title: Measuring shear-wave speed with point shear-wave elastography and MR elastography: a phantom study.
abstract: To compare shear-wave speed (SWS) measured by ultrasound-based point shear-wave elastography (pSWE) and MR elastography (MRE) on phantoms with a known shear modulus, and to assess method validity and variability.
  
  
  
  5 homogeneous phantoms of different stiffnesses were made. Shear modulus was measured by a rheometer, and this value was used as the standard. 10 SWS measurements were obtained at 4 different depths with 1.0-4.5 MHz convex (4C1) and 4.0-9.0 MHz linear (9L4) transducers using pSWE. MRE was carried out once per phantom, and SWSs at 5 different depths were obtained. These SWSs were then compared with those from a rheometer using linear regression analyses.
  
  
  
  SWSs obtained with both pSWE as well as MRE had a strong correlation with those obtained by a rheometer (R2>0.97). The relative difference in SWS between the procedures was from -25.2% to 25.6% for all phantoms, and from -8.1% to 6.9% when the softest and hardest phantoms were excluded. Depth dependency was noted in the 9L4 transducer of pSWE and MRE.
  
  
  
  SWSs from pSWE and MRE showed a good correlation with a rheometer-determined SWS. Although based on phantom studies, SWSs obtained with these methods are not always equivalent, the measurement can be thought of as reliable and these SWSs were reasonably close to each other for the middle range of stiffness within the measurable range.
authors.affiliation: Hospital of the National Institute of Radiological Sciences, National Institutes of Quantum and Radiation Science and Technology, Chiba, Japan.
authors.forename: Riwa
authors.initials: R
authors.lastname: Kishimoto
authors.affiliation: Center for Frontier Medical Engineering, Chiba University, Chiba, Japan.
authors.forename: Mikio
authors.initials: M
authors.lastname: Suga
authors.affiliation: Center for Frontier Medical Engineering, Chiba University, Chiba, Japan.
authors.forename: Atsuhisa
authors.initials: A
authors.lastname: Koyama
authors.affiliation: Hospital of the National Institute of Radiological Sciences, National Institutes of Quantum and Radiation Science and Technology, Chiba, Japan.
authors.forename: Tokuhiko
authors.initials: T
authors.lastname: Omatsu
authors.affiliation: Hospital of the National Institute of Radiological Sciences, National Institutes of Quantum and Radiation Science and Technology, Chiba, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Tachibana
authors.affiliation: Hospital of the National Institute of Radiological Sciences, National Institutes of Quantum and Radiation Science and Technology, Chiba, Japan.
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Ebner
authors.affiliation: Hospital of the National Institute of Radiological Sciences, National Institutes of Quantum and Radiation Science and Technology, Chiba, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Obata
mesh_terms: D055119:Elastic Modulus; D054459:Elasticity Imaging Techniques / Q000295:instrumentation* / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012212:Rheology; D033081:Shear Strength; D013016:Sound; D014159:Transducers
keywords: acoustic radiation force impulse; elastography; rheometer; shear wave