Ultrasonics - Field characterization - Infrared imaging techniques for determining temperature elevation in tissue-mimicking material and at the radiation surface of a transducer in still air

IEC TS 63070:2019 is applicable to ultrasonic equipment designed for the medical field of application. It covers both diagnostic and therapeutic (physiotherapy and HITU) equipment.
This document describes transducer evaluation by the infrared imaging technique using a split TMM-phantom for qualitative and quantitative estimation of temperature distributions in tissue-mimicking material, resulting from absorption of ultrasound and from heating of the transducer itself.
This document also describes a method to measure transducer-surface temperature, while the transducer is driven under the still-air condition.

General Information

Status
Published
Publication Date
14-Feb-2019
Technical Committee
Current Stage
PPUB - Publication issued
Completion Date
15-Feb-2019
Ref Project

Buy Standard

Technical specification
IEC TS 63070:2019 - Ultrasonics - Field characterization - Infrared imaging techniques for determining temperature elevation in tissue-mimicking material and at the radiation surface of a transducer in still air
English language
26 pages
sale 15% off
Preview
sale 15% off
Preview

Standards Content (sample)

IEC TS 63070
Edition 1.0 2019-02
TECHNICAL
SPECIFICATION
colour
inside
Ultrasonics – Field characterization – Infrared imaging techniques for
determining temperature elevation in tissue-mimicking material and at the
radiation surface of a transducer in still air
IEC TS 63070:2019-02(en)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyright © 2019 IEC, Geneva, Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form

or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from

either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC

copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or

your local IEC member National Committee for further information.
IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC

The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes

International Standards for all electrical, electronic and related technologies.
About IEC publications

The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the

latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org

The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,

variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English

committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.

and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished

Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary

details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and

once a month by email. French extracted from the Terms and Definitions clause of

IEC publications issued since 2002. Some entries have been

IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and

If you wish to give us your feedback on this publication or CISPR.
need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
---------------------- Page: 2 ----------------------
IEC TS 63070
Edition 1.0 2019-02
TECHNICAL
SPECIFICATION
colour
inside
Ultrasonics – Field characterization – Infrared imaging techniques for
determining temperature elevation in tissue-mimicking material and at the
radiation surface of a transducer in still air
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.140.50 ISBN 978-2-8322-6417-1

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

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TS 63070:2019 © IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms and definitions ...................................................................................................... 8

4 Symbols and abbreviated terms ....................................................................................... 8

5 Methods of use ................................................................................................................ 8

5.1 General ................................................................................................................... 8

5.2 Consideration of perfusion ...................................................................................... 9

5.3 Effects of environment ............................................................................................ 9

6 IR-camera specifications ................................................................................................. 9

6.1 General ................................................................................................................... 9

6.2 Test ........................................................................................................................ 9

6.3 Calibration .............................................................................................................. 9

7 Phantom specification and construction ......................................................................... 10

7.1 Split TMM specifications ....................................................................................... 10

7.2 Periodic validation ................................................................................................ 10

8 Measurement procedure ................................................................................................ 10

8.1 Split TMM setup .................................................................................................... 10

8.1.1 General ......................................................................................................... 10

8.1.2 Emissivity ...................................................................................................... 11

8.1.3 Procedure ...................................................................................................... 11

8.2 Still-air setup ........................................................................................................ 12

8.2.1 General ......................................................................................................... 12

8.2.2 Emissivity ...................................................................................................... 12

8.2.3 Procedure ...................................................................................................... 12

9 Uncertainty determination .............................................................................................. 12

Annex A (informative) Measurement example using a split TMM setup ................................ 13

A.1 General ................................................................................................................. 13

A.2 Measurement setups ............................................................................................. 13

A.3 Procedures ........................................................................................................... 16

A.4 Data analysis ........................................................................................................ 17

A.5 Improved split TMM-phantom ................................................................................ 18

Annex B (informative) Measurement procedure under the condition of still air ...................... 20

B.1 General ................................................................................................................. 20

B.2 Measurement setups ............................................................................................. 20

B.3 Procedures ........................................................................................................... 20

Annex C (informative) Guidance on uncertainty determination ............................................. 23

Bibliography .......................................................................................................................... 25

Figure A.1 – Concept of measurement .................................................................................. 14

Figure A.2 – Setups for thermal equilibrium and measurement .............................................. 15

Figure A.3 – Analysis of thermal image ................................................................................. 18

Figure A.4 – Improved split TMM phantom ............................................................................ 19

---------------------- Page: 4 ----------------------
IEC TS 63070:2019 © IEC 2019 – 3 –

Figure B.1 – Example of a measurement setup for the transducer surface-temperature

test in still air using an infrared camera ................................................................................. 21

Figure B.2 – Flow chart of the transducer surface-temperature test in still air using an

infrared camera .................................................................................................................... 22

Table A.1 – Results of measurement .................................................................................... 18

---------------------- Page: 5 ----------------------
– 4 – IEC TS 63070:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ULTRASONICS – FIELD CHARACTERIZATION –
INFRARED IMAGING TECHNIQUES FOR DETERMINING
TEMPERATURE ELEVATION IN TISSUE-MIMICKING MATERIAL AND
AT THE RADIATION SURFACE OF A TRANSDUCER IN STILL AIR
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

The main task of IEC technical committees is to prepare International Standards. In

exceptional circumstances, a technical committee may propose the publication of a Technical

Specification when

• the required support cannot be obtained for the publication of an International Standard,

despite repeated efforts, or

• the subject is still under technical development or where, for any other reason, there is the

future but no immediate possibility of an agreement on an International Standard.

Technical Specifications are subject to review within three years of publication to decide

whether they can be transformed into International Standards.

IEC TS 63070, which is a Technical Specification, has been prepared by IEC technical

committee 87: Ultrasonics.
---------------------- Page: 6 ----------------------
IEC TS 63070:2019 © IEC 2019 – 5 –
The text of this Technical Specification is based on the following documents:
Draft TS Report on voting
87/677/DTS 87/688A/RVDTS

Full information on the voting for the approval of this Technical Specification can be found in

the report on voting indicated in the above table.

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

Terms in bold in the text are defined in Clause 3.

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• transformed into an International Standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
---------------------- Page: 7 ----------------------
– 6 – IEC TS 63070:2019 © IEC 2019
INTRODUCTION

This Technical Specification describes primarily how to measure temperature elevation

generated by an ultrasound transducer by using an infrared (IR) camera system aimed at

insonified tissue-mimicking material located in still air.

Split TMM (tissue-mimicking material) is configured as a phantom to observe temperature

elevation and distribution for assessing fields generated by diagnostic ultrasound equipment

and by physiotherapy and high intensity therapeutic ultrasound (HITU) equipment.

Temperature measurement of the radiating surface of an ultrasound transducer under the still-

air condition is also considered for the evaluation of extensive temperature distributions as

required in IEC 60601-2-37:2007 and IEC 60601-2-37:2007/AMD1:2015.
---------------------- Page: 8 ----------------------
IEC TS 63070:2019 © IEC 2019 – 7 –
ULTRASONICS – FIELD CHARACTERIZATION –
INFRARED IMAGING TECHNIQUES FOR DETERMINING
TEMPERATURE ELEVATION IN TISSUE-MIMICKING MATERIAL AND
AT THE RADIATION SURFACE OF A TRANSDUCER IN STILL AIR
1 Scope

This document is applicable to ultrasonic equipment designed for the medical field of

application. It covers both diagnostic and therapeutic (physiotherapy and HITU) equipment.

This document describes transducer evaluation by the infrared imaging technique using a split

TMM-phantom for qualitative and quantitative estimation of temperature distributions in

tissue-mimicking material, resulting from absorption of ultrasound and from heating of the

transducer itself.

This document also describes a method to measure transducer-surface temperature, while the

transducer is driven under the still-air condition.

NOTE 1 When the transducer is in contact with tissue-mimicking material, the heating of the transducer itself

depends on the actual efficiency of the transducer, on the specific conditions for thermal transfer to or from the

tissue-mimicking material, and on the transmitting/receiving electronic circuits, such as a switching circuit or pre-

amplifier in some cases.

NOTE 2 The test objects specified in this document are for the measurement of temperature rise and not for the

determination of thermal index, which is, by definition in IEC 62359:2010 and IEC 62359:2010/AMD1:2017, an

algebraic combination of acoustical field quantities and therefore is not a physically measurable quantity.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their

content constitutes requirements 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 60601-2-5:2009, Medical electrical equipment – Part 2-5: Particular requirements for the

basic safety and essential performance of ultrasonic physiotherapy equipment

IEC 60601-2-37:2007, Medical electrical equipment – Part 2-37: Particular requirements for

the basic safety and essential performance of ultrasonic medical diagnostic and monitoring

equipment
IEC 60601-2-37:2007/AMD1:2015

IEC 60601-2-62:2013, Medical electrical equipment – Part 2-62: Particular requirements for

the basic safety and essential performance of high intensity therapeutic ultrasound (HITU)

equipment
IEC 61161:2013, Ultrasonics – Power measurement – Radiation force balances and
performance requirements

IEC 62127-1:2007, Ultrasonics – Hydrophones – Part 1: Measurement and characterization of

medical ultrasonic fields up to 40 MHz
IEC 62127-1:2007/AMD1:2013

ISO 18434-1:2008, Condition monitoring and diagnostics of machines – Thermography –

Part 1: General procedures
---------------------- Page: 9 ----------------------
– 8 – IEC TS 63070:2019 © IEC 2019
3 Terms and definitions
For the purposes of this document, the terms and definitions given in

IEC 62127-1:2007, IEC 62127-1:2007/AMD1:2013, IEC 61161:2013, IEC 60601-2-37:2007,

IEC 60601-2-37:2007/AMD1:2015, IEC 60601-2-5:2009, IEC 60601-2-62:2013, ISO 18434-

1:2008 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
emissivity

ratio of a target surface’s radiance to that of a black body at the same temperature and over

the same spectral interval
[SOURCE: ISO 18434-1:2008, 3.4]
3.2
black body
ideal perfect emitter and absorber of thermal radiation at all wavelengths
[SOURCE: ISO 18434-1:2008, 3.3]
4 Symbols and abbreviated terms
ε emissivity
HITU high intensity therapeutic ultrasound
IR infrared
T temperature
ΔT temperature rise
TMM tissue mimicking material
5 Methods of use
5.1 General

There are several methods to measure temperature rise using an infrared (IR) camera system.

Two of them are further described in this document: the split TMM setup and the “still air”

setup.
Each of these setups has its own procedures and requirements, see Clause 8.
---------------------- Page: 10 ----------------------
IEC TS 63070:2019 © IEC 2019 – 9 –
5.2 Consideration of perfusion

The utilized phantom does not have the functionality of perfusion as a human body. So

perfusion should additionally be taken into account and referred to as necessary
[1] [2] [3] [4] [5] .
5.3 Effects of environment

Due to reflections of infrared radiation, the environment may affect the measurement of the

temperature on a surface. The setup of the IR-camera, the general surroundings and the

surroundings of the target should be such that environmental effects are negligible compared

to the measured temperature rise of the target due to ultrasound.
A suitable procedure is described in A.3 b).
6 IR-camera specifications
6.1 General
For these measurements the IR-camera should have the following specifications.

• The range of measurable temperature should cover 20 °C to 53 °C at minimum. In case

the camera is to be used to measure the effect of HITU fields, the upper limit should be

70 °C or higher.

• The spatial resolution, which is the pixel size in an IR-image, should be equal to or less

than 0,5 mm in lateral and vertical directions.

• The number of pixels of the thermal image should suffice for displaying the area required

for observing the split TMM-phantom and the other setups that are used for tuning the

focus, checking the scale and measuring the ambient temperature.

• The nominal temperature resolution should be less than 0,1 °C or 5 % of the temperature

rise, whichever is larger. For example, it should be equal to or less than 0,25 °C when the

measured temperature rise is 5 °C.

• PC-control may be useful for making the camera settings and for recording and analysing

IR-images.

In general, thermal drift of the IR-camera, whether cooled or non-cooled, should be minimized

and, when necessary, measured and corrected during analysis.
6.2 Test

Performance of a general functionality test is recommended for the IR-camera before

beginning the measurement. A suitable test entails checking normal operation with no

malfunction or alarms for temperature measurement after the warm-up time. Refer to the

operations manual of the IR-camera for details.
6.3 Calibration

The IR-camera should have been calibrated within a year before use by a method traceable to

a primary measurement standard. Calibration should also verify image uniformity and ambient

temperature compensation in the specified temperature range. It is typically performed using

a planar thermal-radiation source (a reference source) calibrated against a standard black

body. This calibration may also be done using thin film thermocouples.
A suitable procedure is described in [6].
____________
Numbers in square brackets refer to the Bibliography.
---------------------- Page: 11 ----------------------
– 10 – IEC TS 63070:2019 © IEC 2019
7 Phantom specification and construction
7.1 Split TMM specifications

Measurement of the temperature inside a phantom is one goal for observations by the IR-

camera. So one of the most important requirements of the phantom is its ability to be split into

two pieces of TMM with flat (or slightly convex) cross-sectional surfaces that can be exposed

to the IR-camera. TMM is vulnerable to dehydration and mechanical damage. A practical

phantom may be kept in a rigid housing in order to avoid dehydration and malfunction caused

by cracking the TMM during the operation of combination and separation during the

measurement procedure. See Annex A.

The TMM should have acoustic and thermal properties that mimic the appropriate tissue of

the human body. The emissivity of the split surface should be known. One of the applicable

materials equivalent to soft tissue is specified in IEC 60601-2-37:2007 and

IEC 60601-2-37:2007/AMD1:2015; its emissivity was determined in [7] to be 0,94 by

comparison with black body tape.

Minimizing multiple reflections of ultrasound between the transducer and the bottom surface

of the phantom should be taken into consideration. Lining material, which is used in other

circumstances to absorb ultrasound propagating in a water tank and has a high attenuation

property, may be appropriately placed at the bottom of the phantom to be effective for this

purpose. Bone-mimicking material or sterilized bone fragments [8] [9] [10] should be used as

necessary with soft-tissue mimicking material.

If high temperature rise is expected in the TMM, such as when heating with a HITU system,

then the properties of the TMM should be known and stable, over the range of expected

temperature rises during the measurement.
7.2 Periodic validation

Periodic validation should be performed from the viewpoint of both acoustic and thermal

properties. The specified values of attenuation coefficient, thermal conductivity and heat

capacity in IEC 60601-2-37:2007 and IEC 60601-2-37:2007/AMD1:2015 should be maintained

within the specified tolerances. The period between validations should be one year.

The replacement with new split TMM phantom should be considered when the structural

abnormality like cracks and/or the degradation like change of colour are found by visual

inspection.

The properties of the selected tissue-mimicking phantom should be appropriate to the tissue

being simulated and the purpose of the measurement.
8 Measurement procedure
8.1 Split TMM setup
8.1.1 General

In an infrared measurement there are two phases: first, the ultrasound transducer coupled to

the TMM (see recommendation in the last paragraph of 8.1.1) is driven and it generates an

acoustic field in the TMM. Heat is generated inside the TMM. Secondly, after a given time of

insonation, the configuration of the phantom is changed to allow the IR-camera to observe the

two-dimensional temperature distribution over a cross-sectional plane that was inside the

TMM during the first phase.

To enable IR-measurements inside the TMM, the TMM consists of two blocks, which make

contact during the heating phase and which have to be quickly separated directly after

---------------------- Page: 12 ----------------------
IEC TS 63070:2019 © IEC 2019 – 11 –

switching off the electrical drive to the transducer, so that the temperature distribution over

the separated surface can be measured by the IR-camera. To pull the blocks firmly together

and subsequently to separate them quickly, a mechanism has to be built on which the blocks

are stable, secure and movable. The IR-camera looks at the front surface (split surface) of the

TMM after opening. The infrared picture has to be saved in a format (two-dimensional, colour-

coded) that can be processed off-line to calculate, for example, the one-dimensional

temperature profiles in lateral and axial directions.

The thermal cooling rate, in air on the exposed surface, after opening the TMM-blocks, has

been measured to be about 0,3 °C/s in the first 20 s after switching off the ultrasound

radiation. Corrections are to be made by extrapolation back to the moment of opening the split

TMM-blocks and switching off the ultrasound (It is assumed that these occur at the same

time.).

Care should be taken that the pressure to keep the two parts of TMM together is not changing

the properties of the TMM. Appropriate pressure is required to realize the firm combination of

TMM blocks while also avoiding destruction. Refer to A.3 c).
8.1.2 Emissivity

The appropriate emissivity value for the split TMM should be applied either at the time of

measurement or during later analysis. See [7] for example.
8.1.3 Procedure

Annex A gives an example of IR-measurement procedures from setups to obtained results.

The sequential steps in the procedure are as follows.

a) Initial temperature equilibrium of TMM: In order to obtain initial stability and uniformity of

the temperature distribution on the cross-sectional surface, the wrapped TMM is kept for

more than one hour on the laboratory table.

b) Focus adjustment of IR-camera: The focus adjustment of the IR-camera is performed

according to manufacturer’s recommendations for obtaining maximum temperature with

the sharpest edge.

The location and angle of TMM to the IR-camera should be adjusted and be recorded to

minimize the reflection of unexpected IR-signals, which are mainly generated by the

IR-camera itself.

c) Coupling of TMM: A set of two split TMM-blocks [(A) and (B)] is made by coupling their

cross-sectional surfaces under water that is in thermal equilibrium with the ambient

temperature. This process is for making tight acoustic and thermal coupling between a

pair of TMM-blocks before the measurement.

d) Alignment of transducer: The alignment of the transducer is performed for coincidence

between the scan plane of the transducer and the cross-sectional plane of the split TMM.

e) Shielding from stray IR-radiation and air currents: A cardboard box surrounding the

phantom is closed.

f) Driving the transducer: The transducer is driven for a certain period, for example,

three minutes. This drive period is an example for presenting the measurement procedure.

The insonation time should be specified depending on the purpose of measurement.

g) Acquiring the infrared image: The infrared image is quickly acquired for the cross-sectional

surface of the split TMM-block (B) just after the split TMM-block (A) is decoupled and

temperature by extrapolation backward to opening time should
removed. The correction of

be considered when the cooling is not negligible between the times of opening the TMM-

blocks and recording the IR-image.
---------------------- Page: 13 ----------------------
– 12 – IEC TS 6
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.