Multimodality Ultrasound Utilizing Microvascular Flow Imaging and Shear Wave Elastography to Guide Fine-Needle Aspiration of Thyroid Lesions: A Prospective Study Validating Pattern-Based Microvascular Classification

<b><i>Background:</i></b> Most current guidelines recommend fine-needle aspiration (FNA) biopsy of thyroid nodules based on grayscale ultrasound (GUS) features, but the biopsy rate for benign nodules remains high. Our aim was to construct a new pattern-based microvascular classification (PBMC) for thyroid nodules to develop and validate predictive multimodality US models based on GUS, microvascular flow imaging, and shear wave elastography, and compare FNA decision accuracy with the American College of Radiology Thyroid Imaging Reporting and Data System (ACR TI-RADS). <b><i>Methods:</i></b> This prospective study included consecutive patients with thyroid nodules who underwent multimodality US examinations from September 2022 to December 2023. Using PBMC, lesions were divided into three categories: malignant signs (convergence sign, piercing sign, and spoke wheel sign), benign signs (ring sign), and other vascular patterns. Univariate and multivariable logistic regression analyses were conducted to determine the odds ratios (ORs) of US features, including vascular signs, and construct predictive models based on multimodality US. Multimodality US models were validated with internal cross-validation and evaluated based on discrimination, calibration, and decision curve analyses. <b><i>Results:</i></b> Overall, 793 thyroid nodules confirmed using pathological analysis (248 benign and 545 malignant) in 599 participants (mean age, 43 years ±11 [SD]) were included. In univariate logistic regression analyses, malignant vascular signs showed a positive association with malignant nodules (OR: 10.43, 95% confidence interval [CI]: 5.76, 18.88; <i>p</i> < 0.01), whereas benign vascular signs were inversely associated with malignancy (OR: 0.10, 95% CI: 0.06, 0.16; <i>p</i> < 0.01). Four multivariable models incorporated GUS features, Young's modulus, and PBMC. The highest area under the receiver operating characteristic curve (AUC) was 0.95 (95% CI: 0.82, 0.97) for the multimodality US model, and the lowest AUC was 0.62 (95% CI: 0.57, 0.66) for ACR TI-RADS based on GUS (<i>p</i> < 0.001). At a 71% risk threshold, multimodality US avoided 27% (95% CI: 21, 34) of FNA procedures, compared with 13% (95% CI: 0, 38) with TI-RADS (<i>p</i> < 0.001). <b><i>Conclusion:</i></b> Visual assessment of microvascular morphology patterns may improve differentiation of benign and malignant thyroid nodules and potentially reduce the risk of unnecessary biopsy of benign thyroid nodules.