Efficacy of 99mTc-DTPA orbital SPECT/CT on the evaluation of lacrimal gland inflammation in patients with thyroid associated ophthalmopathy

Abstract

To investigate the values of orbital single photon emission computed tomography/computerized tomography (SPECT/CT) with 99mTc-diethylene triamine pentaacetic acid (99mTc-DTPA) on the evaluation of lacrimal gland inflammation in patients with thyroid associated ophthalmopathy (TAO). Methods: A total of 58 TAO patients were retrospectively recruited for this study, all of whom were categorized into all active group and all inactive group based on the clinical active score (CAS). Another 12 patients with the negative images on SPECT/CT served as a normal control group (NC). All patients were undergone the 99mTc-DTPA orbit SPECT/CT. Quantitative parameters of lacrimal gland including width, length, volume, and the count ratio of region of interest (ROI) drawn on lacrimal gland to the region of occipital brain (target/non-target ratio, T/NT), were measured on axial and coronal slices, respectively. Quantitative parameters were compared among the 3 groups, and the diagnostic value on discrimination of TAO patients from inactive to active ones was evaluated. Results: All parameters in TAO patients (except the length on coronal slices and the mean radioactive counts of axial T/NT in the TAO inactive group) were much greater than those in the NC group (P<0.05). All parameters in the TAO active group (except the length on axial and coronal slices) were much greater than those in the TAO inactive group (P<0.05). There were significant lineal positive correlations between the parameters in all TAO patients (except the length on coronal slices ) and CAS. The best diagnostic value was detected by the max radioactive counts of axial T/NT (area under the curve=0.82, P<0.01). Conclusion: As an invasive imaging modality, 99mTc-DTPA orbital SPECT/CT is helpful to estimate the lacrimal gland inflammation and to assess the disease activity in TAO patients.