## 3 The Opportunities and Challenges of Ultrasound-Based Elastography in Children NAFLD
performed a study on 68 pediatric patients with histologically proven NASH according to the Brunt scoring system, and found that SWE established correctly the fibrosis stage in 57 of 68 patients (84%), with higher accuracy in patients with advanced fibrosis. The authors encountered that 6.7 kPa might be a reliable cutoff value for delineating fibrosis stages [112]. Similar findings were reported by [PERSON] et al. on 67 children with histologically proven NAFLD according to the Kleiner's system, who stated that TE is a useful non-invasive indicator of clinically significant liver fibrosis guiding the proper selection of patients that require liver biopsy [115]. Another recent meta-analysis involving 723 patients underlined that TE represents is a highly accurate method for the diagnosis of liver fibrosis in children with a sensitivity of 95% and a specificity of 90% in the setting of significant liver fibrosis, above stage 2 [118]. The most relevant studies that assessed NAFLD in children using ultrasound-elastography based methods are described in Table 4.  
Conventional ultrasound might also reveal certain liver abnormalities indicative of liver steatosis or fibrosis, such as abnormal echogenicity or focal lesions, but its capacity is definitely overpassed by elastography. Therefore, a study that compared SWE and conventional ultrasound findings in children with obesity and normal weight ones pointed out that mean SWE velocity values were significantly higher in the obese group with abnormal liver echogenicity at conventional ultrasound that in those with apparently normal aspect of liver, but the authors failed in identifying a significant difference in normal weight children [68]. In terms of conventional ultrasound, similar findings were identified by [PERSON] et al., who showed that children with overweight/obesity are more frequently identified with abnormal liver aspects, such as hepatomegaly and hyperchogenicity as compared to normal weight ones [5]. Thus, conventional ultrasound might represent the first step in assessing children with obesity and diagnosing NAFLD [119] in order to guide them for elastography staging, which is definitely associated with greater costs. Contrarily, a study performed on 148 school-aged children concluded as a result of ARFI examination that significant liver fibrosis might be present even in the setting of normal laboratory parameters or normal ultrasound liver aspect [120]. \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline \multirow{2}{*}{**Author, Year, and Country**} & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } & \multicolumn{3}{c}{**Elastography**} & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{} \end{tabular} } \\  & & & & & & \\ \cline{1-1} \cline{6-6} \cline{8-8}  & \multirow{2}{*}{
\begin{tabular}{} \end{tabular} } & & & **Age (Years)** & & & **Gold** \\ \cline{1-1} \cline{6-6} \cline{8-8}  & & & **Mean/Median * & **Diagnosis** & **Standard and Score** & **(TE/p-SWE/2D-SWE)** & **Values** & **Standard/Cut-off** \\ \cline{1-1} \cline{6-6} \cline{8-8}  & & & & **Type** & **SWE** & **AUROC** \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Elastography in children with nonalcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH) compared to histological findings obtained by liver biopsy (gold standard).