Evaluation of the Relationship Between Resistive Index, Elastographic Stiffness, and TIRADS Category in Thyroid Nodules

Objective:To investigate the relationship between Doppler-derived resistive index(RI) values, TI-RADS categories, and shear-wave elastography(SWE) parameters in solid thyroid nodules, and to determine whether RI contributes additional value to imaging-based characterization.Material-Methods:This retrospective study included 52 patients with 52 solid thyroid nodules larger than 1 cm. All nodules were evaluated with grayscale ultrasonography, Doppler sonography, and SWE. TI-RADS categories were assigned according to standard B-mode criteria. Vascularity was classified into four Doppler patterns, and RI was measured from intranodular arterial flow in nodules exhibiting pattern 2 or 3 vascularization. SWE measurements included mean shear-wave velocity(Vmean) and velocity standard deviation(Vsd). Associations between RI and demographic(age,sex), morphologic(nodule size,TI-RADS),and elastographic(Vmean,Vsd) variables were analyzed using correlation and nonparametric tests. Histopathology was available only in a limited subgroup and was therefore not used as a primary endpoint.Results:The mean age was 49.28±14.55 years; 88.5% of patients were male. TI-RADS categories were TI-RADS 2 in 19 nodules(36.5%), TI-RADS 3 in 29 nodules(55.8%), and TI-RADS 4 in 4 nodules(7.7%). Mean nodule diameter was 17.06±6.63 mm. Vmean and Vsd were 2.47±0.86 m/s and 0.62±0.39 m/s, respectively. Mean RI was 0.52±0.14. RI showed no significant association with age, sex, nodule side, size, Vmean, or Vsd. Although RI values were slightly higher in TI-RADS≥3 nodules compared to lower TI-RADS categories, this difference was not statistically significant(p=0.054).Conclusion:In this preliminary cohort, RI was not significantly associated with TI-RADS classification or SWE-derived stiffness parameters. These findings suggest that RI offers limited additional diagnostic value beyond conventional ultrasonography and elastography in the structural evaluation of thyroid nodules.