title: Acoustic radiation force impulse imaging in paediatric patients: normal liver values.
abstract: OBJECTIVE
  The objective of this study was to obtain a normal value for liver shear wave velocities (SWVs) in healthy paediatric patients and to investigate variations concerning age, sex, and different approaches, depths, and lobes of measurements.
  
  
  METHODS
  A total of 150 healthy children (2 months-17 years) were examined with acoustic radiation force impulse (ARFI) technology by an experienced paediatric radiologist, after receiving an informed consent. Measurements obtained were divided according to group age (n = 50, 0-5 years; n = 50, 6-11 years; n = 50, 12-17 years); sex (male-female); lobe (right-left lobe); approach (intercostal-subcostal), and depth of measurements (1-5 and 5-6 cm for the youngest group; 2-6 to 6-8 cm for the 2 other groups). Comparative analyses were performed with measurements obtained at right and left lobes, with different depths and approaches. Differences between age and sex were also analysed.
  
  
  RESULTS
  Mean SWV in the right liver lobe was 1.07 ± 0.10 m/s. No significant differences were found according to sex or among different probe locations. SWVs were, however, significantly higher within left lobe in comparison with right liver lobe (1.07 ± 0.10 m/s, right; 1.21 ± 0.16 m/s, left). Depth of measurements also influenced SWV values obtained, being slightly lower at deeper locations. Regarding the age significant differences were found for children <6 years old compared with other age groups.
  
  
  CONCLUSIONS
  ARFI analysis seems to be influenced by age, depth, and lobe of measurements. A mean SWV value of 1.07 ± 0.10 m/s for healthy paediatric population with the possibility of reaching 1.12 m/s in the case of younger children was found. ARFI values were more consistently obtained analysing right liver lobe and depths lower than 5 to 6 cm.
authors.affiliation: *Pediatric Hospital, Medical Imaging Department and Faculty of Medicine, University Hospital of Coimbra, Coimbra †Science and Technology Faculty, University Nova of Lisbon, Lisbon, Portugal.
authors.forename: Hugo
authors.initials: H
authors.lastname: Matos
authors.forename: Ana
authors.initials: A
authors.lastname: Trindade
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Noruegas
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D004548:Elasticity; D054459:Elasticity Imaging Techniques; D005260:Female; D006801:Humans; D007223:Infant; D008099:Liver / Q000000981:diagnostic imaging*; D008297:Male; D012016:Reference Values; D012737:Sex Factors; D014783:Viscosity