title: Assessing heating distribution by therapeutic ultrasound on bone phantoms and in vitro human samples using infrared thermography.
abstract: BACKGROUND
  Bioheat models have been proposed to predict heat distribution in multilayered biological tissues after therapeutic ultrasound (TUS) stimulation. However, evidence on its therapeutic benefit is still controversial for many clinical conditions. The aim of this study was to evaluate and to compare the TUS heating distribution on commercially available bone phantoms and in vitro femur and tibia human samples, at 1 MHz and several ultrasonic pulse regimens, by means of a thermographic image processing technique.
  
  
  METHODS
  An infrared camera was used to capture an image after each 5-min 1-MHz TUS stimulation on bone phantoms, as well as in vitro femur and tibia samples (N = 10). An intensity-based processing algorithm was applied to estimate temperature distribution. Sections of five femurs in the coronal plane were also used for the evaluation of heat distribution inside the medullar canal.
  
  
  RESULTS
  Temperature increased up to 8.2 and 9.8 °C for the femur and tibia, respectively. Moreover, the temperature increased up to 10.8 °C inside the medullar canal. Although temperature distributions inside the region of interest (ROI) were significantly different (p < 0.001), the average and standard deviation values for bone phantoms were more similar to the femur than to the tibia samples. Pulsed regimens caused lower increments in temperature than continuous sonication, as expected.
  
  
  CONCLUSIONS
  Commercially available bone phantoms could be used in research focusing on thermal effects of ultrasound. Small differences in mean and standard deviation temperatures were observed between bone samples and phantoms. Temperature can reach more than 10 °C inside the medullar canal on a fixed probe position which may lead to severe cellular damage.
authors.affiliation: Biomedical Ultrasound Laboratory (Applied Research Department), Estácio de Sá University, Rua do Bispo, n. 83 - Block F, Rio Comprido, Rio de Janeiro 20261-063 Brazil.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Sellani
authors.affiliation: Biomedical Ultrasound Laboratory (Applied Research Department), Estácio de Sá University, Rua do Bispo, n. 83 - Block F, Rio Comprido, Rio de Janeiro 20261-063 Brazil.
authors.forename: Dalila
authors.initials: D
authors.lastname: Fernandes
authors.affiliation: Biomedical Ultrasound Laboratory (Applied Research Department), Estácio de Sá University, Rua do Bispo, n. 83 - Block F, Rio Comprido, Rio de Janeiro 20261-063 Brazil.
authors.forename: Abigail
authors.initials: A
authors.lastname: Nahari
authors.affiliation: Biomedical Ultrasound Laboratory (Applied Research Department), Estácio de Sá University, Rua do Bispo, n. 83 - Block F, Rio Comprido, Rio de Janeiro 20261-063 Brazil.
authors.forename: Melissa Fabrício
authors.initials: MF
authors.lastname: de Oliveira
authors.affiliation: Globus Sports and Health Technology, Via Vittorio Veneto, 52, 31013 Codognè, TV Itália.
authors.forename: Christiana
authors.initials: C
authors.lastname: Valois
authors.affiliation: Biomedical Engineering Program, COPPE/Federal University of Rio de Janeiro, Av. Horácio Macedo, 2030. Technology Center, Block H - Room H327, Cidade Universitária, Rio de Janeiro, 21941-914 Brazil.
authors.forename: Wagner C A
authors.initials: WC
authors.lastname: Pereira
authors.affiliation: Biomedical Ultrasound Laboratory (Applied Research Department), Estácio de Sá University, Rua do Bispo, n. 83 - Block F, Rio Comprido, Rio de Janeiro 20261-063 Brazil.
authors.forename: Christiano B
authors.initials: CB
authors.lastname: Machado
keywords: Bioeffects; Bone; Heating; In vitro methods; Therapeutic ultrasound; Tissue-mimicking phantoms