Tc-99m DTPA orbital SPECT/CT guided Selection for riamcinolone Acetonide Injection in Patients with Thyroid Associated Ophthalmopathy

Objectives: In Thyroid Associated Ophthalmopathy(TAO), only patients with immunologically active disease respond to immunosuppressive therapy. Previous studies demonstrated that elevated orbital Tc-99m diethylenetriamine-pentaacetic-acid (DTPA) single photon emission computed tomography/computed tomography (SPECT/CT) reflects inflammatory activity. We therefore investigate whether TAO patients with high DTPA uptake would benefit from immunosuppressive therapy, and determine whether this method is suitable for predicting the effectiveness of this therapy.

Methods: Forty-eight TAO patients (male,22, age 43±12 years) suspected active TAO were retrospectively enrolled, and 14 patients(male,6, age 43±13 years) were served as the normal control. All patients received Tc-99m DTPA orbital SPECT/CT scan in the initial visit. 90 orbits received 20mg triamcinolone 40mg/ml perispherical injection once a week, for 7 weeks. After 5.8 ±1.9 months, a follow-up scan was performed in all TAO patients. Thickness and DTPA uptake ratio (UR) of each extraocular muscles(EOM), including lateral rectus(LR), medial rectus(MR), superior rectus(SR), inferior rectus(IR), and their changes after therapy were assessed.

Results: The thickness and DTPA uptake ratio of each EOM in 90 orbits of TAO patients were higher than that in 28 orbits of normal controls(all P<0.01).We stratified TAO patients according to the initial clinical activity score into two groups: active group(CAS>3,n=57) and inactive group(CAS&#8804;3,n=33) . In active group, the thickness and DTPA UR of all EOMs were declined after treatment( all P<0.05). The inactive group yielded the similar results, whereas no difference of DTPA UR of MR and IR was observed after treatment(both P>0.05). Average change in DTPA UR of each EOM after treatment was positively correlated with the initial DTPA UR(LR: r=0.70; MR: r=0.67; SR r=0.68; IR r=0.59; P<0.001).

Conclusions: As an invasive imaging modality, Tc-99m DTPA orbital SPECT/CT is helpful for assessment of disease activity in TAO patients. TAO with a high DTPA uptake may predict the response to orbital triamcinolone acetonide treatment.