Could superb microvascular imaging or shear wave elastography tell us the growth record of suspicious thyroid nodules measuring ≤ 10 mm? A retrospective study.

purposeIdentifying TR5 nodules smaller than 10 mm that have increased in size is an important issue in clinical practice. Our study investigated whether superb microvascular imaging (SMI) and shear wave elastography (SWE) could help identify previous enlargement in ACR TI-RADS 5 (TR5) thyroid nodules measuring ≤ 10 mm.

methodsEach nodule underwent ultrasound examination for SMI and SWE. VImax is the largest vascular index between the transverse and longitudinal sections. The SWV ratio is the ratio of thyroid nodules to peripheral glands. The enlargement of thyroid nodules was defined as a growth rate > 2 mm/y or an increase in size of > 3 mm in the largest dimension.

resultsOf all 51 TR5 TNs, 25 (49.0%) were defined as enlarged nodules. Regarding vascular and elasticity features, enlarged nodules were more likely to present intra-nodular vascularity (80.0% vs. 46.2%, p = 0.03), had higher VImax (21.18 ± 8.31 vs. 15.77 ± 9.96, p = 0.03), and lower mean SWV-ratio (1.27 ± 0.38 vs. 1.66 ± 0.37, p < 0.001) compared with stable nodules. Multivariable logistic regression showed that mean of SWV-ratio (β=-3.35, p = 0.005), initial size (β=-1.06, p = 0.003), and intra-nodular vascularity (β = 1.97, p = 0.049) were independent predictors of nodule growth, whereas VImax was not significant. A logistic regression model incorporating these three variables demonstrated excellent discriminative ability, with an area under the ROC curve of 0.882 (95% CI, 0.786-0.977) based on 2000 bootstrap iterations.

conclusionIn our study, intranodular vascularity and a low shear wave velocity ratio may help identify those nodules that have experienced enlargement. Owing to the small sample size and retrospective study design of our study, more prospective studies with large sample sizes should be conducted to study the value of SMI and SWE in managing suspicious thyroid nodules.