Amendment 1 - Ultrasonics - Pulse-echo scanners - Part 1: Techniques for calibrating spatial measurement systems and measurement of point-spread function response

Amendement 1 - Ultrasons - Scanners à impulsion et écho - Partie 1: Techniques pour l'étalonnage des systèmes de mesure spatiaux et des mesures de la réponse de la fonction de dispersion ponctuelle du système

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Publication Date
09-Jul-2017
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IEC 61391-1:2006/AMD1:2017 - Amendment 1 - Ultrasonics - Pulse-echo scanners - Part 1: Techniques for calibrating spatial measurement systems and measurement of point-spread function response
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IEC 61391-1
Edition 1.0 2017-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
A MENDMENT 1
AM ENDEMENT 1
Ultrasonics – Pulse-echo scanners –
Part 1: Techniques for calibrating spatial measurement systems and
measurement of system point-spread function response
Ultrasons – Scanners à impulsion et écho –
Partie 1: Techniques pour l'étalonnage des systèmes de mesure spatiaux et des
mesures de la réponse de la fonction de dispersion ponctuelle du système
IEC 61391-1:2006-07/AMD1:2017-07 (en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 61391-1
Edition 1.0 2017-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
A MENDMENT 1
AM ENDEMENT 1
Ultrasonics – Pulse-echo scanners –
Part 1: Techniques for calibrating spatial measurement systems and
measurement of system point-spread function response
Ultrasons – Scanners à impulsion et écho –
Partie 1: Techniques pour l'étalonnage des systèmes de mesure spatiaux et des
mesures de la réponse de la fonction de dispersion ponctuelle du système
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.140.50 ISBN 978-2-8322-5557-5

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

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® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 61391-1:2006/AMD1:2017
© IEC 2017
FOREWORD
This amendment has been prepared by IEC technical committee 87: Ultrasonics.

This bilingual version (2018-04) corresponds to the monolingual English version, published in

2017-07.
The text of this amendment is based on the following documents:
FDIS Report on voting
87/650/FDIS 87/653/RVD

Full information on the voting for the approval of this amendment can be found in the report

on voting indicated in the above table.
The French version of this amendment has not been voted upon.

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

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

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

related to the specific publication. At this date, the publication will be
• 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.
____________
2 Normative references
Replace:

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

the frequency range 0,5 MHz to 15 MHz
with:

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

medical ultrasonic fields up to 40 MHz
Insert the following new normative references in proper numerical sequence:
---------------------- Page: 4 ----------------------
IEC 61391-1:2006/AMD1:2017 – 3 –
© IEC 2017

IEC 60050-801:1994, International Electrotechnical Vocabulary – Chapter 801: Acoustics and

electroacoustics

IEC 60050-802:2011, International Electrotechnical Vocabulary – Part 802: Ultrasonics

3 Terms and definitions
Replace the first two paragraphs with the following new paragraph:

For the purposes of this document, the terms and definitions given in IEC 60050-801:1994,

IEC 60050-802:2011, IEC 62127-1:2007 and the following apply. See also related

International Standards, Technical Specifications and Technical Reports for definitions and

explanations [1] [2] [3] [4] [34] [35] [36] [37] [38] [39].
3.25
point-spread function
PSF
Add the following new sentence at the end of the NOTE:
The problem is solved by PSF mapping – see Annex D.
Add the following new terms and definitions to Clause 3, starting with 3.45.
3.45
accuracy
closeness of agreement between a test result and the accepted reference value
[SOURCE: ISO 5725-1:1994, 3.6]
3.46
axial resolution in a PSF-map

twice the Half-Width-at-Half-Maximum (HWHM) of a function’s trace created from a set of

increasing pixel values, commencing near zero and terminating at the first maximum value

(centre of the PSF) and representing the leading edge of the echo signal from a point reflector

located on the main beam axis

Note 1 to entry: The axial resolution in a PSF map differs from the axial resolution specified by 3.5. It is used

for the PSF-mapping only to simplify the data acquisition.

Note 2 to entry: A detailed explanation of the axial resolution in the PSF-map measuring method is in D.6.1.4.

Note 3 to entry: The axial resolution mainly depends on the ultrasound frequency used, not on sonograph

construction.
Note 4 to entry: Axial resolution in a PSF-map is expressed in metres.
3.47
brightness
luminance as perceived by the human visual system
[SOURCE: IEC 62563-1:2009, 3.1.2]
3.48
contrast

ratio of the difference of the luminance of two image areas, L − L , divided by the average of

1 2
the two luminance values:
---------------------- Page: 5 ----------------------
– 4 – IEC 61391-1:2006/AMD1:2017
© IEC 2017
C = 2 (L − L )/(L + L )
1 2 1 2
[SOURCE: IEC 62563-1:2009, 3.1.6]
3.49
dynamic imaging
real-time imaging

imaging with a frame rate that is high enough to observe moving structures in apparently

continuous motion
3.50
elevational resolution in a PSF-map

difference of point-reflector displacements in passing through the scanning plane in an

elevational direction, which result in decreases of MER of −6 dB compared to the MER-value

in the beam centre

Note 1 to entry: The elevational resolution in a PSF-map differs from the elevational resolution specified by

3.12. It is used for the PSF-mapping only to simplify the data acquisition.
Note 2 to entry: Detailed explanation of the method is in D.6.1.3.
Note 3 to entry: Elevational resolution in a PSF-map is expressed in metres.
3.51
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
3.52
profile line

set of pixel values ordered along an abscissa according to the sequence during their

acquisition
3.53
lateral resolution in a PSF-map
Full-Width at Half-Maximum (FWHM) of the PSF, measured in a lateral direction

Note 1 to entry: The lateral resolution in a PSF-map differs from the lateral resolution specified by 3.17. It is

used for the PSF-mapping only to simplify the data acquisition.
Note 2 to entry: Detailed explanation of the method is in D.6.1.2.
Note 3 to entry: Lateral resolution in a PSF-map is expressed in metres.
3.54
measuring grid

matrix of points specified by Cartesian coordinates x and z defined in a plane parallel to the

i j
scanning plane

Note 1 to entry: Each point determines the position (x ,z ) in which individual measurement of PSF is performed.

i j

Note 2 to entry: The step ∆x is defined as an increment x – x in the lateral direction. The step ∆z is defined as

i+1 i
an increment z – z in the axial direction.
j+1 j
3.55
performance evaluation
tests performed to assess specific absolute performance of the object tested

Note 1 to entry: Typical times for ultrasound-system performance evaluation are at pre-purchase evaluation,

new- and repaired-system acceptance testing, at time of performance difficulties, and at end-of-useful-life

evaluations.
---------------------- Page: 6 ----------------------
IEC 61391-1:2006/AMD1:2017 – 5 –
© IEC 2017
[SOURCE: IEC TS 62736:2016, 3.5]
3.56
precision

closeness of agreement between independent test results obtained under stipulated

conditions
[SOURCE: ISO 5725-1:1994, 3.12]
3.57
scanning window

area on the surface of the test tank dedicated for transducer application to obtain a suitable

sonogram of the target

Note 1 to entry: It is important that the scanning window be covered by flexible foil made of material with similar

acoustic properties to the working liquid to avoid ultrasound field reflections and absorption.

Note 2 to entry: The foil flexibility should assure proper acoustical contact of any type of curved transducer.

Note 3 to entry: It is important that the foil covering the scanning-window be tough enough to prevent its damage

during coupling the measured transducer to the scanning window, to prevent resultant leakage of working liquid

from the measuring tank.

Note 4 to entry: The scanning window has the identical function as the test object scanning surface in the

case of tissue-mimicking test objects (see 3.34).
3.58
side-lobe signal

echo signal generated by ultrasound signal transmitted/received in a direction different from

the central axis of the transducer
3.59
test tank

tank designed to be suitable for providing specified kind of tests, which is filled with a

working liquid and equipped with scanning window(s)
Replace the title of Clause 4 with the following new title:
4 Symbols and abbreviated terms
Add the following symbols and abbreviated terms to Clause 4:
D diameter of the reflector sphere
A greatest a evaluated for whole measured volume
r,max r,max
a MER pixel value evaluated from ROI
r,max

a (x,y,z) MER pixel value evaluated from ROI scanned for reflector in position (x,y,z)

r,max
C contrast
overall gain

I(x,y,z) ROI specified in a digital picture of scan stored with reflector in position (x,y,z)

M number of quantization levels defined by M = 2 where m is number of pixel
bits
p pixel size in lateral (azimuthal) direction
p pixel size in axial direction
R axial resolution in a PSF-map
A,PSF
R elevational resolution in a PSF-map
E,PSF
R lateral resolution in a PSF-map
L,PSF
---------------------- Page: 7 ----------------------
– 6 – IEC 61391-1:2006/AMD1:2017
© IEC 2017
W value of FWHM (full width at half of maximum)
F,HM
W value of HWHM (half width at half of maximum)
H,HM
W normalized W according to Formula (D.3) in D.6.1.2
F,HM,n F,HM
W normalized W according to Formula (D.3) in D.6.1.2
H,HM,n H,HM
λ ultrasound wavelength in the working liquid, calculated from the nominal
frequency of the transducer used
ATGC automatic time-gain compensation
FWHM full width at half of maximum
HFHM half width at half of maximum
LUT look-up table
MER maximum echo received
PSF point-spread function
RF radio frequency
ROI region of interest
TGC time-gain compensation
US ultrasound
6.1 Test methods
Replace:
c) a tank containing degassed working liquid.
with:

c) a tank equipped with target holder to position the target at accurately specified

positions and containing degassed working liquid.
Replace:
The specifications of these devices are given in the annexes.
with:
The specifications of these devices are given in Annexes A, B, C and D.
8.2 Test methods
Replace:
b) a tank containing degassed liquid;
with:

b) a tank containing degassed liquid and, optionally, movable targets as described in

Clause C.4 and D.5.4.2;
8.4.1 General
Add, at the end of 8.4.1, the following new sentence:

“A setting should be specified by a test instruction for each test, if it differs from the general

recommendations. See D.5.2.”
---------------------- Page: 8 ----------------------
IEC 61391-1:2006/AMD1:2017 – 7 –
© IEC 2017
8.5.1 General

Add, to the end of the fifth paragraph starting “To overcome this limitation …”, the following

new text:

“The complications generated by interference and multiple reflections inside the spherical

target may be solved by time-domain analysis of the received echo when a larger and/or

highly reflective sphere is used. See D.5.4.2.”
8.5.4 Scan slice thickness (elevational PSF and LSF) or elevational resolution
Add, at the end of 8.5.4, the following new text:

“The most accurate and flexible method to derive the complex set of parameters based on the

PSF mapping analysis is described in Annex D.”
C.4 Movable single filament or wire in water (Figures C.3, C.4)
Add, at the end of Clause C.4, the following new single-sentence paragraph:

“The use of a movable spherical target for assessing quality parameters derived by PSF-

mapping analysis is described in Annex D. ”
Insert after Annex C the following new Annex D
---------------------- Page: 9 ----------------------
– 8 – IEC 61391-1:2006/AMD1:2017
© IEC 2017
Annex D
(informative)
Quality parameters derived by PSF-mapping analysis
D.1 General

A quality assessment system is vitally needed to provide an accurate and well-defined set of

production-quality parameters for new or refurbished scanners or transducers in acceptance

tests before their introduction to medical practice. It is important that products delivered by

third-party sales groups, system-refurbishers and/or transducer manufacturers be carefully

tested to be able to declare technical parameters of their products to be comparable to those

of the new, originally manufactured systems. The methods used for quality assessment in

medical applications are not certain and accurate enough to be used for such kinds of

technical performance evaluation. PSF-mapping analysis gives reliable parameters suitable

for this kind of tests. These parameters do not directly indicate the effectivity of a clinical

diagnostic process, even though a close correlation between the assessed technical quality

and success in the diagnostic process may be expected [40].

The ultrasound scanner used as a diagnostic system is composed of the system-control/user-

interface unit and the ultrasonic-transducer assembly. Either unit can contain the transmitter-

and the receiver- electronic systems and some of the beam-former electronics. The

ultrasonic transducer converts electrical signals to ultrasound field and vice versa. Electrical

and acoustic parameters of the transducer determine quality of the scanning ultrasound

beam. The electronic system controls the transmitted and received ultrasound signal,

conversion from mechanical to electrical signals, and the signal processing and conversion to

video-signal inputted to the imaging unit. The imaging unit transfers the information to the

human preceptors. The PSF-distribution analysis evaluates qualitative parameters of the

whole ultrasound-scanner system, excluding the display unit. The analysed signal is affected

by the quality of the whole imaging cycle, and the transmitting and receiving parts of the

scanner. The analysed system function is affected by a complex set of control functions.

Therefore, it is important that the combination of the control settings of the scanner be exactly

specified and recorded as a part of the measurement.
D.2 Method

Annex D describes a method for precise and reliable measurement of several qualitative

parameters of whole ultrasound scanning systems including both the transmitting and

receiving parts of the systems, excluding the parameters of scanner display. The method is

based on PSF-distribution analysis over a scanning area. In the case of PSF-mapping, the

measured parameters are derived by analysis of sonograms generated by scanning a

spherical target moving over a defined scanning volume on a specified trajectory.

The PSF-mapping system evaluates a set of parameters acquired over a user-defined area in

one scanning plane of a B-mode grey-scale sonogram, scanned in a tank filled by degassed

working liquid and using one measuring procedure. The whole target sonogram is not

evaluated in the PSF-mapping analysis. The test signal is obtained by reflection of a

transmitted ultrasound wave from a point-reflector surface and working-liquid boundary only.

The point reflector used is a highly reflective sphere of diameter D [41].

The method is suitable for all kinds of echo(reflections)-evaluating sonographs using different

types of beam-forming and plane-wave compounding of ultrasound signal in the frequency

range 0,5 MHz to 50 MHz. The upper frequency limit is determined by a ball target of

minimum diameter available to assure reflection effectivity and fulfil the condition λ ≤ D ≤ 4λ,

where λ is the ultrasound wavelength in the working liquid [42]. Further limiting factors are a

minimum size of step and precise mechanical construction of the positioning system to assure

measurement reliability and adequate scan size.
---------------------- Page: 10 ----------------------
IEC 61391-1:2006/AMD1:2017 – 9 –
© IEC 2017

The method is relevant for all the types of transducers used with these scanners, including

• mechanical probes including annular arrays,
• electronic phased arrays,
• linear arrays,
• curved arrays,
• two-dimensional arrays, and
• 3D-volume scanning probes based on a combination of the above types.

The PSF-measuring system is not a tissue-mimicking object. It is dedicated to performing

accurate, stable and reliable measurements under conditions appropriate to achieving these

measurements of parameters, some of which may be obtained by use of sophisticated

electronic measurements of the scanner’s electronic system and some by PSF-mapping

analysis only [43].
The following data are acquired and are analysed using the method:

a) the ROI digital image stored for the scanned-plane axis in each point of the measuring

grid;
b) the echo-signal amplitude distribution over the measured area;

c) the distribution of the parameter W which is Full-Width-at-Half-Maximum (FWHM) of

F,HM

the point-spread function (PSF) in the azimuthal direction over the measured area;

d) the distribution of the parameter W Half-Width-at-Half-Maximum (HWHM) of the
H,HM
point-spread function (PSF) in the axial direction over the measured area;

e) the peak echo-amplitude received a (x,y,z) at each y step of the target position in the

r,max k
elevation (transversal) direction;

f) the (x,y,z) coordinates set for stored position of the point reflector generating a (x,y,z)

r,max

from MER in each point of the measuring grid (position in centre of ultrasound beam).

Data analysis derives the following ultrasound scanner parameters and functions:
1) focal areas in both the azimuth and the elevation directions;
2) visualization of the distribution of ultrasound scanning lines;
3) manufacturer’s preloaded TGC function;
4) width (elevation) of the scanning plane over the depth of scan;
5) side-lobes signal-level distribution in the scan plane;
6) amplification uniformity in the azimuth direction;
7) scan geometry linearity and accuracy.
D.3 Environmental conditions

The most temperature-sensitive parameters are those assessing geometry of the sonogram

and related calculations. The temperature-dependent deviations may be compensated

mathematically from known working-liquid temperature and thermal coefficient of speed of

sound.
Water condensation on electronic system components should be avoided.
D.4 General requirements of the method

Ultrasound waves produce a PSF-signal that is neither singular nor isotropic. Furthermore,

the ultrasound PSF can be asymmetrical, having different axial and lateral dimensions, and it

---------------------- Page: 11 ----------------------
– 10 – IEC 61391-1:2006/AMD1:2017
© IEC 2017

also varies with distance from the transducer in both the axial and the azimuthal directions.

Thus, it is important that many different measurements of the PSF at different positions and

depths be performed to obtain representative values of the system’s imaging performance at

specific positions along the beam axis. It is also important that the measured area be covered

by a grid of the measuring points, the density of which is determined by the expected

parameters and the accuracy of the measurement [44].

NOTE For example, determination of a focal point’s position may need an axial step ∆z = 5 mm; visualization of

scanning lines demands an azimuthal step ∆x = 0,1 mm for a conventional linear transducer of nominal frequency

3 MHz.
The following features are necessary to apply the PSF-analyser to the sonograph:
a) The sonograph to be tested:

– video-signal output of live, dynamic scanning available in analog (composite) or digital

(DVI-D, HDMI) form;

– operating instructions or skilled operator to assure proper manipulation and operating

adjustment;

– record of proper evidence and registration of the measurement process, including

identification of operator and all apparatus used, record of parameters preset in the

measured system, record of environmental conditions, including a time stamp.
b) The basic configuration of the measurement tank:
– The scanning window(s) is(are) localized in the side wall(s) of the tank.

– The spherical-target positioning system is fixed on top of the tank, controlling

movement of the target fixed in a holder.
– Filling the tank with degassed working liquid is recommended to prevent bubble

generation in the working fluid. Bubbles may mimic the point reflector and/or produce

spurious reflections from the point reflector after having accumulated on it, due to

surface tension.
– Temperature should be kept in the specified range to eliminate measurement

uncertainties generated by dependence of the speed of ultrasound propagation upon

temperature.
c) The transducer:

– The transducer is acoustically coupled to the scanning window by standard coupling

ultrasound gel. The scanning window is covered by tough, flexible foil made of

material with similar acoustic properties to the working liquid to avoid ultrasound field

reflections and absorption.

– The scanning plane is oriented in the horizontal direction and the transducer is fixed to

keep the whole slice thickness below the water surface. It is important that the lateral

orientation of the transducer be specified.
d) The positioning system:

– A computer-controlled micromanipulator is used to move the target or transducer to a

determined position. It is important that mechanical construction, accuracy and

stability of the positioning system correspond with ultrasound frequency. The shorter

the wavelength, the more accurate and robust the system should be to avoid
systematic measuring errors.
e) The control and analysing system:

– The software controls the video-signal acquisition, determines ROI, selects and saves

the ROI frames to be used for analysis and finally maintains the complex analysis of

the stored information.
– The basic parameters used for PSF-analysis are the W (Full Width at Half
F,HM
Maximum, i.e. at −6 dB down from a ) and the pixel level of noise at an area
r,max
without reflections.
---------------------- Page: 12 ----------------------
IEC 61391-1:2006/AMD1:2017 – 11 –
© IEC 2017

– The W depends upon the intensity of the received signal. Therefore, it is important

F,HM

that the receiving gain and output power be properly adjusted to utilize the whole

dynamic range of the analyser.
D.5 Measuring conditions
D.5.1 General

In Figure D.1 a principal schematic of the PSF-analyser is introduced. The PSF-analyser

consists of the data-acquisition components (test-tank and point-reflector parts of the

schema), a linear transducer, a personal computer (PC) with video-signal input, running

acquisition and analysis software. The sonograph being measured is shown with a linear

transducer but the results analysis is displayed for a sector-scan transducer to illustrate

transducer-type independency of the system.
Tested system
Sono-
graph
Video
ROI
PSF
IEC
Figure D.1 – Principal schematic of the PSF-analyser function
D.5.2 Sonograph
D.5.2.1 General

Sonographs are equipped with a large set of different control functions to ensure optimal

handling of received ultrasound signals to create the best image. These control functions

affect remarkably the measurement results because the method evaluates the signal after it

has passed through a whole imaging system. Therefore, it is important that all the

adjustments and settings be carefully documented in the measuring protocol to be available

for use for r
...

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