A European comparison of medical ultrasonic field measurements: Interpreting IEC 61157

A European comparison of measurements of medical ultrasonic fields at diagn ostic levels has been carried out. The exercise, led by the United Kingdom' s Nation al Physical Laboratory (NPL), also aimed to assess the ability of participants to apply the measurement procedures set out in the specificati on standard IEC 61157:1992 entitled "Requirements for the declaration of th e acoustic output of medical diagnostic ultrasound equipment". Ten organisa tions representing seven different EC countries (Austria, Finland, Germany, the Netherlands, Spain, Sweden, United Kingdom) and including national mea surement institutions, academic organisations and hospital medical physics departments, took part in a series of measurements on a Dynamic Imaging por table diagnostic scanner and on an NPL pulsed ultrasound check source. Accu rate measurement of tightly-focused highly-shocked acoustic fields requires the use of hydrophones with small diameter active elements and wide bandwi dths. In the view of the authors, the extent of a laboratory's previous exp erience in working to IEC 61157 may contribute to its ability to make succe ssful measurements to this standard.