Ultrasonics - Flow measurement systems - Flow test object

Specifies parameters for a flow Doppler test object representing a blood vessel of known diameter at a certain depth in human tissue, carrying a steady flow. Establishes a flow Doppler test object which can be used to assess various aspects of the performance of Doppler diagnostic equipment.

Ultraschall - Durchflussmesssysteme - Durchfluss-Doppler-Prüfobjekt

Ultrasons - Systèmes de mesure de débit - Montage pour essai de débit

Ultrasonics - Flow measurement systems - Flow test object (IEC 61685:2001)

General Information

Status
Published
Publication Date
11-Oct-2001
Technical Committee
Drafting Committee
Parallel Committee
Current Stage
6060 - Document made available
Completion Date
12-Oct-2001

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SLOVENSKI STANDARD
SIST EN 61685:2002
01-september-2002
Ultrasonics - Flow measurement systems - Flow test object (IEC 61685:2001)
Ultrasonics - Flow measurement systems - Flow test object
Ultraschall - Durchflussmesssysteme - Durchfluss-Doppler-Prüfobjekt
Ultrasons - Systèmes de mesure de débit - Montage pour essai de débit
Ta slovenski standard je istoveten z: EN 61685:2001
ICS:
17.120.01 0HUMHQMHSUHWRNDWHNRþLQQD Measurement of fluid flow in
VSORãQR general
17.140.50 Elektroakustika Electroacoustics
SIST EN 61685:2002 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61685:2002
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SIST EN 61685:2002
EUROPEAN STANDARD EN 61685
NORME EUROPÉENNE
EUROPÄISCHE NORM October 2001
ICS 17.140.50
English version
Ultrasonics -
Flow measurement systems -
Flow test object
(IEC 61685:2001)
Ultrasons - Ultraschall -
Systèmes de mesure de débit - Durchflussmesssysteme -
Montage pour essai de débit Durchfluss-Doppler-Prüfobjekt
(CEI 61685:2001) (IEC 61685:2001)

This European Standard was approved by CENELEC on 2001-09-01. 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, Czech Republic,

Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,

Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
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

© 2001 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 61685:2001 E
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SIST EN 61685:2002
EN 61685:2001 - 2 -
Foreword

The text of document 87/202/FDIS, future edition 1 of IEC 61685, prepared by IEC TC 87, Ultrasonics,

was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61685 on

2001-09-01.
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) 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 information only.

In this standard, annexes B and ZA are normative and annexes A, C, D, E and F are informative.

Annex ZA has been added by CENELEC.
__________
Endorsement notice

The text of the International Standard IEC 61685:2001 was approved by CENELEC as a European

Standard without any modification.
__________
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SIST EN 61685:2002
- 3 - EN 61685:2001
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

This European Standard incorporates by dated or undated reference, provisions from other

publications. These normative references are cited at the appropriate places in the text and the

publications are listed hereafter. For dated references, subsequent amendments to or revisions of any

of these publications apply to this European Standard only when incorporated in it by amendment or

revision. For undated references the latest edition of the publication referred to applies (including

amendments).

NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.
Publication Year Title EN/HD Year
IEC 61102 1991 Measurement and characterisation of EN 61102 1993
ultrasonic fields using hydrophones in
the frequency range 0,5 MHz to 15 MHz
IEC 61206 1993 Ultrasonics - Continuous-wave Doppler EN 61206 1995
systems - Test procedures
IEC 61895 1999 Ultrasonics - Pulsed Doppler diagnostic--
systems - Test procedures to determine
performance
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SIST EN 61685:2002
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SIST EN 61685:2002
INTERNATIONAL IEC
STANDARD
61685
First edition
2001-07
Ultrasonics –
Flow measurement systems –
Flow test object
Ultrasons –
Systèmes de mesure de débit –
Montage pour essai de débit
 IEC 2001  Copyright - all rights reserved

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 the publisher.

International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: +41 22 919 0300 e-mail: inmail@iec.ch IEC web site http://www.iec.ch
Commission Electrotechnique Internationale
PRICE CODE
International Electrotechnical Commission
For price, see current catalogue
---------------------- Page: 7 ----------------------
SIST EN 61685:2002
– 2 – 61685  IEC:2001(E)
CONTENTS

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

INTRODUCTION ....................................................................................................................5

1 Scope .............................................................................................................................. 6

2 Normative references ....................................................................................................... 6

3 Definitions........................................................................................................................ 6

4 List of symbols ............................................................................................................... 11

5 General outline of flow Doppler test object...................................................................... 12

6 Specification of the flow Doppler test object.................................................................... 12

6.1 General................................................................................................................. 12

6.2 Blood-mimicking fluid (BMF).................................................................................. 13

6.3 Tube ..................................................................................................................... 14

6.4 Tissue-mimicking material (TMM).......................................................................... 15

6.5 Geometry.............................................................................................................. 15

7 Precautions to prevent changes in the composition of the blood-mimicking fluid

(BMF) ............................................................................................................................ 15

8 Specifications for labelling.............................................................................................. 16

Annex A (informative) Rationale concerning the position of this standard.............................. 17

Annex B (normative) Formulae relating various quantities .................................................... 20

Annex C (informative) Rationale for the numerical values chosen in this standard ................ 21

Annex D (informative) Description of an example flow Doppler test object ............................ 23

Annex E (informative) Schematic diagram of a possible flow circuit ...................................... 32

Annex F (informative) Measuring methods ........................................................................... 33

Bibliography ......................................................................................................................... 34

Figure 1 – Three configurations for Doppler flow test objects................................................. 12

Figure D.1 – The main elements of a flow test object ............................................................ 24

Figure D.2 – Backscattering coefficient of BMF as a function of frequency ............................ 26

Figure D.3 – Attenuation of TMM () and BMF ({{) as a function of frequency ...................... 26

Figure D.4 – Attenuation of ultrasound by material of tube wall, as a function of

frequency ............................................................................................................................. 27

Figure D.5 – Deformation of velocity spectrum of parabolic flow by attenuation due to

tube wall (wall thickness 1,5 mm).......................................................................................... 28

Figure D.6 – Backscattering coefficient of two samples of TMM as a function of

frequency ............................................................................................................................. 29

Figure D.7 – The quotient of attenuation by TMM (1-way passage) and frequency as a

function of frequency ............................................................................................................ 29

Figure D.8 – Testing for penetration depth ............................................................................ 31

Figure E.1 – Schematic diagram of a possible flow circuit, showing the place of the flow

Doppler test object ............................................................................................................... 32

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SIST EN 61685:2002
61685  IEC:2001(E) – 3 –

Table 1 – Typical ranges of parameters for blood at 37 °C, where f is the acoustic-

working frequency in hertz .................................................................................................... 13

Table 2 – Specification of blood-mimicking fluid (BMF).......................................................... 13

Table 3 – Parameters of tissue-mimicking material (TMM) .................................................... 15

Table A.1 – Parameters concerning CW Doppler .................................................................. 18

Table A.2 – Additional parameters concerning pulsed Doppler and colour flow ...................... 19

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SIST EN 61685:2002
– 4 – 61685  IEC:2001(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ULTRASONICS – FLOW MEASUREMENT SYSTEMS –
FLOW TEST OBJECT
FOREWORD

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

all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.

3) The documents produced have the form of recommendations for international use and are published in the form

of standards, technical specifications, technical reports or guides and they are accepted by the National

Committees in that sense.

4) In order to promote international unification, IEC National Committees undertake to apply IEC International

Standards transparently to the maximum extent possible in their national and regional standards. Any

divergence between the IEC Standard and the corresponding national or regional standard shall be clearly

indicated in the latter.

5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with one of its standards.

6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject

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

International Standard IEC 61685 has been prepared by IEC Technical Committee 87:

Ultrasonics.
The text of this standard is based on the following documents:
FDIS Report on voting
87/202/FDIS 87/208/RVD

Full information on the voting for the approval of this 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 3.

Annexes A, C, D, E and F are for information only.
Annex B forms an integral part of this standard.

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

2006. At this date, the publication will be
reconfirmed;
withdrawn;
replaced by a revised edition, or
amended.
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SIST EN 61685:2002
61685  IEC:2001(E) – 5 –
INTRODUCTION

The purpose of this International Standard is to establish a flow Doppler test object for the

acceptance testing, quality assurance testing and clinical calibration of Doppler systems,

working at a frequency between 2 MHz and 10 MHz. As the response of Doppler systems

depends on the signal level and on the spectral contents of the signal, it is desirable to test

some aspects of a Doppler system with a test object that mimics the in vivo situation. A flow

Doppler test object is particularly useful for

− testing the influence of the size and the depth of the blood vessel on the signal recorded by

a Doppler system;

− testing the response of a Doppler system with a spectrum of blood velocities typical of the

in vivo situation.

This flow test object is not intended as a phantom mimicking clinical conditions.

The basis of this International Standard is given by IEC Technical Report 61206:1993

Ultrasonics – Continuous Wave Doppler systems – Test procedures. In annex A the position of

this standard in relation to IEC 61206 and IEC 61895 is described. This standard only declares

parameters that can be measured with the test object. Measurement methods are given in

IEC 61206 and IEC 61895.

This International Standard deals only with the flow Doppler test object in a restricted sense,

i.e. the section in which the ultrasonic measurements are performed. Where the whole of the

set-up is meant, the phrase 'flow rig' is used. The prescriptions of this International Standard

define the ultrasonic properties and the flow pattern in the measurement section of the flow

test object. For other aspects of the flow rig (i.e. generating and measuring flows) standard

engineering practice has to be followed.

The flow conditions are simplified as much as possible: a steady flow through a straight tube

with a circular cross-section. Generalisation of the flow conditions to other geometries and time

dependent flows is required in order to test some instrument functions. This generalisation is

not undertaken in this International Standard.

In annex D, an example flow Doppler test object is described which complies with the

requirements of this International Standard. Compliance with this International Standard can

also be fulfilled by measuring the properties of the materials to be used, and complying with

the values given in this International Standard.

In literature [1], [2] the nomenclature about the primary measurand of Doppler systems is

confused. 'Doppler frequency' and 'velocity' occur on equal footing. In 'velocity' often a

correction for Doppler angle has been included. To avoid this ambiguity, in this International

Standard the term 'Doppler frequency' is preferred. In case a Doppler system is declared to

measure velocity, it is intended that measured values are converted to Doppler frequency,

using acoustic working frequency and, if applicable, Doppler angle.
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SIST EN 61685:2002
– 6 – 61685  IEC:2001(E)
ULTRASONICS – FLOW MEASUREMENT SYSTEMS –
FLOW TEST OBJECT
1 Scope

This International Standard specifies parameters for a flow Doppler test object representing

a blood vessel of known diameter at a certain depth in human tissue, carrying a steady flow.

This International Standard establishes a flow Doppler test object which can be used to

assess various aspects of the performance of Doppler diagnostic equipment.
2 Normative references

The following normative documents contain provisions which, through reference in this text,

constitute provisions of this International Standard. For dated 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

references, the latest edition of the normative document referred to applies. Members of IEC

and ISO maintain registers of currently valid International Standards.
IEC 61206:1993, Ultrasonics – Continuous-wave Doppler systems – Test procedures

IEC 61102:1991, Measurement and characterisation of ultrasonic fields using hydrophones in

the frequency range 0,5 MHz to 15 MHz

IEC 61895:1999, Ultrasonics – Pulsed Doppler diagnostic systems – Test procedures to

determine performance
3 Definitions

For the purposes of this International Standard, the following definitions apply:

3.1
–3 dB Doppler frequency

frequency at which the power per unit frequency in the Doppler spectrum is half (–3 dB) of the

maximum value
3.2
–3 dB sample volume

volume of a region in space for which the Doppler system gives a response to a point Doppler

target that is above –3 dB from the maximal response, taking account of the effects of both

transmission and reception
Unit: cubic millimetre, mm
3.3
–3 dB sample volume length

largest dimension of the –3 dB sample volume in the direction of the beam alignment axis

(see 3.5 of IEC 61102)
Unit: millimetre, mm
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SIST EN 61685:2002
61685  IEC:2001(E) – 7 –
3.4
–3 dB sample volume width
largest value of the dimension of the –3 dB sample volume along an axis which is

perpendicular to the beam alignment axis. In case the Doppler system has a scan plane, the

axes are taken in the scan plane and perpendicular to the scan plane
Unit: millimetre, mm
3.5
acoustic-working frequency

frequency of an acoustic signal based on the output observed by a hydrophone placed in an

acoustic field: it is the arithmetic mean of the two frequencies at which the amplitude of the

acoustic pressure spectrum is 3 dB below the peak amplitude
[conforms to 3.4.2 of IEC 61102]
Unit: hertz, Hz
3.6
aliasing

false indication of signal frequency as a result of sampling at too low a frequency

NOTE The threshold for aliasing depends on pulse repetition frequency and a possible base line shift.

3.7
average frequency of the Doppler spectrum

parameter estimated by clinical Doppler systems for the short-time average in a Doppler

spectrum, ignoring the contributions from noise

NOTE The average frequency of the Doppler spectrum is generally determined for a small time interval,

typically 2 ms to 20 ms).
Unit: hertz, Hz
3.8
axial response range

depth range in tissue over which a signal from a specific target plus noise is at least 3 dB

above the noise level
[see 2.4.1 of IEC 61206]
Unit: millimetre, mm
3.9
blood-mimicking fluid (BMF)

fluid which simulates blood acoustically and is moved at a known flow rate through the flow

Doppler test object
3.10
channel separation

ratio of the signal level in the signal channel corresponding to the movement in the test object

(the desired output voltage) and the signal level in the opposite channel (the undesired output

voltage)

NOTE Channel separation is to be quoted in decibels as twenty times the logarithm of the desired output to the

undesired output voltage.
[see 2.6.1 of IEC 61206]
Unit: decibel, dB
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SIST EN 61685:2002
– 8 – 61685  IEC:2001(E)
3.11
colour display spatial resolution

minimum separation in space for which two separate moving point targets or line targets can

be resolved

NOTE The colour display spatial resolution is measured in three directions: 1) along the beam alignment axis,

2) the direction perpendicular to the scan plane and 3) the direction in the scan plane perpendicular to the beam

alignment axis.
Unit: millimetre, mm
3.12
dead zone boundary

boundary of the region close to the transducer in which the system is insensitive to movement

3.13
depth of measurement

distance from the surface of the tissue-mimicking material to the centre of the tube. In case

various attenuating materials, not being tissue-mimicking material or blood-mimicking

material, are present in the ultrasonic path, the depth of measurement is taken to be the

equivalent distance in the tissue-mimicking material, from the surface of the tissue-

mimicking material to the centre of the tube, over which the attenuation is the same as that in

the actual path in the flow Doppler test object
(see also annex B)
Symbol: M
Unit: millimetre, mm
3.14
Doppler angle

acute angle between the Doppler beam axis used for the Doppler measurement and the axis of

the tube
Symbol: θ
Unit: degree, °
3.15
Doppler angle error
difference between the measurement of the Doppler angle and its true value
Unit: degree, °
3.16
Doppler frequency –3 dB response range

frequency region in the Doppler spectrum around the frequency where power per unit

frequency is maximal, which is delimited by the nearest –3 dB Doppler frequencies

Unit: hertz, Hz

NOTE The Doppler frequency response range at another signal level may be used in an analogous way.

3.17
Doppler frequency non-linearity error

largest frequency deviation of a data point from the least squares fitted line through the origin

in a plot of Doppler frequency versus observed velocity over the Doppler frequency –3 dB

response range
[see 2.3.2 of IEC 61206]
Unit: hertz, Hz
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SIST EN 61685:2002
61685  IEC:2001(E) – 9 –
3.18
Doppler frequency response
Doppler signal level (in dB) as a function of Doppler frequency
3.19
dynamic range

ratio (in decibels) between the largest Doppler signal which can be processed by the system

without generating spurious outputs and the smallest Doppler signal which can be detected

NOTE Dynamic range is a measure of the ratio between the maximum allowable signal from clutter and the mini-

mum signal level at which flow can be detected.
Unit: decibel, dB
3.20
fixed target effect on sensitivity

change in Doppler output level (in decibels) when a strongly reflecting stationary structure (a

perfect reflector, see 2.3.3.2 of IEC 61206) is brought into the Doppler beam
Unit: decibel, dB
3.21
flow Doppler test object

physical model of blood flowing within a vessel that is embedded in soft tissue. The object is

composed of tissue-mimicking material through which blood-mimicking material is caused

to flow
3.22
frequency to colour translation table

table which describes the way in which Doppler frequencies are mapped to colours for display

3.23
highest detectable Doppler frequency

Doppler frequency corresponding to the highest observed velocity which can be determined

unambiguously (without aliasing)
Unit: hertz, Hz
3.24
inner diameter
inner diameter of the tube through which the blood-mimicking fluid flows
Symbol: D
Unit: millimetre, mm
3.25
inlet length

distance over which the tube must have a uniform cross-section in order to ensure that a well

defined velocity distribution develops which is independent of the flow conditions at the entry of

the tube
Symbol: L
Unit: millimetre, mm
3.26
intrinsic spectral broadening

width of the frequency region over which the spectral intensity is above –3 dB from its maximal

value, when the Doppler system observes a moving target having a single velocity
Unit: hertz, Hz
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SIST EN 61685:2002
– 10 – 61685  IEC:2001(E)
3.27
lowest detectable Doppler frequency

Doppler frequency corresponding to the lowest observed velocity which can be distinguished

from noise
Unit: hertz, Hz
3.28
maximum frequency of the Doppler spectrum

parameter estimated by a Doppler system for the highest occurring frequency in a Doppler

spectrum, ignoring the contributions from noise

NOTE 1 The maximum frequency of the Doppler spectrum corresponds to the highest velocity occurring in the

sample volume at a certain time.

NOTE 2 Clinical Doppler systems generally determine the maximum frequency of the Doppler spectrum for a

small time interval (typically 2 ms to 20 ms).
Unit: hertz, Hz
3.29
observed velocity

component of the velocity of a scatterer that is directed towards or away from the transducers

[definition 1.3.10 of IEC 61206]
3.30
parabolic velocity profile

axisymmetrical flow distribution in a cross-section of the tube, in which the velocity decreases

in proportion to the square of the distance from the tube’s axis, and the velocity at the tube

wall is zero
3.31
penetration depth

maximum depth in tissue-mimicking material from which a Doppler signal can be detected

from noise
Unit: millimetre, mm
3.32
sample volume position error

difference between the centre of the sample volume on the image and its true position

Unit: millimetre, mm
3.33
tissue-mimicking material (TMM)

material whose pertinent ultrasonic properties (sound velocity, attenuation and scattering) are

similar to those of soft tissue
3.34
tube
conduit which carries the blood-mimicking fluid (BMF) flow

NOTE The word tube also applies to the case of a hole in the tissue-mimicking material.

3.35
volume flow measurement error

100 times the absolute value of the difference between the Doppler measurement of a

particular volume flow rate and its true value, divided by the true value

NOTE The volume flow measurement error has a sign and is reported as a percentage.

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SIST EN 61685:2002
61685  IEC:2001(E) – 11 –
3.36
wall thickness
thickness of the wall of the tube

NOTE In the case of a hole in the tissue-mimicking material, the value of the wall thickness is zero.

Symbol: w
Unit: millimetre, mm
3.37
working distance

distance between the transducer and a specific target in tissue-mimicking material when the

signal is maximal
Unit: millimetre, mm
3.38
zero-velocity noise level

r.m.s. voltage of the signal (in dB) on the Doppler output connector under the condition that the

moving portion of the Doppler test object is stopped
Unit: decibel, dB

NOTE 1 Generally the zero-velocity noise level is the sum of the system noise level and the clutter noise level.

NOTE 2 Zero-velocity noise level is reported as dB with respect to 1 mV r.m.s.
4 List of symbols
c = velocity of sound
c = velocity of sound in the wall material
c = velocity of sound in the tissue-mimicking material
c = velocity of sound in the blood-mimicking fluid
D = inner diameter of tube
f = acoustic-working frequency of the investigated equipment
h = path length in TMM
L = inlet length
M = depth of measurement
q = flow rate of blood-mimicking fluid
Re = Reynolds number
v = local velocity of blood-mimicking fluid
v = velocity averaged over the cross-section of the tube
avg
v = the highest velocity occurring in a cross-section of the tube
max
w = wall thickness of tube
Z = characteristic acoustic impedance
α = attenuation coefficient of sound
η = viscosity of a blood-mimicking fluid
θ = Doppler angle
ρ = density of material

σ = differential scattering cross-section in the backward direction per unit volume, also called

backscatter coefficient
NOTE For quantities marked with an asterisk, formulae are given in annex B.
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SIST EN 61685:2002
– 12 – 61685  IEC:2001(E)
5 General outline of flow Doppler test object

An example showing the place of the flow Doppler test object in a complete measurement

system (flow rig) is shown in annex E.

The flow Doppler test object consists of a block of material which mimics the ultrasonic

properties (sound velocity, attenuation and scattering) of soft tissue. In a straight cylindrical

conduit flow a blood-mimicking fluid (BMF) represents flowing blood. The arrangement of

tissue-mimicking material (TMM) and conduit is such that the Doppler transducer can

observe the BMF flow through a range of depths in tissue. Three different forms of a flow

Doppler test object exist:

− the conduit is made of a tube above which a triangular block of TMM is present (figure 1a);

− the conduit is made of a tube lying inside the TMM (figure 1b);
− the conduit
...

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