## 1 Introduction  
Myocardial strain represents a critical parameter for quantifying myocardial deformation throughout the cardiac cycle [1]. It provides detailed insights into the heart's mechanical function, particularly that of the myocardium, which is the heart's muscular tissue. The three primary strain categories are circumferential, radial, and longitudinal, which can be measured to reflect different aspects of cardiac function impairment [2]. Circumferential strain assesses deformation around the heart's circumference, radial strain evaluates myocardial thickening, and longitudinal strain examines changes along the length of the heart. Each component offers unique insights into myocardial performance and potential dysfunction [3, 4]. Strain measurements have demonstrated the ability to detect overall and localized myocardial dysfunction, distinguish between various typesof cardiac diseases, and serve as an earlier indicator of myocardial disease compared to ejection fraction (EF) [5]. Various imaging techniques have been developed to evaluate myocardial strain and further refine the assessment of ventricular function, considering the intricate architecture of the heart [6; 7]. Among these imaging techniques, transthoracic echocardiography (TTE) is the principal imaging modality for assessing myocardial strain primarily because of its widespread availability, ease of use, and non-invasive nature [8]. Advanced imaging techniques such as speckle tracking echocardiography (STE) and three-dimensional echocardiography offer detailed and accurate assessments of myocardial strain, providing valuable insights into myocardial function [9]. However, these modalities have limitations that can affect their application in clinical settings. These include the angle dependency of tissue Doppler ultrasound, the limitations of the acoustic window, and the precision and reproducibility of echocardiographic measurements, including strain imaging, which can vary significantly based on the operator's experience and skill [1]. Cardiac magnetic resonance (CMR) imaging is often regarded as the primary method for analyzing myocardial strain due to its superior image quality, high spatial resolution, and comprehensive assessment capabilities [10; 11; 12]. Cardiac magnetic resonance-feature tracking (CMR-FT) is an emerging technique that uses cine images acquired during routine CMR imaging. This technique involves following the actual boundary of the myocardium over time, enabling assessment of myocardial strain and motion without using contrast agents. Moreover, CMR-FT offers a non-contrast alternative to imaging techniques such as STE. For this reason, myocardial strain measurement is widely used in medical imaging diagnostics. It provides advantages over STE in terms of superior image quality. CMR-FT reports significantly fewer non-analyzable segments and larger fields of view compared to STE. This is particularly beneficial in patients with suboptimal echocardiogram image quality due to ultrasound dropouts, reverberations, or poor imaging windows [13; 14]. In the literature, several studies have explored the use of strain analysis in CMR image analysis [15; 16; 17; 18]. These studies primarily focus on myocardial strain in healthy and pathological adults, providing valuable insights into various cardiovascular conditions and the effectiveness of different treatments. However, the research on myocardial strain in pediatric populations is still limited. The unique physiological and developmental characteristics of children's hearts require specialized approaches and normative data for accurate assessment. Expanding studies to include pediatric populations is crucial for improving the diagnosis and treatment of congenital heart diseases and other pediatric cardiac conditions. Thus, some studies were dedicated to improving the importance of strain analysis in the pediatric population focused on the early diagnosis of Duchenne muscular dystrophy (DMD) cardiomyopathy [19; 20; 21; 22; 23; 24].