Application of SUV max of extraocular muscle on 99Tc m-DTPA orbital SPECT/CT for evaluating activity of thyroid associated ophthalmopathy / 中华核医学与分子影像杂志

ABSTRACT

Objective:To investigate the feasibility of maximum standardized uptake value (SUV max) of extraocular muscle during 99Tc m-diethylene triamine pentaacetic acid (DTPA) orbital SPECT/CT imaging for the clinical diagnosis and evaluation of thyroid associated ophthalmopathy (TAO). Methods:From July 2019 to April 2020, 38 patients (13 males, 25 females, age 15-77 (48.8±13.7) years; 76 eyes) diagnosed with TAO and 11 healthy volunteers (2 males, 9 females, age 20-87 (53.5±20.2) years; 22 eyes) were enrolled retrospectively from the Second Hospital of Dalian Medical University. According to the clinical activity score (CAS), 76 eyes were divided into active group (46 eyes) and inactive group (30 eyes). All subjects underwent 99Tc m-DTPA orbital SPECT/CT imaging, then SUV max and uptake ratio (UR) of extraocular muscles were measured and calculated by 3 nuclear medicine physicians. The corrected SUV max was obtained after correction. Kruskal-Wallis rank sum test and Bonferroni test were used to compare the differences of corrected SUV max and UR among the three groups. Spearman rank correlation analysis was used to analyze the correlation between corrected SUV max /UR and CAS. The receiver operating characteristic (ROC) curve analysis was used to evaluate the diagnostic efficacy of corrected SUV max and UR. Intra-class correlation coefficient (ICC) was used for reliability analysis to evaluate the consistency of corrected SUV max and UR among the 3 measurers. Results:The corrected SUV max of the extraocular muscles in the active group, inactive group and control group were 15.96(10.99, 19.63), 7.98(6.80, 9.28), 7.59(6.59, 8.20) respectively ( H=42.196, P<0.001), and UR were 2.17(1.65, 2.79), 1.22(1.03, 1.39), 1.12(0.99, 1.36) respectively ( H=40.642, P<0.001). The corrected SUV max and UR of the extraocular muscles in the active group were significantly higher than those in the inactive group ( H values -4.971, -5.053, both P<0.001) and in the control group ( H values -5.681, -5.436, both P<0.001), while there was no significant difference between the inactive group and the control group ( H values -1.190, -0.796, both P>0.05). Both corrected SUV max and UR were positively correlated with CAS ( rs values 0.653, 0.615, both P<0.001). The area under the ROC curve of corrected SUV max was 0.851, and the threshold value of corrected SUV max for distinguishing active and inactive periods was 10.125, with the sensitivity of 80.4%(37/46) and the specificity of 86.7%(26/30). The area under the ROC curve of UR was 0.845, and the threshold value for differentiating active and inactive periods was 1.565, with the sensitivity of 80.4%(37/46) and the specificity of 86.7%(26/30). The ICC of corrected SUV max and UR were 0.966(95% CI 0.953-0.976, P<0.001) and 0.618(95% CI 0.436-0.744, P<0.001) respectively. Conclusion:Compared with UR, SUV max may be a more promising index for estimating disease activity of orbits in patients with TAO.