Usefulness of two-point Dixon T2-weighted imaging in thyroid-associated ophthalmopathy: comparison with conventional fat saturation imaging in fat suppression quality and staging performance

Abstract

Objective:To compare the two-point Dixon T2weighted imaging (T2WI) with conventional fat-sat T2WI in fat suppression (FS) quality and staging performance for patients with TAO.Methods:We enrolled 37 thyroid-associated ophthalmopathy (TAO) patients and 15 healthy controls who underwent both coronal two-point Dixon and fat-sat T2WI. Qualitative (overall imaging quality, FS uniformity) and quantitative [signal intensity ratio of extraocular muscle (EOM-SIR)] parameters were assessed between the two-point Dixon T2WI and fat-sat T2WI. Additionally, water fraction of intraorbital fat (IF-WF) was measured on Dixon image. Dixon-EOM-SIR, Fat-sat-EOM-SIR and Dixon-IF-WF values were compared between active and inactive TAO groups, and the diagnostic efficiency for the active phase were evaluated.Results:Two-point Dixon T2WI showed significantly higher overall image quality score, FS uniformity score as well as EOM-SIR value than fat-sat T2WI in both TAO and control groups (all p < 0.05). Active TAOs had significantly higher Dixon-EOM-SIR (p < 0.001), Fat-sat-EOM-SIR (p < 0.001) and Dixon-IF-WF (p = 0.001) than inactive TAOs. ROC curves analyses indicated that Dixon-EOM-SIR ≥3.32 alone demonstrated the highest staging sensitivity (75.0%). When integrating Dixon-EOM-SIR ≥3.32 and Dixon-IF-WF ≥0.09, improved staging efficiency and specificity could be achieved (area under the curve, 0.872; specificity, 97.1%).Conclusion:Compared with conventional fat-sat technique, two-point Dixon T2WI offers better image quality, as well as improved staging sensitivity and specificity for TAO. Dixon T2WI is suggested to be used to evaluate the patients with TAO in clinical practice.Advances in knowledge:Two-point Dixon T2WI offers better image quality than fat-sat T2WI. Dixon-EOM-SIR alone demonstrated the highest staging sensitivity. Combining with Dixon-IF-WF showed improved staging efficiency and specificity. Dixon T2WI is suggested to be used to evaluate TAO patients in clinical practice.