IEC 61391-2:2010

Ultrasonics - Pulse-echo scanners - Part 2: Measurement of maximum depth of penetration and local dynamic range

IEC 61391-2:2010 defines terms and specifies methods for measuring the maximum depth of penetration and the local dynamic range of real time ultrasound B MODE scanners. The types of transducers used with these scanners include:
- mechanical probes;
- electronic phased arrays;
- linear arrays;
- curved arrays;
- two-dimensional arrays;
- three-dimensional scanning probes based on a combination of the above types.
All scanners considered are based on pulse-echo techniques. The test methodology is applicable for transducers operating in the 1 MHz to 15 MHz frequency range operating both in fundamental mode and in harmonic modes that extend to 15 MHz. However, testing of harmonic modes above 15 MHz is not covered by this standard.

Ultrasons - Scanners à impulsion et écho - Partie 2: Mesure de la profondeur maximale de pénétration et de la plage dynamique locale

La CEI 61391-2:2010 définit les termes et spécifie les méthodes de mesure de la profondeur maximale de pénétration et de la plage dynamique locale des scanners ultrasoniques en temps réel, en mode B. Les types de transducteurs utilisés avec ces scanners comprennent ce qui suit:
- sondes à balayage mécanique;
- réseaux de phase électroniques;
- réseaux linéaires (barrettes);
- réseaux courbes;
- réseaux bidimensionnels;
- sondes à balayage tridimensionnel, basées sur une combinaison des types ci-dessus.
Tous les scanners considérés sont basés sur les techniques "impulsion et écho". La méthodologie d'essai est applicable aux transducteurs fonctionnant dans la gamme des fréquences entre 1 MHz et 15 MHz, en mode fondamental et en modes harmoniques allant jusqu'à 15 MHz. Toutefois, les essais en modes harmoniques, au-dessus de 15 MHz, ne sont pas couverts par la présente norme.

General Information

• Status: Published
• Publication Date: 13-Jan-2010
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 17.140.50 - Electroacoustics
• Technical Committee: TC 87 - Ultrasonics
• Drafting Committee: WG 9 - TC 87/WG 9
• Current Stage: PPUB - Publication issued
• Start Date: 15-Apr-2010
• Completion Date: 14-Jan-2010

Overview

IEC 61391-2:2010 - Ultrasonics - Pulse-echo scanners - Part 2 specifies standardized test methods and terms for measuring two core performance metrics of real‑time ultrasound B‑mode (pulse‑echo) scanners:

• Maximum depth of penetration (system sensitivity)
• Local dynamic range (ability to display low‑level echoes near strong echoes)

The standard applies to pulse‑echo B‑mode scanners and the broad range of transducers they use (mechanical probes, phased arrays, linear/curved arrays, 2D and 3D probes) operating in the 1 MHz to 15 MHz frequency band. It covers both fundamental and harmonic modes that fall within this frequency range (harmonic modes above 15 MHz are excluded).

Key Topics and Requirements

• Scope and definitions for B‑mode scanners and scan geometry, aligned with IEC 61391‑1 terminology.
• Measurement methodology for:
  • Determining maximum depth of penetration using dedicated penetration phantoms (Annex A).
  • Measuring local dynamic range using acoustic‑signal injection and acoustically‑coupled burst techniques, and using phantoms with inclusions or reflectors (Annex B, figures provided).
• Test objects (phantoms): descriptions of suitable phantom types and guidance on reporting phantom specifics with test results.
• Data access: procedures assume access to digitized image data; where not available, frame‑grabber capture is acceptable.
• Environmental and equipment conditions, instrumentation required, and recommended analysis practices for reliable, reproducible measurements.
• Frequency recommendations: designed for 1–15 MHz operation; phantom manufacturers are encouraged to extend phantom specifications above 15 MHz where appropriate.

Practical Applications - Who Uses This Standard

• Ultrasound equipment manufacturers - to specify and validate scanner performance for product datasheets and design verification.
• Test laboratories and QA/acceptance teams - for factory acceptance, routine performance checks, and maintenance verification.
• Clinical engineers and hospital biomedical departments - to assess whether imaging systems meet operational sensitivity and contrast‑range needs for clinical tasks.
• Regulatory and procurement specialists - to compare devices objectively and support compliance evidence.
• R&D teams - to benchmark front‑end/back‑end design choices (transducers, beamformers, image processing).

Benefits include standardized, repeatable measurements that enable meaningful comparisons of maximum penetration depth and local dynamic range across different makes and models.

Related Standards (if applicable)

• IEC 61391‑1:2006 - Techniques for calibrating spatial measurement systems and measurement of system point‑spread function.
• IEC 62127‑1:2007 - Hydrophones: measurement and characterization of medical ultrasonic fields (up to 40 MHz).
• IEC 60601‑1 - General requirements for basic safety and essential performance of medical electrical equipment.

Keywords: IEC 61391-2, ultrasonics, pulse-echo scanners, maximum depth of penetration, local dynamic range, B‑mode, transducers, phantoms, ultrasound test methods, 1–15 MHz.

Standards Content (Sample)

IEC 61391-2 ®
Edition 1.0 2010-01
INTERNATIONAL
STANDARD
Ultrasonics – Pulse-echo scanners –
Part 2: Measurement of maximum depth of penetration and local dynamic range

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IEC 61391-2 ®
Edition 1.0 2010-01
INTERNATIONAL
STANDARD
Ultrasonics – Pulse-echo scanners –
Part 2: Measurement of maximum depth of penetration and local dynamic range

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
W
ICS 17.140.50 ISBN 978-2-88910-513-7
– 2 – 61391-2 © IEC:2010(E)
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope.8
2 Normative references .8
3 Terms and definitions .8
4 General requirement.13
5 Environmental conditions.13
6 Equipment and data required.14
6.1 General .14
6.2 Phantoms.14
6.2.1 Phantoms required .14
6.2.2 Phantom for maximum depth of penetration.14
6.2.3 Phantoms to estimate local dynamic range .15
6.3 Test equipment for measuring local dynamic range .15
6.4 Digitized image data.17
7 Measurement methods .19
7.1 System sensitivity: maximum depth of penetration.19
7.1.1 Scanning system settings .19
7.1.2 Image acquisition .19
7.1.3 Analysis.20
7.2 Local dynamic range .22
7.2.1 Scanning system settings .22
7.2.2 Measurement method .22
7.2.3 Type II testing for measuring local dynamic range .23
7.2.4 Estimating local dynamic range using backscatter contrast.24
Annex A (informative) Phantom for determining maximum depth of penetration .26
Annex B (informative) Local dynamic range using acoustical test objects.28
Bibliography.35
Figure 1 – Arrangement for measuring local dynamic range using an acoustic-signal
injection technique.16
Figure 2 – Arrangement for measuring local dynamic range using an acoustically-
coupled burst generator .17
Figure 3 – Image of the penetration phantom.20
Figure 4 – Mean digitized image data value vs. depth for the phantom image data
(A(j)) and for the noise image data (A'(j)) .21
Figure 5 – Digitized-image data vs. attenuator setting during local dynamic range
measurements using acoustic signal injection.23
Figure 6 – Image of phantom with inclusions (circles) .24
Figure 7 – Ensemble-average mean pixel value vs. backscatter contrast of inclusions.25
Figure A.1 – Phantom for maximum depth of penetration tests.26
Figure B.1 – Possible arrangement of reflectors for determining local dynamic range .29
Figure B.2 – Displayed intensity (or image pixel value) vs. reflector reflection
coefficient .30
Figure B.3 – Flat ended wire test object for determining local dynamic range.32

61391-2 © IEC:2010(E) – 3 –
Figure B.4 – The experimentally observed backscattering cross section of flat-ended
stainless-steel wires as a function of diameter for three frequencies: U 9.6 MHz;  :
4.8 MHz; ‘: 2.4 MHz [33].33

– 4 – 61391-2 © IEC:2010(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ULTRASONICS –
PULSE-ECHO SCANNERS –
Part 2: Measurement of maximum depth
of penetration and local dynamic range
FOREWORD
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61391-2 has been prepared by IEC technical committee 87:
Ultrasonics.
The text of this standard is based on the following documents:
Enquiry draft Report on voting
87/400/CDV 87/426/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
Terms in bold in the text are defined in Clause 3.

61391-2 © IEC:2010(E) – 5 –
A list of all parts of the IEC 61391 series, published under the general title Ultrasonics –
Pulse-echo scanners, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this standard may be issued at a later date.

– 6 – 61391-2 © IEC:2010(E)
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.
This standard is being published in two or more parts:
• Part 1 deals with techniques for calibrating spatial measurement systems and
measurement of system point spread function response;
• Part 2 deals with measurement of system sensitivity (maximum depth of penetration) and
local dynamic range.
This standard describes test procedures for measuring the maximum depth of penetration
and the local dynamic range of these imaging systems. Procedures should be widely
acceptable and valid for a wide range of types of equipment. Manufacturers should use the
standard to prepare their specifications; users should employ the standard to check
performance against those specifications. The measurements can be carried out without
interfering with the normal working conditions of the machine.
Typical phantoms are described in Annex A. The structures of the phantoms are not specified
in detail; instead, suitable types of overall and internal structures for phantoms are described.
Similar commercial versions of these test objects are available. The specific structure of a test
object selected by the user should be reported with the results obtained when using it.
The performance parameters described herein and the corresponding methods of
measurement have been chosen to provide a basis for comparison between similar types of
apparatus of different makes but intended for the same kind of diagnostic application. The
manufacturer’s specifications of maximum depth of penetration and local dynamic range
must allow comparison with the results obtained from the tests described in this standard. It is
intended that the sets of results and values obtained from the use of the recommended
methods will provide useful criteria for predicting performance with respect to these
parameters for equipment operating in the 1 MHz to 15 MHz frequency range. However,
availability and some specifications of test objects, such that they are similar to tissue in vivo,
are still under study for the frequency range 10 MHz to15 MHz.
The procedures recommended in this standard are in accordance with IEC 60601-1 [1] and
IEC 61391-1.
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 for a specific
task 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.
The paradigm used for the framework of this standard is to consider the ultrasound imaging
system to be composed architecturally of a front-end (generally consisting of the ultrasound
transducer, amplifiers, digitizers and beamformer), a back-end (generally consisting of signal
conditioning, image formation, image processing and scan conversion) and a display
(generally consisting of a video monitor but also including any other output device). Under
ideal conditions it would be possible for users to test performance of these components of the
system independently. It is recognized, however, that some systems and lack of some
laboratory resources might prevent this full range of measurements. Thus, the specifications
and measurement methods described in this standard refer to image data that are provided in

61391-2 © IEC:2010(E) – 7 –
a digitalized format by the ultrasound machine and that can be accessed by users. Some
scanners do not provide access to digitized image data. For this group of scanners, tests can
be done by utilizing frame grabbers to record images. Data can then be analyzed in a
computer in the same manner as for image data provided directly by the scanner.

– 8 – 61391-2 © IEC:2010(E)
ULTRASONICS –
PULSE-ECHO SCANNERS –
Part 2: Measurement of maximum depth
of penetration and local dynamic range
1 Scope
This part of IEC 61391 defines terms and specifies methods for measuring the maximum
depth of penetration and the local dynamic range of real-time ultrasound B-MODE
scanners. The types of transducers used with these scanners include:
– mechanical probes;
– electronic phased arrays;
– linear arrays;
– curved arrays;
– two-dimensional arrays;
– three-dimensional scanning probes based on a combination of the above types.
All scanners considered are based on pulse-echo techniques. The test methodology is
applicable for transducers operating in the 1 MHz to 15 MHz frequency range operating both
in fundamental mode and in harmonic modes that extend to 15 MHz. However, testing of
harmonic modes above 15 MHz is not covered by this standard.
NOTE Phantom manufacturers are encouraged to extend the frequency range to which phantoms are specified to
enable tests of systems operating at fundamental and harmonic frequencies above 15 MHz.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 61391-1:2006, Ultrasonics – Pulse-echo scanners – Part 1:Techniques for calibrating
spatial measurement systems and measurement of system point spread function response
IEC 62127-1:2007, Ultrasonics – Hydrophones – Part 1: Measurement and characterization of
medical ultrasonic fields up to 40 MHz
3 Terms and definitions
For the purposes of this document the following terms and definitions apply:
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
[IEC 61391-1:2006, definition 3.1]

61391-2 © IEC:2010(E) – 9 –
3.2
acoustic scan line (scan line)
one of the component lines which 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
[IEC 61391-1:2006, definition 3.26]
3.3 acoustic working frequency
arithmetic mean of the frequencies f and f at which the amplitude of the acoustic pressure
1 2
spectrum first falls 3dB below the main peak amplitude.
[IEC 61391-1:2006, definition 3.3, modified]
3.4
attenuation coefficient
at a specified frequency, the fractional decrease in plane wave amplitude per unit path length
in the medium, specified for one-way propagation
–1 –1
Units: m (attenuation coefficient is expressed in dB m by multiplying the fractional
decrease by 8,686 dB.)
NOTE 1 When describing the attenuation properties of a material, the variation of attenuation with frequency
b
should be given. This may be done by expressing a(f), the attenuation coefficient at frequency f, as a(f) = a f ,
o
where f is in MHz, a is the attenuation coefficient at 1 MHz and b is a constant determined by least-squares fitting
o
to experimental data points.
NOTE 2 This parameter specifies the medium’s attenuation only; it excludes reflective losses at interfaces
enclosing the medium and signal decreases due to diffraction.
NOTE 3 See also specific attenuation coefficient.
3.5
B-mode
method of echo-signal display in which the amplitude of the echo signal is represented by
modulation of the brightness of the corresponding point on the display
NOTE The location of the point is determined from the transit time of the acoustic pulse and an assumed value for
sound speed in tissues; for B-mode imaging, it is also determined from the relative position and orientation of the
acoustic scan line.
3.6
B-scan
class of data acquisition geometry in which echo information is acquired from points lying in
an ultrasonic scan plane containing interrogating ultrasonic beams
[IEC 61391-1:2006, definition 3.9]
3.7
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
–1 –1
Units: m steradian
NOTE The frequency dependency should be addressed at places where backscatter coefficient is used, if
frequency influences results significantly.
[IEC 61391-1:2006, definition 3.6, modified]

– 10 – 61391-2 © IEC:2010(E)
3.8
backscatter contrast
ratio between the backscatter coefficients of two objects or regions
[IEC 61391-1:2006, definition 3.7, modified]
3.9
beam axis
the longitudinal axis of the pulse-echo response of a given acoustic scan line, a pulse-echo
equivalent to the transmitted beam axis of IEC 62127-1
[IEC 61391-1:2006, definition 3.8, modified]
3.10
digitized image data
two-dimensional set of pixel values derived from the ultrasound echo signals that form an
ultrasound image
3.11
displayed acoustic dynamic range
20 log of the ratio of the amplitude of the maximum echo that does not saturate the display
to that of the minimum echo that can be distinguished in the same or similar location of the
display under the scanner test settings
Unit: dB
NOTE On most B-mode scanners echo-signal compression is applied in the receiver, so the displayed acoustic
dynamic range exceeds the input-signal dynamic range capabilities of the monitor.
3.12
display threshold (B-mode)
display luminance just above the luminance when no echo signal is present
3.13
display saturation (B-mode)
display luminance at which an increase in echo-signal level or an increase in system
sensitivity produces no change in luminance
3.14
dynamic range
see local dynamic range; see also displayed dynamic range and global dynamic range
3.15
field-of-view
area in the ultrasonic scan plane from which ultrasound information is acquired to produce
one image frame
NOTE 1 This area can correspond to a two-dimensional or three-dimensional field.
NOTE 2 Definition differs from that of 61391-1 in that it is restricted to the region from which information is
acquired.
[IEC 61391-1:2006, definition 3.13 modified]
3.16
frame rate
number of sweeps comprising the full-frame refresh rate that the ultrasonic beam makes per
second through the field-of-view
[IEC 61391-1:2006, definition 3.14]

61391-2 © IEC:2010(E) – 11 –
NOTE This parameter usually differs from the image display rate on the scanner monitor.
3.17
gain
ratio of the output to the input of a system, generally an amplifying system, usually expressed
in decibels.
[IEC 61391-1:2006, definition 3.15]
NOTE The ratio applies for a constant and known acoustical system output.
3.18
global dynamic range
ratio of the maximum to the minimum echo-signal amplitude, even with changes of settings,
that a scanner can process without distortion of the output signal
3.19
harmonic imaging
method of imaging in which ultrasound is transmitted at a fundamental frequency and is
detected at harmonic frequencies
NOTE Harmonics are generated by the propagation medium or by nonlinear reflectors. The resulting harmonic
signal is displayed as an image or part of the image.
3.20
local dynamic range
20 log of the ratio, of the minimum echo amplitude that yields the maximum grey level in the
digitized image to that of the echo that yields the lowest grey level at the same location in the
image and the same settings
Unit: dB
NOTE 1 For an 8-bit image memory, the maximum gray level in the digitized image will be 255.
NOTE 2 Some documents refer to local dynamic range as the range of echo signals required to vary the display
brightness from barely discernible to maximum brightness at a given location [1]. However, this international
standard applies the name local dynamic range to the digitized image data rather than data viewed on the image
monitor. The name displayed acoustic dynamic range is the equivalent to local dynamic range, but applied to
data viewed on the image monitor.
NOTE 3 This quantity is influenced by the grey scale (dynamic) transfer function associated with the echo display.
3.21
maximum depth of penetration
maximum distance in a tissue-mimicking phantom of specified properties for which the ratio of
the digitized B-mode image data from background scatterers to the digitized B-mode image
data displaying only electronic noise equals 1,4
Unit: m
NOTE The phantom and noise-only images are obtained using identical system settings.
3.22
operating condition
any one of the possible particular control settings for a discrete or a combined operating
mode
3.23
operating mode (discrete)
mode of operation of medical diagnostic ultrasonic equipment in which the purpose of the
excitation of the ultrasonic transducer or ultrasonic transducer element group is to utilize only
one diagnostic methodology
– 12 – 61391-2 © IEC:2010(E)
NOTE Examples of discrete operating modes are A-mode (A), M-mode (M), static B-mode (sB), real-time B-
mode (B), continuous wave Doppler (cwD), pulsed Doppler (D), static flow-mapping (sD) and real-time flow-
mapping Doppler (rD) generally using only one type of acoustic pulse at a given depth.
[IEC 62127-1:2007, definition 3.39.2]
3.24
operating mode (combined)
mode of operation of a system that combines more than one discrete operating mode
[IEC 62127-1:2007, definition 3.39.1]
3.25
perfect planar (or specular) reflector
an interface that has a reflection coefficient of 1,0 and whose dimensions are large compared
to the local width of the ultrasound beam
NOTE 1 The pressure-amplitude reflection coefficient of a water-to-air interface is 0,9994 (derived from Zw =
–2 –1 –2 –1
1480 000 kgm s and Za = 413 kgm s )
NOTE 2 In practical measurements a variety of targets may be used. These can all be referred to the perfect
planar reflector by calculation or by careful comparison.
3.26
phantom
a volume of material behaving in essentially the same manner as tissue of the same
dimensions, with respect to absorption and scattering of the ultrasound radiation in question,
used for dosimetry or for the evaluation of sonographic images in diagnostic sonography (see
tissue mimicking phantom)
[IEC 60050-881:1983, 881-12-54 modified]
3.27
pulse-echo technique
method of interrogating a region by insonifying it with pulsed sound beams and detecting and
displaying echo signals arising from scatterers or reflectors
3.28
reflection coefficient (sound pressure)
ratio of the reflected pressure amplitude to the incident pressure amplitude for plane waves
incident perpendicularly on a smooth interface separating two media
3.29
scan line
see acoustic scan line
3.30
scan plane
acquired image plane containing the acoustic scan lines
3.31
scan volume
volume from which echo data are acquired and that contribute to a 3D- image
3.32
sensitivity
minimum reflection coefficient in water of a plane reflector, oriented and positioned for
maximum response, which produces a display threshold
NOTE For the purpose of this standard, the maximum depth of penetration for visualizing background echoes in a
phantom is used as an indication of sensitivity.

61391-2 © IEC:2010(E) – 13 –
3.33
specific attenuation coefficient
at a specified frequency, the slope of attenuation coefficient plotted against frequency
–1 –1
Units: dB m MHz
3.34
speckle pattern
image pattern or texture, produced by the interference of echoes from the scattering centres
in tissue of tissue-mimicking material
[3.30 of IEC 61391-1:2006]
3.35
statistically independent images
images acquired from planes or directions such that the normalized cross-correlation of the
underlying speckle pattern over a fixed region of interest, prior to any speckle reduction
smoothing, is less than 0,2
NOTE Statistically independent images are obtained from a phantom containing randomly distributed scatterers
by translating the scanning plane, steering the beam, etc., such that the underlying speckle pattern changes
sufficiently to reduce the correlation. Images whose speckle target cross-correlation is ~0,2 or lower are sufficiently
de-correlated to implement measurements in this standard.
3.36
test object
device containing one or more groups of object configurations embedded in a tissue-
mimicking material or another medium (see also phantom, tissue-mimicking phantom)
[IEC 61391-1:2006, definition 3.33]
3.37
tissue-mimicking material
material in which the propagation velocity (speed of sound), reflection, scattering, and
attenuation properties are similar to those of soft tissue for ultrasound in the frequency range
1 MHz to 15 MHz
[IEC 61391-1:2006, definition 3.36, modified]
3.38
tissue-mimicking phantom
object comprising tissue-mimicking material
4 General requirement
The manufacturer’s specification shall allow comparison with the results obtained from the
tests described in this standard.
5 Environmental conditions
All measurements shall be performed within the following ambient conditions:
– temperature, 23°C ± 3°C;
– relative humidity, 45 % to 75 %;
– atmospheric pressure, 86 kPa to 106 kPa.
Properties of ultrasound phantoms, such as speed of sound and attenuation coefficient, are
known to vary with temperature. Consult the specifications published by the phantom
manufacturer to determine whether the expected acoustic properties are maintained under the

– 14 – 61391-2 © IEC:2010(E)
above environmental conditions. If not, the environmental conditions over which expected and
reproducible results can be obtained from the phantom or test object shall be adopted for
tests.
6 Equipment and data required
6.1 General
The test procedures described in this document shall be carried out using tissue-mimicking
phantoms and electronic test equipment, together with digitized image data acquired from the
ultrasound scanner.
6.2 Phantoms
6.2.1 Phantoms required
An ultrasound phantom is required for performance of measurements complying with this
standard. A phantom that contains a large, uniform region is required for determining the
maximum depth of penetration. The uniform region shall extend over at least one third of the
width of the imaged field when the depth setting is either at 20 cm or at its maximum value, if
this is less than 20 cm. The acoustical properties of this phantom are specified in 6.2.2.
Test apparatus for measuring local dynamic range as called for in this standard is outlined in
6.2. However, users may also estimate the local dynamic range. Properties of phantoms that
can be used for these estimates are outlined in 6.2.3.
6.2.2 Phantom for maximum depth of penetration
The maximum depth of penetration expresses the maximum range at which echoes from
weakly reflecting scatterers in a phantom having defined properties can be detected at a
1)
specified level above noise [5-12] . A phantom for measuring the maximum depth of
penetration is shown in Figure A.1 in Annex A. The essential components of this phantom
include a block of tissue-mimicking material with background scatterers that give rise to echo
signals. The tissue-mimicking material shall have the following properties:
–1
Speed of sound: (1 540 ± 15) m s at 3 MHz
–3
Density: (1,00) ± 0,03 g cm
–1 –1
Specific attenuation coefficient (0,7 ± 0,05) dB cm MHz in the 1 MHz to 15 MHz
frequency range
–4 –1 –1
Backscatter coefficient:  (3 × 10 cm sr ) ± 3 dB at 3 MHz; with a “frequency to
n
the n” (f ) dependence, where 2 < n < 4 from 1 MHz to
15 MHz. The value of the backscatter coefficient of the
phantom shall be reported as a function of frequency,
together with the results obtained with the phantom.
Dimensions: The phantom shall provide a uniformly scattering and
attenuating field that extends to a depth of at least 20 cm
for testing penetration depth at low frequencies (less than
5 MHz). The lateral and elevational dimensions shall be
such that there is at least a 6 cm wide by 6 cm thick region
of uniform tissue-mimicking material at distances
corresponding to the maximum depth of penetration for the
scanner and transducer under study. Larger cross-
sections may be required to provide a uniform region when
testing 3-D scanning systems.
___________
1)
Figures in square brackets refer to the Bibliography.

61391-2 © IEC:2010(E) – 15 –
Suitable phantoms for this test can be constructed using, for example, water-based gels
having microscopic inhomogeneities that are uniformly distributed throughout to produce the
desired attenuation level [13-18]. Such phantoms also require solid particles, such as 40-
micrometer diameter glass beads to provide backscattered signals at a controlled amplitude
)
[18,19]. A number of manufacturers can produce tissue-mimicking materials and phantoms
that follow these specifications.
6.2.3 Phantoms to estimate local dynamic range
An estimate of the local dynamic range can be obtained easily in the clinic by scanning
phantoms that contain spherical, cylindrical or truncated cylindrical objects, whose
backscatter coefficients vary by known amounts relative to the background material [20].
Backscatter variations of up to 24 dB (15 dB greater than the background, 9 dB less than the
)
background) are available in some commercially available phantoms .
6.3 Test equipment for measuring local dynamic range
The most convenient method for measuring local dynamic range is to use signal injection,
whereby acoustic pulses having precisely controlled amplitudes are applied to the imaging
system transducer directly [21-24]. Figure 1 presents a typical setup. The measurement
)
requires a signal generator that produces sine-wave voltage signals at a frequency that is
within the bandwidth of the transducer-imaging system under test. A planar, single-element
transducer, whose centre frequency also is within the bandwidth of the system transducer,
serves as a coupling device between the signal generator and the system transducer. The
diameter of the coupling transducer should be smaller than 1/3 the aperture of the system
transducer. A test should be performed to determine the dependence of the acoustic output of
the coupling transducer with driving voltage. This can be done using methods described in
IEC 61161:1992 [4]. The coupling transducer is driven with a sinusoidal voltage signal by the
signal generator. The acoustic output of the coupling transducer should be proportional to the
driving voltage to within 2,0 dB for acoustic signal level variations equal to the local dynamic
range of the ultrasound system under test.
)
An external electrical attenuator is placed between the signal generator and the coupling
transducer. Alternatively, some signal generators have suitable built-in attenuators. The
attenuator should have a range of at least 100 dB over the 1 MHz to 15 MHz range.
___________
2)
These include, for example, ATS Labs; Bridgeport, CT, USA (www.atslabs.com); CIRS, Norfolk, VA, USA
(www.cirsinc.com); and Gammex/RMI, Middleton, WI, USA (www.gammex.com). This information is given for
the convenience of users of this document and does not constitute an endorsement by IEC of these companies.
3)
An example of a suitable phantom is the Model 439 general purpose phantom, ATS Labs, Bridgeport, CT, USA
(www.atslabs.com). This information is given for the convenience of users of this document and does not
constitute an endorsement by IEC of this product.
4)
For example, the Model 33220A Function Generator, Agilent Technologies, Santa Clara, CA, USA. This
information is given for the convenience of users of this document and does not constitute an endorsement by
IEC of this product.
5)
For example, the Model 839, Kay Elemetrics Corp, Pine Brook, NJ, USA. This information is given for the
convenience of users of this document and does not constitute an endorsement by IEC of this product.

– 16 – 61391-2 © IEC:2010(E)
IEC  2606/09
Key:
1 Displayed B - mode signal
2 Ultrasound system
3 Signal generator
4 Attenuator
5 System transducer
6 Coupling transducer
Figure 1 – Arrangement for measuring local dynamic range
using an acoustic-signal injection technique
An equivalent alternative arrangement uses a custom designed burst generator [21] for this
measurement (Figure 2). With such units, in response to each transmit pulse from the imaging
system transducer, the coupling transducer produces an electrical-voltage signal that triggers
the burst generator. Following a user-defined time delay, which typically is between 10ҏμs and
100 μs depending on the field of view of the scanner, the generator produces one or more
electrical pulses. These are applied to the coupling transducer, which then transmits a series
of acoustic pulses into the system transducer. After signal- and image-processing by the
ultrasound system, these pulses are presented as apparent echoes in the image memory and
on the B-mode image display. The location of the apparent echo signals on the image
depends on the time delay set in the burst generator and on the area on the system
transducer aperture that is in contact with the coupling transducer. The generator must
provide signal level variations that extend over a range that is greater than the local dynamic
range of the system under test.

61391-2 © IEC:2010(E) – 17 –
IEC  2607/09
Key:
1 Displayed B - mode signal
2 Ultrasound system
3 Attenuator
4 Burst delay
5 Triggered burst generator
6 Coupling transducer
7 System transducer
Figure 2 – Arrangement for measuring local dynamic range using
an acoustically-coupled burst generator
A third possible arrangement applies signal injection directly to the ultrasound system. With
this arrangement, conditioned signals of known amplitude, frequency, and duration are fed
into the system amplifiers, bypassing the transducer. With such arrangements, precisely
controlled changes in simulated echo-signal amplitude can be introduced, and the system
response to these changes can be quantified. Direct injection has been used extensively on
systems employing single-element transducers [22-24]. Devices that apply signal injection for
imaging systems employing transducer arrays are becoming commercially available as well,
and these are noted in 7.2.3 below.
6.4 Digitized image data
Test criteria described in this document are applied to digitized image data derived from the
ultrasound scanner being evaluated. In all cases, image-pixel brightness (gray) levels for all
spatial locations in the image must be available. Image data typically are in a matrix
consisting of at least 300 × 300 pixels and at least 8 bits (255 levels) of gray-scale resolution.

– 18 – 61391-2 © IEC:2010(E)
Scanners for which this standard applies may be grouped according to the source of the
digitized image data. The first group includes systems for which digitized image data are
directly available from the scanner or over an image network. Sources of digitized image data
from this group include the following:
Direct DICOM [25]-images from the scanner. Image data in a DICOM format are available on
most scanners. Software capable of transferring and opening DICOM formatted images is
available.
Digital image files available from the scanner itself. This method is used by most scanner
manufacturers for in-house quality-control testing and image-processing development.
Capabilities often exist to extend the method for use by clinical personnel using, for example,
file-transfer-protocol (ftp) resources. Alternatively, many scanners provide image files on
removable media, such as USB-thumb drives, magneto-optical disks, zip disks, or CD-ROM,
and these are appropriate sources of digital images data as well.
Image-archiving systems. Many imaging centers use commercially available Picture Archiving
and Communication Systems (PACS) for viewing and storing ultrasound-image data.
Manufacturers of PACS systems usually provide means to acquire images in an
uncompressed format, such as a 'tiff' (Tagged Image File Format) or a DICOM (Digital
Imaging and Communications in Medicine [25])-format, to workstations that have access
rights to the image data.
A second group of scanners includes those simpler devices that do not provide digitized
image data but provide standard video signals, image data that can be captured into a
computer and then analyzed. For these scanners, a video-frame grabber may be used to
acquire digitized image data. The video signal grabbing has to be provided under exactly
specified conditions to avoid or minimize signal distortions. Specific care and attention has to
be taken for the following parameters:
The input dynamic range of the video-frame grabber has to be adjusted according to the
maximum signal amplitude of the video output.
The digitizing amplitude resolution (given by the pixel byte size) must be better than that of
the gray-scale resolution of the video-output signal. A minimum of 8 bits or 256 gray levels is
required.
Conversion-function linearity has to be assured.
The spatial resolution (given by the pixel size) of the digital picture must be better than the
original video line density of the image.
The video-capture frame rate of the video-frame grabber must be high enough to allow
acquisition of data to keep up with input data rates, if the imaged field is moved. Keep in mind
the difference between scanning frame rate and output video frame rate.
A cable matched for input/output impedance has to be used to avoid reflections in the line.
Alternatively, some post-processing software on ultrasound scanners enables the user to
determine the pixel values within a selected region of interest (ROI). For some tests, such as
determining local dynamic range, this tool is convenient for monitoring the image pixel value.
The digitized image data must be representative of those on the display monitor of the
scanner. Thus, image data derived from the scanner shall not undergo any post-processing
modifications before being subjected to analysis as described in this standard.

61391-2 © IEC:2010(E) – 19 –
7 Measurement methods
Measurement results will depend on the system transducer, frequency, and the operating
conditions and mode. These shall be specified for s
...

IEC 61391-2 ®
Edition 1.0 2010-01
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STANDARD
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INTERNATIONALE
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Ultrasonics – Pulse-echo scanners –
Part 2: Measurement of maximum depth of penetration and local dynamic range

Ultrasons – Scanners à impulsion et écho –
Partie 2: Mesure de la profondeur maximale de pénétration et de la plage
dynamique locale
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IEC 61391-2 ®
Edition 1.0 2010-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Ultrasonics – Pulse-echo scanners –
Part 2: Measurement of maximum depth of penetration and local dynamic range

Ultrasons – Scanners à impulsion et écho –
Partie 2: Mesure de la profondeur maximale de pénétration et de la plage
dynamique locale
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
W
CODE PRIX
ICS 17.140.50 ISBN 978-2-88912-019-2
– 2 – 61391-2 © IEC:2010
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope.8
2 Normative references .8
3 Terms and definitions .8
4 General requirement.13
5 Environmental conditions.13
6 Equipment and data required.14
6.1 General .14
6.2 Phantoms.14
6.2.1 Phantoms required .14
6.2.2 Phantom for maximum depth of penetration.14
6.2.3 Phantoms to estimate local dynamic range .15
6.3 Test equipment for measuring local dynamic range .15
6.4 Digitized image data.17
7 Measurement methods .19
7.1 System sensitivity: maximum depth of penetration.19
7.1.1 Scanning system settings .19
7.1.2 Image acquisition .19
7.1.3 Analysis.20
7.2 Local dynamic range .22
7.2.1 Scanning system settings .22
7.2.2 Measurement method .22
7.2.3 Type II testing for measuring local dynamic range .23
7.2.4 Estimating local dynamic range using backscatter contrast.24
Annex A (informative) Phantom for Determining Maximum Depth of Penetration.26
Annex B (informative) Local dynamic range using acoustical test objects.28
Bibliography.35

Figure 1 – Arrangement for measuring local dynamic range using an acoustic-signal
injection technique.
Figure 2 – Arrangement for measuring local dynamic range using an acoustically-
coupled burst generator .17
Figure 3 – Image of the penetration phantom.20
Figure 4 – Mean digitized image data value vs. depth for the phantom image data
(A(j)) and for the noise image data (A'(j)) .21
Figure 5 – Digitized-image data vs. attenuator setting during local dynamic range
measurements using acoustic signal injection.23
Figure 6 – Image of phantom with inclusions (circles) .24
Figure 7 – Ensemble-average mean pixel value vs. backscatter contrast of inclusions .25
Figure A.1 – Phantom for maximum depth of penetration tests.26
Figure B.1 – Possible arrangement of reflectors for determining local dynamic range .29
Figure B.2 – Displayed intensity (or image pixel value) vs. reflector reflection
coefficient .30

61391-2 © IEC:2010 – 3 –
Figure B.3 – Flat ended wire test object for determining local dynamic range.32
Figure B.4 – The experimentally observed backscattering cross section of flat-ended
stainless-steel wires as a function of diameter for three frequencies: U 9.6 MHz; :
4.8 MHz; ‘: 2.4 MHz [33].33

– 4 – 61391-2 © IEC:2010
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ULTRASONICS –
PULSE-ECHO SCANNERS –
Part 2: Measurement of maximum depth
of penetration and local dynamic range

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61391-2 has been prepared by IEC technical committee 87:
Ultrasonics.
This bilingual version, published in 2010-06, corresponds to the English version.
The text of this standard is based on the following documents:
Enquiry draft Report on voting
87/400/CDV 87/426/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.

61391-2 © IEC:2010 – 5 –
The French version of this standard has not been voted upon.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
Terms in bold in the text are defined in Clause 3.
A list of all parts of the IEC 61391 series, published under the general title Ultrasonics –
Pulse-echo scanners, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – 61391-2 © IEC:2010
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.
This standard is being published in two or more parts:
• Part 1 deals with techniques for calibrating spatial measurement systems and
measurement of system point spread function response;
• Part 2 deals with measurement of system sensitivity (maximum depth of penetration) and
local dynamic range.
This standard describes test procedures for measuring the maximum depth of penetration
and the local dynamic range of these imaging systems. Procedures should be widely
acceptable and valid for a wide range of types of equipment. Manufacturers should use the
standard to prepare their specifications; users should employ the standard to check
performance against those specifications. The measurements can be carried out without
interfering with the normal working conditions of the machine.
Typical phantoms are described in Annex A. The structures of the phantoms are not specified
in detail; instead, suitable types of overall and internal structures for phantoms are described.
Similar commercial versions of these test objects are available. The specific structure of a test
object selected by the user should be reported with the results obtained when using it.
The performance parameters described herein and the corresponding methods of
measurement have been chosen to provide a basis for comparison between similar types of
apparatus of different makes but intended for the same kind of diagnostic application. The
manufacturer’s specifications of maximum depth of penetration and local dynamic range
must allow comparison with the results obtained from the tests described in this standard. It is
intended that the sets of results and values obtained from the use of the recommended
methods will provide useful criteria for predicting performance with respect to these
parameters for equipment operating in the 1 MHz to 15 MHz frequency range. However,
availability and some specifications of test objects, such that they are similar to tissue in vivo,
are still under study for the frequency range 10 MHz to15 MHz.
The procedures recommended in this standard are in accordance with IEC 60601-1 [1] and
IEC 61391-1.
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 for a specific
task 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.
The paradigm used for the framework of this standard is to consider the ultrasound imaging
system to be composed architecturally of a front-end (generally consisting of the ultrasound
transducer, amplifiers, digitizers and beamformer), a back-end (generally consisting of signal
conditioning, image formation, image processing and scan conversion) and a display
(generally consisting of a video monitor but also including any other output device). Under
ideal conditions it would be possible for users to test performance of these components of the
system independently. It is recognized, however, that some systems and lack of some
laboratory resources might prevent this full range of measurements. Thus, the specifications
and measurement methods described in this standard refer to image data that are provided in

61391-2 © IEC:2010 – 7 –
a digitalized format by the ultrasound machine and that can be accessed by users. Some
scanners do not provide access to digitized image data. For this group of scanners, tests can
be done by utilizing frame grabbers to record images. Data can then be analyzed in a
computer in the same manner as for image data provided directly by the scanner.

– 8 – 61391-2 © IEC:2010
ULTRASONICS –
PULSE-ECHO SCANNERS –
Part 2: Measurement of maximum depth
of penetration and local dynamic range

1 Scope
This part of IEC 61391 defines terms and specifies methods for measuring the maximum
depth of penetration and the local dynamic range of real-time ultrasound B-MODE
scanners. The types of transducers used with these scanners include:
– mechanical probes;
– electronic phased arrays;
– linear arrays;
– curved arrays;
– two-dimensional arrays;
– three-dimensional scanning probes based on a combination of the above types.
All scanners considered are based on pulse-echo techniques. The test methodology is
applicable for transducers operating in the 1 MHz to 15 MHz frequency range operating both
in fundamental mode and in harmonic modes that extend to 15 MHz. However, testing of
harmonic modes above 15 MHz is not covered by this standard.
NOTE Phantom manufacturers are encouraged to extend the frequency range to which phantoms are specified to
enable tests of systems operating at fundamental and harmonic frequencies above 15 MHz.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 61391-1:2006, Ultrasonics – Pulse-echo scanners – Part 1:Techniques for calibrating
spatial measurement systems and measurement of system point spread function response
IEC 62127-1:2007, Ultrasonics – Hydrophones – Part 1: Measurement and characterization of
medical ultrasonic fields up to 40 MHz
3 Terms and definitions
For the purposes of this document the following terms and definitions apply:
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
[IEC 61391-1:2006, definition 3.1]

61391-2 © IEC:2010 – 9 –
3.2
acoustic scan line (scan line)
one of the component lines which 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
[IEC 61391-1:2006, definition 3.26]
3.3 acoustic working frequency
arithmetic mean of the frequencies f and f at which the amplitude of the acoustic pressure
1 2
spectrum first falls 3dB below the main peak amplitude.
[IEC 61391-1:2006, definition 3.3, modified]
3.4
attenuation coefficient
at a specified frequency, the fractional decrease in plane wave amplitude per unit path length
in the medium, specified for one-way propagation
–1 –1
Units: m (attenuation coefficient is expressed in dB m by multiplying the fractional
decrease by 8,686 dB.)
NOTE 1 When describing the attenuation properties of a material, the variation of attenuation with frequency
b
should be given. This may be done by expressing a(f), the attenuation coefficient at frequency f, as a(f) = a f ,
o
where f is in MHz, a is the attenuation coefficient at 1 MHz and b is a constant determined by least-squares fitting
o
to experimental data points.
NOTE 2 This parameter specifies the medium’s attenuation only; it excludes reflective losses at interfaces
enclosing the medium and signal decreases due to diffraction.
NOTE 3 See also specific attenuation coefficient.
3.5
B-mode
method of echo-signal display in which the amplitude of the echo signal is represented by
modulation of the brightness of the corresponding point on the display
NOTE The location of the point is determined from the transit time of the acoustic pulse and an assumed value for
sound speed in tissues; for B-mode imaging, it is also determined from the relative position and orientation of the
acoustic scan line.
3.6
B-scan
class of data acquisition geometry in which echo information is acquired from points lying in
an ultrasonic scan plane containing interrogating ultrasonic beams
[IEC 61391-1:2006, definition 3.9]
3.7
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
–1 –1
Units: m steradian
NOTE The frequency dependency should be addressed at places where backscatter coefficient is used, if
frequency influences results significantly.
[IEC 61391-1:2006, definition 3.6, modified]

– 10 – 61391-2 © IEC:2010
3.8
backscatter contrast
ratio between the backscatter coefficients of two objects or regions
[IEC 61391-1:2006, definition 3.7, modified]
3.9
beam axis
the longitudinal axis of the pulse-echo response of a given acoustic scan line, a pulse-echo
equivalent to the transmitted beam axis of IEC 62127-1
[IEC 61391-1:2006, definition 3.8, modified]
3.10
digitized image data
two-dimensional set of pixel values derived from the ultrasound echo signals that form an
ultrasound image
3.11
displayed acoustic dynamic range
20 log of the ratio of the amplitude of the maximum echo that does not saturate the display
to that of the minimum echo that can be distinguished in the same or similar location of the
display under the scanner test settings
Unit: dB
NOTE On most B-mode scanners echo-signal compression is applied in the receiver, so the displayed acoustic
dynamic range exceeds the input-signal dynamic range capabilities of the monitor.
3.12
display threshold (B-mode)
display luminance just above the luminance when no echo signal is present
3.13
display saturation (B-mode)
display luminance at which an increase in echo-signal level or an increase in system
sensitivity produces no change in luminance
3.14
dynamic range
see local dynamic range; see also displayed dynamic range and global dynamic range
3.15
field-of-view
area in the ultrasonic scan plane from which ultrasound information is acquired to produce
one image frame
NOTE 1 This area can correspond to a two-dimensional or three-dimensional field.
NOTE 2 Definition differs from that of 61391-1 in that it is restricted to the region from which information is
acquired.
[IEC 61391-1:2006, definition 3.13 modified]
3.16
frame rate
number of sweeps comprising the full-frame refresh rate that the ultrasonic beam makes per
second through the field-of-view
[IEC 61391-1:2006, definition 3.14]

61391-2 © IEC:2010 – 11 –
NOTE This parameter usually differs from the image display rate on the scanner monitor.
3.17
gain
ratio of the output to the input of a system, generally an amplifying system, usually expressed
in decibels.
[IEC 61391-1:2006, definition 3.15]
NOTE The ratio applies for a constant and known acoustical system output.
3.18
global dynamic range
ratio of the maximum to the minimum echo-signal amplitude, even with changes of settings,
that a scanner can process without distortion of the output signal
3.19
harmonic imaging
method of imaging in which ultrasound is transmitted at a fundamental frequency and is
detected at harmonic frequencies
NOTE Harmonics are generated by the propagation medium or by nonlinear reflectors. The resulting harmonic
signal is displayed as an image or part of the image.
3.20
local dynamic range
20 log of the ratio, of the minimum echo amplitude that yields the maximum grey level in the
digitized image to that of the echo that yields the lowest grey level at the same location in the
image and the same settings
Unit: dB
NOTE 1 For an 8-bit image memory, the maximum gray level in the digitized image will be 255.
NOTE 2 Some documents refer to local dynamic range as the range of echo signals required to vary the display
brightness from barely discernible to maximum brightness at a given location [1]. However, this international
standard applies the name local dynamic range to the digitized image data rather than data viewed on the image
monitor. The name displayed acoustic dynamic range is the equivalent to local dynamic range, but applied to
data viewed on the image monitor.
NOTE 3 This quantity is influenced by the grey scale (dynamic) transfer function associated with the echo display.
3.21
maximum depth of penetration
maximum distance in a tissue-mimicking phantom of specified properties for which the ratio of
the digitized B-mode image data from background scatterers to the digitized B-mode image
data displaying only electronic noise equals 1,4
Unit: m
NOTE The phantom and noise-only images are obtained using identical system settings.
3.22
operating condition
any one of the possible particular control settings for a discrete or a combined operating
mode
3.23
operating mode (discrete)
mode of operation of medical diagnostic ultrasonic equipment in which the purpose of the
excitation of the ultrasonic transducer or ultrasonic transducer element group is to utilize only
one diagnostic methodology
– 12 – 61391-2 © IEC:2010
NOTE Examples of discrete operating modes are A-mode (A), M-mode (M), static B-mode (sB), real-time B-
mode (B), continuous wave Doppler (cwD), pulsed Doppler (D), static flow-mapping (sD) and real-time flow-
mapping Doppler (rD) generally using only one type of acoustic pulse at a given depth.
[IEC 62127-1:2007, definition 3.39.2]
3.24
operating mode (combined)
mode of operation of a system that combines more than one discrete operating mode
[IEC 62127-1:2007, definition 3.39.1]
3.25
perfect planar (or specular) reflector
an interface that has a reflection coefficient of 1,0 and whose dimensions are large compared
to the local width of the ultrasound beam
NOTE 1 The pressure-amplitude reflection coefficient of a water-to-air interface is 0,9994 (derived from Zw =
–2 –1 –2 –1
1480 000 kgm s and Za = 413 kgm s )
NOTE 2 In practical measurements a variety of targets may be used. These can all be referred to the perfect
planar reflector by calculation or by careful comparison.
3.26
phantom
a volume of material behaving in essentially the same manner as tissue of the same
dimensions, with respect to absorption and scattering of the ultrasound radiation in question,
used for dosimetry or for the evaluation of sonographic images in diagnostic sonography (see
tissue mimicking phantom)
[IEC 60050-881:1983, 881-12-54 modified]
3.27
pulse-echo technique
method of interrogating a region by insonifying it with pulsed sound beams and detecting and
displaying echo signals arising from scatterers or reflectors
3.28
reflection coefficient (sound pressure)
ratio of the reflected pressure amplitude to the incident pressure amplitude for plane waves
incident perpendicularly on a smooth interface separating two media
3.29
scan line
see acoustic scan line
3.30
scan plane
acquired image plane containing the acoustic scan lines
3.31
scan volume
volume from which echo data are acquired and that contribute to a 3D- image
3.32
sensitivity
minimum reflection coefficient in water of a plane reflector, oriented and positioned for
maximum response, which produces a display threshold
NOTE For the purpose of this standard, the maximum depth of penetration for visualizing background echoes in a
phantom is used as an indication of sensitivity.

61391-2 © IEC:2010 – 13 –
3.33
specific attenuation coefficient
at a specified frequency, the slope of attenuation coefficient plotted against frequency
–1 –1
Units: dB m MHz
3.34
speckle pattern
image pattern or texture, produced by the interference of echoes from the scattering centres
in tissue of tissue-mimicking material
[3.30 of IEC 61391-1:2006]
3.35
statistically independent images
images acquired from planes or directions such that the normalized cross-correlation of the
underlying speckle pattern over a fixed region of interest, prior to any speckle reduction
smoothing, is less than 0,2
NOTE Statistically independent images are obtained from a phantom containing randomly distributed scatterers
by translating the scanning plane, steering the beam, etc., such that the underlying speckle pattern changes
sufficiently to reduce the correlation. Images whose speckle target cross-correlation is ~0,2 or lower are sufficiently
de-correlated to implement measurements in this standard.
3.36
test object
device containing one or more groups of object configurations embedded in a tissue-
mimicking material or another medium (see also phantom, tissue-mimicking phantom)
[IEC 61391-1:2006, definition 3.33]
3.37
tissue-mimicking material
material in which the propagation velocity (speed of sound), reflection, scattering, and
attenuation properties are similar to those of soft tissue for ultrasound in the frequency range
1 MHz to 15 MHz
[IEC 61391-1:2006, definition 3.36, modified]
3.38
tissue-mimicking phantom
object comprising tissue-mimicking material
4 General requirement
The manufacturer’s specification shall allow comparison with the results obtained from the
tests described in this standard.
5 Environmental conditions
All measurements shall be performed within the following ambient conditions:
– temperature, 23°C ± 3°C;
– relative humidity, 45 % to 75 %;
– atmospheric pressure, 86 kPa to 106 kPa.
Properties of ultrasound phantoms, such as speed of sound and attenuation coefficient, are
known to vary with temperature. Consult the specifications published by the phantom
manufacturer to determine whether the expected acoustic properties are maintained under the

– 14 – 61391-2 © IEC:2010
above environmental conditions. If not, the environmental conditions over which expected and
reproducible results can be obtained from the phantom or test object shall be adopted for
tests.
6 Equipment and data required
6.1 General
The test procedures described in this document shall be carried out using tissue-mimicking
phantoms and electronic test equipment, together with digitized image data acquired from the
ultrasound scanner.
6.2 Phantoms
6.2.1 Phantoms required
An ultrasound phantom is required for performance of measurements complying with this
standard. A phantom that contains a large, uniform region is required for determining the
maximum depth of penetration. The uniform region shall extend over at least one third of the
width of the imaged field when the depth setting is either at 20 cm or at its maximum value, if
this is less than 20 cm. The acoustical properties of this phantom are specified in 6.2.2.
Test apparatus for measuring local dynamic range as called for in this standard is outlined in
6.2. However, users may also estimate the local dynamic range. Properties of phantoms that
can be used for these estimates are outlined in 6.2.3.
6.2.2 Phantom for maximum depth of penetration
The maximum depth of penetration expresses the maximum range at which echoes from
weakly reflecting scatterers in a phantom having defined properties can be detected at a
1)
specified level above noise [5-12] . A phantom for measuring the maximum depth of
penetration is shown in Figure A.1 in Annex A. The essential components of this phantom
include a block of tissue-mimicking material with background scatterers that give rise to echo
signals. The tissue-mimicking material shall have the following properties:
–1
Speed of sound: (1 540 ± 15) m s at 3 MHz
–3
Density: (1,00) ± 0,03 g cm
–1 –1
Specific attenuation coefficient (0,7 ± 0,05) dB cm MHz in the 1 MHz to 15 MHz
frequency range
–4 –1 –1
Backscatter coefficient:  (3 × 10 cm sr ) ± 3 dB at 3 MHz; with a “frequency to
n
the n” (f ) dependence, where 2 < n < 4 from 1 MHz to
15 MHz. The value of the backscatter coefficient of the
phantom shall be reported as a function of frequency,
together with the results obtained with the phantom.
Dimensions: The phantom shall provide a uniformly scattering and
attenuating field that extends to a depth of at least 20 cm
for testing penetration depth at low frequencies (less than
5 MHz). The lateral and elevational dimensions shall be
such that there is at least a 6 cm wide by 6 cm thick region
of uniform tissue-mimicking material at distances
corresponding to the maximum depth of penetration for the
scanner and transducer under study. Larger cross-
sections may be required to provide a uniform region when
testing 3-D scanning systems.
___________
1)
Figures in square brackets refer to the Bibliography.

61391-2 © IEC:2010 – 15 –
Suitable phantoms for this test can be constructed using, for example, water-based gels
having microscopic inhomogeneities that are uniformly distributed throughout to produce the
desired attenuation level [13-18]. Such phantoms also require solid particles, such as 40-
micrometer diameter glass beads to provide backscattered signals at a controlled amplitude
)
[18,19]. A number of manufacturers can produce tissue-mimicking materials and phantoms
that follow these specifications.
6.2.3 Phantoms to estimate local dynamic range
An estimate of the local dynamic range can be obtained easily in the clinic by scanning
phantoms that contain spherical, cylindrical or truncated cylindrical objects, whose
backscatter coefficients vary by known amounts relative to the background material [20].
Backscatter variations of up to 24 dB (15 dB greater than the background, 9 dB less than the
)
background) are available in some commercially available phantoms .
6.3 Test equipment for measuring local dynamic range
The most convenient method for measuring local dynamic range is to use signal injection,
whereby acoustic pulses having precisely controlled amplitudes are applied to the imaging
system transducer directly [21-24]. Figure 1 presents a typical setup. The measurement
)
requires a signal generator that produces sine-wave voltage signals at a frequency that is
within the bandwidth of the transducer-imaging system under test. A planar, single-element
transducer, whose centre frequency also is within the bandwidth of the system transducer,
serves as a coupling device between the signal generator and the system transducer. The
diameter of the coupling transducer should be smaller than 1/3 the aperture of the system
transducer. A test should be performed to determine the dependence of the acoustic output of
the coupling transducer with driving voltage. This can be done using methods described in
IEC 61161:1992 [4]. The coupling transducer is driven with a sinusoidal voltage signal by the
signal generator. The acoustic output of the coupling transducer should be proportional to the
driving voltage to within 2,0 dB for acoustic signal level variations equal to the local dynamic
range of the ultrasound system under test.
)
An external electrical attenuator is placed between the signal generator and the coupling
transducer. Alternatively, some signal generators have suitable built-in attenuators. The
attenuator should have a range of at least 100 dB over the 1 MHz to 15 MHz range.
___________
2)
These include, for example, ATS Labs; Bridgeport, CT, USA (www.atslabs.com); CIRS, Norfolk, VA, USA
(www.cirsinc.com); and Gammex/RMI, Middleton, WI, USA (www.gammex.com). This information is given for
the convenience of users of this document and does not constitute an endorsement by IEC of these companies.
3)
An example of a suitable phantom is the Model 439 general purpose phantom, ATS Labs, Bridgeport, CT, USA
(www.atslabs.com). This information is given for the convenience of users of this document and does not
constitute an endorsement by IEC of this product.
4)
For example, the Model 33220A Function Generator, Agilent Technologies, Santa Clara, CA, USA. This
information is given for the convenience of users of this document and does not constitute an endorsement by
IEC of this product.
5)
For example, the Model 839, Kay Elemetrics Corp, Pine Brook, NJ, USA. This information is given for the
convenience of users of this document and does not constitute an endorsement by IEC of this product.

– 16 – 61391-2 © IEC:2010
IEC  2606/09
Key:
1 Displayed B - mode signal
2 Ultrasound system
3 Signal generator
4 Attenuator
5 System transducer
6 Coupling transducer
Figure 1 – Arrangement for measuring local dynamic range
using an acoustic-signal injection technique
An equivalent alternative arrangement uses a custom designed burst generator [21] for this
measurement (Figure 2). With such units, in response to each transmit pulse from the imaging
system transducer, the coupling transducer produces an electrical-voltage signal that triggers
the burst generator. Following a user-defined time delay, which typically is between 10 μs and
100 μs depending on the field of view of the scanner, the generator produces one or more
electrical pulses. These are applied to the coupling transducer, which then transmits a series
of acoustic pulses into the system transducer. After signal- and image-processing by the
ultrasound system, these pulses are presented as apparent echoes in the image memory and
on the B-mode image display. The location of the apparent echo signals on the image
depends on the time delay set in the burst generator and on the area on the system
transducer aperture that is in contact with the coupling transducer. The generator must
provide signal level variations that extend over a range that is greater than the local dynamic
range of the system under test.

61391-2 © IEC:2010 – 17 –
IEC  2607/09
Key:
1 Displayed B - mode signal
2 Ultrasound system
3 Attenuator
4 Burst delay
5 Triggered burst generator
6 Coupling transducer
7 System transducer
Figure 2 – Arrangement for measuring local dynamic range using
an acoustically-coupled burst generator
A third possible arrangement applies signal injection directly to the ultrasound system. With
this arrangement, conditioned signals of known amplitude, frequency, and duration are fed
into the system amplifiers, bypassing the transducer. With such arrangements, precisely
controlled changes in simulated echo-signal amplitude can be introduced, and the system
response to these changes can be quantified. Direct injection has been used extensively on
systems employing single-element transducers [22-24]. Devices that apply signal injection for
imaging systems employing transducer arrays are becoming commercially available as well,
and these are noted in 7.2.3 below.
6.4 Digitized image data
Test criteria described in this document are applied to digitized image data derived from the
ultrasound scanner being evaluated. In all cases, image-pixel brightness (gray) levels for all
spatial locations in the image must be available. Image data typically are in a matrix
consisting of at least 300 × 300 pixels and at least 8 bits (255 levels) of gray-scale resolution.

– 18 – 61391-2 © IEC:2010
Scanners for which this standard applies may be grouped according to the source of the
digitized image data. The first group includes systems for which digitized image data are
directly available from the scanner or over an image network. Sources of digitized image data
from this group include the following:
Direct DICOM [25]-images from the scanner. Image data in a DICOM format are available on
most scanners. Software capable of transferring and opening DICOM formatted images is
available.
Digital image files available
...