A new method for measuring the effective radiating area of physiotherapy treatment heads.
This paper describes the investigation and validation of a new method for measuring the effective radiating area (AER) of physiotherapy ultrasound treatment heads. The method is based on the use of a conventional radiation force balance, but employs special attenuating apertures that are used to selectively mask off different areas of the treatment head. The resultant reduction in the radiating surface is accompanied by a decrease in output power that is measured using the force balance. The AER of the treatment head is derived from an analysis of the measurements, which essentially involves initially evaluating the minimum area through which 75% of the acoustic power is transmitted. AER values derived using the new method are presented for 17 treatment heads representative of the range of physiotherapy systems commonly used in clinical practice. These are compared to reference values derived using hydrophone scanning, according to the recently published International Standard, IEC 1689. Typical levels of agreement between values of AER derived using the two techniques are +/- 11%. The potential of the method as a rapid, relatively low-cost, means of measuring treatment head AER, applicable in both manufacturing and hospital environments, is assessed.
Zeqiri
B
B
Centre for Mechanical and Acoustical Metrology, National Physical Laboratory, Teddington, Middlesex, UK.
Hodnett
M
M
D005069:Evaluation Studies as Topic; D006801:Humans; D016014:Linear Models; D008722:Methods; D055585:Physical Phenomena; D010825:Physics; D014464:Ultrasonic Therapy / Q000295:instrumentation* / Q000379:methods / Q000706:statistics & numerical data