title: Temperature increases in the human achilles tendon during ultrasound treatments with commercial ultrasound gel and full-thickness and half-thickness gel pads.
abstract: BACKGROUND
  Although originally manufactured for use in diagnostic imaging of internal structures, 2-cm-thick gel pads are also used as conducting media for therapeutic ultrasound over areas with bony prominences. Research on the ability of these pads to conduct enough energy to adequately heat tissues has provided mixed results. However, this research has mainly been performed on the triceps surae muscle, an area over which gel pads are not typically used. We wondered how much heating might be produced if a thinner pad was used over a tendon.
  
  
  OBJECTIVE
  To compare temperature rises in the human Achilles tendon during ultrasound treatments using ultrasound gel, a 2-cm-thick pad, and a 1-cm-thick pad.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  University therapeutic modality laboratory.
  
  
  METHODS
  Forty-eight healthy volunteers (24 women, 24 men).
  
  
  METHODS
  We inserted a rigid thermocouple 1 cm deep into the Achilles tendon. Ultrasound was delivered at the following settings: 3 MHz, continuous, 1 W/cm(2), 10 minutes.
  
  
  METHODS
  Temperature was recorded every 30 seconds for 10 minutes.
  
  
  RESULTS
  Temperature increased the most in the ultrasound gel group (increase = 13.3 degrees C, peak = 42 degrees C). The 1-cm-thick pad resulted in higher tendon temperature (increase = 9.3 degrees C, peak = 37.8 degrees C) than the 2-cm-thick pad (increase = 6.5 degrees C, peak = 4.8 degrees C). The 1-cm pad produced approximately 30% more heating than the 2-cm pad (SE = 0.72, P < .03).
  
  
  CONCLUSIONS
  The thinner pad transmitted ultrasound more efficiently than the thicker pad. Thus, a gel pad of less than 1-cm thickness might be useful for superficial areas, such as the hands and ankles.
authors.affiliation: Department of Exercise Sciences, Brigham Young University, Provo, UT 84602, USA. David_Draper@byu.edu
authors.forename: David O
authors.initials: DO
authors.lastname: Draper
authors.forename: Clinton G
authors.initials: CG
authors.lastname: Edvalson
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Knight
authors.forename: Dennis
authors.initials: D
authors.lastname: Eggett
authors.forename: Joseph
authors.initials: J
authors.lastname: Shurtz
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging*; D000293:Adolescent; D000328:Adult; D001831:Body Temperature; D003430:Cross-Sectional Studies; D005260:Female; D005782:Gels; D006358:Hot Temperature / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D018084:Ultrasonography, Interventional / Q000295:instrumentation / Q000379:methods*; D055815:Young Adult
chemical_list: D005782:Gels