## 4 Discussion  
This study evaluated left ventricular strain measurements using the CMR-FT technique to describe the utility of myocardium strain assessment for early diagnosis in pediatric patients, especially to detect subclinical cardiac abnormalities in DMD patients without cardiac symptoms. The method used the automatic segment LV contours at both the end-systole and end-diastole phases using the CVI42 software. Then, the CMR-FT technique was used to analyze the GCS, GRS, and GLS, since this technique can provide comprehensive insights into the myocardial function and mechanical deformation of the heart in different phases of the cardiac cycle. The LV volumes and EF were measured using endocardi and epicardium contours during the ED and ES phases without including papillary muscles. A comparative analysis was carried out with existing studies to assess the performance and demonstrate the clinical contribution of the proposed work. The average age of the healthy controls was 11.30 \(\pm\) 2.72 years. The cardiac functions and volumes indexed to BSA were normal. The average age of the DMD population was 10.56 \(\pm\) 1.79 years. The DMD patients had normal cardiac chamber volumes. At the same time, the mean LVEF of the DMD boys was at the lower standard limit: 56.14 \(\pm\) 3.51%. All DMD patients had statistically significantly lower weight, height, and body surface area than the healthy controls. Various studies showed the same finding [19; 20; 21; 22; 23; 24]. This is explained by a reduced growth velocity in DMD boys [19]. The current study has revealed that DMD patients exhibit decreased GCS, GLS, and GRS compared to healthy controls. For example, [PERSON] et al. [21] revealed that DMD cardiomyopathyopathy is associated with a notable decline in the GCS. The mean GCS assessed via CMR-FT was considerably lower in the DMD patients than in the controls: \(-\)18.8 \(\pm\) 6.1% vs. \(-\)25.5 \(\pm\) 3.2%; \(p\)-value \(<\) 0.05, with notable variations observed at anterolateral, inferolateral, as well as inferior segments. A related study has highlighted the myocardial strain as an important marker of myocardial dysfunction in individuals with DMD using CMR-FT [23]. In comparison, the current study achieved for the DMD patients a GCS of \(-\)16.71 \(\pm\) 4.18% vs. \(-\)16.12 \(\pm\) 3.55%, GLS: \(-\) 14.9 \(\pm\) 41.91% vs. \(-\)13.79 \(\pm\) 5.28% and GRS: 38.3 \(\pm\) 9.80% vs. 27.24 \(\pm\) 2.44. Another research study by [PERSON] et al. [25] performed a study using CMR in 30 DMD-associated cardiomyopathy and 30 age-matched DMD patients without associated cardiomyopathyopathy patients. They proved that before DMD-associated cardiomyopathy onset, GRS and GCS were significantly lower in DMD-associated cardiomyopathy compared with DMD without associated cardiomyopathy (25.1 \(\pm\) 6.0 vs. 29.0 \(\pm\) 6.3, \(p\) = 0.011; \(-\)15.4% \(\pm\) 2.4 vs. \(-\)17.3% \(\pm\) 2.6, \(p\) = 0.003). The study suggest that cardiac MRI strain analysis is a valuable tool for predicting the onset of DMD-associated cardiomyopathy. Additionally, a study on DMD patients compared CMR imaging with TTE, including TDI and STE, for diagnosing cardiomyopathy in boys with DMD at an early ambulatory stage [24]. The results demon \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Variable**} & \multicolumn{2}{c}{**GCS (\%)**} & \multicolumn{2}{c}{**GLS (\%)**} & \multicolumn{2}{c}{**GRS (\%)**} \\ \cline{2-7}  & \(\beta\) & \(p\)**-Value** & \(\beta\) & \(p\)**-Value** & \(\beta\) & \(p\)**-Value** \\ \hline ES wall thickness (mm) & \(-\)0.26 & **0.002** & \(-\)0.09 & **0.003** & 0.06 & 0.82 \\ ED wall thickness (mm) & 0.20 & 0.319 & \(-\)0.06 & 0.730 & 0.03 & 0.92 \\ Wall thickening (\%) & \(-\)0.30 & **0.010** & \(-\)0.29 & **0.040** & 0.08 & 0.78 \\ \hline \hline \end{tabular} \(\beta\): standardized coefficients (beta). Significant \(p\)-values are indicated in bold.  
\end{table} 
Table 6: Results of the multivariable linear regression of the myocardial global strain.