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Therapeutic Ultrasound: Risk Associated with Poor Calibration
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INFORMATION SHEET
Therapeutic Ultrasound: Risk Associated with Poor Calibration Mike McCabe Stephen Pye Key Words Ultrasound, instruments, calibration.
Introduction Scottish Healthcare Supplies works on behalf of the Scottish Office investigating adverse incidents within the Scottish Health Service. Problems with therapeutic ultrasound machines came to light which were the result of equipment being poorly calibrated. This led to inconsistencies in treatment and even injuries to patients. We therefore prepared a Safety Action Notice to alert users to the potential problems and corrective action. This has been circulated within the NHS in Scotland. The main text of the notice is published here to bring it to the attention of users of such equipment outside Scotland and in the private sector. It may be photocopied and circulated without restriction.
Background Therapeutic ultrasound equipment is widely used for the treatment of acute soft tissue injuries, chronic inflammation and other conditions. A number of incidents have been reported which have highlighted discrepancies in the operation and power output of therapeutic ultrasound machines. These include new machines that did not operate at all or operated at maximum power output irrespective of the chosen setting, and older machines which had not been adequately calibrated since purchase. Lack of adequate calibration and operational testing can result in inconsistencies of treatment and patient injury from excessive power outputs.
Physiotherapy, May 1997, V a l 83, no 5
Action All therapeutic ultrasound machines should be enrolled in a programme of annual calibration in accordance with the international standard IEC 601-2-5 (1984). The acoustic output should be tested at each treatment frequency over a range of power settings from maximum output t o 10%of maximum output and on both pulsed and continuous wave settings. A radiation force balance should be used whose calibration is traceable to National Measurement Standards. In addition, it is suggested that staff undertake a weekly quantitative test to ensure the equipment is operating within the parameters specified a t the time of calibration. This may be by means of a simple calorimeter o r water balance test. Advice should be sought from medical physics staff regarding suitable methods and test protocols. The correct calibration of new equipment should be established before being put into clinical use. This may be done by immediately enrolling the equipment in a calibration programme, or by obtaining a traceable certificate of calibration from the manufacturer. Such a certificate should identify that the equipment has been tested over the range of outputs as described above. Authors Mike McCabe BSc, Incident Reporting and Investigation Centre, Scottish Healthcare Supplies. Stephen Pye PhD is principal physicist, Department of Medical Physics and Medical Engineering, Western General Hospital, Edinburgh.
Address for Correspondence Mr M McCabe, Scottish Healthcare Supplies, Trinity Park House, South Trinity Road, Edinburgh EH3 3SH.
INFORMATION SHEET
Therapeutic Ultrasound: Risk Associated with Poor Calibration Mike McCabe Stephen Pye Key Words Ultrasound, instruments, calibration.
Introduction Scottish Healthcare Supplies works on behalf of the Scottish Office investigating adverse incidents within the Scottish Health Service. Problems with therapeutic ultrasound machines came to light which were the result of equipment being poorly calibrated. This led to inconsistencies in treatment and even injuries to patients. We therefore prepared a Safety Action Notice to alert users to the potential problems and corrective action. This has been circulated within the NHS in Scotland. The main text of the notice is published here to bring it to the attention of users of such equipment outside Scotland and in the private sector. It may be photocopied and circulated without restriction.
Background Therapeutic ultrasound equipment is widely used for the treatment of acute soft tissue injuries, chronic inflammation and other conditions. A number of incidents have been reported which have highlighted discrepancies in the operation and power output of therapeutic ultrasound machines. These include new machines that did not operate at all or operated at maximum power output irrespective of the chosen setting, and older machines which had not been adequately calibrated since purchase. Lack of adequate calibration and operational testing can result in inconsistencies of treatment and patient injury from excessive power outputs.
Physiotherapy, May 1997, V a l 83, no 5
Action All therapeutic ultrasound machines should be enrolled in a programme of annual calibration in accordance with the international standard IEC 601-2-5 (1984). The acoustic output should be tested at each treatment frequency over a range of power settings from maximum output t o 10%of maximum output and on both pulsed and continuous wave settings. A radiation force balance should be used whose calibration is traceable to National Measurement Standards. In addition, it is suggested that staff undertake a weekly quantitative test to ensure the equipment is operating within the parameters specified a t the time of calibration. This may be by means of a simple calorimeter o r water balance test. Advice should be sought from medical physics staff regarding suitable methods and test protocols. The correct calibration of new equipment should be established before being put into clinical use. This may be done by immediately enrolling the equipment in a calibration programme, or by obtaining a traceable certificate of calibration from the manufacturer. Such a certificate should identify that the equipment has been tested over the range of outputs as described above. Authors Mike McCabe BSc, Incident Reporting and Investigation Centre, Scottish Healthcare Supplies. Stephen Pye PhD is principal physicist, Department of Medical Physics and Medical Engineering, Western General Hospital, Edinburgh.
Address for Correspondence Mr M McCabe, Scottish Healthcare Supplies, Trinity Park House, South Trinity Road, Edinburgh EH3 3SH.