Evaluation of ultrasound accuracy in thyroid mass measurement and its impact on 131I treatment for Graves’ disease

Background Thyroid mass is crucial for 131 I treatment of Graves’ disease (GD). However, the accuracy of ultrasound (US) - based thyroid mass measurement remains controversial. Methods This retrospective study included patients who underwent thyroid US and CT scans. The differences correlation, and agreement in thyroid mass measurements between the two methods were analyzed. Data from GD patients who received their first 131 I treatment were collected and evaluated at a 6-month follow-up. Regression analyses identified clinical factors for treatment efficacy and developed a predictive model. Results A statistically significant difference was observed in thyroid mass measurements exceeding 20 g between US and CT. (Z = -11.493, P<0.001). Despite a strong correlation between the two methods (r = 0.9809, P=0.001), the average relative error remained substantial (0.19 ± 11.65%). Poor agreement was observed between CT and US (mean bias: 16.65g; ICC = 0.179, p = 0.087). Disease duration, FT 4 level, 24 - hour radioactive iodine uptake, 131 I dose and thyroid mass were identified as independent risk factors influencing the efficacy of the initial 131 I treatment (p<0.05). Based on these factors, a predictive model was developed and evaluated using ROC curves, DCA and CAL. The model demonstrated an AUC of 0.663 (95% CI = 0.631-0.695). Conclusion US may underestimate the true thyroid mass in large-mass cases; therefore, CT calibration is recommended before initiating 131 I treatment. The proposed predictive model provides valuable guidance for optimizing initial 131 I treatment in patients with GD.