BS-EN-62359-2005.pdf

BRITISH STANDARD BS EN 62359:2005 Ultrasonics Field characterization Test methods for the determination of thermal and mechanical indices related to medical diagnostic ultrasonic fields The European Standard EN 62359:2005 has the status of a British Standard ICS 17.140.50 ? Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:54:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 62359:2005 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 January 2006 © BSI 31 January 2006 ISBN 0 580 47353 8 National foreword This British Standard is the official English language version of EN 62359:2005. It is identical with IEC 62359:2005. 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 committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal 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 UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 43 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:54:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EUROPEAN STANDARD EN 62359 NORME EUROPÉENNE EUROPÄISCHE NORM October 2005 CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels © 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 62359:2005 E ICS 17.140.50 English version Ultrasonics Field characterization Test methods for the determination of thermal and mechanical indices related to medical diagnostic ultrasonic fields (IEC 62359:2005) Ultrasons Caractérisation du champ Essais pour la détermination des indices d'échauffement et mécaniques des champs d'ultrasons utilisés pour le diagnostic médical (CEI 62359:2005) Ultraschall Charakterisierung von Feldern - Prüfverfahren für die Ermittlung des thermischen und des mechanischen Indexes bezogen auf medizinisch- diagnostische Ultraschallfelder (IEC 62359:2005) This European Standard was approved by CENELEC on 2005-09-13. CENELEC members are bound to comply with the CEN/CENELEC Internal 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 member. 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. CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:54:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 62359:2005 2 Foreword The text of document 87/300/FDIS, future edition 1 of IEC 62359, prepared by IEC TC 87, Ultrasonics, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 62359 on 2005-09-13. The following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2006-07-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2008-10-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 62359:2005 was approved by CENELEC as a European Standard without any modification. _ Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:54:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 3 EN 62359:2005 CONTENTS INTRODUCTION.4 1 Scope 5 2 Normative references .5 3 Terms and definitions .5 4 List of symbols .14 5 Test methods for determining the mechanical index and the thermal index.15 5.1 General.15 5.2 Determination of mechanical index.16 5.3 Determination of thermal index general .16 5.4 Determination of thermal index in non-scanning mode16 5.5 Determination of thermal index in scanning mode.18 5.6 Calculations for combined-operating mode.19 5.7 Summary of measured quantities for index determination .19 Annex A (informative) Relationships with other standards.21 ANNEX B (informative) Guidance notes for measurement of output power in scanning mode22 B.1 Measurement of output power, P, in scanning modes .22 B.2 Creating a 1 cm azimuthal wide window using a mask of absorbing material or a 1 cm-wide radiation force balance target .22 B.3 Creating a 1 cm azimuthal window using electronic control.25 B.4 Measurement of bounded output power25 Annex C (informative) Rationale and derivation of index models .26 C.1 Definition specific to this annex26 C.2 Mechanical index (MI) .27 C.3 Thermal index (TI) .28 ANNEX D (informative) Guidance on the interpretation of TI and MI .40 ANNEX ZA (normative) Normative references to international publications with their corresponding European publications43 Figure B.1 Suggested 1 cm-wide aperture mask .24 Figure B.2 Suggested orientation of transducer, mask slit and RFB target.24 Figure B.3 Suggested orientation of transducer and 1 cm RFB target24 Figure C.1 Focused transducer with a large aperture 35 Figure C.2 Focused transducer with smaller aperture (1 cm2) .35 Figure C.3 Focused transducer with a weak focus (Aeq 1 cm2) 36 Figure C.4 Weakly focused transducer .36 Table 1 Summary of combination formulae for each of the THERMAL INDEX categories.19 Table 2 Summary of the acoustic quantities required for the determination of the indices 20 Table C.1 THERMAL INDEX categories and models28 Table C.2 Thermal index formulae33 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:54:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 62359:2005 4 INTRODUCTION Medical diagnostic ultrasonic equipment is widely used in clinical practice for imaging and monitoring purposes. Equipment normally operates at frequencies in the low megahertz frequency range and comprises an ultrasonic transducer acoustically coupled to the patient and associated electronics. There is an extremely wide range of different types of systems in current clinical practice. The ultrasound entering the patient interacts with the patient's tissue and this interaction can be considered in terms of both thermal and non-thermal effects. The purpose of this International Standard is to specify methods of determining thermal and non-thermal exposure indices which can be used to help in assessing the hazard caused by exposure to a particular ultrasonic field used for medical diagnosis or monitoring. It is recognised that these indices have limitations and a knowledge of the indices at the time of an examination is not sufficient in itself to make an informed clinical risk assessment. It is intended that these limitations will be addressed in future revisions of this standard and as scientific understanding increases. Under certain conditions specified in IEC 60601-2-37 these indices are displayed on medical ultrasonic equipment intended for these purposes. Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:54:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 5 EN 62359:2005 ULTRASONICS FIELD CHARACTERIZATION TEST METHODS FOR THE DETERMINATION OF THERMAL AND MECHANICAL INDICES RELATED TO MEDICAL DIAGNOSTIC ULTRASONIC FIELDS 1 Scope This International Standard is applicable to medical diagnostic ultrasound fields. This standard establishes parameters related to thermal and non-thermal aspects of diagnostic ultrasonic fields; methods for the determination of an exposure parameter relating to temperature rise in theoretical tissue-equivalent models, resulting from absorption of ultrasound; methods for the determination of an exposure parameter appropriate to certain non- thermal effects. NOTE In this standard where multiples or submultiples of SI units are used this is clearly stated and the usage is self-consistent. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60601-2-37, Medical electrical equipment Part 2-37: Particular requirements for the safety of ultrasonic medical diagnostic and monitoring equipment IEC 61102:1991, Measurement and characterisation of ultrasonic fields using hydrophones in the frequency range 0,5 MHz to 15 MHz IEC 61157:1992, Requirements for the declaration of the acoustic output of medical diagnostic ultrasonic equipment IEC 61161:1992, Ultrasonic power measurement in liquids in the frequency range 0,5 MHz to 25 MHz 1) Amendment 1 (1998) 3 Terms and definitions For the purposes of this International standard, the terms and definitions given in IEC 61102:1991, IEC 61157:1992 and IEC 61161:1998 (several of which are repeated below for convenience) and the following apply. 3.1 acoustic attenuation coefficient coefficient intended to account for ultrasonic attenuation of tissue between the source and a specified point Symbol: 1) A consolidated edition (1.1) exists, including IEC 61161:1992 and its Amendment 1 (1998). Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:54:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 62359:2005 6 Unit: decibels per centimetre per megahertz, dB cm1 MHz1 3.2 acoustic working frequency arithmetic mean of the most widely separated frequencies f1 and f2 at which the amplitude of the pressure spectrum of the acoustic signal is 3 dB lower than the peak amplitude 3.4.2 of IEC 61102:1991, modified Symbol: fawf Unit: megahertz, MHz 3.3 attenuated output power value of the acoustic output power after attenuation and at a specified distance from the transducer, and given by dB) /10- ( awf 10 fz PP = where is the acoustic attenuation coefficient; z is the distance from the source to the point of interest; fawf is the acoustic working frequency; P is the output power measured in water. Symbol: P Unit: milliwatts, mW 3.4 attenuated peak-rarefactional acoustic pressure value of the peak-rarefactional acoustic pressure after attenuation and at a specified point, and given by dB)/20(- rr, awf 10 )()( fz zpzp = where is the acoustic attenuation coefficient; z is the distance from the source to the point of interest; fawf is the acoustic working frequency; pr(z) is the peak-rarefactional acoustic pressure measured in water. Symbol: pr, Unit: megapascals, MPa 3.5 attenuated pulse-average intensity value of the acoustic pulse-average intensity after attenuation and at a specified point, and given by dB)/10- ( papa, awf 10 )( fz zII = Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:54:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 7 EN 62359:2005 where is the acoustic attenuation coefficient; z is the distance from the source to the point of interest; fawf is the acoustic working frequency; Ipa(z) is the pulse-average intensity measured in water. Symbol: Ipa, Unit: watts per centimetre squared, W cm2 3.6 attenuated pulse-intensity integral value of the pulse-intensity integral after attenuation and at a specified point, and given by dB)/10- ( pipi, awf 10 fz II = where is the acoustic attenuation coefficient; z is the distance from the source to the point of interest; fawf is the acoustic working frequency; Ipi is the pulse-intensity integral measured in water. Symbol: Ipi, Unit: millijoules per centimetre squared, mJ cm2 3.7 attenuated spatial-peak temporal-average intensity value of the spatial-peak temporal-average intensity after attenuation and at a specified distance z, and given by dB) /10- ( zptazpta, awf 10 )()( fz zIzI = where is the acoustic attenuation coefficient; z is the distance from the source to the point of interest; fawf is the acoustic working frequency; Izpta(z) is the spatial-peak temporal-average intensity, at a specified distance z measured in water. Symbol: Izpta,(z) Unit: milliwatts per centimetre squared, mW cm2 3.8 attenuated temporal-average intensity value of the temporal-average intensity after attenuation and at a specified point, and given by dB)/10(- tata, awf 10 )()( fz zIzI = where is the acoustic attenuation coefficient; Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:54:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 62359:2005 8 z is the distance from the source to the point of interest; fawf is the acoustic working frequency; Ita(z) is the temporal-average intensity measured in water. Symbol: Ita,(z) Unit: milliwatts per centimetre squared, mW cm2 3.9 beam area area in a specified plane perpendicular to the beam-alignment axis consisting of all points at which the pulse-intensity integral is greater than a specified fraction of the maximum pulse- intensity integral in that plane 3.6 of IEC 61102:1991, modified NOTE For measurement purposes the pulse intensity integral can be taken as being proportional to the pulse pressure-squared integral 3.10 beam alignment axis straight line joining the points of maximum pulse intensity integral measured at several different distances in the far field. For the purposes of alignment, this line may be projected to the face of the ultrasonic