title: Tissue elasticity estimated by acoustic radiation force impulse quantification depends on the applied transducer force: an experimental study in kidney transplant patients.
abstract: OBJECTIVE
  Acoustic radiation force impulse (ARFI) quantification estimates tissue elasticity by measuring shear-wave velocity (SWV) and has been applied to various organs. We evaluated the impact of variations in the transducer force applied to the skin on the SWV ultrasound measurements in kidney transplant cortex and ARFI's ability to detect fibrosis in kidney transplants.
  
  
  METHODS
  SWV measurements were performed in the cortex of 31 patients with kidney allografts referred for surveillance biopsies. A mechanical device held the transducer and applied forces were equal to a compression weight of 22, 275, 490, 975, 2,040 and 2,990 g.
  
  
  RESULTS
  SWV group means were significantly different by repeat measures ANOVA [F(2.85,85.91) = 84.75, P < 0.0005 for 22, 275, 490, 975 and 2,040 g compression weight] and also by pairwise comparisons. Biopsy specimens were sufficient for histological evaluation in 29 of 31 patients. Twelve had grade 0, 11 grade 1, five grade 2 and one grade 3 fibrosis. One-way ANOVA showed no difference in SWV performed with any of the applied transducer forces between grafts with various degrees of fibrosis.
  
  
  CONCLUSIONS
  SWV measurements in kidney transplants are dependent on the applied transducer force and do not differ in grafts with different grades of fibrosis.
  
  
  CONCLUSIONS
  • Acoustic radiation force impulses (ARFI) can quantify tissue elasticity during ultrasound examinations.                         • Elasticity estimated by ARFI in kidney transplants depends on applied transducer force.                         • ARFI quantification cannot detect renal allograft fibrosis.                         • ARFI elasticity estimates may in general vary with applied transducer force.
authors.affiliation: Department of Radiology and Nuclear Medicine, Rikshospitalet, Oslo University Hospital, Sognsvannsveien 20, 0027, Oslo, Norway. trygve.syversveen@rikshospitalet.no
authors.forename: Trygve
authors.initials: T
authors.lastname: Syversveen
authors.forename: Karsten
authors.initials: K
authors.lastname: Midtvedt
authors.forename: Audun E
authors.initials: AE
authors.lastname: Berstad
authors.forename: Knut
authors.initials: K
authors.lastname: Brabrand
authors.forename: Erik H
authors.initials: EH
authors.lastname: Strøm
authors.forename: Andreas
authors.initials: A
authors.lastname: Abildgaard
mesh_terms: D000328:Adult; D000368:Aged; D054459:Elasticity Imaging Techniques / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D016030:Kidney Transplantation / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D055815:Young Adult