## 3 Results
### Comparison of Elastography Techniques: SE versus 2D-SWE in Diagnosing Thyroid Nodules  
Following the main aim of this research, elastography parameters were compared, as displayed in Table 6 and Figure 7. Significant differences were identified between the median values in all five parameters quantifying tissue elasticity: the mean (Mean EI) and maximum (Max EI) elasticity index, the SWE ratio, the qualitative SE evaluation (Asteria score) and the strain ratio, when comparing malignant versus benign nodules.  
The two parameters are comparable in terms of diagnostic accuracy (90.4% for Mean EI versus 89.3% for the strain ratio). In terms of ROC curve statistics, both tests proved to have excellent results (AUC > 0.9). The difference between the ROC curves was not significant (difference between areas, 0.0645; \(p\)-value, 0.0952). The specificity and NPV were  
Figure 4: Risk upgrade from intermediate risk in B-mode to high risk in B-mode + SWE due to increased stiffness (Mean EI = 68.2 kPa). Pathology report confirmed PTC.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**AUC**} & \multicolumn{2}{c}{**Cut-Off**} & \multirow{2}{*}{**Sensitivity**} & \multirow{2}{*}{**Specificity**} & \multirow{2}{*}{**PPV**} & \multirow{2}{*}{**NPV**} \\  & & & & & & \\ \hline Qualitative assessment & \multirow{2}{*}{0.848} & \multirow{2}{*}{\textgreater{2}} & \multirow{2}{*}{89.6\%} & \multirow{2}{*}{69.2\%} & \multirow{2}{*}{56.5\%} & \multirow{2}{*}{93.7\%} \\ (Asteria score) & & & & & & \\ Strain ratio & 0.905 & \textgreater{}3.9 & 82.7\% & 92.3\% & 82.8\% & 92.3\% \\ \hline \hline \end{tabular} AUC—the area under the receiver operating characteristic curve; PPV—positive predictive value; NPV—negative predictive value.  
\end{table}
Table 5: The diagnostic performance of SE parameters: Asteria score and strain ratio for the presence of thyroid malignancy, using the pathology report as reference.  
slightly improved for the Mean EI compared to the strain ratio (95.4% and 91.2% versus 92.3% and 92.3%).  
Figure 8 displays the comparison of ROC curves for the two elastography parameters: Mean EI for SWE and strain ratio for SE, for conventional US and for the combination of elastography and B-mode US, respectively.  
Figure 5: The performance of SE parameters in the diagnosis of thyroid cancer (receiver operating characteristic curve): the strain ratio and Asteria score/colormap analysis.  
Figure 6: Risk upgrade from intermediate risk in B-mode to high risk in B-mode + SE due to increased stiffness (Asteria 3). Pathology report confirmed PTC.  
The two elastography evaluations were compared using the best-performing parameters for each type of evaluation: the Mean EI value for 2D-SWE and the strain ratio for SE. The two elastography methods were compared to conventional ultrasound, and to the combined B-mode and elastography assessments, as displayed in Table 7.  
As displayed in Table 8, the vast majority of cancers were stiff, regardless of the elastographic technique that was used. The majority of benign lesions were soft, regardless of the elastography technique that was used for measurements. There was a disagreement between the two evaluations in a total of 13 cases (13.8%).