IEC TS 62791:2022
(Main)Ultrasonics - Pulse-echo scanners - Low-echo sphere phantoms and method for performance testing of grey-scale medical ultrasound scanners applicable to a broad range of transducer types
Ultrasonics - Pulse-echo scanners - Low-echo sphere phantoms and method for performance testing of grey-scale medical ultrasound scanners applicable to a broad range of transducer types
IEC TS 62791:2022 defines terms and specifies methods for quantifying detailed imaging performance of real-time, ultrasound B-mode scanners. Detail is assessed by imaging phantoms containing small, low-echo spherical targets in a tissue-mimicking background and analysing sphere detectability. Specifications are given for phantom properties. In addition, procedures are described for acquiring images, conducting qualitative analysis of sphere detectability, and carrying out quantitative analysis by detecting sphere locations and computing their contrast-to-noise ratios. With appropriate choices in design, results can be applied, for example:
• to assess the relative ability of scanner configurations (scanner make and model, scan head and console settings) to delineate the boundary of a tumour or identify specific features of tumours;
• to choose scanner control settings, such as frequency or the number and location of transmit foci, which maximize spatial resolution;
• to detect defects in probes causing enhanced sidelobes and spurious echoes.
The types of transducers used with these scanners include:
a) phased arrays,
b) linear arrays,
c) convex arrays,
d) mechanical sector scanners,
e) 3-D probes operating in 2-D imaging mode, and
f) 3-D probes operating in 3-D imaging mode for a limited number of sets of reconstructed 2 D images.
The test methodology is applicable for transducers operating in the 1 MHz to 23 MHz frequency range.
IEC TS 62791:2022 cancels and replaces the first edition published in 2015. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition.
a) It introduces necessary corrections to the analysis methods; these have been published in the literature.
b) It increases the range of contrast levels of low-echo spheres in phantoms that meet this Technical Specification. Previous specification was -20 dB, but two additional levels, -6 dB and either -30 dB or, if possible, -40 dB, are now specified.
c) It includes a wider range of uses of the methodology, including testing the effectiveness of scanner pre-sets for specific clinical tasks and detecting flaws in transducers and in beamforming.
d) It decreases the manufacturing cost by decreasing phantoms' dimensions and numbers of low-echo, backscattering spheres embedded in each phantom.
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IEC TS 62791 ®
Edition 2.0 2022-07
TECHNICAL
SPECIFICATION
colour
inside
Ultrasonics – Pulse-echo scanners – Low-echo sphere phantoms and method
for performance testing of grey-scale medical ultrasound scanners applicable to
a broad range of transducer types
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IEC TS 62791 ®
Edition 2.0 2022-07
TECHNICAL
SPECIFICATION
colour
inside
Ultrasonics – Pulse-echo scanners – Low-echo sphere phantoms and method
for performance testing of grey-scale medical ultrasound scanners applicable to
a broad range of transducer types
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 11.040.50; 17.140.50 ISBN 978-2-8322-3922-3
– 2 – IEC TS 62791:2022 © IEC 2022
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 10
2 Normative references . 10
3 Terms and definitions . 11
4 Symbols . 15
5 General and environmental conditions . 16
6 Equipment required . 17
6.1 General . 17
6.2 Phantom geometries . 17
6.2.1 Low-contrast phantoms for assessing the ability to delineate tumour
boundaries . 17
6.2.2 High-contrast phantoms to evaluate scanner performance, tune scanner
pre-sets, and detect defects in probes . 18
6.2.3 Total internal reflection surfaces . 19
6.2.4 Spatially random distribution of low-echo spheres. 19
6.3 Ultrasonic properties of the tissue-mimicking (TM) phantoms . 19
7 Data acquisition assuming a spatially random distribution of low-echo spheres . 20
7.1 Methodology . 20
7.1.1 General . 20
7.1.2 Mechanical translation . 20
7.1.3 Manual translation with cine-loop recording . 21
7.2 Storage of digitized image data . 22
7.3 Digital image files available from the scanner itself . 23
7.4 Image archiving systems . 23
8 Automated data analysis for quantifying low-echo sphere detectability . 23
8.1 General . 23
8.2 Computation of mean pixel values (MPVs) . 23
8.3 Additional restrictions for sector images . 29
8.3.1 Convex arrays . 29
8.3.2 Phased arrays . 30
8.4 Determination of the LSNR -value for a given depth interval . 30
m
8.4.1 Preliminaries . 30
8.4.2 Computation of LSNR for depth interval label d . 31
md
8.4.3 Standard error corresponding to each LSNR -value . 31
md
9 Visual assessments of images . 31
9.1 Image comparisons . 31
9.2 Semi-quantitative image analysis . 32
Annex A (informative) Example of a phantom for performance testing in the 1 MHz to
7 MHz frequency range . 34
Annex B (informative) Illustrations of the computation of LSNR -values as a function
md
of depth . 36
Annex C (informative) Sufficient number of data images to assure reproducibility of
results . 43
C.1 General . 43
C.2 Phantom with 3,2-mm-diameter, −20 dB low-echo sphere, having two
spheres per millilitre . 43
C.3 Phantom with 2-mm-diameter, −20 dB spheres and eight spheres per
millilitre . 48
Annex D (informative) Example of a phantom for performance testing in the 7 MHz to
23 MHz frequency range . 52
Annex E (informative) Determination of low-echo sphere positions to within D/8 in x-,
y- and z-Cartesian coordinates . 54
E.1 Procedure . 54
E.2 Argument for the choice of seven MPV nearest-neighbour sites for
determining the centres of low-echo spheres . 56
Annex F (informative) Tests of total internal reflection produced by alumina and plate-
glass, plane reflectors . 57
Annex G (informative) Results of a test of reproducibility of LSNR as a function of
md
depth for a phantom with 4-mm-diameter, −20 dB spheres, having two spheres per
millilitre . 64
Annex H (informative) Results for low-echo sphere concentration dependence of
LSNR as a function of depth for phantoms with 3,2-mm-diameter, −20 dB spheres . 66
md
Annex I (informative) Comparison of two different makes of scanner with similar
transducers and console settings . 70
Annex J (informative) Special considerations for 3-D probes . 72
J.1 3-D probes operating in 2-D imaging mode . 72
J.2 2-D arrays operating in 3-D imaging mode for determining LSNR -values as
md
a function of depth for reconstructed images . 72
J.3 Mechanically driven 3-D probes operating in 3-D imaging mode . 72
Bibliography . 73
Figure 1 – Flow chart . 22
Figure 2 – Schematic of the image plane nearest to the nth low-echo sphere and not
influenced by the presence of an image boundary . 25
Figure 3 – Modification of Figure 2 showing a vertical image boundary (solid line) and
a parallel dashed line, between which (MPV) values are excluded from computation
ijk
of S or σ in Formula (2) . 26
mBn Bn
Figure 4 – Limiting case of Figure 3 where the vertical image boundary is tangent to
the imaged low-echo sphere . 27
Figure 5 – Modification of Figure 2 showing a 45° sector image boundary (solid line)
and a parallel dashed line, between which (MPV) values are excluded from
ijk
computation of S or σ in Formula (2) . 28
mBn Bn
Figure 6 – Limiting case of Figure 5 where the 45° sector image boundary is tangent to
the imaged low-echo sphere . 29
Figure 7 – Usefulness of simple visual inspection of images of a standardized low-echo
sphere phantom . 32
Figure 8 – Zones over which at least half of the spheres appear clearly outlined as a
nearly full-size circle and are free of echoes (Zone 1) or an average of more than one
sphere per slice can be discerned (Zone 2) . 33
Figure A.1 – End view of the phantom applicable for 1 MHz to 7 MHz showing the
spatially random distribution of 3,2-mm-diameter, −6 dB spheres . 34
Figure A.2 – Top view of phantom with 3,2-mm-diameter, −6 dB spheres . 35
Figure B.1 – Convex-array image of a prototype 4-mm-diameter, −20 dB sphere
phantom for use in the 1 MHz to 7 MHz frequency range . 36
– 4 – IEC TS 62791:2022 © IEC 2022
Figure B.2 – Auxiliary figures relating to Figure B.1 . 37
Figure B.3 – Results corresponding to Figure B.1 and Figure B.2, demonstrating
reproducibility . 38
Figure B.4 – Results corresponding to Figure B.1, Figure B.2 and Figure B.3 . 39
Figure B.5 – One of 80 parallel, linear-array images of the phantom containing
4-mm-diameter, −20 dB spheres, imaged at 4 MHz with the transmit focus at 3 cm
depth . 39
Figure B.6 – Three successive images of the set of 80 frames addressed in Figure B.5,
where imaging planes were separated by D/4 equal to 1 mm . 40
Figure B.7 – Results fo
...
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