Abstract
Objective To determine the value of 99Tcm-DTPA orbit SPECT/CT in evaluating the activity of thyroid-associated ophthalmopathy (TAO). Methods The 99Tcm-DTPA orbit SPECT/CT imaging data of 66 orbits of 33 patients [13 men and 20 women, age (45.36±13.44) years old] were retrospectively analyzed, along with the clinical activity score (CAS) and MRI of the 21 patients (42 orbits) . The orbit/occipital area's uptake ratio (UR) was calculated by the ROI. The activity of each extraocular muscle (EOM) on the SPECT/ CT and MRI images was assessed by visual analysis. MRI score of every orbit was obtained according to the number of active EOM, the range of which was 0-4 . As for the CAS, ≥3 represented the active stage, and the others denote the inactive stage. The UR between the active TAO and inactive TAO was compared using t test, the correlation between the UR and CAS/MRI score was calculated by Spearman analysis, and the consistency of the activity of every EOM assessed by SPECT/CT and MRI was evaluated by Kappa test. The receiver operating characteristic (ROC) curve was depicted to determine the diagnostic efficiency of SPECT/CT using CAS as the gold standard. Results ① CAS was moderately correlated with the UR of all the 66 orbits (r=0.441, P=0.000). The UR of the inactive group (1.20±0.58) was significantly lower than that of the active group (1.56±0.57) (t=-2.476, P=0.016). The area under the curve of the ROC was 0.679. The threshold differentiating the inactive phase from the active one was 1.20, with the sensitivity of 79.5% and with the specificity being 55.6%. ② The MRI score of the 42 orbits was significantly correlated with UR (r=0.515, P=0.000). The UR of the inactive group (1.00±0.60) was significantly lower than that of the active group (1.72±0.45) according to the MRI score (t=−4.438, P=0.000). ③ The activity of the 168 muscles assessed by 99Tcm-DTPA SPECT/CT was moderately consistent with that assessed by MRI (kappa=0.569, P=0.000). Conclusions 99Tcm-DTPA orbit SPECT/CT is a reliable and objective method to evaluate the activity of TAO, and it will be helpful in clinical practice. Key words: Thyroid-associated ophthalmopathy; Activity; Single photon emission computed tomography computed tomography; Diethylene-triaminepentaacetic acid
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