2-D ultrasound imaging Article Cerebral Palsy Child Child, Preschool Children with cerebral palsies Clinical practices Coefficient of variation Correlation coefficient Diseases Elasticity Elasticity Imaging Techniques Female Gastrocnemius muscle Humans Male Medical imaging Muscle Muscle structure Muscle, Skeletal Observer Variation Reliability Reproducibility of Results Shear flow Shear wave elastography Shear waves Spastic muscles Tibialis anterior Ultrasonics Ultrasonography