title: Parameters affecting different acoustic radiation force impulse applications in the diagnosis of fibrotic liver changes.
abstract: OBJECTIVE
  To analyze the virtual touch tissue quantification (VTTQ) and virtual touch imaging quantification (VTIQ) techniques, and identify possible factors that may influence VTTQ and VTIQ measurements.
  
  
  METHODS
  One hundred and eighty-six (104 women/82 men) of 323 subjects met the inclusion criteria (age > 18 years, no history of chronic or gastrointestinal disease, body-mass index (BMI) < 30 kg/m², a fasting period of at least three hours, no history of hepatotoxic pharmaceuticals, alcohol consumption < 24 g/d in men and < 12 g/d in women, and normal findings upon ultrasound examination of the abdomen). Measurements were taken at depths of 50 mm with VTTQ, 15 mm and 25 mm with VTIQ in the right hepatic lobe, and at 15 mm with only VTIQ in the left hepatic lobe. The examiner acquired six measurements per position, thereby giving 24 measurements in total.
  
  
  RESULTS
  The 95% confidence intervals of mean were 1.23-1.29 m/s for VTTQ and 1.29-1.37 m/s, 1.17-1.23 m/s, and 1.48-1.57 m/s for VTIQ in a depth of 15 mm and 25 mm in the right hepatic lobe and 15 mm in the left hepatic lobe. Only superficial measurements in the right hepatic lobe with the VTIQ method exhibited an effect of age on shear wave velocity. Measurements acquired using the 6C1 probe with the VTTQ method showed no dependence on BMI. By comparison, BMI influenced measurements taken with the VTIQ method using the 9L4 probe in the superficial and deep areas of the right hepatic lobe, as well as in the left hepatic lobe (P = 0.0160, P = 0.0019, P = 0.0173, respectively). Gender influenced measurements at depths of 50 mm with VTTQ and 25 mm with VTIQ in the right hepatic lobe (P = 0.0001, P = 0.0269). Significant differences were found between measurements with the 6C1 (VTTQ) and 9L4 probes (VTIQ) (P = 0.0067), between superficial and deep measurements (P < 0.0001), and between the right and left lobes of the liver (P < 0.0001).
  
  
  CONCLUSIONS
  Measurements in the right lobe and deep regions are preferable. Gender differences must be considered. BMI must be considered when assessing VTIQ technology.
authors.affiliation: Sabrina Galgenmueller, Wolfgang Kratzer, Suemeyra Oeztuerk, Mark M Haenle, Department of Internal Medicine I, University Hospital Ulm, 89081 Ulm, Germany.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Galgenmueller
authors.affiliation: Sabrina Galgenmueller, Wolfgang Kratzer, Suemeyra Oeztuerk, Mark M Haenle, Department of Internal Medicine I, University Hospital Ulm, 89081 Ulm, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Jaeger
authors.affiliation: Sabrina Galgenmueller, Wolfgang Kratzer, Suemeyra Oeztuerk, Mark M Haenle, Department of Internal Medicine I, University Hospital Ulm, 89081 Ulm, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kratzer
authors.affiliation: Sabrina Galgenmueller, Wolfgang Kratzer, Suemeyra Oeztuerk, Mark M Haenle, Department of Internal Medicine I, University Hospital Ulm, 89081 Ulm, Germany.
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Schmidt
authors.affiliation: Sabrina Galgenmueller, Wolfgang Kratzer, Suemeyra Oeztuerk, Mark M Haenle, Department of Internal Medicine I, University Hospital Ulm, 89081 Ulm, Germany.
authors.forename: Suemeyra
authors.initials: S
authors.lastname: Oeztuerk
authors.affiliation: Sabrina Galgenmueller, Wolfgang Kratzer, Suemeyra Oeztuerk, Mark M Haenle, Department of Internal Medicine I, University Hospital Ulm, 89081 Ulm, Germany.
authors.forename: Mark M
authors.initials: MM
authors.lastname: Haenle
authors.affiliation: Sabrina Galgenmueller, Wolfgang Kratzer, Suemeyra Oeztuerk, Mark M Haenle, Department of Internal Medicine I, University Hospital Ulm, 89081 Ulm, Germany.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Mason
authors.affiliation: Sabrina Galgenmueller, Wolfgang Kratzer, Suemeyra Oeztuerk, Mark M Haenle, Department of Internal Medicine I, University Hospital Ulm, 89081 Ulm, Germany.
authors.forename: Tilmann
authors.initials: T
authors.lastname: Graeter
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging*; D008103:Liver Cirrhosis / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012737:Sex Factors; D055815:Young Adult
keywords: Acoustic radiation force impulse; Elasticity imaging techniques; Liver; Reference standards; Ultrasonography; Virtual touch imaging and quantification; Virtual touch tissue quantification