## 3 Results  
A total of 200 images were captured and included for analysis, 50 per experienced examiner and 50 per novice examiner. From these 200 images, 200 measurements were obtained from the lateral areas and 200 measurements from the central area of the images. Table 1 shows inter-examiner reliability (agreement between two examiners expressed as the difference between their measurements to obtain information regarding the extent to which the results can be reproduced under the same conditions) and instrument variability data of SR calculations (considered as the extent to which measurements diverge from the average value). In general, the agreement between examiners and variability of measurements was higher in the central area than in the lateral areas of the images (the difference between examiners for each location ranged between 0.00-0.13 and 0.00-0.01, respectively). Thus, the experience of the examiner was relevant for the concordance of the measurements in the lateral areas of the images (_p_ < 0.05), but not for the central area (_p_ > 0.05). Like reliability, validity is another concept used to evaluate the quality research. Even if an instrument shows excellent reliability and results are reproducible, they might not be correct. Therefore, validity provides information regarding the accuracy of one instrument comparing a known value with the obtained value. Validity estimates of semi-quantitative elastography for calculating SR within the same image are reported in Table 2. In general, the experience level of the examiner does not seem to be an influential factor since the error and absolute error differences showed no significant differences between novice and experienced examiners (_p_ > 0.05). However, the mean error of measurements was significantly higher (_p_ < 0.001) in the lateral areas compared to the central area of the image (0.14 \(\pm\) 0.05 and 0.05 \(\pm\) 0.02 respectively). SR calculations of the experienced and novice \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Examiner 1** & **Examiner 2** & **Examiner 3** & **Examiner 4** \\  & **(Experienced)** & **(Experienced)** & **(Novice)** & **(Novice)** \\  & **(n = 50 Images)** & **(n = 50 Images)** & **(n = 50 Images)** & **(n = 50 Images)** \\ \hline \hline \multicolumn{5}{c}{_Lateral areas of the image_} \\ \hline SR obtained \({}^{\dagger}\) & 0.96 & 0.98 & 1.09 & 1.10 \\
95\% CI (Lower; upper limits) & 0.92; 1.00 & 0.90; 1.05 & 1.04; 1.14 & 1.03; 1.16 \\ Variability of the measurements (\%) & 14.75 & 17.50 & 17.40 & 15.42 \\  & 0.01 \(\pm\) 0.04 a & & 0.11 \(\pm\) 0.05 d,\({}^{\ddagger}\) \\ Difference between examiners & 0.12 \(\pm\) 0.03 b,\({}^{\ddagger}\) & & 0.12 \(\pm\) 0.04 e,\({}^{\dagger}\) \\  & 0.13 \(\pm\) 0.04 c,\({}^{\ddagger}\) & & 0.00 \(\pm\) 0.04 f \\ \hline \multicolumn{5}{c}{_Central area of the image_} \\ \hline SR obtained & 0.97 & 0.97 & 0.96 & 0.97 \\
95\% CI & 0.95; 0.98 & 0.95; 0.99 & 0.94; 0.98 & 0.94; 1.00 \\ Variability of the measurements (\%) & 5.61 & 5.38 & 6.94 & 7.80 \\  & 0.00 \(\pm\) 0.01 a & & 0.01 \(\pm\) 0.01 d & \\ Difference between examiners & 0.00 \(\pm\) 0.01 b & & 0.00 \(\pm\) 0.01 e & \\  & 0.00 \(\pm\) 0.02 c & & 0.01 \(\pm\) 0.02 f \\ \hline \multicolumn{5}{c}{_Differences between measurement locations_} \\ \hline SR difference & 0.00 \(\pm\) 0.02 & 0.00 \(\pm\) 0.04 & 0.13 \(\pm\) 0.02 * & 0.11 \(\pm\) 0.03 * \\ \hline \hline \end{tabular}  
* Examiner 1–Examiner 2; b Examiner 1–Examiner 3; c Examiner 1–Examiner 4; d Examiner 2–Examiner 3; e Examiner 2–Examiner 4; f Examiner 3–Examiner 4;
* Significant differences between measurements in the lateral areas and the central area (_p_ < 0.001); f Significant differences between examiners were found (_p_ < 0.05).  
\end{table} 
Table 1: Inter-examiner reliability and variability of semi-quantitative elastography stiffness ratio measurements. examiners in the central area showed no statistically significant differences with the known reference (\(p>0.05\)).