Acoustic radiation force impulse imaging-normal values of liver stiffness in healthy children

Acoustic radiation force impulse imaging (ARFI) is a recent ultrasound technique to assess tissue stiffness. Our aim was to describe the feasibility and to define normal ARFI values in liver in children. ARFI values were measured in 103 children (ages 2 weeks to 17 years) divided into four age groups, at a minimum depth of 3 cm. In 20 children, measurements were done at 3-, 4- and 5-cm depth in the liver to assess the suitability of measurement location. The impact of age groups and of depth groups was examined using multilevel models. The precision of the measurements was determined using intraclass correlation coefficient (ICC). There was no statistical difference between measurements taken at different ages, with a mean propagation velocity of 1.12 m/s (range: 0.73 to 1.45 m/s). There was no significant difference according to the depth of the regions of interest (up to 5 cm). The ICC was 0.77 (95% CI 0.69-0.83). ARFI is feasible in children at any age with an acceptable reliability. The depth of measurements in the liver seems to have no influence on test results. We set the standard ARFI elastography values for healthy liver in children.