IEC 61828:2020
- provides definitions for the transmitted field characteristics of focusing and nonfocusing transducers for applications in medical ultrasound;
- relates these definitions to theoretical descriptions, design, and measurement of the transmitted fields of focusing transducers;
- gives measurement methods for obtaining defined field characteristics of focusing and nonfocusing transducers;
- specifies beam axis alignment methods appropriate for focusing and nonfocusing transducers.
IEC 61828:2021 relates to focusing ultrasonic transducers operating in the frequency range appropriate to medical ultrasound (0,5 MHz to 40 MHz) for both therapeutic and diagnostic applications. It shows how the characteristics of the transmitted field of transducers can be described from the point of view of design, as well as measured by someone with no prior knowledge of the construction details of a particular device. The transmitted ultrasound field for a specified excitation is measured by a hydrophone in either a standard test medium (for example, water) or in a given medium. This document applies only to media where the field behaviour is essentially like that in a fluid (i.e. where the influence of shear waves and elastic anisotropy is small), including soft tissues and tissue-mimicking gels. Any aspects of the field that affect their theoretical description or are important in design are also included. These definitions would have use in scientific communications, system design and description of the performance and safety of systems using these devices.
IEC 61828:2021 incorporates definitions from other related standards where possible, and supplies more specific terminology, both for defining focusing characteristics and for providing a basis for measurement of these characteristics.

IEC 61828:2021 cancels and replaces the first edition published in 2001. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) Clause 6 on Measurement procedures has been replaced by Clause 6: "Acoustic field measurement: equipment" and Clause 7: "Measurement procedure" and related definitions.
b) Reorganization of definitions and measurement section to accommodate specific sets of measurements for focusing, nonlinearity, beam axis alignment, beam area, beam maximum, numerical projection, plane wave, high intensity therapeutic ultrasound, multiple sources, spatial impulse response and compound plane waves. Clause 3 has been moved to Annex B.
c) The normative references have been updated and the Bibliography has been expanded from 8 to 40 references.
d) Twelve figures have been updated and seven new figures (B.1, B.3, B.7, B.10, B.11, B.12, B.13, B.14) have been added to facilitate measurements and be consistent with measurement terminology.
e) New measurements have been added for time delays, arrays, plane waves and spatial impulse response.
f) Annex A has been expanded to provide general guidance on pulsed waves, system responses, focusing gains and minimum beamwidth estimation.
g) New annexes have been added: • Annex B (informative) Rationale for focusing and nonfocusing definitions • Annex E (informative) Uncertainties; • Annex F (informative) Transducer and hydrophone positioning systems; • Annex G (informative) Planar scanning of a hydrophone to determine acoustic output power; • Annex H (informative) Properties of water; In addition, Annex A was reorganized and new Clauses A.1, A.5 and A.6 were added. h) Guidelines for remaining within the manufacturer’s pressure and intensity hydrophone limits and the determination of the extent of nonlinearity in the field have been added.