The measurement methods in the new proposed IEC standard on the testing and calibration of ultrasound therapy equipment are based on the use of hydrophones to map the ultrasonic fields in planes perpendicular to the direction of the ultrasonic beam at different distances from the transducer face. A definition of beam cross-sectional area (BCA) will be used but there is a need to test the validity of the definition over a wide range of transducers and for ones functioning correctly and incorrectly. It is also proposed to develop simplified measurement techniques and to obtain relevant information on the ultrasound field produced by the transducer. Beam non-uniformity and hot spots (high ultrasonic energy sports within the total field) should also be investigated.
Rapid measurement procedures for the BCSA2 (Beam Cross Sectional Area) and BCSA0 have been developed and tested. A factor for converting the BCSA0 to the ERA (Effectve Radiating Area) has been theoretically determined. Validation measurements for the BNR (Beam Non-uniformity Ratio) have been carried out. The overall uncertainties are 5-8% for all measurements using raster scans (95% confidence level). Validation measurements at NPL and TNO generally showed very close agreement. The measurement methods developed in the project will be introduced into the proposed revision of the IEC standard on the testing and calibration of therapeutic equipment.