[Evaluation of inflammatory activity in thyroid associated ophthalmopathy by SPECT/CT with 99mTc-DTPA]

To evaluate the inflammatory activity in thyroid associated ophthalmopathy (TAO) by 99mTc-diethylene triamine pentaaceticacid (99mTc-DTPA) orbital single-photon emission computed tomography (SPECT)/CT.
 Methods: A total of 48 patients were enrolled from Xiangya Hospital of Central South University between October 2016 and March 2017. According to clinical active score (CAS), 93 eyes were divided into a TAO active group (n=72) and a TAO inactive group (n=21). All patients underwent 99mTc-DTPA orbital SPECT/CT examination, and the DTPA uptake in extraocular muscle belly was supposed to be positive. The results of 99mTc-DTPA orbital SPECT/CT examination were compared with those of CAS score evaluation.
 Results: The uptake rate (UR) of 99mTc-DTPA in the TAO active group was higher than that in the TAO inactive group (P<0.01). There was a linear positive correlation between UR and its CAS scores in all patients (r=0.767, P<0.01). Five cases (7 eyes) showed inconsistent results between 99mTc-DTPA orbital SPECT/CT examination and CAS score. Among the 7 eyes, 6 eyes showed myocarditis lesions in 99mTc-DTPA orbital SPECT/CT examination while its CAS was no more than 3; meanwhile, there was 1 eye with CAS>3, but 99mTc-DTPA orbital SPECT/CT examination showed negative myocarditis lesions.
 Conclusion: 99mTc-DTPA orbital SPECT/CT is consistent with the CAS score in evaluation of the disease activity of TAO; 99mTc-DTPA orbital SPECT/CT may be more objective and accurate to evaluate TAO than CAS.