IEC TR 61390:2022

Ultrasonics - Real-time pulse-echo systems - Test procedures to determine performance specifications

IEC TR 61390:2022 describes representative methods of measuring the performance of complete real-time medical ultrasonic imaging equipment in the frequency range 0,5 MHz to 23 MHz.
This document is relevant for real-time ultrasonic scanners based on the pulse-echo principle, for the types listed below:
- mechanical sector scanner;
- electronic phased array sector scanner;
- electronic linear array scanner;
-electronic curved array sector scanner;
- water-bath scanner based on any of the above four scanning mechanisms;
- plane-wave/fast imaging scanners;
- combination of several of the above methods (e.g. a linear array phased at the edge to produce a sector there to enlarge the field of view.
The methods described are based on evaluation of:
- sonograms obtained by scanning of tissue mimicking objects (phantoms);
- sonograms obtained by scanning of artificial, low- or highly reflective targets in suitable environments;
- parameters of the ultrasound field transmitted by the measured scanner.
This document does not relate to methods for measuring electrical parameters of the scanner’s electronic systems.
IEC TR 61390:2022 cancels and replaces the first edition published in 1996. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) Several additional phantom designs are included in the main body of the document;
b) Several additional transducer types are included in the Scope;
c) Methods of analysis are presented in new Annex B.

General Information

• Status: Published
• Publication Date: 05-Sep-2022
• ICS: 11.040.50 - Radiographic equipment
• Technical Committee: TC 87 - Ultrasonics
• Drafting Committee: WG 9 - TC 87/WG 9
• Current Stage: PPUB - Publication issued
• Start Date: 06-Sep-2022
• Completion Date: 11-Oct-2022

Overview

IEC TR 61390:2022 - Ultrasonics - Real-time pulse-echo systems - Test procedures to determine performance specifications - is a technical report from the IEC that defines representative test procedures for measuring the performance of complete real‑time medical ultrasonic imaging equipment operating in the 0.5 MHz to 23 MHz band. The report covers pulse‑echo scanners (mechanical sector, electronic phased‑array sector, linear array, curved array, water‑bath scanners, plane‑wave/fast imaging scanners and hybrid arrangements) and specifies methods based on:

• Sonograms from tissue‑mimicking objects (phantoms)
• Sonograms from artificial low‑ or high‑reflective targets
• Measured parameters of the transmitted ultrasound field

Note: IEC TR 61390:2022 does not specify methods for measuring electrical parameters of scanner electronics. This edition updates the 1996 first edition and adds new phantom designs, additional transducer types and analysis methods (Annex B).

Key topics and technical requirements

The report organizes practical test procedures and equipment guidance. Major topics include:

• Recommended equipment (Clause 6.1): hydrophones, oscilloscopes/transient recorders, spectrum analyzers, pulse generators, degassed water tanks, target holders/positioning systems, tissue‑mimicking phantoms, and evaluation software
• Test settings and display/sensitivity optimizations (Clause 6.2)
• Measured performance parameters (Clause 6.3), including:
  • Acoustic working‑frequency bandwidth
  • Axial, lateral and elevational resolution
  • Contrast‑detail resolution and display sonic contrast
  • Detectability of non‑ or minimally‑scattering regions
  • Dead zone, proximal/distal working limits and depth of penetration
  • Slice thickness, beam shape and uniformity degradation
  • Displayed dynamic range, M‑mode calibration and measurement accuracy
• Phantom descriptions and tissue‑mimicking materials (Annex A)
• Analysis methods for complex phantoms (Annex B), including automated segmentation and beam profile analysis

Practical applications and who uses this standard

IEC TR 61390:2022 is a practical reference for:

• Ultrasound scanner manufacturers - for design verification, performance claims and R&D
• Independent test laboratories and conformity assessment bodies - for standardized performance testing
• Clinical/biomedical engineering teams - for acceptance testing and periodic quality assurance
• Regulators and procurement specialists - to interpret and compare imaging performance specifications
• Research groups developing novel transducers or imaging modes (plane‑wave/fast imaging)

Use cases include verifying resolution and contrast performance with tissue‑mimicking phantoms, mapping beam profiles, quantifying depth of penetration, and validating display accuracy.

Related standards

IEC TR 61390:2022 complements other IEC and medical‑device standards covering ultrasonic equipment safety, electrical performance and clinical requirements. Consult the IEC standards catalogue for related ultrasonics and medical electrical equipment publications.

Keywords: IEC TR 61390:2022, ultrasonics, real‑time pulse‑echo systems, medical ultrasonic imaging, test procedures, performance specifications, tissue‑mimicking phantoms, hydrophone, resolution, contrast, slice thickness.

Standards Content (Sample)

IEC TR 61390 ®
Edition 2.0 2022-09
TECHNICAL
REPORT
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Ultrasonics – Real-time pulse-echo systems –
Test procedures to determine performance specifications
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IEC TR 61390 ®
Edition 2.0 2022-09
TECHNICAL
REPORT
colour
inside
Ultrasonics – Real-time pulse-echo systems –

Test procedures to determine performance specifications

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 11.040.50 ISBN 978-2-8322-5638-1

– 2 – IEC TR 61390:2022 © IEC 2022
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Environmental conditions . 18
5 Recommended equipment . 19
6 Test methods . 19
6.1 Instruments . 19
6.1.1 General . 19
6.1.2 Hydrophones . 19
6.1.3 Oscilloscope or other transient recorder . 19
6.1.4 Spectrum analyzer . 20
6.1.5 Pulse generator . 20
6.1.6 Tissue-mimicking test objects . 20
6.1.7 Tank and degassed water . 20
6.1.8 High or low reflective target . 20
6.1.9 Target holder and/or positioning system . 20
6.1.10 Computing system to run computer-assisted evaluation software . 21
6.1.11 Software to evaluate quality parameters . 21
6.2 Test settings . 21
6.2.1 General . 21
6.2.2 Display settings (focus, brilliance, contrast) . 21
6.2.3 Sensitivity settings (frequency, suppression, output power, overall gain,
TGC, automatic TGC) . 21
6.2.4 Final optimisation . 22
6.2.5 Recording system . 22
6.3 Tested quantities / parameters and procedures . 22
6.3.1 General . 22
6.3.2 Acoustic working-frequency bandwidth . 23
6.3.3 Resolution . 23
6.3.4 Contrast-detail resolution . 25
6.3.5 Non- or minimally-scattering region detectability . 25
6.3.6 Dead zone and proximal and distal working limits . 28
6.3.7 Slice thickness. 28
6.3.8 Depth of penetration . 28
6.3.9 Displayed dynamic range . 29
6.3.10 Display error or position recording error . 29
6.3.11 Measurement system accuracy . 29
6.3.12 M-mode calibration . 30
6.3.13 Beam shape . 30
6.3.14 Uniformity-degradation (element or channel) test . 31
Annex A (informative) Test objects and tissue-mimicking material . 32
A.1 Test object structures . 32
A.2 Tissue-mimicking materials . 32
A.3 Description of test objects . 32

A.3.1 Soft tissue-mimicking test object . 32
A.3.2 Axial resolution test object . 33
A.3.3 Multi-purpose resolution test object . 34
A.3.4 Contrast test objects . 36
A.3.5 Low-scattering sphere void test object . 37
A.3.6 Randomly positioned, embedded low-echo spheres phantom . 38
A.3.7 Cylindrical-void phantom . 39
A.3.8 Edinburgh pipe phantom . 40
A.3.9 Crossed-threads phantom . 42
Annex B (informative) Test procedures . 47
B.1 Analysis of random-void phantoms . 47
B.1.1 Automated segmentation and sorting of voids . 47
B.1.2 Procedure for detecting voids and assigning contrast-scaled spherical
objects to them for display of the best imaging zones . 48
B.2 Analysis of beam profiles using cross-threads phantoms . 50
B.2.1 Test procedure for crossed-threads phantom . 50
B.2.2 Analysis of display sonic contrast when using a foam phantom . 50
Bibliography . 53

Figure 1 – Beam geometry . 11
Figure 2 – Reticulated foam with random voids . 26
Figure A.1 – Soft tissue-mimicking test object . 33
Figure A.2 – Axial resolution test object . 34
Figure A.3 – Multi-purpose resolution test object . 35
Figure A.4 – Slice-thickness measurement and calculation . 36
Figure A.5 – Contrast test object . 37
Figure A.6 – Non-scattering spheres test object . 38
Figure A.7 – End view of the phantom applicable for 2 MHz to 7 MHz showing the
spatially random distribution of 4-mm diameter spheres . 39
Figure A.8 – Essential components of Satrapa's cylindical-void phantom . 40
Figure A.9 – Structures of foams . 40
Figure A.10 – Schematic of Edinburgh pipe phantom showing anechoic pipes within
the tissue mimicking material . 41
Figure A.11 – Image from a preclinical ultrasound scanner operating at 55 MHz
showing the length over which a 92-micron pipe can be visualised in the scan plane . 42
Figure A.12 – 3D-thread phantom . 43
Figure A.13 – Beam profiles calculated from the single-filament images . 43
Figure A.14 – Thread groups with threads stretched at 45º angles to each other . 44
Figure A.15 – (above) Azimuthal and elevational beam profiles obtained from a

filament phantom; (below) Constant depth (C-images) from a random-void phantom. 45
Figure A.16 – Beam profiles calculated for a matrix probe . 45
Figure B.1 – Segmentation of voids performed following void contrast (void signal
amplitude) ranking and transfer in small spheres like a “container” to the corresponding
contrast fraction . 48
Figure B.2 – WCR-plot for 10 fractions with the reference level set to 70 . 49
Figure B.3 – Screen shots of rotating volume images of a random-void phantom using
gray-scale (left) and VDR -levels (right) in transparent mode . 49
i
– 4 – IEC TR 61390:2022 © IEC 2022
Figure B.4 – Screen shot of a rotating-volume image of random-void phantom after
automatic segmentation . 50
Figure B.5 – Determination of display sonic contrast (symbolic) . 51
Figure B.6 – Result of 3D-display sonic contrast determination (example) . 51
Figure B.7 – A Signal-to-Noise Ratio (SNR) chart, giving only "signal“ without "noise“,

expressed in dB . 52

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ULTRASONICS – REAL-TIME PULSE-ECHO SYSTEMS –

Test procedures to determine performance specifications

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TR 61390 has been prepared by IEC technical committee 87: Ultrasonics. It is a Technical
Report.
This second edition cancels and replaces the first edition published in 1996. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Several additional phantom designs are included in the main body of the document;
b) Several additional transducer types are included in the Scope;
c) Methods of analysis are presented in new Annex B.

– 6 – IEC TR 61390:2022 © IEC 2022
The text of this Technical Report is based on the following documents:
Draft Report on voting
87/771/DTR 87/796A/RVDTR
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 Report 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
described in greater detail at www.iec.ch/standardsdev/publications.
NOTE Words in bold in the text are defined in Clause 3.
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 at tissue boundaries. Furthermore, the number of ultrasonic pulse-echo scanners
using plane-wave imaging technology is increasing.
Alternatively, a scanner can transmit a wide-field wave-front or several transmit-beams and
record from the whole transducer array the echoes backscattered from tissue boundaries [1]
[2] . The latter is followed by software beamforming, picking several parts of the wide beam or
in this way selecting one of the simultaneously transmitted beams to obtain adequate resolution.
Plane-wave techniques cannot compete with physical, transmit beam-forming for maximum
depth of imaging at a given bandwidth, maximum resolution and minimum acoustic exposure.
Ultrasonic scanners are widely used in medical practice to produce images of many soft-tissue
organs throughout the human body. A variety of transducer types is employed to operate in a
transmit/receive mode for generating/receiving the ultrasonic signals.
This document describes test procedures that should be widely acceptable and valid for a wide
range of types of equipment. Manufacturers should use this document to prepare their own
specifications, while users should use this document to check manufacturers’ specifications.
The measurements can be carried out without interfering with the normal working conditions of
the machine. The structures of the test objects, test equipment and measuring systems have
not been specified in detail; rather, suitable types of overall and internal structures are
described, together with typical test objects, in Annex A. The specific structure of a test object
and test equipment should be reported, together with the results obtained using them. Similar
commercial versions of these test objects are available.
The performance parameters selected and the corresponding methods of measurement have
been chosen to provide a basis for comparison with the manufacturers’ specifications and
between similar types of apparatus of different makes, intended for the same kind of diagnostic
application. The manufacturers’ specifications should allow comparison with the results
obtained from the tests described in this document. Specific values of parameters and the
tolerances on them have not been recommended, since these are constantly changing.
Furthermore, it is intended that the sets of results and values obtained from the use of the
recommended methods will provide useful criteria for predicting the performance of equipment
in appropriate diagnostic applications.
The procedures recommended in this document are in accordance with IEC 60601-1:2005.
Where a diagnostic system accommodates more than one option in respect of a particular
system component, for example the transducer, it is intended that each option be regarded as
a separate system. However, it is considered that the performance of a machine is adequately
specified, if measurements are undertaken for the most significant combinations of machine-
control settings and accessories. Further evaluation of equipment is obviously possible but this
should be considered as a special case rather than a routine requirement.
Data relating to measuring methods, principles and equipment that are common to two or more
sections of this report are given in Annex A. Specific test procedures are given in Annex B.
The measurement of acoustic output power levels and the assessment of electrical safety are
dealt with in other IEC standards; they are therefore specifically excluded from this document.

Numbers in square brackets refer to the Bibliography.

– 8 – IEC TR 61390:2022 © IEC 2022
ULTRASONICS – REAL-TIME PULSE-ECHO SYSTEMS –

Test procedures to determine performance specifications

1 Scope
This document describes representative methods of measuring the performance of complete
real-time medical ultrasonic imaging equipment in the frequency range 0,5 MHz to 23 MHz.
NOTE The frequency range given represents, in general, the widely used range in hospitals at the date of
publication; special medical applications use higher frequencies for imaging but mainly in research or pre-clinical
imaging.
This document is relevant for real-time ultrasonic scanners based on the pulse-echo principle,
for the types listed below:
• mechanical sector scanner;
• electronic phased array sector scanner;
• electronic linear array scanner;
• electronic curved array sector scanner;
• water-bath scanner based on any of the above four scanning mechanisms;
• plane-wave/fast imaging scanners;
• combination of several of the above methods (e.g. a linear array phased at the edge to
produce a sector there to enlarge the field of view.
The methods described are based on evaluation of:
• sonograms obtained by scanning of tissue mimicking objects (phantoms);
• sonograms obtained by scanning of artificial, low- or highly reflective targets in suitable
environments;
• parameters of the ultrasound field transmitted by the measured scanner.
This document does not relate to methods for measuring electrical parameters of the scanner’s
electronic systems.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp

3.1
A-scan
class of data acquisition geometry in one dimension, in which echo strength information is
acquired from points lying along a single beam axis and displayed as amplitude versus time of
flight or distance
[SOURCE: IEC 61391-1:2006, 3.1]
3.2
A-mode
amplitude-modulated display
method of presentation of A-scan information in which the ultrasonic transducer-target
distance is represented on one axis (normally horizontal) and the echo amplitude on the other
axis
[SOURCE: IEC TR 60854:1986, 3.17, modified – Replacement of "echo information" with "A-
scan information" and "transducer to target distance" with "ultrasonic transducer-target
distance"]
3.3
acceptance testing
evaluation of system performance after delivery of a purchased or repaired system and before
authorisation for payment
3.4
acoustic clutter
noise artifact in ultrasound images that appears as diffuse echoes overlying signals of interest
Note 1 to entry: Sources of acoustic clutter include sound reverberation in tissue layers, scattering from off-axis
structures, ultrasound beam distortion, returning echoes from previously transmitted pulses and random acoustic or
electronic noise
3.5
acoustic scan line
one of the component lines that form a B-mode image on an ultrasound monitor, where each
line is the envelope-detected A-scan line, in which the echo amplitudes are converted to
brightness values
[SOURCE: IEC 61391-1:2006, 3.26]
3.6
acoustic-working frequency
centre frequency
arithmetic mean of the frequencies f and f at which the amplitude of the acoustic pressure
1 2
spectrum is 3 dB below the peak amplitude
[SOURCE: IEC 61391-1:2006, 3.3]
3.7
axial resolution
minimum separation along the beam axis of two equally scattering volumes or targets at a
specified depth for which two distinct echo signals can be displayed
[SOURCE: IEC 61391-1:2006, 3.5]

– 10 – IEC TR 61390:2022 © IEC 2022
3.8
B-scan
brightness-modulated display scan
class of data-acquisition geometry in which echo information is acquired from points lying in an
ultrasonic scan plane containing interrogating ultrasonic beams
Note 1 to entry: B-scan is a colloquial term for B-mode scan or image.
3.9
B-mode
brightness-modulated display
method of presentation of B-scan information, in which a particular section through an imaged
object is represented in a conformal way by the plane of the display and echo amplitude is
represented by local brightness or optical density of the display
[SOURCE: IEC 61391-1:2006, 3.10, modified – Replacement of "scan plane" with "plane"]
3.10
backscatter coefficient
at a specified frequency, the mean acoustic power scattered by a specified object in the 180°
direction with respect to the direction of the incident beam, per unit solid angle per unit volume,
divided by the incident beam intensity, the mean power being obtained from different spatial
realizations of the scattering volume
Note 1 to entry: The frequency dependency should be addressed at places where backscatter coefficient is used,
if frequency influences results significantly.
-1 -1
Note 2 to entry: Backscatter coefficient is expressed in units of 1 per metre times 1 per steradian (m sr )”.
[SOURCE: IEC 61391-1:2006, 3.6, modified – In the definition, addition of "at a specified
frequency", and addition of two new Notes to entry]
3.11
backscatter contrast
ratio between the backscatter coefficients of two objects or regions
[SOURCE: IEC 61391-2:2010, 3.8]
3.12
bandwidth
difference in the most widely separated frequencies f and f at which the magnitude of the
1 2
acoustic pressure spectrum drops 3 dB below the peak magnitude, at a specified point in the
acoustic field
Note 1 to entry: Bandwidth is expressed in hertz (Hz).
[SOURCE: IEC 62127-1:2007, 3.6, modified – Replacement of "becomes" with "drops"]
3.13
beam axis
straight line that passes through the beam centrepoints of two planes perpendicular to the line
which connects the point of maximal pulse-pressure-squared integral with the centre of the
external transducer aperture
Note 1 to entry: See Figure 2 .
Note 2 to entry: The location of the first plane is the location of the plane containing the maximum pulse-pressure-
squared integral or, alternatively, is one containing a single main lobe which is in the focal Fraunhofer zone. The
location of the second plane is as far as is practicable from the first plane and parallel to the first with the same two
orthogonal scan lines (x and y axes) used for the first plane. This alternative definition, eliminating reference to the

centre of the external transducer aperture, is necessary when the pressure distribution among the transducer
elements is not symmetric about the external transducer aperture.
Note 3 to entry: In a number of cases, the term pulse-pressure-squared integral is replaced in the above definition
by any linearly related quantity, for examples:
a) in the case of a continuous wave signal, the term pulse-pressure-squared integral is replaced by mean square
acoustic pressure as defined in IEC 61689:2022, 3.29.;
b) in cases where signal synchronisation with the scan frame is not available, the term pulse-pressure-squared
integral can be replaced by temporal average intensity.
Note 4 to entry: Definition is modified compared to 4.2.14 of IEC 61828:2020 – "aperture" replaces "surface
plane".
Figure 1 – Beam geometry
3.13.1
beam centrepoint
position determined by the 2D centroid of a set of pulse-pressure-squared integrals
measured over the -6 dB beam-area in a specified plane
Note 1 to entry: Methods for determining 2D centroids are described in Annex C of IEC 61828:2020.
[SOURCE: IEC 62359:2010, 3.14]
3.13.2
external transducer aperture
part of the surface of the ultrasonic transducer or ultrasonic transducer element group
assembly that emits ultrasonic radiation into the propagation medium
Note 1 to entry: This surface is assumed to be either directly in contact with the patient or in contact with a water
or liquid path to the patient.
Note 2 to entry: The ultrasonic transducer element group is usually offset from this surface by a lens, matching
layers and possibly fluid.
[SOURCE: IEC 62127-1:2007, 3.27, modified]

– 12 – IEC TR 61390:2022 © IEC 2022
3.13.3
pulse-pressure-squared integral
ppsi
time integral of the square of the instantaneous acoustic pressure at a particular point in an
acoustic field integrated over the acoustic pulse waveform
Note 1 to entry: The pulse-pressure-squared integral is expressed in pascals squared second (Pa s).
Note 2 to entry: Definition adapted from 3.50 of IEC 62127-1:2007.
3.14
contrast detail
3.14.1
contrast detail detectability
minimum diameter of an object, at specified control settings and range, which can be
distinguished on the display with a specified level of confidence, as a function of the
backscatter contrast of the object with respect to the background, said contrast being varied
in steps over a wide range
3.14.2
contrast-detail resolution
minimum difference in echo amplitude, which can be detected for a scattering or reflecting
structure of specified properties, embedded in a particular tissue-mimicking material
Note 1 to entry: The specified properties include shape, size or speed of sound.
3.15
dead zone
distance from the test object scanning surface to the nearest test-object target that can be
unequivocally imaged
Note 1 to entry: This concept is now rarely useful unless the transducer is damaged. It was defined historically
for line targets lying parallel to the length of linear array elements. Dead zone has been superseded by proximal
and distal working limits.
3.15.1
proximal working limit
distance from the test object scanning surface to the nearest depth at which spherical low-
scattering masses can be unequivocally detected
3.15.2
distal working limit
distance from the test object scanning surface to the furthest depth at which spherical low-
scattering masses can be unequivocally detected
3.16
depth of penetration
maximum distance from the scanning surface of tissue-mimicking material to the embedded
test object beyond which the speckle pattern echoes are no longer detectable
3.17
display curve
curve of signal level amplitude sent to the display as a function of the linear signal
3.18
linear signal
amplitude of the voltage generated across the transducer element, that is assumed, generally
correctly, to be proportional to the integrated pressure across the element face

3.19
display frame rate
rate at which complete images are presented on the output display
3.20
display sonic contrast
display acoustic contrast
C
DS
relative difference between any pixel value in a resolved void without inclusions and the mean
pixel value over a region in the image corresponding to background material at approximately
the same depth and lateral location
C = f × px × R / R d (1)
DS NL D Dp
where
R  is the dynamic range in dB;
D
R is the dynamic range in pixel-values;
Dp
px is the difference between main- and side-lobe maxima in pixel-values;
f is a correction factor for non-linear image processing; for linear image processing, f = 1.

NL NL
Note 1 to entry: Display sonic contrast as treated here assumes that the display curve is the log of the signal
pressure amplitude and thus can be expressed in decibels by accounting for the displayed dynamic range, ignoring
other nonlinear image processing in the system prior to the display. It is best to test for display sonic contrast using
an available display curve most closely approximating that logarithmic relationship.
Note 2 to entry: See B.2.2.
3.21
displayed dynamic range
ratio, expressed in decibels, of the amplitude of the maximum echo that does not saturate the
display to the minimum echo that can be distinguished electronically from the background under
the scanner test settings
[SOURCE: IEC 61391-1:2006, 3.11, modified – Replacement of "in the display" with "from the
background"]
3.22
elevational resolution
transversal resolution
for two line-targets parallel to the scanned plane, minimum separation of two line-targets at a
specified depth in a test object made of tissue-mimicking material for which two distinct echo
signals can be displayed
Note 1 to entry: The plane of separation between the targets should be perpendicular to the beam-alignment axis.
3.23
field-of-view
area in the scan plane that is insonated by the ultrasound beam during the acquisition of echo
data to produce one image frame
[SOURCE: IEC 61391-1:2006, 3.13, modified – Deletion of "ultrasonic" before "scan plane"]
3.24
frame rate
number of sweeps comprising the full-frame refresh rate that the ultrasonic beam makes per
second through the field-of-view
[SOURCE: IEC 61391-1:2006, 3.14]

– 14 – IEC TR 61390:2022 © IEC 2022
3.25
grey scale
range of values of image brightness, being either continuous between two extreme values or, if
discontinuous, including discrete values
[SOURCE: IEC 61391-1:2006, 3.16, modified – Replacement of "including at least three
discrete values" with "including discrete values"]
3.26
lateral resolution
azimuthal resolution
for two line-targets perpendicular to the scanned plane, minimum separation of two line-
targets at a specified depth in a test object made of tissue-mimicking material for which two
distinct echo signals can be displayed
Note 1 to entry: The plane of separation between the targets should be perpendicular to the beam axis.
Note 2 to entry: For linear arrays the terminology is typically azimuthal resolution.
[SOURCE: IEC 61391-1:2006, 3.17, modified – Rewording of the definition, and addition of two
Notes to entry]
3.27
line target
filament
line reflector, whose scattering-surface dimensions are so small that it cannot be distinguished
(except by signal amplitude) by the imaging system from a similar target, whose scattering
surface is an order of magnitude smaller
Note 1 to entry: Line-targets are appropriate for 2D scanning systems.
[SOURCE: IEC 61391-1:2006, 3.19, modified – Replacement of "cylindrical reflector" with "line
reflector", and "diameter is" with "scattering-surface dimensions are". Rewording of the whole
definition]
3.28
low-scattering sphere
low-echo sphere
sphere of material with less backscatter than the background over the range of applicable
frequencies
Note 1 to entry: The term "low-echo sphere" is used frequently in IEC TS 62791:2022.
3.29
M-scan
time-motion scan
class of acquisition geometry in which echo information from moving structures is acquired from
points lying along a single beam axis
Note 1 to entry: The echo information is presented using an M-mode display.
[SOURCE: IEC 61391-1:2006, 3.21]
3.30
M-mode
time-motion mode
method of presentation of M-scan information in which the motion of structures along a fixed
ultrasonic beam axis is depicted by presenting their positions on a vertical line, which moves
across a display to show the variation with time of the echo

[SOURCE: IEC 61391-1:2006, 3.20, modified – Addition of "vertical"]
3.31
maximum depth of penetration
maximum depth in a tissue-mimicking test object of specified properties for which the ratio of
data from background scatterers to data displaying only electronic noise, both derived from the
digitized B-mode images, equals 1,4
Note 1 to entry: The phantom and noise-only images are obtained using identical system settings.
Note 2 to entry: Maximum depth of penetration is expressed in metres (m).
[SOURCE: IEC 61391-2:2010, 3.21, modified – Replacement of "phantom" with "test object",
"digitalized B-mode image data" with "data", and "the digitized B-mode image data displaying
only electronic noise" with " data displaying only electronic noise, both derived from the digitized
B-mode images"]
3.32
nominal frequency
ultrasonic frequency of operation of an ultrasonic transducer or ultrasonic transducer
element group quoted by the designer or manufacturer
[SOURCE: IEC 61157:2007, 3.16]
3.33
overall gain
basic level of gain that is uniform for the whole scan area but modified by TGC relative to the
depth of the scan
Note 1 to entry: Overall gain is usually expressed in decibels (dB).
[SOURCE: IEC 61391-1:2006/AMD1:2017, 3.51, modified]
3.34
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 gray-scale display the pixel value is converted to a luminance by some, usually monotonic,
M
function. The set of integer values representing the gray 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.
3.35
point target
point reflector, whose scattering surface dimensions are so small that it cannot be distinguished
(except by signal amplitude) by the imaging system from a similar target, whose scattering
surface is an order of magnitude smaller
Note 1 to entry: Point targets are appropriate for 3D scanning systems.
Note 2 to entry: The backscatter cross section of a standard point target should be a simple function of frequency
over the range of frequencies studied.
[SOURCE: IEC 61391-1:2006, 3.24, modified – Moving "The backscatter cross section of a
standard point target should be a simple function of frequency over the range of frequencies
studied." to a Note to entry]
– 16 – IEC TR 61390:2022 © IEC 2022
3.36
position recording error
display error
distance between the centre of the image of a target in an image of a test object and the test
object’s correct position, as defined by the positions of the remaining targets or of a single
reference target
3.37
quality assurance
QA
simple periodic testing to verify the stability of an imaging system’s elementary performance
Note 1 to entry: This term is distinguished from performance evaluation, which is more rigorous testing of absolute
performance, typically performed by more skilled personnel for purposes such as acceptance testing.
3.38
real-time B-scan
class of data acquisition and presentation in which B-scans are automatically and repetitively
performed at display frame rates
Note 1 to entry: Display frame rates are typically greater than five per second.
3.39
scan line
for automatic scanning systems, the beam-alignment axis either for a particular ultrasonic
transducer element or for a single or multiple excitation of an ultrasonic transducer or of an
ultrasonic transducer element group
3.40
scan plane
acquired image plane containing the acoustic scan lines
[SOURCE: IEC 61391-2:2010, 3.30]
3.41
slice thickness
thickness, perpendicular to the scan plane and at a stated depth in the test object, of that
region of the test object from which acoustic information is displayed
[SOURCE: IEC 61391-1:2006, 3.29, modified – Deletion of "ultrasonic" before "scan plane"]
3.42
speckle pattern
image pattern or texture produced by the interference of echoes from the scattering centres in
tissue-mimicking material
[SOURCE: IEC 61391-1:2006, 3.30, modified – Deletion of "tissue or" before "tissue-
mimicking material"]
3.43
target
ultrasound-reflecting object in a phantom
Note 1 to entry: Usually a line target or, for 3D imaging systems, possibly a point target.
3.44
test object
device containing one or more groups of target configurations embedded in a tissue-
mimicking material or another medium

[SOURCE: IEC 61391-1:2006, 3.33, modified – Replacement of "object" with "target"]
3.45
test-object scanning surface
surface on a test object, recommended for ultrasonic transducer location during a test
procedure
[SOURCE: IEC 61391-1:2006, 3.34, modified – Replacement of "on the tissue-mimicking test
object" with "on a test object"; addition of "ultrasonic"]
3.46
time-gain compensation
TGC
change in amplifier gain with time, introduced to compensate for loss in echo amplitude with
increasing depth due to attenuation in tissue
[SOURCE: IEC 61391-1:2006, 3.35]
3.47
tissue-mimicking material
TMM
material in which th
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