title: Acoustic radiation force impulse imaging (ARFI) for non-invasive detection of liver fibrosis: examination standards and evaluation of interlobe differences in healthy subjects and chronic liver disease.
abstract: OBJECTIVE
  Acoustic radiation force impulse imaging (ARFI) is a non-invasive method for the quantification of liver stiffness. We aimed to develop standards for the measuring procedure and studied the impact of different measuring sites.
  
  
  METHODS
  ARFI was tested in a tissue phantom and in 50 healthy volunteers. In addition, 116 patients with chronic liver disease underwent ARFI. The results were compared with histological staging (non-viral liver disease) and transient elastography (hepatitis C). ARFI diagnostic performance was evaluated with receiver operating characteristic curves.
  
  
  RESULTS
  ARFI results were not normally distributed in >20% of cases. Deep inspiration significantly increased ARFI values by 13% (p < 0.05). The mean shear-wave velocity in healthy individuals was 1.28 ± 0.19 m/s in the left liver lobe and 1.15 ± 0.17 m/s in the right liver lobe (p < 0.001). Similarly, in 79/116 patients with chronic liver disease a significant difference of shear-wave velocity between both liver lobes was detected. The histological staging correlated with ARFI results of the biopsy site (r = 0.661, p < 0.001) in non-viral liver disease (n = 47). The mean shear-wave velocity in cases with F1 and F2 fibrosis was increased in the left compared with the right liver lobe (2.1 ± 0.73 m/s vs. 1.75 ± 0.89 m/s, p = 0.041). Similar results were obtained in patients with hepatitis C (n = 69).
  
  
  CONCLUSIONS
  Our study strengthens the necessity for definition of examination standards and demonstrates the usefulness of ARFI in non-viral liver disease. Interlobe variations of liver stiffness demand further investigation.
authors.affiliation: Department of Internal Medicine, University Hospital Leipzig, Liebigstrasse 20, Leipzig, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Karlas
authors.forename: Cornelia
authors.initials: C
authors.lastname: Pfrepper
authors.forename: Johannes
authors.initials: J
authors.lastname: Wiegand
authors.forename: Christian
authors.initials: C
authors.lastname: Wittekind
authors.forename: Marie
authors.initials: M
authors.lastname: Neuschulz
authors.forename: Joachim
authors.initials: J
authors.lastname: Mössner
authors.forename: Thomas
authors.initials: T
authors.lastname: Berg
authors.forename: Michael
authors.initials: M
authors.lastname: Tröltzsch
authors.forename: Volker
authors.initials: V
authors.lastname: Keim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D002648:Child; D002908:Chronic Disease; D054459:Elasticity Imaging Techniques / Q000295:instrumentation / Q000592:standards*; D005260:Female; D019698:Hepatitis C, Chronic / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging*; D008103:Liver Cirrhosis / Q000000981:diagnostic imaging* / Q000473:pathology; D008107:Liver Diseases / Q000000981:diagnostic imaging / Q000473:pathology; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D012372:ROC Curve; D055815:Young Adult