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.

OBJECTIVE

To compare the two-point Dixon weighted imaging (WI) with conventional fat-sat WI 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 WI. Qualitative (overall imaging quality, FS uniformity) and quantitative [signal intensity ratio of extraocular muscle (EOM-SIR)] parameters were assessed between the two-point Dixon WI and fat-sat WI. 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 WI showed significantly higher overall image quality score, FS uniformity score as well as EOM-SIR value than fat-sat WI in both TAO and control groups (all < 0.05). Active TAOs had significantly higher Dixon-EOM-SIR ( < 0.001), Fat-sat-EOM-SIR ( < 0.001) and Dixon-IF-WF ( = 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 WI offers better image quality, as well as improved staging sensitivity and specificity for TAO. Dixon WI is suggested to be used to evaluate the patients with TAO in clinical practice.

ADVANCES IN KNOWLEDGE

Two-point Dixon WI offers better image quality than fat-sat WI. Dixon-EOM-SIR alone demonstrated the highest staging sensitivity. Combining with Dixon-IF-WF showed improved staging efficiency and specificity. Dixon WI is suggested to be used to evaluate TAO patients in clinical practice.