Ultrasonics - Transducers - Definitions and measurement methods regarding focusing for the transmitted fields

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a) Clause 6 on Measurement procedures has been replaced by Clause 6: "Acoustic field measurement: equipment" and Clause 7: "Measurement procedure" and related definitions.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.

Ultrasons - Transducteurs - Définitions et méthodes de mesure pour la focalisation des champs transmis

L'IEC 61828:2020
– donne les définitions des caractéristiques du champ transmis de transducteurs focalisants et non focalisants pour des applications ultrasonores médicales;
– établit la relation entre ces définitions et les descriptions théoriques, la conception et le mesurage des champs transmis par des transducteurs focalisants;
– donne des méthodes de mesure pour l'obtention de caractéristiques du champ définies des transducteurs focalisants et non focalisants;
– donne des méthodes d'alignement de l'axe du faisceau adaptées aux transducteurs focalisants et non focalisants.
Le présent document se réfère à des transducteurs ultrasoniques focalisants fonctionnant dans la plage de fréquences appropriée pour des applications ultrasonores médicales (soit de 0,5 MHz à 40 MHz) aussi bien thérapeutiques que diagnostiques. Le présent document spécifie comment les caractéristiques du champ transmis par les transducteurs peuvent être décrites du point de vue de la conception et mesurées par une personne n'ayant aucune connaissance préalable des détails de construction d'un appareil spécifique. Le champ ultrasonique émis pour une excitation spécifiée est mesuré par un hydrophone dans un milieu d'essai normalisé (de l'eau, par exemple) ou dans un milieu donné. Le présent document s'applique uniquement à des milieux dans lesquels le comportement du champ est essentiellement similaire à celui constaté dans un fluide (c'est-à-dire dans lesquels l'influence des ondes tourbillonnaires et de l'anisotropie élastique est faible), cela comprenant les tissus mous et les gels imitant un tissu. Tous les aspects du champ affectant leur description théorique ou qui sont importants pour la conception sont aussi inclus. Ces définitions sont utiles dans des communications scientifiques, pour la conception d'appareils et pour la description du rendement et de la sécurité de systèmes utilisant ces dispositifs.
Le présent document reprend, lorsque c’est possible, quelques définitions d'autres normes connexes et fournit une terminologie plus spécifique, aussi bien pour la définition des caractéristiques de focalisation que pour procurer une base pour le mesurage de ces caractéristiques.
L'IEC 61828:2020 annule et remplace la première édition parue en 2001. Cette édition constitue une révision technique.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) L'Article 6 relative aux procédures de mesure a été remplacé par l'Article 6: "Mesurage du champ acoustique: équipement", et par l'Article 7: "Procédure de mesure" et définitions connexes.
b) Réorganisation des définitions et de la section relative aux mesurages pour établir un ensemble spécifique de mesurages pour la focalisation, la non-linéarité, l'alignement de l'axe du faisceau, la surface du faisceau, le maximum de faisceau, la projection numérique, l'onde plane, les ultrasons thérapeutiques de haute intensité, les sources multiples, la réponse impulsionnelle spatiale et les ondes planes composées. L’Article 3 a été transféré à l’Annexe B.
c) Les références normatives ont été mises à jour et la Bibliographie étendue de 8 à 40 références.
d) Douze figures ont été mises à jour et sept autres (Figures B.1, B.3, B.7, B.10, B.11, B.12, B.13, B.14) ont été ajoutées pour faciliter les mesurages et assurer la cohérence avec la terminologie de mesure.
e) De nouveaux mesurages ont été ajoutés pour les délais de réponse, les réseaux, les ondes planes et la réponse impulsionnelle spatiale.
f) L'Annexe A a été étendue pour fournir des recommandations générales relatives aux ondes à impulsions, aux réponses du système, aux gains de focalisation et à l'estimation de la largeur de faisceau minimale.
g) De nouvelles annexes ont été ajoutées:
- Annexe B (informative) Justification des définitions des concepts de focalisation et de non-focalisation;
- Annexe E (informative) Incertitudes;
- Annexe F (informative) Systèmes de positionnement du trans

General Information

Status
Published
Publication Date
14-Dec-2020
Technical Committee
Current Stage
PPUB - Publication issued
Completion Date
15-Dec-2020
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IEC 61828
Edition 2.0 2020-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Ultrasonics – Transducers – Definitions and measurement methods
regarding focsusing for the transmitted fields
Ultrasons – Transducteurs – Définitions et méthodes de mesure
pour la focalisation des champs transmis
IEC 61828:2020-12(en-fr)
---------------------- Page: 1 ----------------------
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IEC 61828
Edition 2.0 2020-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Ultrasonics – Transducers – Definitions and measurement methods
regarding focsusing for the transmitted fields
Ultrasons – Transducteurs – Définitions et méthodes de mesure
pour la focalisation des champs transmis
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.140.50 ISBN 978-2-8322-9019-4

Warning! Make sure that you obtained this publication from an authorized distributor.

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® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 61828:2020 © IEC 2020
CONTENTS

FOREWORD ........................................................................................................................... 6

INTRODUCTION ..................................................................................................................... 8

1 Scope .............................................................................................................................. 9

2 Normative references ...................................................................................................... 9

3 Terms and definitions .................................................................................................... 10

4 Symbols ........................................................................................................................ 41

5 Independent measurement of total acoustic output power .............................................. 44

6 Acoustic field measurement: equipment ......................................................................... 44

6.1 Hydrophone .......................................................................................................... 44

6.1.1 General ......................................................................................................... 44

6.1.2 Sensitivity of a hydrophone ............................................................................ 44

6.1.3 Directional response of a hydrophone ............................................................ 45

6.1.4 Effective hydrophone radius .......................................................................... 45

6.1.5 Choice of the size of a hydrophone active element ........................................ 45

6.1.6 Hydrophone pressure limits ........................................................................... 46

6.1.7 Hydrophone intensity limits ............................................................................ 46

6.1.8 Hydrophone cable length and amplifiers ........................................................ 47

6.2 Requirements for positioning and water baths ....................................................... 47

6.2.1 General ......................................................................................................... 47

6.2.2 Positioning systems ....................................................................................... 47

6.2.3 Water bath ..................................................................................................... 48

6.3 Requirements for data acquisition and analysis systems ....................................... 49

6.4 Requirements and recommendations for ultrasonic equipment being

characterized ........................................................................................................ 50

7 Measurement procedure ................................................................................................ 50

7.1 General ................................................................................................................. 50

7.2 Preparation and alignment .................................................................................... 50

7.2.1 General drive and field conditions .................................................................. 50

7.2.2 Initial adjustment to driving voltage ................................................................ 51

7.2.3 Preparation of source transducer ................................................................... 52

7.2.4 Aligning an ultrasonic transducer and hydrophone ......................................... 52

7.2.5 Finding the beam axis .................................................................................... 53

7.2.6 Measurements to determine field level conditions .......................................... 55

7.2.7 Determining if transducer is focusing ............................................................. 56

7.2.8 Measuring other beamwidth parameters of a focusing transducer .................. 57

7.2.9 Measuring the beam area parameters ............................................................ 58

7.2.10 Measuring additional beam maximum based parameters ............................... 59

7.2.11 Alternative: calculation of focal parameters using numerical projection .......... 60

7.2.12 Plane wave transmitted fields ........................................................................ 61

7.2.13 Steered plane waves ..................................................................................... 61

7.2.14 Measurements of high intensity therapeutic ultrasound fields ......................... 61

7.2.15 Calculation of I ........................................................................................... 62

7.2.16 Further evaluation for sidelobes and pre-focal maxima .................................. 63

7.3 Considerations for scanning transducers and transducers with multiple

sources ................................................................................................................. 65

7.3.1 Automatic scanning transducers .................................................................... 65

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IEC 61828:2020 © IEC 2020 – 3 –

7.4 Spatial impulse response and beamplots .............................................................. 65

7.4.1 General ......................................................................................................... 65

7.4.2 Point target .................................................................................................... 66

7.4.3 Beamplots and beam contour plots ................................................................ 66

7.5 Plane wave compounding ..................................................................................... 66

Annex A (informative) Background for the transmission/ Characteristics of focusing

transducers ........................................................................................................................... 67

A.1 General ................................................................................................................. 67

A.2 Field of piston source ............................................................................................ 68

A.3 Focusing with a lens ............................................................................................. 68

A.4 Focusing with a concave transducer ..................................................................... 71

A.5 Geometric focusing gains ...................................................................................... 73

A.6 Beamwidth estimation ........................................................................................... 74

Annex B (informative) Rationale for focusing and nonfocusing definitions ............................ 79

B.1 Overview............................................................................................................... 79

B.1.1 Background information ................................................................................. 79

B.1.2 General ......................................................................................................... 79

B.1.3 Focusing transducers .................................................................................... 79

B.1.4 Focusing methods ......................................................................................... 80

B.1.5 Known and unknown focusing transducers ..................................................... 81

B.1.6 Focusing and beamwidth ............................................................................... 81

B.1.7 Focusing parameter definitions ...................................................................... 82

B.1.8 Applications of focusing definitions ................................................................ 82

B.1.9 Relation of present definitions to physiotherapy transducers (treatment

heads) ........................................................................................................... 82

B.1.10 Relation of present definitions to therapeutic transducers .............................. 82

B.2 System and measurement requirements ............................................................... 83

B.2.1 General ......................................................................................................... 83

B.2.2 Transmitted pressure waveforms .................................................................. 83

B.2.3 Transmitted fields ......................................................................................... 83

B.2.4 The scan plane and the steering of beams ..................................................... 83

B.2.5 Pulse echo field measurements ..................................................................... 84

Annex C (informative) Methods for determining the beam axis for well-behaved beams ....... 94

C.1 Comparisons of beam axis search methods .......................................................... 94

C.2 Beamwidth midpoint method ................................................................................. 95

Annex D (informative) Methods for determining the beam axis for beams that are not

well behaved ......................................................................................................................... 97

Annex E (informative) Uncertainties ..................................................................................... 99

E.1 General ................................................................................................................. 99

E.2 Overall (expanded) uncertainty ............................................................................. 99

E.3 Common sources of uncertainty ............................................................................ 99

Annex F (informative) Transducer and hydrophone positioning systems ............................. 101

Annex G (informative) Planar scanning of a hydrophone to determine acoustic output

power ................................................................................................................................. 102

G.1 Overview............................................................................................................. 102

G.2 General principle ................................................................................................ 102

G.3 Hydrophone scanning methodology..................................................................... 103

G.3.1 General methodology ................................................................................... 103

G.3.2 Particular considerations for implementation for HITU fields ........................ 104

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– 4 – IEC 61828:2020 © IEC 2020

G.4 Corrections and sources of measurement uncertainty ......................................... 104

G.4.1 Uncertainty in the hydrophone calibration ................................................... 104

G.4.2 Planar scanning .......................................................................................... 104

G.4.3 Attenuation factor of water: unfocusing transducers ................................... 104

G.4.4 Attenuation factor of water: focusing transducers ....................................... 105

G.4.5 Received hydrophone signal ........................................................................ 105

G.4.6 Integration ................................................................................................... 105

G.4.7 Finite size of the hydrophone ....................................................................... 106

G.4.8 Partial extent of integration .......................................................................... 106

G.4.9 Non-linear propagation ................................................................................ 106

G.4.10 Directional response .................................................................................... 106

G.4.11 Noise ........................................................................................................... 107

G.4.12 Intensity approximated by derived intensity .................................................. 107

Annex H (informative) Properties of water .......................................................................... 108

H.1 General ............................................................................................................... 108

H.2 Attenuation coefficient for propagation in water ................................................... 109

Bibliography ........................................................................................................................ 110

Figure A.1 – Beam contour plot: contours at −6 dB, −12 dB, and −20 dB for a 5 MHz

transducer with a radius of curvature of D = 50 mm centred at location 0,0 (bottom

centre of graph) .................................................................................................................... 76

Figure A.2 – Types of geometric focusing ............................................................................. 76

Figure A.3 – Transducer options ........................................................................................... 77

Figure A.4 – Parameters for describing a focusing transducer of known geometry ................ 78

Figure A.5 – Path difference parameters for describing a focusing transducer of known

geometry .............................................................................................................................. 78

Figure B.1 – Electronic focusing along z by transmit beamforming in the scan plane xz ......... 84

Figure B.2 – Field parameters for a nonfocusing transducer of known geometry. For

example, for a circularly symmetric geometry, transducers have a diameter 2a and a

beam axis along z ................................................................................................................. 85

Figure B.3 – Phased array geometry and construction for electronic focusing in the

azimuth plane and mechanical lens focusing in the elevation plane ...................................... 85

Figure B.4 – Field parameters for a focusing transducer of known geometry ......................... 86

Figure B.5 – Definitions for pressure-based field measurements for an unknown

transducer geometry ............................................................................................................. 86

Figure B.6 – Beamwidth focus for transducers of known and unknown geometry .................. 87

Figure B.7 – Beam maximum parameters .............................................................................. 88

Figure B.8 – Pressure focus for a transducer of known geometry (design case) .................... 88

Figure B.9 – Pressure focus for a transducer of unknown geometry (measurement

case) .................................................................................................................................... 89

Figure B.10 – Beam area parameters .................................................................................... 89

Figure B.11 – Beam axis parameters: pulse-pressure-squared-integral level relative to

the beam maximum in decibels (dB) plotted against axial distance ....................................... 90

Figure B.12 – Beamplot parameters ...................................................................................... 91

Figure B.13 – Schematic diagram of the different planes and lines in an ultrasonic field

for a rectangular transducer .................................................................................................. 92

Figure B.14 – Schematic diagram of the different planes and lines in an ultrasonic field

for a circular transducer ........................................................................................................ 93

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IEC 61828:2020 © IEC 2020 – 5 –

Figure C.1 – x-axis scan at 9 cm depth for the first focal zone with beam centre ................... 95

Figure C.2 – x-axis scan at 4,4 cm depth for the second focal zone ...................................... 95

Figure D.1 – Asymmetric beam showing relative acoustic pressure versus sample

number for the beamwidth midpoint method .......................................................................... 98

Figure F.1 – Schematic diagram of the ultrasonic transducer and hydrophone degrees

of freedom .......................................................................................................................... 101

Table C.1 – Standard deviations for x and y scans using three methods of determining

the centre of the beam .......................................................................................................... 94

Table C.2 – Decibel beamwidth levels for determining midpoints .......................................... 96

Table H.1 – Speed of sound, c, and characteristic acoustic impedance, ρ c, as a

function of temperature, for propagation in water ................................................................ 108

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– 6 – IEC 61828:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ULTRASONICS –TRANSDUCERS – DEFINITIONS AND MEASUREMENT
METHODS REGARDING FOCUSING FOR THE TRANSMITTED FIELDS
FOREWORD

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International Standard IEC 61828 has been prepared by IEC technical committee 87:

Ultrasonics.

This second edition 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.
---------------------- Page: 8 ----------------------
IEC 61828:2020 © IEC 2020 – 7 –

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.

The text of this International Standard is based on the following documents:
FDIS Report on voting
87/746/FDIS 87/749/RVD

Full information on the voting for the approval of this International Standard can be found in the

report on voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

NOTE 1 The following print types are used:
– Requirements: in roman type.
– Notes: small roman type.
– Words in bold in the text are defined in Clause 3.

NOTE 2 There are some inconsistencies in font type for symbols and formulae between some of the normative

references and this document. They will be resolved
...

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