IEC TS 62736:2023
(Main)Ultrasonics - Pulse-echo scanners - Simple methods for periodic testing to verify stability of an imaging system's elementary performance
Ultrasonics - Pulse-echo scanners - Simple methods for periodic testing to verify stability of an imaging system's elementary performance
IEC TS 62736:2023 specifies requirements and methods for periodic testing of the quality of diagnostic medical ultrasound systems using reflection-mode (pulse-echo) imaging. Image measurement and interpretation workstations are included. This document includes minimum sets of such tests intended for frequent users of medical ultrasound systems, for quality assurance professionals in their organizations, or those hired from other quality-control and/or service-provider organizations. The procedures are for a wide range of more common diagnostic ultrasound systems, currently operating from 1 MHz to 40 MHz, although available phantoms meet the specifications only from 1 MHz to 23 MHz.
The tests are defined in three levels, with the simplest and most cost-effective performed most frequently:
- Level 1 comprises five quick tests/observations to be performed daily to monthly by those normally operating the systems.
- Level 2 includes one necessary test for all systems in addition to those of Level 1, two Level 1 tests performed more rigorously, two tests that are for special situations or equipment, and one that is just optional, included because it is highly developed. Level 2 tests are performed annually by those with meaningful quality assurance training.
- Level 3 extends the two special situations tests to all systems, adds one optional test and includes a periodic review of the QA programme.
Frequent distance-measurement accuracy tests are recommended in this document only for certain classes of position encoding that are not now known to be highly stable and without bias. QA in all dimensions is recommended in this document as the first test for such systems.
The test methodology is applicable for transducers operating in the 1 MHz to 23 MHz frequency range. The types of transducers used with these scanners include
a) electronic phased arrays,
b) linear arrays,
c) convex arrays,
d) mechanical transducers,
e) two-dimensional arrays operated in a 2D imaging mode,
f) transducers operating in 3D imaging mode for a limited number of sets of reconstructed 2D images, and
g) three-dimensional scanning transducers based on a combination of the above types.
All tests on scanners considered here evaluate basic pulse-echo techniques and might detect most failures in other modes. Dedicated Doppler systems, or other systems for detection of blood motion, are excluded from this scope as specialized equipment is required to test them. Such test equipment can be specific to the intended application of the Doppler system. This document includes definition of terms and specifies methods for measuring the maximum relative depth of penetration of real-time ultrasound B MODE scanners, though this penetration measure is listed as less frequently applied.
IEC TS 62736:2023 cancels and replaces the first edition published in 2016. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) expansion of the applicable types of transducers and the frequency range of application;
b) extension of test protocols and image assessments, including for very-low-echo spheres;
c) revision of phantom designs and their acoustic properties, consistent with the second edition of IEC TS 62791;
d) inclusion of luminance tests for system-image display consistency at scanner and remote monitors;
e) addition of special considerations for 3D-imaging transducers (Annex D) and workbook examples (Annex E).
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IEC TS 62736 ®
Edition 2.0 2023-01
TECHNICAL
SPECIFICATION
colour
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Ultrasonics – Pulse-echo scanners –
Simple methods for periodic testing to verify stability of an imaging system's
elementary performance
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IEC TS 62736 ®
Edition 2.0 2023-01
TECHNICAL
SPECIFICATION
colour
inside
Ultrasonics – Pulse-echo scanners –
Simple methods for periodic testing to verify stability of an imaging system's
elementary performance
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.140.50 ISBN 978-2-8322-6345-7
– 2 – IEC TS 62736:2023 © IEC 2023
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 9
2 Normative references . 10
3 Terms and definitions . 10
4 Symbols and abbreviated terms . 14
4.1 Symbols . 14
4.2 Abbreviated terms . 16
5 General recommendation . 17
6 Environmental conditions . 17
7 Quality assurance levels . 18
7.1 General . 18
7.2 Level 1 tests . 19
7.3 Level 2 tests . 19
7.4 Level 3 tests . 20
8 Equipment and data required . 20
8.1 Phantoms and software. 20
8.1.1 General . 20
8.1.2 Phantoms for Level 2 and Level 3 quality assurance . 20
8.1.3 Additional phantom specifications for Level 2 quality assurance . 21
8.1.4 Additional phantom specifications for Level 3 quality assurance and
optional Level 2 tests . 23
8.2 Image data . 24
8.2.1 Digital-image data . 24
8.2.2 Image-archiving systems . 25
8.3 Expectations of system suppliers . 26
9 Level 1 test methods . 26
10 Level 2 measurement methods . 27
10.1 Mechanical inspection . 27
10.2 Image uniformity for transducer element and channel integrity . 27
10.2.1 General . 27
10.2.2 Apparatus scanning procedures and system settings . 27
10.2.3 Image acquisition. 28
10.2.4 Analysis . 29
10.3 Randomly distributed high-contrast sphere visualization . 30
10.3.1 Methodology . 30
10.3.2 Procedure . 33
10.3.3 Data recording . 35
10.4 Image displays; system and interpretation; maximum relative depth of
penetration; spatial resolution . 35
10.5 Distance and other spatial measurements . 35
11 Level 3 measurement methods . 35
11.1 General . 35
11.2 Maximum relative depth of penetration . 36
11.2.1 Assessment . 36
11.2.2 Scanning system settings . 36
11.2.3 Image acquisition. 37
11.2.4 Analysis . 38
11.2.5 Commentary . 39
11.3 System-image display . 40
11.3.1 General . 40
11.3.2 Level 1 tests of the US system and interpretation-station display . 41
11.3.3 Level 2 and Level 3 display tests . 42
11.4 Distance and other spatial measurements . 45
11.4.1 General . 45
11.4.2 Apparatus and scanning system settings . 45
11.4.3 Image acquisition. 45
11.4.4 Analysis . 45
11.5 Performance in clinical use and evaluation of QA programme . 45
Annex A (informative) Example phantoms for full coupling with curved arrays,
particularly for image uniformity tests . 46
Annex B (informative) Available analysis software . 50
B.1 Open source software for assessment or tracking of ultrasound image QA
data . 50
B.2 Example of QA control chart . 52
Annex C (informative) Electronic test methods and test methods provided by the
manufacturers – Relation to clinical significance . 54
Annex D (informative) Special considerations for 3D imaging transducers . 55
D.1 General . 55
D.2 2D transducers and 3D mechanically driven transducers operating in 2D
imaging mode . 55
D.3 2D arrays operating in 3D imaging mode for determining LSNR values for
md
reconstructed images as a function of depth or distance from the central
plane . 55
D.4 Mechanically driven 3D transducers operating in 3D imaging mode . 55
Annex E (informative) Example workbook database for tracking high-contrast, low-
echo sphere visibility and luminance of the display . 56
Bibliography . 63
Figure 1 – Median-averaged image (right) and its lateral profile (left) . 30
Figure 2 – Examples of portable apparatus for moving the transducer: a) and c) in
equal, chosen increments or b) at a known rate . 32
Figure 3 – Example of visual estimation of the two defined depth zones in which
spheres can be detected with two degrees of fidelity and clarity . 33
Figure 4 – Additional examples of visual estimation of the depth Zone 1 and Zone 2,
each of which represents a certain degree of fidelity and clarity (IEC 62791) . 34
Figure 5 – Maximum relative depth of penetration – image acquisition . 37
Figure 6 – Mean digitized image-data value versus depth for the phantom image data
(A(j)) and for the noise-image data (A'(j)) . 39
Figure 7 – TG18-QA test pattern for visual evaluation testing [21],[33] . 41
Figure 8 – Examples of TG18-LN luminance patterns for luminance measurements [21] . 42
Figure 9 – TG270-ULN uniformity and luminance test pattern (TG270-ULN8-127 with
background 8-bit grey level 127 is shown) [33] . 44
Figure A.1 – Example phantom for image-uniformity and maximum relative depth of
penetration tests . 46
– 4 – IEC TS 62736:2023 © IEC 2023
Figure A.2 – Example compact phantom for image uniformity tests . 47
Figure A.3 – Photograph and drawing of a three-in-one phantom which provides for
determination of distance measurement precision and bias, image-uniformity, very-low-
echo sphere visualization, and depth of penetration [39] . 48
Figure A.4 – Two temporally stable, inexpensive phantoms for image uniformity tests . 49
Figure B.1 – Example of data analysis for the transducer evaluated to generate
Figure 1 . 51
Figure B.2 – Control chart for a dip in the middle of the profile for one transducer (TD)
model, C9-4 and the specified serial number (S/N) . 53
Figure E.1 – Current and previous measurements and trendlines providing luminance
at various grey levels, fractional slope of luminance and deviation from DICOM GSDF
in ΔJND per grey level (IEC 62563-2) . 62
Table 1 – Overview to the symbols and definitions of the QA terms, other than those
for the display . 15
Table 2 – Overview of the symbols and definitions of the display QA terms . 16
Table 3 – Abbreviated terms . 17
Table 4 – Outline of tests by level . 18
Table 5 – Ultrasound image display QA tests . 44
Table B.1 – Output of image uniformity analysis . 52
Table E.1 – Transducer record and baseline high-contrast, low-echo-sphere
visualization test data . 57
Table E.2 – Database of periodic sphere visualization results . 58
Table E.3 – Completed short QA data entry example form for monitor luminance
evaluation using test pattern – QA18 . 59
Table E.4 – Blank, short QA data entry evaluation form for monitor luminance using
test pattern – QA18 . 60
Table E.5 – Analysis of luminance measurements . 61
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ULTRASONICS – PULSE-ECHO SCANNERS –
Simple methods for periodic testing to verify stability
of an imaging system's elementary performance
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TS 62736 has been prepared by IEC technical committee 87: Ultrasonics. It is a Technical
Specification.
This second edition cancels and replaces the first edition published in 2016. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) expansion of the applicable types of transducers and the frequency range of application;
b) extension of test protocols and image assessments, including for very-low-echo spheres;
c) revision of phantom designs and their acoustic properties, consistent with the second
edition of IEC TS 62791;
d) inclusion of luminance tests for system-image display consistency at scanner and remote
monitors;
– 6 – IEC TS 62736:2023 © IEC 2023
e) addition of special considerations for 3D-imaging transducers (Annex D) and workbook
examples (Annex E).
The text of this Technical Specification is based on the following documents:
Draft Report on voting
87/777/DTS 87/791/RVDTS
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Specification is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
defined in greater detail at www.iec.ch/standardsdev/publications.
Terms in bold in the text are defined in Clause 3.
Symbols and formulae are in Times New Roman italic.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document 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.
INTRODUCTION
An ultrasonic pulse-echo scanner produces images of tissue in a scan plane by sweeping a
narrow, pulsed beam of ultrasound through the section of interest and detecting the echoes
generated by reflection at tissue boundaries and by scattering within tissues. Various
transducer types are employed to operate in a transmit/receive mode to generate/detect the
ultrasonic signals. Ultrasonic scanners are widely used in medical practice to produce images
of soft-tissue organs throughout the human body. As ultrasound systems are usually employed
under rigorous time restrictions and in diverse environments to help make decisions that are
often critical to patients' wellbeing, it is important that the systems perform consistently at the
level initially provided and accepted in initial tests, for example, those of IEC TS 62791,
IEC 61391-1, 61391-2, and IEC 62563-2. This document provides methods to verify the stability
of an imaging system's elementary performance.
This document is deemed necessary because substandard ultrasound-system performance is
often accepted or remains undetected in the absence of unequivocal and documented tests.
The most common of the failures, in all but the oldest systems nearing retirement, are sub-
performance of a transducer-array element or lens or of a cable or electronic channel. There is
approximately a 14 % transducer-failure rate and a 10 % system-failure rate per year on first
testing [1],[2],[3],[4],[5],[5],[7],[8],[9],[10],[11],[12] . Sensitive image uniformity tests for these
transducer- and channel-failures are presented here for use daily to monthly (Level 1), annually
(Level 2) and biennially (Level 3).
This common occurrence of suboptimal diagnostic examinations has created an urgent need to
standardize quality-assurance (QA) and performance-evaluation procedures to promote
improved efficacy of diagnostic examinations through widespread use of effective QA
procedures and to dispel myths as to their utility. Proposers believe, however, that existing
national and international standards and guides [1],[3],[12],[13],[14] specify or recommend too
many tests and inappropriate tests for detecting and discriminating the common flaws in
diagnostic ultrasound systems during routine QA. These practices include tests, such as spatial
resolution, which are low-yield and belong in performance-evaluation procedures, rather than
QA.
Modern flat-panel display technology is more stable than, and generally far superior to, earlier
cathode ray tube (CRT) displays. However, these displays can still exhibit luminance drift, as
well as problems such as defective pixels. They still need to be evaluated periodically.
Detection of failures by these recommended pulse-echo tests will probably also detect most
failures affecting the operation of other modes, such as colour-flow, harmonic-, elasticity- and
compound-imaging. The failures might be more pronounced in these other modes and the
fraction of failures in other modes detected by these tests has not been reported.
Image-uniformity QA is applicable to transducers operating in the wide 1 MHz to 40 MHz
frequency range, as the requirements for phantoms are not stringent for this test. The other
tests could be made applicable up to 40 MHz [15],[16] when the depth of penetration
measurement is allowed to be relative, rather than absolute, and phantom stability is verified.
NOTE Phantom manufacturers are encouraged to extend the frequency range to which phantoms are specified to
enable relative depth-of-penetration tests of systems operating at fundamental and harmonic frequencies above
23 MHz.
System-manufacturing and repair companies, as well as those performing more complete
performance evaluation for acceptance, replacement, or research might well employ other or
additional tests that are not within the scope of this document. More complete tests than those
included in the three levels for periodic testing and for assessment at times of particular
importance or concern are specified in IEC 61391-1, IEC 61391-2 and IEC TS 62791. These
more complete tests are categorized as performance evaluation, rather than quality
___________
Numbers in square brackets refer to the Bibliography.
– 8 – IEC TS 62736:2023 © IEC 2023
assurance or frequent periodic testing. It is possible that good, automated analysis of the high-
contrast sphere tests will reduce both the need for optional tests listed here, and for most, more
complete performance evaluation. Full assessment of distance-measurement accuracy might
still be required if automated, 3D distance measurement calibration is not added to the high-
contrast sphere tests.
Uniformity tests of transducers not readily amenable to transducer-element testing by the simple
image-uniformity procedures specified here (for example, phased-array and 2D-array
transducers) are not included in the scope. They are usually evaluated well by careful
performance of the high-contrast sphere tests. System manufacturers are encouraged to
provide pulsing patterns of the transducer elements to allow testing of individual elements or
small-enough groups of elements to enable users to detect significant element failure or to
provide access to another implemented and explained element-test programme.
ULTRASONICS – PULSE-ECHO SCANNERS –
Simple methods for periodic testing to verify stability
of an imaging system's elementary performance
1 Scope
This document, which is a Technical Specification, specifies requirements and methods for
periodic testing of the quality of diagnostic medical ultrasound systems using reflection-mode
(pulse-echo) imaging. Image measurement and interpretation workstations are included.
NOTE Usually, "periodic testing" is referred to as "quality control (QC)" or quality assurance (QA).
This document includes minimum sets of such tests intended for frequent users of medical
ultrasound systems, for quality assurance professionals in their organizations, or those hired
from other quality-control and/or service-provider organizations. The procedures are for a wide
range of more common diagnostic ultrasound systems, currently operating from 1 MHz to
40 MHz, although available phantoms meet the specifications only from 1 MHz to 23 MHz.
The tests are defined in three levels, with the simplest and most cost-effective performed most
frequently:
Level 1 comprises five quick tests/observations to be performed daily to monthly by those
normally operating the systems.
Level 2 includes one necessary test for all systems in addition to those of Level 1, two Level 1
tests performed more rigorously, two tests that are for special situations or equipment, and one
that is just optional, included because it is highly developed. Level 2 tests are performed
annually by those with meaningful quality assurance training.
Level 3 extends the two special situations tests to all systems, adds one optional test and
includes a periodic review of the QA programme.
Frequent distance-measurement accuracy tests are recommended in this document only for
certain classes of position encoding that are not now known to be highly stable and without
bias. QA in all dimensions is recommended in this document as the first test for such systems.
The test methodology is applicable for transducers operating in the 1 MHz to 23 MHz frequency
range. The types of transducers used with these scanners include
a) electronic phased arrays,
b) linear arrays,
c) convex arrays,
d) mechanical transducers,
e) two-dimensional arrays operated in a 2D imaging mode,
f) transducers operating in 3D imaging mode for a limited number of sets of reconstructed 2D
images, and
g) three-dimensional scanning transducers based on a combination of the above types.
All tests on scanners considered here evaluate basic pulse-echo techniques and might detect
most failures in other modes. Dedicated Doppler systems, or other systems for detection of
blood motion, are excluded from this scope as specialized equipment is required to test them.
Such test equipment can be specific to the intended application of the Doppler system.
– 10 – IEC TS 62736:2023 © IEC 2023
This document includes definition of terms and specifies methods for measuring the maximum
relative depth of penetration of real-time ultrasound B-MODE scanners, though this
penetration measure is listed as less frequently applied.
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 60050-802, International Electrotechnical Vocabulary – Part 802: Ultrasonics
(available at )
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-802 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
quality assurance
QA
regularly performed procedures to ensure consistent performance
Note 1 to entry: Quality control is a part of quality assurance. Another term used is quality maintenance.
3.2
performance evaluation
set of tests performed to assess specific absolute performance of the object tested
Note 1 to entry: Typical times for ultrasound system performance evaluation are at pre-purchase evaluation, new
and repaired system acceptance testing, according to IEC 61391-1 and IEC 61391-2 and
[1],[17],[18],[19],[20],[21],[22], and at times of performance difficulties and end-of-useful-life evaluations. Level 3
QA tests include many of those recommended for such performance evaluation.
3.3
phantom
device designed to mimic some aspects of the human body for the purposes of testing or training
3.4
addressable patch
smallest addressable group of transducer elements
3.5
pixel value
integer value of a processed signal level or integer values of processed colour levels, provided
to the display for a given pixel
Note 1 to entry: In a grey-scale display the pixel value is converted to a luminance by some, usually monotonic,
M
function. The set of integer values representing the grey scale runs from 0 (black) to (2 − 1) (white), where M is a
positive integer, commonly called the bit depth. Thus, if M = 8, the largest pixel value in the set is 255.
[SOURCE: IEC TS 62791:2022, 3.6]
3.6
mean pixel value
MPV
mean of pixel values detected over a designated area or volume in an image or 3D stack of
images
Note 1 to entry: For low-echo spheres here, MPV is defined for an area A or volume in a phantom image or stack
of images, where A is somewhat smaller than the area of a circle of diameter D. The phrase "somewhat smaller than"
is introduced as partial compensation for the partial volume effect, primarily in the elevational dimension.
Note 2 to entry: The partial volume effect is a term common in computed tomographic, magnetic resonance and
ultrasound imaging. This process refers to the effect of the finite imaging resolution, particularly the slice
thickness. The signal (ie, pixel values) at points near the object boundaries will include contribution from that object
and contributions from the material around it. For example, if the object is a sphere with a diameter close to the
thickness of the slice, then you cannot define a good measurement region in the image of the sphere in which the
signal does not include components from material lying outside the sphere.
3.7
maximum depth of penetration
maximum range in a phantom, with properties meeting the specifications of IEC 61391-2, at
which the mean pixel value corresponding to signals from the weakly reflecting, background
scatterers are 1,4 times the mean pixel value corresponding to images displaying only
electronic noise at that same depth
Note 1 to entry: The maximum depth of penetration is expressed in metres (m) and conventionally in centimetres
(cm).
3.8
maximum relative depth of penetration
maximum range in a phantom, at which the mean pixel value corresponding to images
displaying echoes from weakly reflecting and background scatterers are 1,4 times the mean
pixel value corresponding to images displaying only electronic noise at that same depth
Note 1 to entry: The specified properties of the phantom are somewhat relaxed from those specified in IEC 61391-
2, as modified in IEC/TS 62791:2022, 3.2.
Note 2 to entry: The adjective "relative" is used because the phantom specifications defined in this document are
so loose that measurements of the "maximum range" with different phantoms cannot be compared. The
measurements are only for tests of stability, i.e. comparisons between measurements on the same phantom over
time.
Note 3 to entry: For available phantoms and specifications, see [16],[17], and for a potential alternative measure
of depth of penetration, see [15].
Note 4 to entry: The maximum relative depth of penetration is, by international standards, expressed in metres
(m) and conventionally in centimetres (cm).
3.9
median absolute deviation
MAD
median of the absolute value of the deviations from the median of a data set
Note 1 to entry: The MAD is similar to the standard deviation but, as the median of linear deviations rather than
squared deviations, it is more resilient to outliers [18].
3.10
specific attenuation coefficient
attenuation coefficient at a specified frequency divided by the frequency
Note 1 to entry: The specific attenuation coefficient is usually expressed in decibels per centimetre per
−1 −1
megahertz (dB cm MHz ); extrapolation to other frequencies makes the explicit assumption of linear dependence
of the attenuation coefficient on frequency.
[SOURCE: IEC 61391-2:2010, 3.33, modified by rephrasing "at a specified frequency, the slope
of attenuation coefficient plotted against frequency", which assumes a broadband
measurement.]
– 12 – IEC TS 62736:2023 © IEC 2023
3.11
equivalent sensitivity
sensitivity that is statistically the same or has smaller variance and bias
3.12
backscatter coefficient
intrinsic backscatter coefficient
η
intrinsic property of a material at some frequency, equal to the differential scattering cross-
section per unit volume for a scattering angle of 180°
[SOURCE: IEC TS 62791:2022, 3.2, modified – the note has been deleted.]
3.13
low-echo sphere
hypoechoic sphere
spherical inclusion in a phantom with a backscatter coefficient lower than the backscatter
coefficient of the surrounding tissue-mimicking material
[SOURCE: IEC TS 62791:2022, 3.3]
3.14
very-low-echo sphere
high-contrast, low-echo sphere
sphere with −40 dB, or greater, contrast with its background material
3.15
low-echo sphere diameter
D
diameter of the low-echo spherical inclusions in a phantom
Note 1 to entry: It is generally assumed that all low-echo spheres in a particular phantom have the same diameter
D. The diameter tolerance is ±1 %.
3.16
lesion signal-to-noise ratio
LSNR
ratio of the mean pixel value over a region of a detected target in an image, minus the mean
pixel value over a specified region of the background echo signals, to the standard deviation
of the mean pixel values contributing to the background
Note 1 to entry: This term might also be referred to as the lesion contrast-to-noise ratio.
[SOURCE: IEC TS 62791:2022, 3.11, modified – the note has been replaced with a new note.]
3.17
lesion signal-to-noise ratio for the nth low-echo sphere
LSNR
n
numerical value quantifying the detectability of the nth macroscopically uniform, low-echo
sphere surrounded by a macroscopically uniform, background material and existing in the
volume of a phantom for which image data has been obtained
[SOURCE: IEC TS 62791:2022, 3.12, modified – the notes have been deleted.]
3.18
LSNR
m
mean lesion signal-to-noise ratio
conceptual version of this common term (mean signal-to-noise ratio) for detected low-echo
spheres, whose centres lie within an unspecified volume segment
[SOURCE: IEC TS 62791:2022, 3.13]
3.19
LSNR
md
mean lesion signal-to-noise ratio for depth interval d
mean lesion signal-to-noise ratio for detected low-echo spheres whose centres lie within
the volume segment corresponding to depth interval label d
Note 1 to entry: Low-echo spheres with centres located less than a distance D/2 from a lateral image boundary
are excluded.
[SOURCE: IEC TS 62791:2022, 3.14, modified – the term “mean LSNR” has been removed and
note 2 has been deleted.]
3.20
reference value of mean lesion signal-to-noise ratio
LSNR
md,ref
reference values of LSNR provided by the manufacturer for a given transducer model and
md
settings, or values acquired in acceptance testing or the first or first-N periodic tests on a given
transducer and settings
3.21
useable range
Я
u
range or ranges over which the negative of LSNR is ≥ 1,41
m
Note 1 to entry: Useable range is more fully defined as the useable range for imaging low-echo spheres of a
specified size. It is usually expressed in centimetres [cm].
3.21.1
Я
minimum depth at which the negative of LSNR is ≥ 1,41
m
3.21.2
Я
first maximum depth at which the negative of LSNR is ≥ 1,41
m
3.22
mean useable contrast over the useable range
|LSNR |
mя
mean |LSNR | over the useable range or combined useable ranges of a transducer under
m
given settings
[SOURCE: IEC TS 62791, 3.9 and 3.14 modified]
3.23
clarity index
C
I
figure-of-merit for overall performance of a transducer in imaging specified low-echo spheres
in the employed mode and system, equal to the log absolute value of the mean lesion signal-
to-noise ratio averaged over the useable range times the useable range
Note 1 to entry: Symbolically C represents log|LSNR | x Я , where these symbols are defined in 3.21 and 3.22.
I mя u
– 14 – IEC TS 62736:2023 © IEC 2023
3.24
depth interval
interval between boundaries of contiguous, or overlapping, depth segments into which an image
area is subdivided for computation of LSNR values as a function of depth
md
Note 1 to entry: A rectangular scan area will be subdivided into discrete or overlapping horizontal bands; a sector
scan area will be subdivided into annular ring segments, the angular limits being determined by the sector angle.
Rectilinear projection of these discrete or overlapping area segments in the elevational direction will create volume
segments analogous to slabs and partial cylindrical shells respectively.
[SOURCE: IEC TS 62791:2022, 3.9, modified – in the definition, “or overlapping” has been
added, and in the note the reference to the figure and “with thickness equal to the depth interval
extent ∆” have been deleted.]
3.25
depth interval label
d
integer for identifying depth intervals in an image
Note 1 to entry: d = 1, 2, …, d where 1 is at the least depth and d is at the greatest depth.
max max
[SOURCE: IEC TS 62791:2022, 3.9.1]
3.26
detectability
numerical value quantifying the probability that a human observer will detect an object in an
image having background speckle
[SOURCE: IEC TS 62791:2022, 3.10]
3.27
signal-to-noise ratio
SNR
ratio of signal plus noise at a given depth in the image to noise obtained with a clean transducer
in air at the same depth
Note 1 to entry: The signal-to-noise ratio here is defined specifically in this document for the application of the
maximum depth of penetration measurement. The noise here refers to electronic noise only.
Note 2 to entry: SNR is defined in 61391-2:2010, 7.1.3, in Formula (2).
Note 3 to entry: A more general definition of SNR is given in IEV 702-08-61.
3.28
time gain compensation
TGC
amplification of the signal with time after the transmit pulse to approximately correct for
attenuation by the tissues transited and reduce overly strong signals from tissue boundaries
close to the transducer
4 Symbols and abbreviated terms
4.1 Symbols
The non-display QA parameters defined in this document are listed in Table 1 and sourced from
IEC TS 62791 with some modifications.
Table 1 – Overview to the symbols and definitions of
the QA terms, other than those for the display
Symbol Term or definition Corresponding
Term
A square area in an image plane selected for calculation of MPV 3.6
D low-echo sphere diameter 3.15
d integer for identifying depth intervals 3.25
d integral number of the depth interval chosen as the minimum depth 3.25
min
for applying the data analysis
d greatest integral number of the depth intervals allowed by the 3.25
max
chosen maximum possible depth for data analysis
LSNR lesion signal-to-noise ratio 3.16
LSNR lesion signal-to-noise ratio for the nth low-echo sphere 3.17
n
LSNR conceptual mean lesion signal-to-noise ratio 3.1
...
IEC TS 62736 ®
Edition 2.0 2023-01
REDLINE VERSION
TECHNICAL
SPECIFICATION
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Ultrasonics – Pulse-echo scanners –
Simple methods for periodic testing to verify stability of an imaging system's
elementary performance
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IEC TS 62736 ®
Edition 2.0 2023-01
REDLINE VERSION
TECHNICAL
SPECIFICATION
colour
inside
Ultrasonics – Pulse-echo scanners –
Simple methods for periodic testing to verify stability of an imaging system's
elementary performance
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.140.50 ISBN 978-2-8322-6369-3
– 2 – IEC TS 62736:2023 RLV © IEC 2023
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 9
2 Normative references . 10
3 Terms and definitions . 11
4 Symbols and abbreviated terms . 16
4.1 Symbols . 16
4.2 Abbreviated terms . 17
5 General recommendation . 18
6 Environmental conditions . 18
7 Quality control assurance levels . 19
7.1 General . 19
7.2 Level 1 tests . 21
7.3 Level 2 tests . 21
7.4 Level 3 tests . 22
8 Equipment and data required . 22
8.1 Phantoms and software. 22
8.1.1 General . 22
8.1.2 Phantoms for Level 2 and/or Level 3 quality control assurance . 23
8.1.3 Additional phantom specifications for Level 2 quality control assurance
only . 23
8.1.4 Additional phantom specifications for both Level 2 and Level 3 quality
control assurance and optional Level 2 tests . 26
8.2 Image data . 27
8.2.1 Digital-image data . 27
8.2.2 Image-archiving systems . 28
8.3 Expectations of system suppliers . 29
9 Level 1 test methods . 30
10 Level 2 measurement methods . 30
10.1 Mechanical inspection . 30
10.2 Image uniformity for transducer element and channel integrity . 30
10.2.1 General . 30
10.2.2 Apparatus scanning procedures and system settings . 30
10.2.3 Image acquisition. 32
10.2.4 Analysis . 32
10.3 Randomly distributed high-contrast sphere visualization . 34
10.3.1 Methodology . 34
10.3.2 Procedure . 36
10.3.3 Data recording . 38
10.4 Image displays; system and interpretation; maximum relative depth of
penetration; spatial resolution . 38
10.5 Distance and other spatial measurements . 38
11 Level 3 measurement methods . 38
11.1 General . 38
11.2 Maximum relative depth of penetration . 39
11.2.1 Assessment . 39
11.2.2 Scanning system settings . 39
11.2.3 Image acquisition. 40
11.2.4 Analysis . 41
11.2.5 Commentary . 42
11.3 System-image display . 43
11.3.1 General . 43
11.3.2 Level 1 tests of the US system and interpretation-station display . 44
11.3.3 Level 2 and Level 3 display tests . 45
11.4 Distance and other spatial measurements for mechanically scanned
distances . 49
11.4.1 General . 49
11.4.2 Apparatus and scanning system settings . 49
11.4.3 Image acquisition. 50
11.4.4 Analysis . 50
11.5 Performance in clinical use and evaluation of QA programme . 50
Annex A (informative) Example phantoms for full coupling with curved arrays,
particularly for image uniformity and/or maximum relative depth of penetration tests . 51
Annex B (informative) Available analysis software . 55
B.1 Open source software for assessment for QC or tracking of ultrasound
image uniformity QA data . 55
B.2 Example of QC QA control chart . 57
Annex C (informative) Display test patterns .
Annex C (informative) Electronic test methods and test methods provided by the
manufacturers – Relation to clinical significance . 61
Annex D (informative) Special considerations for 3D imaging transducers . 62
D.1 General . 62
D.2 2D transducers and 3D mechanically driven transducers operating in 2D
imaging mode . 62
D.3 2D arrays operating in 3D imaging mode for determining LSNR values for
md
reconstructed images as a function of depth or distance from the central
plane . 62
D.4 Mechanically driven 3D transducers operating in 3D imaging mode . 62
Annex E (informative) Example workbook database for tracking high-contrast, low-
echo sphere visibility and luminance of the display . 63
Bibliography . 70
Figure 1 – Median-averaged image (right) and its lateral profile (left) . 33
Figure 2 – Examples of portable apparatus for moving the transducer: a) and c) in
equal, chosen increments or b) at a known rate . 35
Figure 3 – Example of visual estimation of the two defined depth zones in which
spheres can be detected with two degrees of fidelity and clarity . 36
Figure 4 – Additional examples of visual estimation of the depth Zone 1 and Zone 2,
each of which represents a certain degree of fidelity and clarity (IEC 62791) . 37
Figure 5 – Maximum relative depth of penetration – image acquisition . 40
Figure 6 – Mean digitized image-data value versus depth for the phantom image data
(A(j)) and for the noise-image data (A'(j)) . 42
Figure 7 – TG18-QA test pattern for visual evaluation testing [21],[33] . 45
Figure 8 – Examples of TG18-LN luminance patterns for luminance measurements [21] . 47
– 4 – IEC TS 62736:2023 RLV © IEC 2023
Figure 9 – TG270-ULN uniformity and luminance test pattern (TG270-ULN8-127 with
background 8-bit grey level 127 is shown) [33] . 48
Figure A.1 – Example phantom for image-uniformity and/or maximum relative depth of
penetration tests . 51
Figure A.2 – Example compact phantom for image uniformity tests . 52
Figure A.3 –Photograph and drawing of a three-in-one phantom which provides for
determination of distance measurement precision and bias, image-uniformity, very-low-
echo sphere visualization, and depth of penetration [39] . 53
Figure A.4 – A compact uniformity phantom of relatively durable rubber material .
Figure A.4 – Two temporally stable, inexpensive phantoms for image uniformity tests . 54
Figure B.1 – On the left the profile of median pixel value is plotted for each image
column in the analysis box shown in the median image on the right for the transducer
in Figure 1, but without the nylon filament obstructing some central elements
Example of data analysis for the transducer evaluated to generate Figure 1 . 56
Figure B.2 – Control chart for a dip in the middle of the profile for one transducer (TD)
model, C9-4 and the specified serial number (S/N) . 58
Figure C.1 – AAPM TG18-UN10 (left) and TG18-UN80 (right) patterns for luminance
uniformity, colour uniformity, and angular response evaluations [35] .
Figure C.2 – Example data entry form for visual display evaluation: left for Figure C.1;
right for Figure C.3 .
Figure C.3 – TG18-CT low-contrast test pattern for the evaluation of the luminance
response of display systems [35] .
Figure E.1 – Current and previous measurements and trendlines providing luminance
at various grey levels, fractional slope of luminance and deviation from DICOM GSDF
in ΔJND per grey level (IEC 62563-2) . 69
Table 1 – Outline of Level 1 tests .
Table 2 – Outline of Level 3 tests additional to those in Table 1 .
Table 1 – Overview to the symbols and definitions of the QA terms, other than those
for the display . 16
Table 2 – Overview of the symbols and definitions of the display QA terms . 17
Table 3 – Abbreviated terms . 18
Table 4 – Outline of tests by level . 19
Table 5 – Ultrasound image display QA tests . 49
Table B.1 – Output of image uniformity analysis . 57
Table E.1 – Transducer record and baseline high-contrast, low-echo-sphere
visualization test data . 64
Table E.2 – Database of periodic sphere visualization results . 65
Table E.3 – Completed short QA data entry example form for monitor luminance
evaluation using test pattern – QA18 . 66
Table E.4 – Blank, short QA data entry evaluation form for monitor luminance using
test pattern – QA18 . 67
Table E.5 – Analysis of luminance measurements . 68
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ULTRASONICS – PULSE-ECHO SCANNERS –
Simple methods for periodic testing to verify stability
of an imaging system's elementary performance
FOREWORD
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6) All users should ensure that they have the latest edition of this publication.
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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 might be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This redline version of the official IEC Standard allows the user to identify the changes made to
the previous edition IEC TS 62736:2016. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.
– 6 – IEC TS 62736:2023 RLV © IEC 2023
IEC TS 62736 has been prepared by IEC technical committee 87: Ultrasonics. It is a Technical
Specification.
This second edition cancels and replaces the first edition published in 2016. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) expansion of the applicable types of transducers and the frequency range of application;
b) extension of test protocols and image assessments, including for very-low-echo spheres;
c) revision of phantom designs and their acoustic properties, consistent with the second
edition of IEC TS 62791;
d) inclusion of luminance tests for system-image display consistency at scanner and remote
monitors;
e) addition of special considerations for 3D-imaging transducers (Annex D) and workbook
examples (Annex E).
The text of this Technical Specification is based on the following documents:
Draft Report on voting
87/777/DTS 87/791/RVDTS
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Specification is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
defined in greater detail at www.iec.ch/standardsdev/publications.
Terms in bold in the text are defined in Clause 3.
Symbols and formulae are in Times New Roman italic.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document 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.
INTRODUCTION
An ultrasonic pulse-echo scanner produces images of tissue in a scan plane by sweeping a
narrow, pulsed beam of ultrasound through the section of interest and detecting the echoes
generated by reflection at tissue boundaries and by scattering within tissues. Various
transducer types are employed to operate in a transmit/receive mode to generate/detect the
ultrasonic signals. Ultrasonic scanners are widely used in medical practice to produce images
of soft-tissue organs throughout the human body. As ultrasound systems are usually employed
under rigorous time restrictions and in diverse environments to help make decisions that are
often critical to patients' wellbeing, it is important that the systems perform consistently at the
level initially provided and accepted in initial tests, for example, those of IEC TS 62791,
IEC 61391-1, 61391-2, and IEC 62563-2. This document provides methods to verify the stability
of an imaging system's elementary performance.
This document is deemed necessary because substandard ultrasound-system performance is
often accepted or remains undetected in the absence of unequivocal and documented tests.
The most common of the failures, in all but the oldest systems nearing retirement, are sub-
performance of a transducer-array element or lens or of a cable or electronic channel. There is
approximately a 14 % transducer-failure rate and a 10 % system-failure rate per year on first
testing [1],[2],[3],[4],[5],[5],[7],[8],[9],[10],[11],[12] . Sensitive image uniformity tests for these
transducer- and channel-failures are presented here for use daily to monthly (Level 1),
biannually annually (Level 2) and biennially (Level 3). With approximately 14 % transducer-
failure rate and 10 % system-failure rate per year on first testing
[1],[2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12], there are, very approximately, 100 000 systems
worldwide routinely performing suboptimal diagnostic exams for part of the year.
This common occurrence of suboptimal diagnostic examinations has created an urgent need to
standardize quality-control (QC) quality-assurance (QA) and performance-evaluation
procedures to promote improved efficacy of diagnostic examinations through widespread use
of effective QC QA procedures and to dispel myths as to their utility. Proposers believe,
however, that existing national and international standards and guides [1],[3],[12],[13],[14]
specify or recommend too many tests and inappropriate tests for detecting and discriminating
the common flaws in diagnostic ultrasound systems during routine QC QA. These practices
include tests, such as spatial resolution, which are low-yield and belong in performance-
evaluation procedures, rather than QC QA.
Modern flat-panel display technology is more stable than, and generally far superior to, earlier
cathode ray tube (CRT) displays. However, LCD these displays can still exhibit luminance drift,
as well as problems such as defective pixels.They still need to be evaluated periodically.
Detection of failures by these recommended pulse-echo tests will probably also detect most
failures affecting the operation of other modes, such as colour-flow, harmonic-, elasticity- and
compound-imaging. The failures might be more pronounced in these other modes and the
fraction of failures in other modes detected by these tests has not been reported.
Image-uniformity QA is applicable to transducers operating in the wide 1 MHz to 40 MHz
frequency range, as the requirements for phantoms are not stringent for this test. The other
tests could be made applicable up to 40 MHz [15],[16] when the depth of penetration
measurement is allowed to be relative, rather than absolute, and phantom stability is verified.
NOTE Phantom manufacturers are encouraged to extend the frequency range to which phantoms are specified to
enable relative depth-of-penetration tests of systems operating at fundamental and harmonic frequencies above
23 MHz.
System-manufacturing and repair companies, as well as those performing more complete
performance evaluation for acceptance, replacement, or research might well employ other or
additional tests that are not within the scope of this document. More complete tests than those
___________
Numbers in square brackets refer to the Bibliography.
– 8 – IEC TS 62736:2023 RLV © IEC 2023
included in the three levels for periodic testing and for assessment at times of particular
importance or concern are specified in IEC 61391-1, IEC 61391-2 and IEC TS 62791. These
more complete tests are categorized as performance evaluation, rather than quality
assurance or frequent periodic testing. It is possible that good, automated analysis of the high-
contrast sphere tests will reduce both the need for optional tests listed here, and for most, more
complete performance evaluation. Full assessment of distance-measurement accuracy might
still be required if automated, 3D distance measurement calibration is not added to the high-
contrast sphere tests.
Uniformity tests of transducers not readily amenable to transducer-element testing by the simple
image-uniformity procedures specified here (for example, phased-array and 2D-array
transducers) are not included in the scope. They are usually evaluated well by careful
performance of the high-contrast sphere tests. System manufacturers are encouraged to
provide pulsing patterns of the transducer elements to allow testing of individual elements or
small-enough groups of elements to enable users to detect significant element failure or to
provide access to another implemented and explained element-test programme.
ULTRASONICS – PULSE-ECHO SCANNERS –
Simple methods for periodic testing to verify stability
of an imaging system's elementary performance
1 Scope
This document, which is a Technical Specification, specifies requirements and methods for
periodic testing of the quality of diagnostic medical ultrasound systems with linear array, curved
linear array, single element, annular array, phased array, matrix linear array transducers and
two-dimensional arrays using reflection-mode (pulse-echo) imaging. Image measurement and
interpretation workstations are included.
NOTE Usually, "periodic testing" is referred to as "quality control (QC)" or quality assurance (QA).
This document represents a minimum set of such tests intended for frequent users of medical
ultrasound systems, for quality control professionals in their organization, or those hired from
other quality-control and/or service-provider organizations. System-manufacturing and repair
companies might well employ other or additional tests. The tests are defined in three levels,
with the simplest and most cost-effective performed most frequently, similarly to [1]. More
complete tests for acceptance testing and for assessment at times of particular importance or
concern are specified in IEC 61391-1, IEC 61391-2 and IEC TS 62791 [15]. These more
complete tests are categorized as performance evaluation, rather than quality control or
frequent periodic testing.
This document also defines terms and specifies methods for measuring (for quality maintenance
or quality control) the maximum relative depth of penetration of real-time ultrasound B-MODE
scanners, though this penetration measure is listed as less frequently applied.
This document includes minimum sets of such tests intended for frequent users of medical
ultrasound systems, for quality assurance professionals in their organizations, or those hired
from other quality-control and/or service-provider organizations. The procedures are for a wide
range of more common diagnostic ultrasound systems, currently operating from 1 MHz to
40 MHz, although available phantoms meet the specifications only from 1 MHz to 23 MHz.
The tests are defined in three levels, with the simplest and most cost-effective performed most
frequently:
Level 1 comprises five quick tests/observations to be performed daily to monthly by those
normally operating the systems.
Level 2 includes one necessary test for all systems in addition to those of Level 1, two Level 1
tests performed more rigorously, two tests that are for special situations or equipment, and one
that is just optional, included because it is highly developed. Level 2 tests are performed
annually by those with meaningful quality assurance training.
Level 3 extends the two special situations tests to all systems, adds one optional test and
includes a periodic review of the QA programme.
Frequent distance-measurement accuracy tests are recommended in this document only for
certain classes of position encoding that are not now known to be highly stable and without
bias. QA in all dimensions is recommended in this document as the first test for such systems.
– 10 – IEC TS 62736:2023 RLV © IEC 2023
The test methodology is applicable for transducers operating in the 1 MHz to 23 MHz frequency
range. The types of transducers used with these scanners include
a) electronic phased arrays,
b) linear arrays,
c) curved convex arrays,
d) mechanical probes transducers,
e) two-dimensional arrays operated in a 2D imaging mode,
f) transducers operating in 3D imaging mode for a limited number of sets of reconstructed 2D
images, and
g) three-dimensional scanning probes transducers based on a combination of the above types.
Transducers not readily amenable to transducer-element testing by the simple image-uniformity
procedures specified (for example, phased array and 2D-array transducers) are tested only
partially by maximum relative depth of penetration. System manufacturers are encouraged to
provide pulsing patterns of the transducer elements to allow testing of individual elements or
small-enough groups of elements to enable users to detect significant element failure or to
provide access to another implemented and explained element-test program. Dedicated
Doppler systems are excluded from coverage here as specialized equipment is required to test
them. This test equipment can be specific to the intended application of the Doppler system.
All scanners considered include basic pulse-echo techniques. The failures to be detected by
the recommended pulse-echo tests also will affect the operation of other modes, such as colour-
flow, harmonic-, elasticity- and compound imaging. The test methodology is applicable for
transducers operating in the 1 MHz to 17 MHz frequency range and could be made applicable
up to 40 MHz, if the depth of penetration were allowed to be relative, rather than absolute, and
phantom stability were verified [15]. Image-uniformity QC is applicable to transducers operating
in the 1 MHz to 40 MHz frequency range as the requirements for phantoms are not stringent.
NOTE Phantom manufacturers are encouraged to extend the frequency range to which phantoms are specified to
enable relative depth-of-penetration tests of systems operating at fundamental and harmonic frequencies above
17 MHz.
All tests on scanners considered here evaluate basic pulse-echo techniques and might detect
most failures in other modes. Dedicated Doppler systems, or other systems for detection of
blood motion, are excluded from this scope as specialized equipment is required to test them.
Such test equipment can be specific to the intended application of the Doppler system.
This document includes definition of terms and specifies methods for measuring the maximum
relative depth of penetration of real-time ultrasound B-MODE scanners, though this
penetration measure is listed as less frequently applied.
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 60050-802, International Electrotechnical Vocabulary – Part 802: Ultrasonics
(available at )
IEC 61391-1, Ultrasonics – Pulse-echo scanners – Part 1: Techniques for calibrating spatial
measurement systems and measurement of system point spread function response
IEC 61391-2, Ultrasonics – Pulse-echo scanners – Part 2: Measurement of maximum depth of
penetration and local dynamic range
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-802 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
quality assurance
QA
regularly performed procedures to ensure consistent performance
Note 1 to entry: Quality control is a part of quality assurance. Another term used is quality maintenance.
3.2
echo from weakly reflecting, background scatterers
echoes from many small targets in which the scattered field is much less intense than the
incident field
3.2
performance evaluation
set of tests performed to assess specific absolute performance of the object tested
Note 1 to entry: Typical times for ultrasound system performance evaluation are at pre-purchase evaluation, new
and repaired system acceptance testing, according to IEC 61391-1 and IEC 61391-2 and
[1],[17],[18],[19],[20],[21],[22], and at times of performance difficulties and end-of-useful-life evaluations. They are
recommended for performance in Level 3 QC tests, though that is not required. Level 3 QA tests include many of
those recommended for such performance evaluation.
3.3
phantom
device designed to mimic some aspects of the human body for the purposes of testing or training
3.4
addressable patch
smallest addressable group of transducer elements
3.5
pixel value
integer value of a processed signal level or integer values of processed colour levels, provided
to the display for a given pixel
Note 1 to entry: In a grey-scale display the pixel value is converted to a luminance by some, usually monotonic,
M
function. The set of integer values representing the grey scale runs from 0 (black) to (2 − 1) (white), where M is a
positive integer, commonly called the bit depth. Thus, if M = 8, the largest pixel value in the set is 255.
[SOURCE: IEC TS 62791:2022, 3.6]
3.6
mean pixel value
MPV
mean of pixel values detected over a designated area or volume in an image or 3D stack of
images
Note 1 to entry: For low-echo spheres here, MPV is defined for an area A or volume in a phantom image or stack
of images, where A is somewhat smaller than the area of a circle of diameter D. The phrase "somewhat smaller than"
is introduced as partial compensation for the partial volume effect, primarily in the elevational dimension.
– 12 – IEC TS 62736:2023 RLV © IEC 2023
Note 2 to entry: The partial volume effect is a term common in computed tomographic, magnetic resonance and
ultrasound imaging. This process refers to the effect of the finite imaging resolution, particularly the slice
thickness. The signal (ie, pixel values) at points near the object boundaries will include contribution from that object
and contributions from the material around it. For example, if the object is a sphere with a diameter close to the
thickness of the slice, then you cannot define a good measurement region in the image of the sphere in which the
signal does not include components from material lying outside the sphere.
3.7
maximum depth of penetration
maximum range at which the ratio of the mean, digitized, B-mode-image data corresponding to
images displaying echoes from weakly reflecting, background scatterers to the mean,
digitized, B-mode-image data corresponding to images displaying only electronic noise equals
1,4, when the echoes from weakly reflecting, background scatterers are generated in a
phantom with properties meeting the specifications of IEC 61391-2.
maximum range in a phantom, with properties meeting the specifications of IEC 61391-2, at
which the mean pixel value corresponding to signals from the weakly reflecting, background
scatterers are 1,4 times the mean pixel value corresponding to images displaying only
electronic noise at that same depth
Note 1 to entry: The maximum depth of penetration is expressed in metres (m) and conventionally in centimetres
(cm).
3.8
maximum relative depth of penetration
maximum range at which the ratio of the mean, digitized, B-mode-image data corresponding to
images displaying echoes from weakly reflecting, background scatterers to the mean,
digitized, B-mode-image data corresponding to images displaying only electronic noise equals
1,4, when the echoes from weakly reflecting, background scatterers are generated in a
phantom with properties meeting specifications more relaxed than those of IEC 61391-2
maximum range in a phantom, at which the mean pixel value corresponding to images
displaying echoes from weakly reflecting and background scatterers are 1,4 times the mean
pixel value corresponding to images displaying only electronic noise at that same depth
Note 1 to entry: The specified properties of the phantom are somewhat relaxed from those specified in IEC 61391-
2, as modified in IEC/TS 62791:2022, 3.2.
Note 2 to entry: The adjective "relative" is used because the phantom specifications defined in this document are
so loose that measurements of the "maximum range" with different phantoms cannot be compared. The
measurements are only for tests of stability, i.e. comparisons between measurements on the same phantom over
time.
Note 3 to entry: For available phantoms and specifications, see [16],[17], and for a potential alternative measure
of depth of penetration, see [15].
Note 4 to entry: The maximum relative depth of penetration is, by international standards, expressed in metres
(m) and conventionally in centimetres (cm).
3.9
quality control
QC
regularly performed procedures to assure consistent performance
Note 1 to entry: A more descriptive term is quality maintenance; quality assurance is also used.
3.9
median absolute deviation
MAD
median of the absolute value of the deviations from the median of a data set
Note 1 to entry: The MAD is similar to the standard deviation but, as the median of linear deviations rather than
squared deviations, it is more resilient to outliers [18].
3.10
specific attenuation coefficient
attenuation coefficient at a specified frequency divided by the frequency
Note 1 to entry: The specific attenuation coefficient is usually expressed in decibels per centimetre per
−1 −1
megahertz (dB cm MHz ); extrapolation to other frequencies makes the explicit assumption of linear dependence
of the attenuation coefficient on frequency.
[SOURCE: IEC 61391-2:2010, 3.33, modified by rephrasing "at a specified frequency, the slope
of attenuation coefficient plotted against frequency", which assumes a broadband
measurement.]
3.11
equivalent sensitivity
sensitivity that is statistically the same or has smaller variance and bias
3.12
backscatter coefficient
intrinsic backscatter coefficient
η
intrinsic property of a material at some frequency, equal to the differential scattering cross-
section per unit volume for a scattering angle of 180°
[SOURCE: IEC TS 62791:2022, 3.2, modified – the note has been deleted.]
3.13
low-echo sphere
hypoechoic sphere
spherical inclusion in a phantom with a backscatter coefficient lower than the backscatter
coefficient of the surrounding tissue-mimicking material
[SOURCE: IEC TS 62791:202
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