## 3 Results
### Shear Wave Elastography  
Table 3 shows the SWE indices of benign and malignant thyroid nodules. The results showed that malignant thyroid nodules were associated with higher SWE indices. The median of \(E_{\text{maximum}}\) of malignant nodules (85.2 \(\pm\) 8.1 kPa) was significantly higher than that of benign nodules (50.3 \(\pm\) 3.1 kPa) (\(p\) \(<\) 0.05). Similarly, the median of \(E_{\text{mean}}\) of malignant nodules was 26.6 \(\pm\) 2.5 kPa and of benign nodules was 20.2 \(\pm\) 1 kPa, and the difference was statistically significant (\(p\) \(<\) 0.05). However, no significant difference was found in \(E_{\text{minimum}}\) between benign and malignant nodules (\(p\) \(>\) 0.05). Since significant difference was found between benign and malignant nodules in \(E_{\text{maximum}}\) and \(E_{\text{mean}}\) only, the evaluation of diagnostic accuracy was performed in these two SWE indices. With the use of ROC curves (Figure 5), the optimal cut-off of \(E_{\text{maximum}}\) and \(E_{\text{mean}}\) in distinguishing benign and \begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**Grey Scale Ultrasound Features**} & \multicolumn{2}{c}{**Number of Nodules (Percentage)**} & \multirow{2}{*}{**(\(p\)-Value**} \\ \cline{2-3} \cline{5-5}  & **Benign (\(n\) = 84)** & & **Malignant (\(n\) = 27)** & \\ \hline Microcalcification & & & \\ Yes & 6 (7.1\%) & 21 (77.8\%) & \textless{}0.05 \\ No & 78 (92.9\%) & 6 (22.2\%) & (0.12–0.49) \\ \hline Tall/width ratio \textgreater{}1 & & & \\ Yes & 11 (13.1\%) & 16 (59.3\%) & \textless{}0.05 \\ No & 73 (86.9\%) & 11 (40.7\%) & (0.29–0.74) \\ \hline Hypoechogenicity & - & - & - \\ Yes & 28 (33.3\%) & 25 (92.6\%) & \textless{}0.05 \\ No & 56 (66.7\%) & 2 (7.4\%) & (0.42–0.71) \\ \hline Irregular margins & & & \\ Yes & 14 (16.7\%) & 15 (55.6\%) & \textless{}0.05 \\ No & 70 (83.3\%) & 12 (44.4\%) & (0.38–0.83) \\ \hline Absent Halo sign & & & \\ Yes & 74 (88.1\%) & 26 (96.3\%) & \textgreater{}0.05 \\ No & 10 (11.9\%) & 1 (3.7\%) & (0.65–1.01) \\ \hline Internal solid educate & & & \\ Yes & 61 (72.6\%) & 27 (100\%) & \textgreater{}0.05 \\ No & 23 (27.4\%) & 0 (0\%) & (0.6–0.8) \\ \hline \end{tabular}
\end{table} 
Table 1: Grey scale sonographic features of benign and malignant thyroid nodules. \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Ultrasound Techniques**} & \multirow{2}{*}{**Sensitivity (\%)**} & \multirow{2}{*}{**Specificity (\%)**} & \multirow{2}{*}{**PPV (\%)**} & \multirow{2}{*}{**NPV (\%)**} & \multirow{2}{*}{**Accuracy (\%)**} & \multirow{2}{*}{**AUC**} \\ \hline \multirow{2}{*}{\(E_{\text{max}}\) (67.3 kPa)} & \multirow{2}{*}{70.4} & \multirow{2}{*}{70.2} & \multirow{2}{*}{43.2} & \multirow{2}{*}{88.1} & \multirow{2}{*}{70.3} & \multirow{2}{*}{0.785} \\  & & & & & & \\ \end{tabular} \begin{tabular}{c} \(E_{\text{max}}\) (67.3 kPa) \\ \hline \multirow{2}{*}{\(E_{\text{mean}}\) (23.1 kPa)} & \multirow{2}{*}{74.1} & \multirow{2}{*}{66.7} & \multirow{2}{*}{41.7} & \multirow{2}{*}{88.9} & \multirow{2}{*}{68.5} & \multirow{2}{*}{0.710} \\  & & & & & & \\ \end{tabular} \begin{tabular}{c} \(E_{\text{max}}\) (67.3 kPa) \\ \hline \multirow{2}{*}{\(E_{\text{mean}}\) (23.1 kPa)} & \multirow{2}{*}{70.4} & \multirow{2}{*}{88.3} & \multirow{2}{*}{57.6} & \multirow{2}{*}{89.7} & \multirow{2}{*}{80.2} & \multirow{2}{*}{0.769} \\  & & & & & & \\ \end{tabular} \
\begin{tabular}{c} \(E_{\text{mean}}\) (23.1 kPa) \\ \hline \multirow{2}{*}{\(\text{GSU}\) + \(E_{\text{max}}\) (67.3 kPa)} & \multirow{2}{*}{74.1} & \multirow{2}{*}{79.8} & \multirow{2}{*}{54.1} & \multirow{2}{*}{90.5} & \multirow{2}{*}{78.4} & \multirow{2}{*}{0.775} \\  & & & & & \\ \end{tabular}
\begin{tabular}{c} \hline \multirow{2}{*}{GSU, grey scale ultrasound, PPV, positive predictive value; NPV, negative predictive value, AUC, area under} \\ \end{tabular} \\ \end{tabular}
\end{table} 
Table 2: Diagnostic performance of grey scale ultrasound (GSU), shear wave elastography (SWE) indices and combination of GSU and SWE in evaluation of thyroid nodules.