title: Elasticity of healthy Achilles tendon decreases with the increase of age as determined by acoustic radiation force impulse imaging.
abstract: OBJECTIVE
  The objective of the study was to investigate the value of acoustic radiation force impulse (ARFI) and its application in Achilles tendon elasticity of healthy volunteers.
  
  
  METHODS
  Bilateral Achilles tendons of 56 healthy individuals were included in the study. The subjects were divided into four age groups. Shear wave velocities (SWVs) of each tendon in the states of relaxation and tension were measured using ARFI technology. We selected the middle section of the Achilles tendon for ARFI measurement. Each Achilles tendon was examined by a musculoskeletal radiologist. Longitudinal images of each tendon were obtained by ultrasound and ARFI elastography. A quantitative assessment of the tissue stiffness was made with virtual touch tissue quantification.
  
  
  RESULTS
  Significant differences in SWVs of Achilles tendon were found between any two age groups in the same status (P < 0.05) and between different status in subjects aged 25-35 years (P < 0.05) and 36-45 years (P < 0.05). SWV of Achilles tendon increased with increasing age in both states of relaxation and tension, which was consistent with the histological feature of ageing tendons. However, there were no significant differences between men and women within any group in the same status (P > 0.05) or between different states in subjects aged 46-55 years (P = 0.308) and 56-65 years (P = 0.362).
  
  
  CONCLUSIONS
  ARFI imaging provides quantitative information about tendon stiffness and represents an excellent supplementary technique to B-mode ultrasound. Furthermore, the elasticity of healthy tendon decreases with increasing age in subjects without disease and long-term heavy load lifting.
authors.affiliation: Department of Ultrasound, Second Hospital of Shandong University, Shandong University Jinan, P.R. China.
authors.forename: Zhengmin
authors.initials: Z
authors.lastname: Ruan
authors.affiliation: Shandong Medical Imaging Research Institute, Shandong University Jinan, P.R. China.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhao
authors.affiliation: Shandong Medical Imaging Research Institute, Shandong University Jinan, P.R. China.
authors.forename: Hengtao
authors.initials: H
authors.lastname: Qi
authors.affiliation: Center of Evidence-based Medicine, Second Hospital of Shandong University Jinan, P.R. China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Ultrasound, Second Hospital of Shandong University, Shandong University Jinan, P.R. China.
authors.forename: Feixue
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Department of Ultrasound, Second Hospital of Shandong University, Shandong University Jinan, P.R. China.
authors.forename: Mei
authors.initials: M
authors.lastname: Wu
authors.affiliation: Department of Radiology, Second Hospital of Shandong University Jinan, P.R. China.
authors.forename: Guangrui
authors.initials: G
authors.lastname: Shao
keywords: Achilles tendon; Acoustic radiation force impulse; elasticity; shear wave velocity