title: Reliable measurement by virtual touch tissue quantification with acoustic radiation force impulse imaging: phantom study.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the factors that may affect shear wave velocity (SWV) measurements by using a phantom.
  
  
  METHODS
  The SWVs (meters per second) of 4 phantom targets and background, each of different hardness (Young modulus, 8-80 kPa), were measured in the virtual touch tissue quantification mode. Ten SWV measurements were performed on each target, and the mean SWV and its standard deviation were calculated. To assess the effect of the distance between the probe and region of interest (ROI) settings, mean SWV measurements of the background at 5 to 80 mm in depth were performed with a convex probe and at 5 to 40 mm with a high-frequency linear probe.
  
  
  RESULTS
  The linear correlation between the nominal Young modulus of the phantom and those calculated from the mean SWV was highly significant for the linear probe (y = 0.98x - 0.70; r(2) = 0.99; P = .0007). For the convex probe, the linear correlation between the nominal Young modulus of the phantom and those calculated from the mean SWV was highly significant between 8 and 40 kPa (y =1.26x + 1.01; r(2) = 0.98; P = .011). Measurement variations for the linear probe were little influenced by the distance between the probe and ROI, but those for the convex probe were dependent on the distance.
  
  
  CONCLUSIONS
  The accuracy of the mean SWV measurement was dependent on the probe used and the distance between the probe and ROI settings. The linear probe provides accurate measurements throughout its range for all but its deepest limit. Measurements of 40 mm or deeper are better performed with a convex probe. Probe selection should be based on individual lesion depth.
authors: Department of Diagnostic Radiology and Nuclear Medicine, Gunma University Hospital, 3-39-22 Showa-machi, Maebashi, Gunma 371-8511, Japan.
authors: Noriko
authors: N
authors: Yamanaka
authors: Chie
authors: C
authors: Kaminuma
authors: Ayako
authors: A
authors: Taketomi-Takahashi
authors: Yoshito
authors: Y
authors: Tsushima
mesh_terms: D055119:Elastic Modulus; D054459:Elasticity Imaging Techniques / Q000379:methods*; D016014:Linear Models; D019047:Phantoms, Imaging; D016012:Poisson Distribution; D015203:Reproducibility of Results