title: Effects of compression force on elasticity index and elasticity ratio in ultrasound elastography.
abstract: OBJECTIVE
  The purpose of this study was to investigate the relationship between compression force and hardness values in ultrasound elastography.
  
  
  METHODS
  Ultrasound elastography was performed using an elastography phantom, comprising inclusions with different elasticities and echogenicities. The compression force was set to approximately 100 gw (light force) and approximately 500 gw (heavy force). The elasticity index (EI) of the inclusion was measured. The EI was a relative hardness value of a structure within an elastographic image. Similarly, the EI of the background was measured as a reference. The elasticity ratio (ER) was calculated as the EI of the inclusion divided by the EI of the reference.
  
  
  RESULTS
  The hardness of the phantom could be discerned with both the EI and ER, regardless of the compression force. The EI and ER with heavy force tended to be higher than those with light force, but the difference was not significant. A strong correlation was observed between the EI and ER of soft structures, whereas the correlation between the EI and ER of hard structures was weak, and the ER values varied widely.
  
  
  CONCLUSIONS
  The EI offers potential as a good indicator for assessing the hardness.
authors.affiliation: Department of Oral and Maxillofacial Radiology, Tokyo Dental College, Chiba, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Imaizumi
authors.forename: Y
authors.initials: Y
authors.lastname: Sasaki
authors.forename: J
authors.initials: J
authors.lastname: Sakamoto
authors.forename: T
authors.initials: T
authors.lastname: Kamio
authors.forename: K
authors.initials: K
authors.lastname: Nishikawa
authors.forename: M
authors.initials: M
authors.lastname: Otonari-Yamamoto
authors.forename: M
authors.initials: M
authors.lastname: Wako
mesh_terms: D003626:Data Display; D004548:Elasticity; D054459:Elasticity Imaging Techniques / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D006244:Hardness; D006801:Humans; D009040:Motion Pictures; D019047:Phantoms, Imaging; D011312:Pressure
keywords: elastography; ultrasonography