Hong Kong Physiotherapy Journal
Volume 26, Issue 1 , Pages 39-44, 2008

How Accurate are Therapeutic Ultrasound Machines?

  • Siobhan Schabrun, B Physio (Hons)

      Affiliations

    • School of Molecular and Biomedical Science (Physiology), University of Adelaide
    • Corresponding Author InformationReprint requests and correspondence to: Siobhan Schabrun, School of Molecular and Biomedical Science (Physiology), University of Adelaide, North Terrace, Adelaide, SA 5000, Australia
    • ,
  • Hayley Walker, B Physio (Hons)

      Affiliations

    • School of Health Sciences, University of South Australia (City East), Adelaide
    • ,
  • Lucy Chipchase, PhD

      Affiliations

    • School of Health and Rehabilitation Sciences, University of Queensland, Brisbane, Queensland, Australia

Received 6 August 2008; accepted 25 November 2008.

Article Outline

Abstract 

Ultrasound machines are frequently used by physiotherapists. Thus, it is imperative that machines are accurate for safe and effective treatments. This study aimed to examine the accuracy of therapeutic ultrasound machines in terms of power output and timing function, and to determine factors that relate to the degree of machine accuracy. An observational design was used. Sixty-four machines were sampled. Machines were tested at three power settings, two frequencies, and pulsed and continuous modes. Timers were assessed for 5- and 10-minute durations. Ultrasound machines were considered inaccurate if they deviated by more than ± 20% and timers if they deviated by ± 10%. Fifty-nine percent (291/492) of power tests were inaccurate, with 79% of these producing less power output than depicted on the dial. Thirty-seven percent of timers were inaccurate, with mechanical timers more inaccurate than digital timers (p < 0.05). Older ultrasound machines were more likely to be inaccurate (p < 0.05). Length of time since machine calibration was also associated with machine inaccuracy at 3 MHz (p < 0.05). There is a high level of power and timer inaccuracy in machines that may be related to machine age and frequency of calibration. This study highlights the need for therapists to be aware of the potential for machine inaccuracy and for stricter guidelines on machine calibration to be introduced.

Key words:  accuracy , physiotherapy , safety , ultrasound

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References 

  1. Robertson V , Ward A , Low J , et al.   Electrotherapy Explained: Principles and Practice . 4th edition. Sydney: Butterworth-Heinemann Elsevier; 2006;
  2. Goh AC , Chok B , Wong WP , et al.   Therapeutic ultrasound: rate of usage, knowledge of use, and opinions on dosimetry . Physiother Singapore . 1999;2:69–83
  3. Lindsay D , Dearness J , Richardson C , et al.   A survey of electromodality usage in private physiotherapy practices . Aust J Physiother . 1990;36:249–256
  4. Lindsay DM , Dearness J , McGinley CC . Electrotherapy usage trends in private physiotherapy practice in Alberta . Physiother Can . 1995;47:30–34
  5. Robertson VJ , Spurritt D . Electrophysical agents: implications of their availability and use in undergraduate clinical placements . Physiotherapy . 1998;84:335–344
  6. Chipchase LS , Trinkle D . Therapeutic ultrasound: clinician usage and perception of efficacy . Hong Kong Physiother J . 2003;21:5–13
  7. Pye S , Milford C . The performance of ultrasound physiotherapy machines in Lothian Region, Scotland, 1992 . Ultrasound Med Biol . 1994;20:347–359
  8. Artho PA , Thyne JG , Warring BP , et al.   A calibration study of therapeutic ultrasound units . Phys Ther . 2002;82:257–263
  9. Pye S . Ultrasound therapy equipment—does it perform? . Physiotherapy . 1996;82:39–44
  10. Rivest M , Quirion-de Girardi C , Seaborne D , et al.   Evaluation of therapeutic ultrasound devices: performance stability over 44 weeks of clinical use . Physiother Can . 1987;39:77–86
  11. International Electrotechnical Committee  . Ultrasonicsphysiotherapy Systems: Performance Requirements and Methods of Measurements in the Frequency Range 0.5 to 5 MHz . Geneva, Switzerland: International Electrotechnical Committee; 1996;
  12. Australian and New Zealand Standards  . Ultrasonics-physiotherapy Systems: Performance Requirements and Methods of Measurements in the Frequency Range 0.5 to 5 MHz (AS/NZS 4713) . Sydney: Standards Australia and Standards New Zealand; 2002;
  13. Australian and New Zealand Standards  . Guide to Testing and Calibration of Ultrasound Therapy Machines (AS/NZS Draft) . Sydney: Standards Australia and Standards New Zealand; 2005;
  14. Kollmann C , Vacariu G , Schuhfried O , et al.   Variations in the output power and surface heating effects of transducers in therapeutic ultrasound . Arch Phys Med Rehabil . 2005;86:1318–1324
  15. Pye S , Zeqiri B . Guidelines for Testing and Calibration of Physiotherapy Machines: Report No. 84 . England: Institution of Physics and Engineering in Medicine; 2001;
  16. Stewart HF , Harris GR , Herman BA , et al.   Survey of use and performance of ultrasonic therapy equipment in Pinellas County, Florida . Phys Ther . 1974;54:707–715
  17. Allen KG , Battye CK . Performance of ultrasonic therapy instruments . Physiotherapy . 1978;64:174–179
  18. Snow CJ . Ultrasound therapy units in Manitoba and Northwestern Ontario: performance evaluation . Physiother Can . 1982;34:185–189
  19. Lloyd JJ , Evans JA . A calibration survey of physiotherapy ultrasound equipment in North Wales . Physiotherapy . 1988;74:56–61
  20. Robertson V , Chipchase LS , Laakso EL , et al.   Guidelines for the Clinical Use of Electrophysical Agents . Australia: Australia Australian Physiotherapy Association; 2001;
  21. Bio-Tek Instruments Inc.  . Digital Ultrasound Wattmeter Model UW-II: Operators Manual . Winooski, VT: Bio-Tek Instruments Inc.; 1989;
  22. Beissner K . Primary measurement of ultrasonic power and dissemination of ultrasonic power reference values by means of standard transducers . Metrologia . 1999;36:313–320
  23. Sutton Y , Shaw A , Zeqiri B . Measurement of ultrasonic power using an acoustically absorbing well . Ultrasound Med Biol . 2003;29:1507–1513
  24. In:  Kitchen S editors. Electrotherapy: Evidence Based Practice . 11th edition. Oxford: Harcourt Publishers Ltd.; 2002;
  25. Ross RN , Sourkes AM , Sandeman JM . Survey of ultrasound therapy devices in Manitoba . Health Phys . 1984;47:595–601
  26. Chapman RH . A survey of output calibrations of ultrasound therapy equipment used in physiotherapy practice . NZ J Physiother . 1986;14:13–14
  27. Hekkenberg RT , Oosterbaan WA , van Beekum WT . Evaluation of ultrasound therapy devices . Physiotherapy . 1986;72:390–395
  28. Guirro R , Britshcy Dos Santos SC . Evaluation of the acoustic intensity of new ultrasound therapy equipment . Ultrasonics . 2002;39:553–557
  29. Robertson VJ . Dosage and treatment response in randomized clinical trials of therapeutic ultrasound . Phys Ther Sport . 2002;3:124–133
  30. Robertson VJ , Baker KG . A review of therapeutic ultrasound: effectiveness studies . Phys Ther . 2001;81:1339–1350
  31. Cunningham SJ . Calibration chaos makes research irrelevant . Physiotherapy . 1997;83:440–441

PII: S1013-7025(09)70006-5

doi:10.1016/S1013-7025(09)70006-5

Hong Kong Physiotherapy Journal
Volume 26, Issue 1 , Pages 39-44, 2008

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