White matter damage occurs in 20% of preterm infants in industrialized countries. These lesions are difficult to evaluate by standard ultrasound. The quantitative elastography is a new medical imaging technique and potentially a diagnostic tool in brain lesions in preterm infants. Shear wave Imaging (SSI) could be of interest in this clinical setting. This technique, already investigated in adults (breast, thyroid or liver fibrosis staging), has not been yet evaluated in neonates.