Vascularity assessment in Hashimoto's thyroiditis: a prospective comparative study with power Doppler and superb microvascular imaging.

Purpose: To quantitatively evaluate the vascularity of the thyroid parenchyma in patients diagnosed with Hashimoto's thyroiditis (HT) compared with healthy controls by using vascularity index (VI) through power Doppler (PD) and color superb microvascular imaging (cSMI) and to determine a threshold VI value to effectively differentiate patients with HT and hypothyroid HT.

Methods: This prospective cross-sectional study involved 73 patients diagnosed with HT and 66 healthy controls. The diagnosis of HT was established based on clinical and laboratory findings. The total volume of the thyroid gland was measured, and the region of interest was drawn manually by delineating the gland boundaries for VI calculation on PD and cSMI. The mean VI for both lobes of the thyroid were computed for each participant. Statistical analyses were conducted using SPSS version 29.0, with receiver operating characteristic curve analysis employed to ascertain the optimal cSMI VI cut-off values for the diagnosis of HT and for patients with hypothyroid HT.

Results: The analysis revealed no significant differences in the total thyroid volume between the HT group and the control group, or between the hypothyroid and euthyroid HT subgroups. The SMI VI values were recorded at 8.85 [interquartile range (IQR): 25%-75%, 6.55-12.6] for patients with HT and 8.40 (IQR: 25%-75%, 6.70-12.8) for the control group, indicating a statistically significant increase in the HT cohort (P < 0.001). Additionally, the PD VI values in patients with HT were significantly higher than in the control group (P < 0.001). A strong positive correlation was identified between thyroid-stimulating hormone levels and cSMI VI in patients with HT (rho = 0.739, P < 0.001), whereas the correlation with PD VI was found to be weak (rho = 0.346, P < 0.001). The optimal cut-off value for SMI VI was 6.75% for the general diagnosis of HT and 8.825% for patients with hypothyroid HT.

Conclusion: This study indicates that the optimal threshold values of 6.75% for the diagnosis of HT and 8.825% for patients with hypothyroid HT suggest that cSMI is an effective and promising diagnostic tool for detecting alterations in thyroid vascularization. Furthermore, there is a strong concordance among radiologists regarding the VI measurements.

Clinical significance: The SMI technique represents a promising diagnostic tool for the detection of subtle alterations in thyroid vascularization. The higher sensitivity of cSMI in comparison to PD positions it as an innovative and effective technology for the assessment of HT, offering valuable insights into disease activity and progression.