title: Determination of normal hepatic elasticity by using real-time shear-wave elastography.
abstract: OBJECTIVE
  To determine normal reference values of liver elasticity and measurement reliability by using real-time shear-wave elastography (SWE) in patients with a range of ages and body mass index (BMI) measurements, with presence or absence of hepatic steatosis.
  
  
  METHODS
  The institutional review board approved this study, and informed consent was waived because of the retrospective nature of the study. Two hundred thirty-eight patients who underwent SWE and ultrasonography-guided liver biopsies on the same day were identified retrospectively. The median kilopascal value of three consecutive measurements was used as a representative value for each subject. One hundred ninety-six patients who were potential donors for living-donor liver transplantation and had biopsy-proven normal (123 nonsteatotic and 73 steatotic) livers as the only histologic abnormality were included in the study. Reference ranges of normal hepatic elasticity were calculated by using lower and upper limits at the 2.5 and 97.5 percentiles. With the upper value of the reference range as a cutoff value, the sensitivity and specificity for the diagnosis of hepatic fibrosis were calculated. Measurement reliability was evaluated by using the intraclass correlation coefficient (ICC). To investigate the effects of potential confounding factors (age, hepatic steatosis, and BMI) on liver elasticity, the Pearson correlation test and the Student t test were performed.
  
  
  RESULTS
  The reference range of normal hepatic elasticity was 2.6-6.2 kPa. With 6.2 kPa as a cutoff value, the sensitivity and specificity for the diagnosis of hepatic fibrosis were 91% (20 of 22 subjects) and 95.9% (188 of 196 subjects), respectively. The overall ICC for the elasticity measurements was 0.924. The potential confounding factors that we considered had negligible effects on the elasticity values.
  
  
  CONCLUSIONS
  Hepatic elasticity values measured with SWE in histologically proven normal livers ranged from 2.6 to 6.2 kPa, with high measurement reliability. The effect of the potential confounding factors on liver elasticity was negligible.
authors.affiliation: From the Department of Radiology and Research Institute of Radiology (C.H.S., S.Y.K., K.W.K., S.J.L., M.G.L.), Department of Gastroenterology (Y.S.L.), Department of Clinical Epidemiology & Biostatistics (J.B.L.), Department of Liver Transplantation Surgery (S.G.L.), and Department of Pathology (E.Y.), Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 138-736, South Korea.
authors.forename: Chong Hyun
authors.initials: CH
authors.lastname: Suh
authors.forename: So Yeon
authors.initials: SY
authors.lastname: Kim
authors.forename: Kyoung Won
authors.initials: KW
authors.lastname: Kim
authors.forename: Young-Suk
authors.initials: YS
authors.lastname: Lim
authors.forename: So Jung
authors.initials: SJ
authors.lastname: Lee
authors.forename: Moon-Gyu
authors.initials: MG
authors.lastname: Lee
authors.forename: JungBok
authors.initials: J
authors.lastname: Lee
authors.forename: Sung-Gyu
authors.initials: SG
authors.lastname: Lee
authors.forename: Eunsil
authors.initials: E
authors.lastname: Yu
mesh_terms: D000328:Adult; D001707:Biopsy, Needle; D054459:Elasticity Imaging Techniques; D005260:Female; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging* / Q000502:physiology*; D008107:Liver Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology; D019520:Living Donors; D008297:Male; D012016:Reference Values; D015203:Reproducibility of Results; D012189:Retrospective Studies; D018084:Ultrasonography, Interventional