BS EN 61828-2002 Ultrasonics - Focusing transducers - Definitions and measurement methods for the transmitted fields《超声学 聚焦振子 发射场定义和测量》.pdf

1、BRITISH STANDARD BS EN 61828:2002 IEC 61828:2001 Ultrasonics Focusing transducers Definitions and measurement methods for the transmitted fields The European Standard EN 61828:2001 has the status of a British Standard ICS 17.140.50 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT L

2、AWBS EN 61828:2002 This British Standard, having been prepared under the direction of the Electrotechnical Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 21 February 2002 BSI 21 February 2002 ISBN 0 580 39012 8 National forew

3、ord This British Standard is the official English language version of EN 61828:2001. It is identical with IEC 61828:2001. The UK participation in its preparation was entrusted to Technical Committee EPL/87, Ultrasonics, which has the responsibility to: A list of organizations represented on this com

4、mittee can be obtained on request to its secretary. From 1 January 1997, all IEC publications have the number 60000 added to the old number. For instance, IEC 27-1 has been renumbered as IEC 60027-1. For a period of time during the change over from one numbering system to the other, publications may

5、 contain identifiers from both systems. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “F

6、ind” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from leg

7、al obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. S

8、ummary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 51 and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEAN STANDARD

9、EN 61828 NORME EUROPENNE EUROPISCHE NORM October 2001 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2001 CENELEC - All rights

10、of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61828:2001 E ICS 17.140.50 English version Ultrasonics - Focusing transducers - Definitions and measurement methods for the transmitted fields (IEC 61828:2001) Ultrasons - Transducteurs focaliseurs - Dfi

11、nitions et mthodes de mesure des champs transmis (CEI 61828:2001) Ultraschall - Fokusierende Wandler - Definitionen und Messverfahren fr die erzeugten Felder (IEC 61828:2001) This European Standard was approved by CENELEC on 2001-09-01. CENELEC members are bound to comply with the CEN/CENELEC Intern

12、al Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC mem

13、ber. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELE

14、C members are the national electrotechnical committees of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.EN 82816:2001 - 2 - Foreword The text of doc

15、ument 87/196/FDIS, future edition 1 of IEC 61828, prepared by IEC TC 87, Ultrasonics, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61828 on 2001-09-01. The following dates were fixed: latest date by which the EN has to be implemented at national level by publicati

16、on of an identical national standard or by endorsement (dop) 2002-06-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2004-09-01 Annexes designated “normative“ are part of the body of the standard. Annexes designated “informative“ are given for inform

17、ation only. In this standard, annex ZA is normative and annexes A, B and C are informative. Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 61828:2001 was approved by CENELEC as a European Standard without any modification. In the official version,

18、 for Bibliography, the following notes have to be added for the standards indicated: IEC 61161:1992 NOTE: Harmonized as EN 61161:1994 (not modified). IEC 62092:2001 NOTE: Harmonized as EN 62092:2001 (not modified). _ 2egaP 1002:82816NE 2002yraurbeF81ISB Page2 EN61828:2001 BSI21February2002CONTENTS I

19、NTRODUCTION 5 1 Scope 6 2 Normative references. 6 3 General . 7 3.1 Focusing transducers . 7 3.1.1 Focusing methods. 7 3.1.2 Known and unknown focusing transducers 7 3.1.3 Focusing and beamwidth 8 3.1.4 New focusing parameter definitions 8 3.1.5 Applications of focusing definitions . 9 3.1.6 Relatio

20、n of present definitions to physiotherapy transducers (treatment heads) . 9 3.2 System and measurement requirements . 9 3.2.1 Transmitted pressure waveforms 9 3.2.2 Radiated fields 9 3.3 General focused field descriptions .10 3.3.1 General field descriptions for transducers of known construction .10

21、 3.3.2 The scan plane and the steering of beams.11 4 Focusing definitions12 4.1 Background information.12 4.2 Definitions .12 5 List of symbols23 6 Measurement procedures .24 6.1 General .24 6.1.1 Set-up25 6.2 Finding the beam axis25 6.3 Determining if transducer is focusing .27 6.4 Measuring other

22、focal parameters of a focusing transducer .28 Annex A (informative) Background for the transmission/ Characteristics of focusing transducers.38 Annex B (informative) Methods for determining the beam axis for well-behaved beams 44 B.1 Comparisons of beam axis search methods .44 B.2 Beamwidth midpoint

23、 method45 Annex C (informative) Methods for determining the beam axis for beams that are not well-behaved 48 Annex ZA (normative) Normative references to international publications with their corresponding European publications51 3egaP 1002:82816NEPage3 EN61828:2001 BSI21February2002Figure 1 Transdu

24、cer options Top: Transducer with a radius of curvature R and a focal length equal to R Middle: Transducer with a plano-concave lens Bottom: Transducer with a plano-convex lens.29 Figure 2 Definitions for focusing measurements when the transducer geometry is unknown .30 Figure 3 Field parameters for

25、non-focusing and focusing transducers 31 Figure 4 Beam contour plot Contours at 6, 12, and 20 dB for a 5 MHz transducer with a diameter of 25 mm and a radius of curvature of 50 mm centred at location 0,0 (bottom centre of graph)32 Figure 5 Parameters for describing a focusing transducer of a known g

26、eometry.33 Figure 6 Path difference parameters for describing a focusing transducer of a known geometry.34 Figure 7 Beamwidth focus in a principal longitudinal plane.35 Figure 8 Types of geometric focusing36 Figure 9 Pressure focus in a principal longitudinal plane 37 Figure B.1 X-axis scan at 9 cm

27、depth for the first focal zone with beam centre.45 Figure B.2 X-axis scan at 4,4 cm depth for the second focal zone 46 Figure C.1 Asymmetric beam showing beamwidth midpoint method .49 Table B.1 Standard deviations for x and y scans using three methods of determining the centre of the beam 44 Table B

28、.2 dB beamwidth levels for determining midpoints .47 4egaP 1002:82816NEPage4 EN61828:2001 BSI21February2002INTRODUCTION Focusing transducers are essential in medical applications for obtaining high-resolution images, Doppler and flow data and for concentrating ultrasonic energy at desired sites for

29、therapy. Present terminology for focusing transducers is inadequate for communicating precisely the characteristics of the focused fields of the wide variety of transducers and transducer array types and focusing means in common usage. This International Standard provides specific definitions approp

30、riate for describing the focused field from a theoretical viewpoint for transducers with known characteristics intended by design. Other specific definitions included in this standard, based on measurement methods, provide a means of determining focusing properties, if any, of a transducer of unknow

31、n field characteristics. The measurement method and definitions provide criteria for determining if the transducer is focusing, as well as a means of describing the focusing properties of the field. Beam axis alignment methods are given for focusing transducers. 5egaP 1002:82816NE 2002yraurbeF81ISB

32、Page5 EN61828:2001 BSI21February2002ULTRASONICS FOCUSING TRANSDUCERS DEFINITIONS AND MEASUREMENT METHODS FOR THE TRANSMITTED FIELDS 1 Scope This International Standard provides definitions for the transmitted field characteristics of focusing transducers for applications in medical ultrasound; relat

33、es these definitions to theoretical descriptions, design, and measurement of the transmitted fields of focusing transducers; gives measurement methods for obtaining defined characteristics of focusing transducers; specifies beam axis alignment methods appropriate for focusing transducers. This Inter

34、national Standard 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 may be described from the poi

35、nt of view of design, as well as measured by someone with no prior knowledge of the construction details of a particular device. The radiated 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. The standa

36、rd 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 d

37、esign 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. This standard incorporates definitions from other related standards 1where possible, and supplies new, more specific ter

38、minology, both for defining focusing characteristics and for providing a basis for measurement of these characteristics. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated

39、references, subsequent amendments to, or revisions of, any of these publications do not apply. However parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated

40、 references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. IEC 60050(801):1994, International Electrotechnical Vocabulary (IEV) Chapter 801: Acoustics and electroacoustics IEC 61102:1991, Measur

41、ement and characterization of ultrasonic fields using hydrophones in the frequency range 0,5 MHz to 15 MHz _ 1Specifically, IEC 61102 and IEC 61157 (see clause 2). 6egaP 1002:82816NE 2002yraurbeF81ISB Page6 EN61828:2001 BSI21February2002IEC 61157:1992, Requirements for the declaration of the acousti

42、c output of medical diagnostic ultrasonic equipment IEC 61689:1996, Ultrasonics Physiotherapy systems Performance requirements and methods of measurement in the frequency range 0,5 MHz to 5 MHz 3 General The information contained in this clause is an introduction to the definitions given in clause 4

43、 and the measurement methods given in clause 6. 3.1 Focusing transducers The term “focusing transducer“ 2is commonly used for a device which has a smaller beamwidth in some regions of the field than a device which is “non-focusing“. A “non- focusing transducer“ can still have a natural focus, so it

44、is necessary to distinguish a focusing transducer as having a greater concentration of pressure amplitude (for a given power output) than a non-focusing transducer at its natural focus. For example, a non- focusing transducer made of a simple disc of uniformly poled piezoelectric material has a beam

45、 whose intensity at its natural focus can be as much as four times the average intensity at the source, and whose 6 dB beamwidth can be approximately half of that at the source. A definition of a focusing transducer is given in 4.2.33 to make a quantitative distinction between focusing and non-focus

46、ing transducers. 3.1.1 Focusing methods The simplest means of intentionally focusing an ultrasonic transducer, borrowed from analogous optical principles, is that of shaping the ultrasonic transducer into a concave form or adding to it a physical lens as illustrated in figure 1. In the top part of t

47、his figure, a transducer curved with a radius R is shown focusing to the centre of curvature, where R is positive by convention. By the geometrical-optics approximation, the focal length F is equal to R and hence is also positive. In the middle of figure 1 is shown a transducer with a plano- concave

48、 lens made of a material with longitudinal velocity, c L , which is curved on one side with a radius, R LENS , and radiates into a medium in which the velocity is c W . In acoustics, c W is typically less than c L , i.e., the index of refraction n (equal to c W /c L ) is less than 1. When this is tr

49、ue, the radius is considered to be negative and the focal length, given by the geometric-acoustics approximation as R LENSdivided by (n 1), is positive. At the bottom of the figure, for comparison, the typical situation for a convex lens in optics is shown: n is greater than 1 and the radius is considered to be positive, so the focal length is positive. 3.1.2 Known and unknown focusing transducers For ultrasonic transduce