I E C TS 62 ® Edition 201 5-09 TE C H N I C AL S P E C I F I C ATI ON colour i n sid e U l tras on i cs – P u l s e-ech o s can n e rs – Low-ech o s ph ere ph an tom s an d m eth od for pe rform an ce tes ti n g of g y-s cal e m e d i cal u l tras ou n d scan n ers appl i cabl e to IEC TS 62791 :201 5-09(en) a broad ran g e of tran s d u ce r types T H I S P U B L I C AT I O N I S C O P YRI G H T P RO T E C T E D C o p yri g h t © I E C , G e n e v a , S wi tz e rl a n d All rights reserved Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either IEC or IEC's member National Committee in the country of the requester If you have any questions about I EC copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or your local I EC member National Committee for further information IEC Central Office 3, rue de Varembé CH-1 21 Geneva 20 Switzerland Tel.: +41 22 91 02 1 Fax: +41 22 91 03 00 info@iec.ch www.iec.ch Ab ou t th e I E C The I nternational Electrotechnical Commission (I EC) is the leading global organization that prepares and publishes I nternational Standards for all electrical, electronic and related technologies Ab o u t I E C p u b l i ca ti o n s The technical content of IEC publications is kept under constant review by the IEC Please make sure that you have the latest edition, a corrigenda or an amendment might have been published I E C Catal og u e - webstore i ec ch /catal og u e The stand-alone application for consulting the entire bibliographical information on IEC International Standards, Technical Specifications, Technical Reports and other documents Available for PC, Mac OS, Android Tablets and iPad I E C pu bl i cati on s s earch - www i ec ch /search pu b The advanced search enables to find IEC publications by a variety of criteria (reference number, text, technical committee,…) It also gives information on projects, replaced and withdrawn publications E l ectroped i a - www el ectroped i a org The world's leading online dictionary of electronic and electrical terms containing more than 30 000 terms and definitions in English and French, with equivalent terms in additional languages Also known as the International Electrotechnical Vocabulary (IEV) online I E C G l os sary - s td i ec ch /g l oss ary More than 60 000 electrotechnical terminology entries in English and French extracted from the Terms and Definitions clause of IEC publications issued since 2002 Some entries have been collected from earlier publications of IEC TC 37, 77, 86 and CISPR I E C J u st Pu bl i s h ed - webstore i ec ch /j u stpu bl i sh ed Stay up to date on all new IEC publications Just Published details all new publications released Available online and also once a month by email I E C C u stom er S ervi ce C en tre - webstore i ec ch /csc If you wish to give us your feedback on this publication or need further assistance, please contact the Customer Service Centre: csc@iec.ch I E C TS 62 ® Edition 201 5-09 TE C H N I C AL S P E C I F I C ATI ON colour i n sid e U l tras on i cs – P u l s e-ech o s can n ers – Low-e ch o s ph e re ph an tom s an d m eth od for perform an ce tes ti n g of g y-s cal e m e d i cal u l tras ou n d scan n ers appl i cabl e to a broad ran g e of tran s d u ce r types INTERNATIONAL ELECTROTECHNICAL COMMISSION ICS 1 040.50; 7.1 40.50 ISBN 978-2-8322-2902-6 Warn i n g ! M ake su re th a t you obtai n ed th i s pu bl i cati on from an au th ori zed d i s tri bu tor ® Registered trademark of the International Electrotechnical Commission –2– I EC TS 62791 : 201 © I EC 201 CONTENTS FOREWORD I NTRODUCTI ON Scope Norm ative references Terms and definitions Sym bols General and environm ental conditions Equipm ent required General Phantom geom etries Phantom s for use in the frequency range MH z to MH z 2 Phantom s for use in the frequency range MH z to M H z including "m icro-convex" arrays Total internal-reflection surfaces Spatiall y random distribution of low-echo spheres Ultrasonic properties of the tissue-mimicking (TM) phantom s Data acquisition assum ing a spatiall y random distribution of low-echo spheres Methodolog y Storage of digitized image data 7 Digital image files available from the scanner itself I m age archiving systems 8 Automated data analysis for quantifying low-echo sphere detectability 8 General 8 Computation of m ean pixel values ( MPVs) 8 Determination of the LSNR m -value for a given depth interval 21 Prelim inaries 21 Computation of the LSNR n -values and LSNR m -value in a given depth interval 21 3 Standard error corresponding to each LSNR n -value 21 Annex A (informative) Example of a phantom for perform ance testing in the MH z to MH z frequency range 22 Annex B (informative) I llustrations of the computation of LSNR m -values as a function of depth 24 Annex C (inform ative) Sufficient num ber of data images to assure reproducibility of results 29 C General 29 C Phantom with low-echo sphere diam eter 3, mm , having spheres per m illilitre 29 C Phantom with mm -diam eter, low-echo spheres and spheres per millilitre 32 Annex D (inform ative) Exam ple of a phantom for performance testing in the M H z to MH z frequency range 36 Annex E (informative) Determination of low-echo sphere positions to within D /8 in x, y and z Cartesian coordinates 39 E Procedure 39 E Argument for the choice of seven MPV nearest-neighbour sites for determ ining the centres of low-echo spheres 40 I EC TS 62791 : 201 © I EC 201 –3– Annex F (informative) Test of total internal reflection produced by alum ina and plateglass, plane reflectors 41 Annex G (inform ative) Results of a test of reproducibility of LSNR m versus depth for a phantom with m m -diam eter low-echo spheres and spheres per millilitre 48 Annex H (inform ative) Results for low-echo sphere-concentration dependence of LSNR m versus depth for phantoms with mm -diam eter spheres 50 Annex I (inform ative) Results for low-echo sphere-concentration dependence of LSNR m versus depth for phantom s with 3, mm -diameter spheres 53 Annex J (inform ative) Com parison of two different makes of scanner with sim ilar transducers and console settings 57 Annex K (informative) Special considerations for 3-D probes 59 K 3-D probes operating in 2-D imaging mode 59 K 2-D arrays operating in 3-D imaging m ode for determ ining LSNR m -values as a function of depth for reconstructed images 59 K Mechanicall y driven 3-D probes operating in 3-D im aging mode 59 Bibliograph y 60 Figure – Flow chart Figure – Schematic of an im age plane 20 Figure A – End view of the phantom applicable for MH z to MH z showi ng the spatiall y random distribution of 4-mm diam eter low-echo spheres 22 Figure A – Top view of phantom with m m -diam eter, low-echo spheres 23 Figure B – Convex-array im age of a prototype mm -diameter low-echo sphere phantom for use in the MH z to MH z frequency range 24 Figure B – Auxiliary figures relating to Figure B 25 Figure B – Results corresponding to Figures B and B 2, demonstrating reproducibility 25 Figure B – Results corresponding to Figures B , B and B 26 Figure B – One of 80 parallel linear-array im ages of the phantom containing m m diameter, low-echo spheres, at MH z with focus at cm 26 Figure B – Three successive im ages of the set of 80, separated by D /4 equal to mm 27 Figure B – Results for the cm -wide, cm -focus, linear array addressed in Figures B and B.6 27 Figure B – Results for the cm -wide, cm -focus, linear array addressed in Figures B 5, B and B 7, using all 80 im age frames corresponding to Figure B.7 28 Figure C.1 – One im age obtained from a phantom containing 3, mm -diameter, lowecho spheres by using a MH z linear array focused at cm 29 Figure C.2 – Reproducibility result for two independent sets of 70 images with a m ean number of low-echo sphere centres that is about per m m -depth interval 30 Figure C.3 – Results obtained by using both sets of 70 independent im ages corresponding to Figure C 30 Figure C.4 – Sector image (curved array) at 4, MH z with m ultiple foci at cm , cm and cm depths; the low-echo spheres are 3, mm in diam eter 31 Figure C.5 – Reproducibility results for a m ultiple-lateral-focus (4 cm, cm and cm) case corresponding to Figure C.4 31 Figure C.6 – Reproducibility results for the case corresponding to Figure C 5, except that there is a single focus at cm depth 32 Figure C.7 – Reproducibility results for the case corresponding to Figure C 5, except that there is a single focus at cm depth 32 –4– I EC TS 62791 : 201 © I EC 201 Figure C – I mage of the phantom containing mm -diam eter, low-echo spheres, made with a curved array having ,5 cm radius of curvature, with its focus at cm 33 Figure C.9 – Reproducibility results corresponding to Figure C 33 Figure C.1 – Results using all 00 images in the image set that gave rise to Figure C.9 34 Figure C.1 – I mage of the phantom containing mm -diameter, low-echo spheres, made with a high-frequency (1 M H z) linear array, laterall y focused at cm 34 Figure C.1 – Reproducibility results corresponding to Figure C 1 35 Figure C.1 – Results using all 200 images in the image set that gave rise to Figure C 35 Figure D.1 – End- and top-view diagram s of the phantom containing mm -diam eter, low-echo spheres for use in the MH z to MH z frequency range 37 Figure D.2 – I m age obtained by using the phantom containing mm -diam eter, lowecho spheres and a pediatric transducer with a radius of curvature of about , cm 38 Figure F – Average of images obtained by using a phased array 42 Figure F – Plot of the data with blue data computed in the left rectangle in Figure F and red data com puted in the right rectangle 42 Figure F – Plot of the data when the reflector is on the right side with blue computed in the left rectangle and red computed in the right rectangle 43 Figure F – The percentage by which the m ean pixel values resulting from reflections differ from the m ean pixel values not involving reflections 44 Figure F – Wide sector (1 53°), cm -radius-of-curvature transducer with alumina reflector on the left 45 Figure F – Plot of the data with blue computed in the left rectangle in Figure F and red com puted in the right rectangle 45 Figure F – Plot of the data when the reflector is on the right side with blue com puted in the left rectangle and red computed in the rig ht rectangle 46 Figure F – The percentage by which the m ean pixel values resulting from reflections differ from the m ean pixel values not involving reflections 46 Figure G – Exam ple image of the phantom with a 4, MH z curved array and two lowecho spheres per m illilitre 48 Figure G – Reproducibility results corresponding to the image set, one of which is shown in Figure G 49 Figure H – Example of an image from the im age set giving rise to the results in Figure H 2; the phantom contained an average of one mm -diam eter, low-echo sphere per millilitre 50 Figure H – Results corresponding to an image set, one of which is shown in Figure H 51 Figure H – Example of an image from the data set giving rise to the results in Figure H 4; the phantom contained an average of two mm -diameter, low-echo spheres per millilitre 51 Figure H – Results corresponding to an image set, one of which is shown in Figure H 52 Figure I – Exam ple of an im age from the m l − data set producing the results shown in Figure I 53 Figure I – Results for the phantom containing four 3, mm -diameter, low-echo spheres per m illilitre 54 Figure I – Exam ple of an im age from the m l − data set producing the results shown in Figure I 54 Figure I – Results for the phantom containing two 3, mm -diameter, low-echo spheres per m illilitre 55 I EC TS 62791 : 201 © I EC 201 –5– Figure I – Exam ple of an image from the ml − data set producing the results shown in Figure I 55 Figure I – Results for the phantom containing one 3, m m -diameter, low-echo sphere per millilitre 56 Figure J – Results for System A scanner and 7CF2 3-D (swept convex array) transducer focused at cm and operated at 4,5 M H z in 2-D m ode 57 Figure J – Results for System B scanner with a 4DC7-3 3-D (convex array) transducer, operated at MH z in 2-D m ode and focused at cm The sector angle and all other console settings mimicked those for the System A case (Figure J ) 57 –6– I EC TS 62791 : 201 © I EC 201 INTERNATI ONAL ELECTROTECHNI CAL COMMISSI ON U L T R AS O N I C S – P U L S E -E C H O S C AN N E RS – L O W -E C H O S P H E RE P H AN T O M S AN D M E T H O D F O R P E RF O RM AN C E T E S T I N G O F G R AY-S C AL E M E D I C AL U L T R AS O U N D S C AN N E RS AP P L I C AB L E T O A B RO AD R AN G E O F T R AN S D U C E R T YP E S FOREWORD ) The I nternati on al Electrotechni cal Comm ission (I EC) is a worl d wid e organization for stan dardization com prisin g all n ation al el ectrotechnical comm ittees (I EC National Comm ittees) The object of I EC is to prom ote internati onal co-operation on all questions concerni ng stand ardi zati on in the el ectrical an d electronic fields To this end and in additi on to other acti vities, I EC publish es I nternational Standards, Techn ical Specifications, Technical Reports, Publicl y Avail abl e Specificati ons (PAS) an d Gu ides (h ereafter referred to as “I EC Publication(s)”) Thei r preparation is entrusted to technical comm ittees; any I EC National Comm ittee interested in the 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person al i nju ry, property d am age or other dam age of any n ature whatsoever, whether di rect or indirect, or for costs (includ i ng leg al fees) and expenses arisi ng out of the publ ication, use of, or relian ce upon, this I EC Publicati on or any other I EC Publications 8) Attention is drawn to th e N orm ative references cited in th is publ ication Use of the referenced publ ications is indispensable for the correct applicati on of this publication The main task of I EC technical com mittees is to prepare I nternational Standards I n exceptional circum stances, a technical com mittee m ay propose the publication of a Technical Specification when • • the required support cannot be obtained for the publication of an I nternational Standard, despite repeated efforts, or the subj ect is still under technical development or where, for an y other reason, there is the future but no imm ediate possibility of an agreem ent on an I nternational Standard Technical Specifications are subject to review within three years of publication to decide whether they can be transform ed into I nternational Standards Technical Specification I EC TS 62791 has been prepared by I EC technical committee 87 Ultrasonics I EC TS 62791 : 201 © I EC 201 –7– The text of this Technical Specification is based on the following docum ents: DTS Report on voting 87/554/DTS 87/570/RVC Full information on the voting for the approval of this Technical Specification can be found in the report on voting indicated in the above table This publication has been drafted in accordance with the I SO/I EC Directives, Part Terms in bol d in the text are defined in Clause The committee has decided that the contents of this publication will remain unchanged until the stability date indicated on the I EC website under "http: //webstore.iec ch" in the data related to the specific publication At this date, the publication will be • • • • • transformed into an I nternational standard, reconfirm ed, withdrawn, replaced by a revised edition, or amended I M P O R T AN T – T h e ' c o l o u r i n s i d e ' th at it tai n s u n d e rs t a n d i n g of c o l o u rs i ts wh i ch c o n te n ts l og o a re U s e rs on th e co ve r p ag e o f th i s c o n s i d e re d s h ou l d to t h e re fo re be p ri n t c o l o u r p ri n t e r A bilingual version of this publication may be issued at a later date p u b l i c ati o n u s e fu l th i s fo r i n d i c ate s th e d o cu m en t c o rre c t u sin g a –8– I EC TS 62791 : 201 © I EC 201 INTRODUCTION Ultrasonic pulse-echo scanners are widel y used in m edical practice to produce images of soft tissue organs throughout the hum an bod y Most ultrasonic pulse-echo scanners produce realtim e im ages of tissue in a scan plane by sweeping a narrow, pulsed beam of ultrasound through the tissue section of interest and detecting the echoes generated by reflection at tissue boundaries and by scattering within tissues Generally, the sweep that generates an im age frame is repeated at least 20 tim es per second, giving rise to the real-time aspect of the displayed image The axes of the pulsed beam s generall y lie in a plane that defines the scan plane Various transducer types are employed to operate in a transm it/receive mode to generate/detect the ultrasonic signals Linear arrays, in which the beam axes are all parallel to one another, resulting in a rectangular im age, consist of a line of hundreds of parallel transducer elem ents with a subset of adjacent elem ents producing one pulse at a time Convex arrays are sim ilar to linear arrays but the element arrangem ents define part of the surface of a short right circular cylinder with the array elements parallel to the axis of the cylinder The radius of curvature of the cylinder (and therefore the array) can have values between 0, cm and cm The convex array generates a sector im age since the beam axes fan out over the scan plane A phased array has a linear arrangem ent of elem ents, where all elem ents act together to form a pulse and the direction and focus of an em itted pulse is determ ined by the timing of excitations of the elem ents The phased array generates a sector image Another type of sector scanner is the mechanical sector scanner in which a single elem ent transducer or an annular array transducer is rotated about a fixed axis during pulse em issions All the foregoing transducer types commonl y operate within the frequency range MH z to M H z, to which this Technical Specification applies A 2-dimensional array (2-D array) is restricted to an array of transducer elements distributed over a square area or a spherical cap Such an array receives echoes from a 3-D volume and can produce im ages corresponding to an y planar surface in that volume A 3-D m echanicall y driven, convex array (3-D MD convex array) m eans a convex array that acquires images as it is rotated m echanicall y about an axis lying in its im age plane or an extension of that plane A 3-D mechanicall y driven, linear array (3-D MD linear array) is sim ilar to a 3-D MD convex array, where the array radius of curvature is infinite and the array is either rotated about an axis or is translated perpendicularl y to the scan plane of the linear array For an overview of current 3-D and 4-D systems, see sections and 2 of [1 ] One means for testing the im aging performance of an ultrasound pulse-echo scanner is to quantify the degree to which a small cyst-like (low-echo) obj ect is distinguished from the surrounding soft tissue, i.e the degree to which a sm all cyst-like (low-echo) obj ect is detectable in the surrounding soft tissue I t is reasonable to assume that the smaller the that can be detected at some position, the better the resolution of the scanner, i e the better it will delineate the boundary of an abnormal obj ect, such as a tumour There are three components of resolution d efined in pulse-echo ultrasound: l o w- ech o s p h e re – axial resolution (parallel to the local pulse propagation direction); – lateral resolution (perpendicular to the local pulse propagation direction and parallel to the scan plane); and – elevational resolution (perpendicular to the local pulse propagation direction and also to the scan plane) Axial resolution usually – but not always – is better than lateral and elevational resolutions Thus, all three com ponents should be given equal weight in measuring A sphere has no preferred orientation and is therefore the best shape for a cyst-like obj ect for two reasons First, all three com ponents of resolution are weighted equall y no m atter what the beam ’s incident direction is Second, the incident beam’s propagation direction will vary d e te ct ab i l i t y The n um bers in squ are brackets refer to the Bibli og raph y – 48 – I EC TS 62791 : 201 © I EC 201 Annex G (informative) Results of a test of reproducibility of LSNR m versus depth for a phantom with mm-diameter low-echo spheres and spheres per millilitre The following results are presented for comparison with those presented in Annex B, which were obtained with a phantom with mm-diameter, low-echo spheres but only one such sphere per millilitre Figure G.1 is an image using a curved array operating at 4,2 MH z with a phantom having two plate-glass reflectors There are two low-echo spheres per m illilitre instead of one such sphere per m illilitre Rather good reproducibility results are shown in Figure G IEC Figure G.1 – Example image of the phantom with a 4,2 M Hz curved array and two low-echo spheres per millilitre – 49 – 80 –1 70 –2 60 Number of spheres Mean LSNR I EC TS 62791 : 201 © I EC 201 –3 –4 –5 –6 –7 –8 Depth (cm ) 10 50 40 30 20 10 -40 41 -80 -40 41 -80 12 0 Depth (cm ) 10 IEC a) M ean LSNR ( LSNR m )-valu es as a function of d epth 12 IEC b) Number of low-echo sph ere centres detected in each mm-depth interval I n the notation ad opted in 2, read LSNR m for M ean LSN R at the ordi nate l abel of the l eft graph Figure G.2 – Reproducibility results corresponding to the image set, one of which is shown in Figu re G.1 – 50 – I EC TS 62791 : 201 © I EC 201 Annex H (informative) Results for low-echo sphere-concentration dependence of LSNR m versus depth for phantoms with mm-diameter spheres One phantom made in J ul y 201 has an average of one 4-m m diam eter, low-echo sphere per millilitre and a second phantom made in October 201 has an average of two such spheres per m illilitre Example images from the data sets are shown in Figures H and H 3, and plots of LSNR m - values versus depth and num ber of detected l ow-echo spheres in each mmdepth interval are shown in Figures H and H I m age acquisition parameters were the sam e for ml − and m l − cases, and those parameters correspond to ordinary B-scans with no special processing such as spatial com pounding or tissue harm onic im aging The focus was at cm IEC Figu re H.1 – Example of an image from the image set giving rise to the results in Figure H.2; the phantom contained an average of one mm-diameter, low-echo sphere per millilitre I n Figure H R is the coefficient of determination R = if the data values and curve-fit values at the corresponding depths are com pletely uncorrelated, and R = if the two sets of values are completel y correlated [1 2] I EC TS 62791 : 201 © I EC 201 – 51 – R = 0, 98 70 –1 60 Number of spheres Mean LSNR –2 –3 –4 –5 –6 40 30 20 10 –7 –8 50 Depth (cm ) 10 12 0 Depth (cm ) 10 IEC a) M ean LSNR ( LSNR m )-valu es versu s depth for an average of one mm-diameter, low-echo sphere per millilitre 12 IEC b) Number of low-echo sph ere centres detected in each mm-depth interval I n the notation ad opted in 2, read LSNR m for M ean LSN R at the ordi nate l abel of the l eft graph Figu re H.2 – Results corresponding to an image set, one of which is shown in Figure H.1 IEC Figure H.3 – Example of an image from the data set giving rise to the results in Figu re H.4; the phantom contained an average of two mm-diameter, low-echo spheres per millilitre – 52 – R = 0, 97 50 45 –1 40 Number of spheres Mean LSNR –2 –3 –4 –5 –6 –7 –8 I EC TS 62791 : 201 © I EC 201 Depth (cm ) 10 12 35 30 25 20 15 10 0 Depth (cm ) IEC a) M ean LSNR ( LSNR m )-val ues versu s depth for an average of two mm-diameter, low-echo spheres per millilitre 10 12 IEC b) Number of low-echo sph ere centres detected in each mm-depth interval I n the notation adopted in 2, read LSNR m for Mean LSNR at the ordin ate label of the left g raph R is the coefficient of d eterm inati on, d efined i n the text above Fig ure H Figu re H.4 – Results corresponding to an image set, one of which is shown in Figure H A concentration dependence is apparentl y dem onstrated with the m inim um LSNR m -value for the m l − phantom at about − 6, and for the m l − phantom at about − 6, The num ber of im ages em ployed for the m l − case is twice that of the m l − case, which m eans the expected number of low-echo spheres for each volume segment determined by the depth interval is the sam e for each At cm depth, based on the average number of spheres per m illilitre, the volume addressed is about 45 m l for both m l − and ml − phantom s N otice that the observed num ber at cm depth for the m l − case is about 35 and for the m l − case is about 28 The difference could be attributed to pairs of spheres being close enough together that they are assum ed to be one sphere and the "centre of mass" is som ewhere between the two spheres’ centres resulting in an LSNR n -value that is less negative than is appropriate I nvestigation of this concentration dependence is ongoing and m ay result in alteration of the software to detect such pairings of spheres, so they can be eliminated from consideration See Annex I where a m uch better controlled experim ent was done to assess concentration dependence using three phantoms containing 3, mm-diameter, low-echo spheres I EC TS 62791 : 201 © I EC 201 – 53 – An n e x I (informative) Re s u l ts fo r l o w -e c h o s p h e re -c o n c e n tra t i o n d e p e n d e n c e o f LSNR m ve rs u s d e p th fo r p h a n to m s w i th , m m -d i a m e te r s p h e re s A set of three phantom s was m ade with flat scanning windows and average low-echo sphere concentrations of m l − , m l − and ml − All spheres were m ade at the sam e tim e Care also was taken to ensure that the background m aterials in all phantom s were identical Thus, no material bias should exist between phantoms Data im ages for all three phantom s were obtained with identical equipment and scan parameters, including the TGC settings I m age acquisition param eters were the sam e for the ml − , ml − and ml − cases and those parameters correspond to ordinary B-scans with no special processing, such as spatial com pounding or tissue harm onic imaging The focus was at cm Results are shown in Figures I to I 280 im ages were used for the ml − phantom, 40 im ages for the ml − phantom and 75 im ages for the ml − phantom (Recall that the lowecho sphere density is ml − for the phantom containing 3, mm-diameter spheres, for which results are shown in Figures C to C ) I n term s of the m ost negative LSNR m curve-fitted values, the ml − phantom has a m inim um at − 1 , 3, the m l − phantom has a minimum at − 1 , 6, and the m l − phantom shows a m inimum at − 2,6 Thus, the m ost negative LSNR m - values span a range of onl y 1 , % with a decrease in low-echo sphere concentration by a factor of /4, indicating that there is little dependence of even the most extrem e LSNR m -values on such sphere concentration; therefore, it is reasonable to assume that the m l − sphere concentration will yield acceptable accuracy Note also that the correlation coefficient of LSNR m -values for m l − (see Figure I 4) and corresponding LSNR m -values for ml − (see Figure I 6) was computed, and is 0, 985 IEC F i g u re I – E xam p l e o f an i m a g e fro m th e m l t h e re s u l t s s h o w n i n −1 F i g u re I d a t a s e t p ro d u c i n g – 54 – R = 0, 97 50 45 –2 40 Number of spheres Mean LSNR –4 –6 –8 –1 –1 –1 –1 I EC TS 62791 : 201 © I EC 201 Depth (cm ) 10 35 30 25 20 15 10 0 Depth (cm ) IEC a) M ean fo r a n LS N R ( LSNR m 10 IEC ) - v a l u e s v e rs u s d e p t h b) N u m b e r o f l o w - e c h o s p h e re c e n t re s d e t e c t e d a v e g e o f fo u r , m m - d i a m e t e r, in each m m -d e p th i n t e rv a l l o w - e c h o s p h e re s p e r m i l l i l i t r e I n the notation adopted in 2, read LSNR m for Mean LSNR at the ordin ate label of the left g raph R is the coefficient of d eterm inati on, d efined i n the text above Fig ure H F i g u re I – R e s u l t s fo r t h e p h a n t o m , m m - d i a m e t e r, ta i n i n g fo u r l o w - e c h o s p h e re s p e r m i l l i l i t re IEC F i g u re I – E x a m p l e o f a n i m a g e fro m t h e m l t h e re s u l t s s h o w n i n −1 F i g u re I d a t a s e t p ro d u c i n g I EC TS 62791 : 201 © I EC 201 R = 0, 96 40 –2 35 –4 30 Number of spheres Mean LSNR – 55 – –6 –8 –1 –1 –1 –1 25 20 15 10 Depth (cm ) 10 Depth (cm ) IEC a) M ean fo r a n LS N R ( LSNR m ) - v a l u e s v e rs u s d e p t h 10 IEC b) N u m b e r o f l o w - e c h o s p h e re c e n t re s d e t e c t e d a v e g e o f t w o , m m - d i a m e t e r, in each m m -d e p th i n t e rv a l l o w - e c h o s p h e re s p e r m i l l i l i t r e I n the notation adopted in 2, read LSNR m for Mean LSNR at the ordin ate label of the left g raph R is the coefficient of d eterm inati on, d efined i n the text above Fig ure H F i g u re I – R e s u l t s fo r t h e p h a n t o m , m m - d i a m e t e r, ta i n i n g two l o w - e c h o s p h e re s p e r m i l l i l i t re IEC F i g u re I – E x a m p l e o f a n i m a g e fro m th e t h e re s u l t s s h o w n i n ml −1 F i g u re I d a t a s e t p ro d u c i n g – 56 – I EC TS 62791 : 201 © I EC 201 R = 0, 94 50 45 40 –2 Number of spheres Mean LSNR –4 –6 –8 –1 –1 –1 –1 6 Depth (cm ) 35 30 25 20 15 10 10 Depth (cm ) IEC a) M ean fo r a n LSN R ( LSNR m ) - v a l u e s v e rs u s d e p t h 10 IEC b) N u m b e r o f l o w - e c h o s p h e re c e n t re s d e t e c t e d a v e g e o f o n e , m m - d i a m e t e r, in each m m -d e p th i n t e rv a l l o w - e c h o s p h e re p e r m i l l i l i t re I n the notation adopted in 2, read LSNR m for Mean LSNR at the ordin ate label of the left g raph R is the coefficient of d eterm inati on, d efined i n the text above Fig ure H F i g u re I – R e s u l t s fo r t h e p h a n t o m , m m - d i a m e t e r, ta i n i n g on e l o w - e c h o s p h e re p e r m i l l i l i t re I EC TS 62791 : 201 © I EC 201 – 57 – Annex J (informative) Comparison of two different makes of scanner with similar transducers and console settings 45 –1 40 –2 35 Number of spheres Mean LSNR Standard B-m ode images obtained with two different commercial ultrasound m edical diagnostic system s were assessed for a focus at cm and convex arrays with nearl y the sam e sector angle Also, the console settings were the sam e except for a sm all difference in nominal frequency Figure J illustrates results for the System A scanner and 7CF2 3-D transducer operated at 4, MH z in 2-D m ode, and Figure J illustrates results for the System B scanner with a 4DC7-3 3-D transducer operated at MH z in 2-D m ode System A appears to outperform System B to a considerable extent –3 –4 –5 –6 –7 25 20 15 10 –8 –9 30 Depth (cm ) 10 12 Depth (cm ) 10 12 IEC IEC 45 –1 40 –2 35 Number of spheres Mean LSNR Figure J.1 – Results for System A scanner and 7CF2 3-D (swept convex array) transducer focused at cm and operated at 4,5 MHz in 2-D mode –3 –4 –5 –6 –7 25 20 15 10 –8 –9 30 Depth (cm ) 10 12 IEC 0 Depth (cm ) 10 12 IEC Figure J.2 – Results for System B scanner with a 4DC7-3 3-D (convex array) transducer, operated at MHz in 2-D mode and focused at cm The sector angle and all other console settings mimicked those for the System A case (Figure J.1 ) Keeping in mind that the m ore negative a Mean LSNR ( LSNR m ) value is, the better the detectability of the low-echo sphere, ultrasound System A outperforms System B at all depths – 58 – I EC TS 62791 : 201 © I EC 201 Also, the backscatter coefficient of the m aterial composing the low-echo spheres is about − 30 dB relative to that of the material com posing the background All LSNR m values would be increased (m ade less negative) if the backscatter coefficient of the m aterial composing the low-echo-spheres were increased Consider an LSNR m value of − to be a threshold for hum an observer detection of the low-echo spheres Then the increase in low-echo sphere backscatter coefficient needed to cause an increase of − − ( − 7, 8) = 5, for System A at a cm depth would be greater than the increase in low-echo sphere backscatter coefficient needed to cause an increase of − − ( − 5) = for System B at a cm depth The implication is that System A would allow detectability for low-echo spheres having a higher backscatter coefficient than would System B Consider, for exam ple, a tumour with dim ensions greater than the low-echo sphere diam eter D For a range of values of (tumour backscatter coefficient)/(background backscatter coefficient), the tum our would be detectable by a human observer using System A, but not detectable using System B Also, when the tum our is detectable, its boundary wou ld be delineated with a resolution of D I EC TS 62791 : 201 © I EC 201 – 59 – Annex K (informative) Special considerations for 3-D probes K.1 3-D probes operating in 2-D imaging mode For 3-D mechanicall y driven probes, the scan plane should be at a known position and orientation relative to the housing of the linear array or convex array so that the scan plane can be m ade perpendicular to the direction of translation (in D /4 increm ents) of the transducer or phantom For 2-D arrays [2] the scan plane should be at a known position and orientation relative to the transducer and be such that the scan plane can be perpendicular to the direction of translation (in D /4 increm ents) of the transducer or phantom while the transducer surface remains entirel y acousticall y coupled to the phantom scanning window K.2 2-D arrays operating in 3-D imaging mode for determining LSNR m -values as a function of depth for reconstructed images The entire em itting surface of the probe should be acousticall y coupled to the scanning window at all tim es during D /4 translations of the probe or phantom , and a complete 3-D data set should be recorded at each position Sets of reconstructed images with "scan planes" perpendicular to the translation direction, all of which are at the sam e position relative to the transducer, can then be analysed to yield LSNR m - values as a function of depth NOTE The l arg e am ount of d ata th at needs to be stored m ay m ake this procedu re im practical K.3 Mechanically driven 3-D probes operating in 3-D imaging mode I t is unlikel y that LSNR m - values versus depth can be generated because it is unlikely that the entire emitting surface of the probe can be acousticall y coupled to the scanning window at all tim es during D /4 translations of the probe or phantom – 60 – I EC TS 62791 : 201 © I EC 201 Bibliography [1 ] Szabo TL Academic Press, Burlington, Massachusets, USA, 201 [2] Madsen EL, Zagzebski JA, M acdonald MC, Frank GR, U ltrasound focal lesion detectability phantoms, , vol 8, pp 1 71 –1 80 (1 991 ) D ia g n o s tic Ultra s o u n d Im a g in g : In s ide Out – Se c o n d Elsevier Editio n , Me d Ph ys [3] Kofler JM Jr, Lindstrom MJ, Kelcz F, Madsen EL, Association of automated and human observer lesion detectability using phantom s, , vol.31 , p.351 –359 (2005) Ultra s o u n d [4] B io l Madsen EL, I nsana MF, Zagzebski J A, Method of data reduction for accurate determination of acoustic backscatter m easurem ents, , vol 76, p 91 3– 923 (1 984) J [5] Me d A co ust So c Am Sigelm ann RA, Reid JM, Analysis and m easurement of ultrasound 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Jr, Madsen EL, Improved method for determining resolution zones in ultrasound phantoms with spherical simulated lesions, , vol 27, p 667–1 676 (2001 ) Ultra s o un d [1 0] m e dic in e , Springer, Berlin, 201 Me d Dawson B and Trapp RG, York, 2004 B a s ic & C lin ica l B io s ta tis tics Ph ys , 4th edition, McGraw-H ill, N ew INTERNATIONAL ELECTROTECHNICAL COMMISSI ON 3, rue de Varembé PO Box 31 CH-1 21 Geneva 20 Switzerland Tel: + 41 22 91 02 1 Fax: + 41 22 91 03 00 info@iec.ch www.iec.ch