背景：尽管侧颈淋巴结（LN）的转移在乳头状甲状腺癌（PTC）中很常见，但是正确诊断超声检查（US）中小的淋巴结转移仍有挑战。利用增强超声检查（CEUS），尤其是使用富氟丁烷造影剂的后血管期CEUS，可能有助于提高PTC患者淋巴结转移的诊断。目的：评估在疑似PTC患者的小侧颈淋巴结（短轴直径≤8mm）中，使用富氟丁烷的CEUS在后血管期的诊断价值。材料和方法：本单中心研究招募了2020年10月至2021年10月连续被确诊为PTC并在US中出现可疑淋巴结的参与者。所有参与者在活检或手术前1周接受intravenous perfluorobutane造影剂CEUS检查，检查结果包括LN的血管期（注射后的5-60秒）和后血管期（注射后的10-30分钟）。基准标准为LN的细胞学和手术病理学评估。计算了声像图特征的敏感性、特异性、阳性预测值、阴性预测值和准确度，并使用多变量 logistic 回归模型评估了US、CEUS和后血管期和US特征的诊断表现。结果：共评估了135名参与者（年龄中位数36岁[IQR，30-46岁]；女性100人），包括161个在US中可疑的LN，其中67个为转移性LN，94个为良性LN。血管期低灌注缺损作为声像图特征的特异性达到96％（94个LN中的90个），后血管期无同位增强（即低增强、部分增强和无增强）的阴性预测值达到100％（83个LN中的83个）。后血管期和US特征的组合的受试者工作特征曲线下面积（AUC）为0.94（95％CI：0.89、0.97），显著高于仅使用US特征的AUC（0.73； 95％CI：0.65、0.79；P＜0.001）。结论：富氟丁烷的CEUS在后血管期的表现非常优秀，可用于诊断PTC参与者的可疑小侧颈淋巴结。以CC BY 4.0许可证发布，此文章的补充材料可供参考。请参考本期编辑Gunabushanam的社论。

Background Although metastasis of lateral cervical lymph nodes (LNs) is common in papillary thyroid carcinoma (PTC), correctly diagnosing small metastatic LNs with US remains challenging. The use of contrast-enhanced US (CEUS), especially the postvascular phase of CEUS with perfluorobutane contrast material, might contribute to improved diagnosis of metastatic LNs in PTC. Purpose To assess the diagnostic value of the postvascular phase of CEUS with perfluorobutane in suspicious small lateral cervical LNs (short-axis diameter ≤8 mm) in patients with PTC. Materials and Methods This single-center study prospectively enrolled consecutive participants with confirmed PTC and suspicious LNs at US from October 2020 to October 2021. All participants underwent CEUS, 1 week before biopsy or surgery, with intravenous perfluorobutane contrast material to visualize the LNs in the vascular phase (5-60 seconds after injection) and postvascular phase (10-30 minutes after injection). The reference standard was cytologic and surgical histologic assessment of the LNs. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of sonographic features were calculated, and the diagnostic performance of US, CEUS, and the combination of postvascular phase and US features was assessed using multivariable logistic regression models. Results A total of 135 participants (median age, 36 years [IQR, 30-46 years]; 100 women) with 161 suspicious LNs at US were evaluated, including 67 metastatic and 94 benign LNs. The specificity of perfusion defect as a sonographic feature in the vascular phase reached 96% (90 of 94 LNs), and the negative predictive value of non-isoenhancement (ie, hypoenhancement, partial enhancement, and no enhancement) in the postvascular phase reached 100% (83 of 83 LNs). The area under the receiver operating characteristic curve (AUC) of the combination of postvascular phase and US features was 0.94 (95% CI: 0.89, 0.97), significantly higher than that of US features alone (AUC, 0.73; 95% CI: 0.65, 0.79; P < .001). Conclusion The postvascular phase of CEUS with perfluorobutane demonstrated excellent performance for diagnosing suspicious small lateral cervical LNs in participants with PTC. Published under a CC BY 4.0 license Supplemental material is available for this article. See also the editorial by Gunabushanam in this issue.