New Multi-Parameters Combination of Technetium-99m-Diethylene-Triamine-Pentaacetate Orbital Single-Photon Emission Computed Tomography/Computed Tomography for the Evaluation of Graves' Orbitopathy Activity.

Purpose: This study investigates the new combined parameters of ^99mTc-DTPA orbital single-photon emission computed tomography/computed tomography (SPECT/CT) for the evaluation of Graves' orbitopathy (GO) activity.

Methods: A retrospective analysis was performed on 41 patients. All the patients undergone the 99mTc-DTPA orbital SPECT/CT and were categorized into active and inactive group based on the standard combined by the clinical active score (CAS), magnet resonance imaging (MRI) and/or follow-up results. Quantitative parameters of lacrimal gland (LG) including the protruding degree of lacrimal gland herniation (LGH) and uptake ratios (URs) of region of interest (ROI) drawn on lacrimal gland and occipital bone. SPECT/CT reading results were based on visual analysis. Parameters were compared between the two groups and the diagnostic value on discrimination of GO activity was also evaluated.

Results: All parameters of SPECT/CT for active GO groups were significantly higher than those of the inactive groups (p<.05). There were notable linear positive correlations between the assumption standard and readings as well as combination models 2 and 3 (r = .794, r = .772, r = .760, respectively). ROC analysis indicated that model 2 provided the highest diagnostic performance, exhibiting an area under the curve (AUC) of .947, a sensitivity of 92.7%, and a specificity of 88.6%.

Conclusions: The combined use of SPECT/CT reading results and DTPA uptake parameters of LG offers a more objective and precise evaluation of active GO. This study further recommends ^99mTc-DTPA SPECT/CT might be serving as a supplementary beneficial approach for CAS in evaluating GO activity.