title: Optimal Acquisition Number for Hepatic Shear Wave Velocity Measurements in Children.
abstract: OBJECTIVE
  To investigate the minimum optimal acquisition number of hepatic shear wave velocities (SWVs) on ultrasound elastography in children.
  
  
  METHODS
  We prospectively performed hepatic supersonic shear wave elastography in children of four groups (group A-C, healthy children, group A with 0-5 years old; group B with 6-10 years old; group C with 11-18 years old; and group D, children with previous Kasai operation) with free breathing (FB) and breath holding (BH) status, if possible. SWVs were measured fifteen times for each child at a 4 cm depth for the right lobe using a 1-6 MHz convex transducer. Mean SWVs from three, five, and seven acquisitions were compared to the mean SWV from fifteen measurements, using an intraclass correlation coefficient (ICC) analyzed with the 1,000 times bootstrap method.
  
  
  RESULTS
  Total eighty-eight children were included (25 children in group A, 30 children in group B, 21 children in group C, and 12 children in group D). The mean SWVs from fifteen measurements in FB status were 5.5 ± 1.3 kPa for groups A-C together and 8.0 ± 2.2 kPa for group D. For all groups together, mean SWVs from the three (ICC 0.944 and 0.937), five (ICC 0.958 and 0.938) and seven (ICC 0.969 and 0.941) acquisitions demonstrated almost perfect agreement with the reference of fifteen acquisitions in both FB and BH status, respectively. A subgroup analysis showed three measurements were in almost perfect agreement during FB for groups B-D and strong agreement (ICC 0.675) for group A.
  
  
  CONCLUSIONS
  Three acquisitions can be enough for hepatic SWVs in children more than 6 years old regardless of breathing status or hepatic pathology. More acquisitions are recommended for children under the age of 5 years during FB.
authors.affiliation: Department of Radiology and Research Institute of Radiological Science, Severance Children's Hospital, Seoul, Korea.
authors.forename: Hyun Joo
authors.initials: HJ
authors.lastname: Shin
authors.affiliation: Department of Radiology and Research Institute of Radiological Science, Severance Children's Hospital, Seoul, Korea.
authors.forename: Myung-Joon
authors.initials: MJ
authors.lastname: Kim
authors.affiliation: Biostatistics Collaboration Unit, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Ha Yan
authors.initials: HY
authors.lastname: Kim
authors.affiliation: Biostatistics Collaboration Unit, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Yun Ho
authors.initials: YH
authors.lastname: Roh
authors.affiliation: Department of Radiology and Research Institute of Radiological Science, Severance Children's Hospital, Seoul, Korea.
authors.forename: Mi-Jung
authors.identifier: http://orcid.org/0000-0003-3244-9171
authors.initials: MJ
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D054459:Elasticity Imaging Techniques; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008099:Liver / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D011446:Prospective Studies; D056152:Respiratory Rate / Q000502:physiology