## 3 Results
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Stiffness Score** & \multicolumn{2}{c}{**Prevalence of Cancer (\%)**} \\ \hline Low-risk SE & Score 1 & 2/22 (9.1\%) \\ Score 2 & 3/20 (15.0\%) \\ \hline High-risk SE & Score 3 & 8/12 (66.6\%) \\ Score 4 & 8/10 (80.0\%) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The prevalence of malignant cases corresponding to qualitative SE classification. At 3D Doppler evaluation, 11 nodules presented with no vascularization in the thyroid tissue surrounding the nodule, 15 nodules had low perinodular vascularization, and 36 nodules had moderate and marked perinodular vascularization. The vast majority of malignant nodules showed significant vascularization in the surrounding tissue. Taking into consideration that lesions with low and absent perinodular vascularization are probably benign and those with moderate to high perinodular vascularization are suggestive of malignancy, volumetric Doppler showed 71.43% sensitivity, 90.7% specificity, a PPV of 78.9%, NPV of 86.7%, and an accuracy of 84.37% in detecting thyroid cancer. The cancer prevalence values in the described 3D Doppler categories are shown in Table 3. When 3D Doppler is considered alone, the area under ROC curve displayed in Figure 4 also shows a very good value (0.85, CI = 0.747\(-\)0.932). Most of the cases that proved malignant on the pathology report (15/21) did show important perinodular 3D vascularization. Although 3D Doppler seems to be a good evaluator by itself, it is more relevant to include it in a more complex algorithm for detecting cancerous lesions. Figure 3: The area under the receiver operating characteristic (AUROC) curve for elastography in the evaluation of cases with Bethesda III and IV cytology compared to the pathology report. When analyzing the group of malignant lesions, a considerable majority (16/21) displayed an elastogram illustrating increased stiffness. Five cases had low stiffness: three follicular neoplasia with unclear prognosis, one papillary cancer, and one follicular cancer. \begin{table}
\begin{tabular}{c c c} \hline \multicolumn{2}{c}{**3D Vascularization**} & \multicolumn{2}{c}{**Prevalence of Cancer (\%)**} \\ \hline Low-risk 3D & Absent & 2/28 (7.1\%) \\ Low & Low & 4/17 (23.5\%) \\ \hline High-risk 3D & Moderate & 6/8 (75\%) \\ Severe & 9/11 (81.8\%) \\ \hline \end{tabular}
\end{table} 
Table 3: The prevalence of malignant cases corresponding to the reported volumetric Doppler evaluation. The risk of malignancy predicted by conventional US alone was compared to the risk upgrade given by the elastographic information, 3D Doppler information, and both volumetric Doppler and elastographic information. The compared sensitivity, specificity, PPV, NPV, and accuracy are presented below in Table 4. We considered iso/hyper or mildly hypoechoic nodules without any suspicious sign as low risk; while those that were intensely hypoechoic as mild risk. In cases where more than two suspicious signs were present, we considered the nodule to belong to the high-risk class. When taking into account all information given by 2B ultrasound as well as both elastography and volumetric Doppler, we considered the most severe ultrasound characteristics: conventional, strain, or perinodular vascularization. There was only an upgrade type of risk evaluation; we did not downgrade the risk category in the presence of low stiffness or absence of perinodular vascularization. There are some other signs in grayscale US that associate a sensitivity of 100%, such as intranodular microcalcifications and the presence of lymph nodes with altered central hilum. However, the low prevalence of these signs does not ensure a good specificity.