title: Acoustic radiation force impulse imaging of kidneys - a phantom study.
abstract: OBJECTIVE
  Since there have been only few works reporting the diagnosis of kidneys using Acoustic Radiation Force Impulse technique and those works do not provide consistent results of shear wave velocity measurements in renal tissue, we have decided to use kidney phantoms with known properties to examine the reliability of the method itself in a controlled setup similar to kidneys examination.
  
  
  METHODS
  Four gelatin-based phantoms imitating different clinical situations were manufactured - two with thick and two with thin renal cortex, each type at a depth similar to a normal-weight or overweight patient. For each phantom, a series of interest points was chosen and for each point 20 Shear Wave Velocity measurements were taken using the build-in Virtual Touch Tissue Quantification™tool in a Siemens Acuson S2000 ultrasound scanner equipped with a 6C1 HD Transducer (Siemens Mountainview, USA).
  
  
  RESULTS
  Mean Shear Wave Velocity values obtained for all the examined points ranged from 2.445 to 3.941 m/s, with standard deviation exceeding 0.1 in only one case out of 29 points, but differing significantly between all points.
  
  
  CONCLUSIONS
  The obtained results indicate that the method is highly reliable as long as the measurement volume contains a uniform tissue region. If the measurement window covers a region with different properties even partially, the obtained results are affected. The variance of measured values on the other hand is not affected by the said non-uniformity of material under examination. Furthermore, the variance of measured values does not show a clear dependency on the depth at which the shear wave velocities are measured.
authors.affiliation: Institute of Metrology and Biomedical Engineering, Warsaw University of Technology, Warsaw, Poland.
authors.forename: Szymon
authors.initials: S
authors.lastname: Cygan
authors.affiliation: Medical University of Warsaw, II Department of Clinical Radiology, Warsaw, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Januszewicz
keywords: ARFI; kidney; phantom; shear wave velocity; ultrasonography