NPL Apertures for Effective Radiating Area (ERA) measurement
The NPL aperture provides a measurement capability to the quality assessment of physiotherapy ultrasound equipment with its aperture accessory for radiation force balances.
A set of novel precision-formed apertures provide a cost-effective and reliable estimate of the effective radiating area (ERA) of physiotherapy treatment heads. They are specifically designed for use with commercially available radiation force balances commonly used for equipment testing. Without apertures measurement of the key safety parameter has demanded the use of expensive and time-consuming beam-plotting techniques using miniature hydrophones.
- The apertures are fabricated from the NPL HAMA absorber material which allows ERA measurements to be made on the majority of treatment heads used in clinical practice.
- Each pack includes a set of apertures ranging in diameter from 4mm to 30mm supplied in a handy carrying box and a comprehensive user guide.
To use, the NPL apertures are simply placed in front of the physiotherapy treatment head, with the resulting reduction in power being measured using the radiation force balance.
The method is described in the paper, A new method for measuring the effective radiating area of physiotherapy treatment heads (Bajram Zeqiri and Mark Hodnett, Ultrasound in Medicine & Biology, Vol. 24:5, 1998, pp. 761-770), and also in the, Guidelines for the testing and calibration of physiotherapy ultrasound machines, (IPEM Report No. 84, Institute of Physics and Engineering in Medicine, 2001).