fusion imaging, alkaline phosphatase (ALP), thyrotropin receptor antibody (TRAb), free triiodothyronine, free thyroxine, thyroid-stimulating hormone serological tests, and clinical data collection from November 2023 to June 2024 were included. Clinical Activity Score (CAS) assessment, diplopia scores, and NOSPECS grading were conducted the day after imaging. Four rectus muscles were outlined as regions of interest on the optimal frame of extraocular muscle imaging and measured for maximum and mean radioactive counts, normalized against average counts of the patient’s optic nerve level occipital bone region (UR1max, UR1mean). Tear gland radioactive uptake was similarly measured for maximum and mean counts normalized against the same region (UR2max, UR2mean). Exophthalmos and extraocular muscle thickening were assessed on CT scans. The correlations between different study parameters and CAS, as well as differences among different NOSPECS grades, were evaluated. ROC curves were used for statistically significant variables. Patients with discrepancies between orbital imaging and CAS results underwent treatment or follow-up to evaluate prognosis and staging.

Results
Active TAO status correlated significantly with UR1max, UR1mean, UR2max, UR2mean, ALP, TRAb, and age, using CAS and radiological imaging as standards. Among these, UR2max showed the strongest correlation. Significant differences (except ALP and TRAb) were found among different NOSPECS grades for the studied variables. Orbital volume, CAS results, radiological imaging, and diplopia scores also showed significant differences among different grades. Forty-two of 45 patients exhibited varying degrees of extraocular muscle thickening, confirming its reliability as a diagnostic criterion for TAO. The most common muscles affected were the inferior and medial rectus muscles, observed in 32 cases. High consistency was found between orbital imaging and CAS staging. Three patients diagnosed as active by imaging (including one with inconsistent CAS and imaging results) showed varying degrees of improvement posttreatment. Patients with nonactive imaging but inconsistent CAS results showed no progression during 3-month follow-up. ROC curves demonstrated high diagnostic efficacy for UR2max, with other indices also showing good diagnostic performance.

Conclusion
Tear glands and extraocular muscles showed high diagnostic value, with tear glands demonstrating relatively higher value. Orbital imaging showed high consistency with CAS grading, providing an objective and comprehensive assessment of ocular involvement compared to CAS scoring alone. ALP and TRAb also demonstrated value in TAO staging, assisting clinical discrimination. Age may also play a significant role.