IPEM Report No 84: Guidelines for the Testing and Calibration of Physiotherapy Ultrasound Machines

Abstract

Institute of Physics and Engineering in Medicine York: IPEM (2001) 67 pp, �20.00, ISBN: 0-904181-98-7 This 67-page soft-cover report has been prepared by an expert group within the Institute of Physics and Engineering in Medicine (IPEM) to provide detailed guidance on the testing and calibration of ultrasound therapy devices. Physiotherapists have long used external energy sources to supplement massage and manipulation for musculo-skeletal therapy. Whilst, recently, there has been a general reduction in use of electrotherapy using radio-frequency radiation, microwaves and interferential devices, ultrasound therapy still remains central to physiotherapy practice. There is now robust evidence that, at least for some injuries, ultrasound accelerates the repair of injured tissue. This has been particularly well demonstrated for bone fracture repair. Managed therapy relies on well-calibrated radiation sources. Unfortunately, there has been less than adequate management of ultrasound output in the past. Several well-documented situations have occurred for which faulty ultrasound equipment has continued in clinical use, either generating no output at all, or, more seriously, operating at maximum power all the time. This report reminds those responsible for managing ultrasound equipment of the need for testing and calibration, and gives detailed advice on procedures for carrying this out. These details are contained in 12 annexes forming the majority of the text. Each annex presents a self-contained aspect of one aspect of testing or calibration, such as the measurement of acoustic power, or an example protocol for machine testing. Each is sufficiently detailed to allow novice technical staff to follow the recommended procedure, or to allow a department to plan to introduce ultrasound field calibration into its practice. Other annexes contain useful additional material, not included in the earlier IPSM Report 58. A procedure for the measurement of effective radiating area, developed by NPL, is carefully described, as is a rapid method for testing the temperature rise due to ultrasound using a simple calorimeter. The next report will, I am sure, consider standardized means to quantify tissue heating and patient dose. Once or twice I felt that quantities were identified but means for their measurement were not specified at the level of detail used elsewhere, for example for beam non-uniformity ratio and rms acoustic pressure. Also, perhaps, the actual problems when using hydrophones in physiotherapy fields were not discussed in sufficient detail, with no mention of the need to carefully control any direct electromagnetic coupling between the transducer and the hydrophone. But these are really minor criticisms. The main (short) text of the report gives rationale, summary of recommendations and guidelines and key references. This is a very practical report, which should be bought and used by all hospital departments with a responsibility for ultrasound therapy equipment, including maintenance departments, physiotherapy departments and medical physics departments. It will underpin competency-based training in medical ultrasound, and will support the NHS National Occupational Standards for Ultrasound Physics and Technology. Being highly practical, I would expect this report to be found in the laboratory or workshop and more rarely in an academic library.