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1、INTERNATIONAL ATOMIC ENERGY AGENCYVIENNADigital mammography offers fundamental advantages over film based mammography.These include the possibility for acquiring quality images at lower radiation dose image recording,processing and archiving as well as the use of artificial intelligence for improvin

2、g diagnostic outcome.Other practical advantages include cost reduction,use of environmentally friendly technology,and the option of obtaining remote expert diagnostic opinion.Image quality in mammography is critical.A switch from screen-film technology to a digital system is preferable only if high

3、quality images can be guaranteed.This publication provides guidance on the establishment of digital mammography facilities and the upgrade of existing facilities.It focuses on planning,designing and operating the high quality mammography service within available resources.No.46Worldwide Implementati

4、on of DigitalMammography ImagingWorldwide Implementation of Digital Mammography ImagingIAEA HUMAN HEALTH SERIES No.46IAEA HUMAN HEALTH SERIESIAEA HUMAN HEALTH SERIESIAEA HUMAN HEALTH SERIES PUBLICATIONSThe mandate of the IAEA human health programme originates from Article II of its Statute,which sta

5、tes that the“Agency shall seek to accelerate and enlarge the contribution of atomic energy to peace,health and prosperity throughout the world”.The main objective of the human health programme is to enhance the capabilities of IAEA Member States in addressing issues related to the prevention,diagnos

6、is and treatment of health problems through the development and application of nuclear techniques,within a framework of quality assurance.Publications in the IAEA Human Health Series provide information in the areas of:radiation medicine,including diagnostic radiology,diagnostic and therapeutic nucl

7、ear medicine,and radiation therapy;dosimetry and medical radiation physics;and stable isotope techniques and other nuclear applications in nutrition.The publications have a broad readership and are aimed at medical practitioners,researchers and other professionals.International experts assist the IA

8、EA Secretariat in drafting and reviewing these publications.Some of the publications in this series may also be endorsed or co-sponsored by international organizations and professional societies active in the relevant fields.There are two categories of publications in this series:IAEA HUMAN HEALTH S

9、ERIESPublications in this category present analyses or provide information of an advisory nature,for example guidelines,codes and standards of practice,and quality assurance manuals.Monographs and high level educational material,such as graduate texts,are also published in this series.IAEA HUMAN HEA

10、LTH REPORTSHuman Health Reports complement information published in the IAEA Human Health Series in areas of radiation medicine,dosimetry and medical radiation physics,and nutrition.These publications include reports of technical meetings,the results of IAEA coordinated research projects,interim rep

11、orts on IAEA projects,and educational material compiled for IAEA training courses dealing with human health related subjects.In some cases,these reports may provide supporting material relating to publications issued in the IAEA Human Health Series.All of these publications can be downloaded cost fr

12、ee from the IAEA web site:http:/www.iaea.org/Publications/index.htmlFurther information is available from:Marketing and Sales UnitInternational Atomic Energy AgencyVienna International CentrePO Box 1001400 Vienna,AustriaReaders are invited to provide their impressions on these publications.Informati

13、on may be provided via the IAEA web site,by mail at the address given above,or by email to:Official.Mailiaea.org.WORLDWIDE IMPLEMENTATION OF DIGITAL MAMMOGRAPHY IMAGINGAFGHANISTANALBANIAALGERIAANGOLAANTIGUA AND BARBUDAARGENTINAARMENIAAUSTRALIAAUSTRIAAZERBAIJANBAHAMASBAHRAINBANGLADESHBARBADOSBELARUSB

14、ELGIUMBELIZEBENINBOLIVIA,PLURINATIONAL STATE OFBOSNIA AND HERZEGOVINABOTSWANABRAZILBRUNEI DARUSSALAMBULGARIABURKINA FASOBURUNDICABO VERDECAMBODIACAMEROONCANADACENTRAL AFRICAN REPUBLICCHADCHILECHINACOLOMBIACOMOROSCONGOCOSTA RICACTE DIVOIRECROATIACUBACYPRUSCZECH REPUBLICDEMOCRATIC REPUBLIC OF THE CONG

15、ODENMARKDJIBOUTIDOMINICADOMINICAN REPUBLICECUADOREGYPTEL SALVADORERITREAESTONIAESWATINIETHIOPIAFIJIFINLANDFRANCEGABONGAMBIAGEORGIAGERMANYGHANAGREECEGRENADAGUATEMALAGUYANAHAITIHOLY SEEHONDURASHUNGARYICELANDINDIAINDONESIAIRAN,ISLAMIC REPUBLIC OF IRAQIRELANDISRAELITALYJAMAICAJAPANJORDANKAZAKHSTANKENYAK

16、OREA,REPUBLIC OFKUWAITKYRGYZSTANLAO PEOPLES DEMOCRATICREPUBLICLATVIALEBANONLESOTHOLIBERIALIBYALIECHTENSTEINLITHUANIALUXEMBOURGMADAGASCARMALAWIMALAYSIAMALIMALTAMARSHALL ISLANDSMAURITANIAMAURITIUSMEXICOMONACOMONGOLIAMONTENEGROMOROCCOMOZAMBIQUEMYANMARNAMIBIANEPALNETHERLANDSNEW ZEALANDNICARAGUANIGERNIGE

17、RIANORTH MACEDONIANORWAYOMANPAKISTANPALAUPANAMAPAPUA NEW GUINEAPARAGUAYPERUPHILIPPINESPOLANDPORTUGALQATARREPUBLIC OF MOLDOVAROMANIARUSSIAN FEDERATIONRWANDASAINT KITTS AND NEVISSAINT LUCIASAINT VINCENT AND THE GRENADINESSAMOASAN MARINOSAUDI ARABIASENEGALSERBIASEYCHELLESSIERRA LEONESINGAPORESLOVAKIASL

18、OVENIASOUTH AFRICASPAINSRI LANKASUDANSWEDENSWITZERLANDSYRIAN ARAB REPUBLICTAJIKISTANTHAILANDTOGOTONGATRINIDAD AND TOBAGOTUNISIATRK?YETURKMENISTANUGANDAUKRAINEUNITED ARAB EMIRATESUNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELANDUNITED REPUBLIC OF TANZANIAUNITED STATES OF AMERICAURUGUAYUZBEKISTANVA

19、NUATUVENEZUELA,BOLIVARIAN REPUBLIC OF VIET NAMYEMENZAMBIAZIMBABWEThe following States are Members of the International Atomic Energy Agency:The Agencys Statute was approved on 23 October 1956 by the Conference on the Statute of the IAEA held at United Nations Headquarters,New York;it entered into fo

20、rce on 29 July 1957.The Headquarters of the Agency are situated in Vienna.Its principal objective is“to accelerate and enlarge the contribution of atomic energy to peace,health and prosperity throughout the world.IAEA HUMAN HEALTH SERIES No.46WORLDWIDE IMPLEMENTATION OF DIGITAL MAMMOGRAPHY IMAGINGIN

21、TERNATIONAL ATOMIC ENERGY AGENCY VIENNA,2023 IAEA,2023Printed by the IAEA in AustriaOctober 2023STI/PUB/2011COPYRIGHT NOTICEAll IAEA scientific and technical publications are protected by the terms of the Universal Copyright Convention as adopted in 1952(Berne)and as revised in 1972(Paris).The copyr

22、ight has since been extended by the World Intellectual Property Organization(Geneva)to include electronic and virtual intellectual property.Permission to use whole or parts of texts contained in IAEA publications in printed or electronic form must be obtained and is usually subject to royalty agreem

23、ents.Proposals for non-commercial reproductions and translations are welcomed and considered on a case-by-case basis.Enquiries should be addressed to the IAEA Publishing Section at:Marketing and Sales Unit,Publishing SectionInternational Atomic Energy AgencyVienna International CentrePO Box 1001400

24、Vienna,Austriafax:+43 1 26007 22529tel.:+43 1 2600 22417email:sales.publicationsiaea.org www.iaea.org/publicationsIAEA Library Cataloguing in Publication DataNames:International Atomic Energy Agency.Title:Worldwide Implementation of Digital Mammography Imaging/International Atomic Energy Agency.Desc

25、ription:Vienna:International Atomic Energy Agency,2023.|Series:IAEA Human Health Series No.46,ISSN 20753772;no.46|Includes bibliographical references.Identifiers:IAEAL 23-01599|ISBN 9789201267238(paperback:alk.paper)|ISBN 9789201268235(pdf)|ISBN 9789201269232(epub)Subjects:Diagnostic imaging.|Diagno

26、stic imaging Methods.|Radiology.|Breast Radiography.|Radiography,Medical.Classification:UDC 615.849|STI/PUB/2011FOREWORDIn medical imaging,digital technologies can have many fundamental advantages over screen-film technology,such as(i)improved efficiency of the use of radiation in forming the image,

27、which allows for dose reduction,(ii)transmission of images electronically and from archival storage in a computer system,(iii)increased robustness to exposure techniques with the disappearance of obvious under-and overexposure failures and(iv)the many image processing and other digital applications,

28、such as artificial intelligence,that can be applied to digital images.Other practical advantages include cost reduction and replacement of chemical developers by a more environmentally friendly detector.Finally,the digital framework allows expert diagnostic judgements to be made available regardless

29、 of the distance between the imaging facility and the expert.These advantages also apply to mammography.However,in mammography,image quality is critical,and a sufficient level of quality is achieved only if system operation is optimized.A switch from screen-film to digital technology ought to be per

30、formed,therefore,only if high quality images can be guaranteed.Optimal system operation and quality control are needed at all levels including for the newest digital systems.It has been recognized that achieving optimized imaging in mammography is a complex multifactorial process that starts with th

31、e design and implementation of a proper infrastructure and the best technology.It requires well trained staff and a rigorous quality assurance programme.While many digital imaging devices exist,there is no unique answer to the best solution in practice,given set resources.It is also recognized that

32、there is no practical guidance on how to transition to digital technology systems.The World Health Organization(WHO)also recognized that a noteworthy number of clinical radiologists had experienced great challenges in implementing digital radiology and that radiology departments could benefit from a

33、n unbiased and independent resource to guide them in this.In 2016,the IAEA and WHO published IAEA Human Health Series No.28,entitled Worldwide Implementation of Digital Imaging in Radiology,a publication intended to address issues associated with the introduction of digital radiology.In response to

34、the need to advise Member States on topics specifically related to mammography,in 2016 the Scientific Committee of the IAEA/WHO Network of Secondary Standards Dosimetry Laboratories recommended that guidance be developed for the implementation of digital mammography technologies.The present publicat

35、ion is a companion to Human Health Series No.28 and provides information on the resources needed for different mammography systems.The IAEA acknowledges the contributions of the drafting committee responsible for the development of this publication in particular,H.Bosmans(Belgium),M.E.Brandan(Mexico

36、),R.A.Jong(Canada),M.Yaffe(Canada)and C.H.Yeong(Malaysia).The IAEA officers responsible for this publication were H.Delis and V.Tsapaki of the Division of Human Health.EDITORIAL NOTEAlthough great care has been taken to maintain the accuracy of information contained in this publication,neither the I

37、AEA nor its Member States assume any responsibility for consequences which may arise from its use.This publication does not address questions of responsibility,legal or otherwise,for acts or omissions on the part of any person.Guidance and recommendations provided here in relation to identified good

38、 practices represent expert opinion but are not made on the basis of a consensus of all Member States.The use of particular designations of countries or territories does not imply any judgement by the publisher,the IAEA,as to the legal status of such countries or territories,of their authorities and

39、 institutions or of the delimitation of their boundaries.The mention of names of specific companies or products(whether or not indicated as registered)does not imply any intention to infringe proprietary rights,nor should it be construed as an endorsement or recommendation on the part of the IAEA.Th

40、e IAEA has no responsibility for the persistence or accuracy of URLs for external or third party Internet web sites referred to in this book and does not guarantee that any content on such web sites is,or will remain,accurate or appropriate.CONTENTS1.INTRODUCTION.11.1.Background.11.2.Objective.11.3.

41、Scope.11.4.Structure.22.A ROAD MAP FOR A MAMMOGRAPHY FACILITY.32.1.Implementation scenarios.33.RESOURCES AND NEEDS.103.1.Project management.103.2.Core considerations.103.3.Specific needs for DDM.183.4.Specific needs for CRM.283.5.Specific needs for an SFM.413.6.Costing and implementation.504.TRANSIT

42、ION FROM SFM TO CRM AND DDM.584.1.General considerations.584.2.Radiation dose considerations.604.3.Impact of transition.624.4.Fixed installations versus mobile services.645.CONCLUSIONS.66APPENDIX I:BREAST CANCER 69APPENDIX II:MAMMOGRAPHY TECHNOLOGY 75APPENDIX III:OTHER BREAST IMAGING MODALITIES 92AP

43、PENDIX IV:MAMMOGRAPHY EQUIPMENT PERFORMANCE 96APPENDIX V:QUALITY MANAGEMENT 100APPENDIX VI:EDUCATION OF PROFESSIONALS IN MAMMOGRAPHY 110APPENDIX VII:EVALUATION OF MAMMOGRAPHY SERVICE 122REFERENCES.127ABBREVIATIONS.137GLOSSARY.139CONTRIBUTORS TO DRAFTING AND REVIEW.1411.INTRODUCTION1.1.BACKGROUNDThe

44、incidence of breast cancer is continuing to rise,particularly in low and middle-income countries(LMICs)1.Mammography is widely used to facilitate the detection of breast cancer at a point earlier in its natural history than is possible by clinical examination 2.It is also the only imaging method for

45、 the early detection of breast cancer that has been demonstrated to contribute to reduced mortality through screening 3.Its use is increasing in LMICs as the incidence of breast cancer increases.Digital mammography systems were introduced in 2000 and offer many advantages over screen-film mammograph

46、y.1.2.OBJECTIVEThe purpose of this publication is to provide guidance on the establishment of digital mammography facilities or upgrade of existing facilities when selecting and implementing new technology for mammography imaging in different resource settings.Guidance and recommendations provided h

47、ere in relation to identified good practices represent expert opinion but are not made on the basis of a consensus of all Member States.1.3.SCOPEThis IAEA publication is intended to assist health care policy decision makers,planners,programme administrators and professionals working in health care i

48、n establishing or upgrading capabilities for diagnostic and screening mammography.The IAEA and other organizations have published guidance around aspects related to breast cancer incidence 4,breast imaging 2,breast cancer prevention,quality assurance(QA)and quality control(QC)of screen-film 5 and di

49、gital systems 2,and QA in screening and diagnosis 6,7.The focus here is explicitly to inform and facilitate decisions and planning on how to select or transition mammography services to the best quality possible with available resources.11.4.STRUCTUREThe present IAEA publication builds on existing g

50、uidance 2,5,8 and presents a road map for how to move from any current situation to one that better addresses the needs of a community.Section 1 presents the background,objective,scope and structure of this publication.Section 2 shows a road map for a mammography facility and helps interested partie

51、s to identify the level of mammography service at which they are currently operating and the level that is feasible with upgraded services.Decision points in the road map are linked to relevant supporting information in subsequent sections and appendices.It also provides an overview of various imple

52、mentation scenarios with more detailed information to facilitate making decisions.Section 3 discusses what is required to implement the different types of service,direct digital mammography(DDM),computed radiography mammography(CRM)or screen-film mammography(SFM).Aspects of equipment,infrastructure,

53、quality needs,maintenance and staff training are included.In addition,the transition between screen-film and digital modalities is discussed in Section 4.More detailed information is provided in the appendices as follows:Appendix I provides a review on breast cancer incidence,mortality and geographi

54、cal factors as well as the principles of breast cancer screening and factors to consider before initiating a screening programme.Appendix II presents an overview of the different types of mammography technologies,including breast tomosynthesis and contrast-enhanced mammography.Appendix III reviews o

55、ther breast imaging modalities such as ultrasound,magnetic resonance imaging(MRI),positron emission tomography(PET)and breast computed tomography(CT).Appendix IV reviews evaluations of physico-technical parameters that describe the performance of mammography systems and presents examples of relation

56、ships between tests and clinical performance.Appendix V reports briefly on QA and QC tests that assure the high quality performance of systems,describes metrics for digital detectors and discusses the importance of artefact evaluation as well as the use of contrast detail phantoms to evaluate system

57、 performance.Appendix VI outlines the needs for professional education and training of key personnel involved in the delivery of high quality mammography services.Finally,Appendix VII shows some examples of existing mammography evaluation programmes implemented in some countries or continents.Ultima

58、tely,this publication potentially pertains to all people for whom the detection of breast cancer would be facilitated by mammography,but the term women is used because it reflects the vast majority of the use of breast imaging.22.A ROAD MAP FOR A MAMMOGRAPHY FACILITYThis section provides a road map

59、to assist health care decision makers,administrators and professionals.Establishment or upgrading of a mammography service is defined by applying various scenarios before deciding further steps.The analysis includes needs for investment and maintenance,as well as the availability of infrastructure a

60、nd human resources that are essential for evolution.Figures 16 are decision trees for various types of medical imaging facilities,and they have been created to guide the transition from a current situation towards improved mammography services.Cross-references to the relevant section in this publica

61、tion are provided to facilitate decisions.Although there are several technical and operational advantages associated with digital systems,it is also acknowledged that there may be differences in the available economic and human resources or infrastructure(e.g.quality of electrical supply)that may im

62、pact decisions that need to be made.Several scenarios exist and are explored to depict the next steps in improvement.If there is no scenario that exactly describes a facility,the two closest scenarios can be investigated.It is assumed as a minimum standard that,if mammography is performed,it is done

63、 using X ray equipment that is explicitly designed for the purposes of mammography in that it has the capability of producing low energy X rays(using different target/filter combinations),a small X ray focal spot,an automatic exposure control(AEC),an integrated compression device,and a mammography g

64、rid and beam collimator designed for imaging the breast.In addition,there ought to be a means available for providing the medical radiation technologist with information on the settings(kilovoltage(kV)and milliampere-seconds(mAs)for the exposure,where the AEC system cannot be used or is uncalibrated

65、.The system design and performance capability need to comply with the relevant current standards of the International Electrotechnical Commission(IEC)9.A general-purpose radiographic unit ought not to be used to carry out mammography.2.1.IMPLEMENTATION SCENARIOSDigital mammography plays a vital role

66、 in the diagnosis and management of breast diseases;however,its implementation needs to be carefully evaluated and justified according to the local scenario.This section discusses the practical implementation of digital mammography in multiple scenarios,such as(a)a facility that has limited resource

67、s and does not have any medical 3imaging equipment;(b)a facility that has limited resources and does not have a mammography system;(c)a hospital with an SFM facility;(d)a hospital with a CRM facility;and(e)a tertiary care hospital with breast imaging.2.1.1.No medical imaging facilityThis scenario is

68、 applied to a facility(e.g.a general clinic)that has limited resources(in terms of financial,human or infrastructure constraints)and does not have any medical imaging equipment yet.In this scenario,implementing other imaging capabilities such as general radiography or CT may be a higher priority tha

69、n mammography.A radiologist,medical radiation technologist and a clinically qualified medical physicist(CQMP)specifically trained in breast imaging are essential for introducing breast imaging.A facility lacking these professionals,even with general training,would have great difficulty establishing

70、high quality mammography.2.1.2.Limited resources no mammographyThis scenario refers to a setting where there is some general radiological imaging,but no mammography system.The term limited resources may refer to financial constraints,but in some cases,it denotes a lack of human resources 4FIG.1.Init

71、ial planning considerations for the implementation of mammography imaging.such as appropriately trained radiologists,medical radiation technologists,CQMPs or service engineers.If there is an identified need for breast imaging,then implementation of a breast imaging facility can be recommended.If scr

72、een-film general radiography is already being used in the facility,then a viable and realistic solution may be to consider initiating SFM.In addition to the need for purchasing an X ray mammography unit,however,dedicated cassettes,screens,films,mammography view boxes and a reading environment will b

73、e needed.A special processor will also be needed for developing mammography films.For chemical film processing,additional daily QC equipment and procedures will be required.Therefore,there are cost and time implications with the implementation of SFM.Furthermore,if no radiologist is available,it wou

74、ld also be necessary to transfer processed films to the location where the images would be reported.This could result in delays in obtaining a diagnosis.It may be more reasonable to initiate DDM in this scenario;or if adequate resources(for both purchase and maintenance)for DDM cannot be obtained,it

75、 is advisable to initiate CRM,although the latter is a less favourable choice than DDM.In all cases,specialized training for the medical radiation technologists on patient positioning,breast compression,exposure and QC will be necessary.In such a facility,the mammograms would likely mainly be used f

76、or diagnostic purposes rather than for screening asymptomatic women.If there is a radiologist available on-site,special training in interpreting mammograms will be required.Otherwise,remote interpretation via tele-mammography could be considered.In any scenario,QC,dose and image quality optimization

77、 as well as patient dose assessment and review ought to be implemented and overseen by a CQMP.Another solution,if appropriate,as part of a regional or national system,would be to consider participating in a mobile mammography programme 5FIG.2.Decision tree for facilities with established mammography

78、 imaging technologies.where a complete system,equipped with a DDM system and a trained medical radiation technologist,visits at regular intervals.Such a plan will also require a regular quality assurance programme(QAP)and optimization of practice for the equipment(see Section 4.4).2.1.3.Hospital wit

79、h an SFM facilityIn this scenario,the case of a local or regional hospital with existing general radiology and SFM systems is discussed.The way forward depends greatly on 6FIG.3.Decision tree for determining the appropriate mammography imaging technology.7FIG.4.Decision tree for a facility with SFM

80、considering an upgrade.FIG.5.Decision tree for a facility with CRM considering an upgrade.the quality of imaging the facility currently achieves,the resources available and the volume of work performed at the facility.If current mammographic imaging quality is compatible with recognized guidelines s

81、uch as those of the American Association of Physicists in Medicine(AAPM)10,American College of Radiology(ACR)11,European Reference Organisation for Quality Assured Breast Screening and Diagnostic Services(EUREF)6 or the IAEA 2,5 and workload demands can be accommodated,then it is reasonable to conti

82、nue with SFM.If it is planned to convert existing general radiography equipment to digital,then a conversion of mammography to either a CRM or DDM system could be considered.If the mammography machine is due for replacement,purchase of a DDM system or,if not feasible,8FIG.6.Decision tree for facilit

83、ies considering a change to their DDM.a CRM system,is recommended.It ought to be mentioned that retrofits for digital detectors and acquisition systems are now available at a lower cost than for a DDM system and may be a viable option;these are preferable to computed radiography(CR)plates 12.It is e

84、ssential in this case that the basic mammography unit(e.g.X ray tube and generator,gantry,compression,etc.)be in appropriate operating condition.If the current quality of an SFM system is not adequate,this ought to ideally be addressed immediately.If image quality improvement is not possible or prac

85、tical,a switch to DDM may be the solution.2.1.4.Hospital with a CRM facilityFor a local or regional hospital with existing general radiology and CRM systems,the way forward will depend greatly on the current quality of imaging achieved as well as the economic resources available and the volume of wo

86、rk performed at the facility.Different scenarios and justifications are elaborated below:(a)The quality and efficiency of mammography could be improved by implementing DDM.If financial resources can be found,such a change is recommended.(b)If the current quality of CRM is not adequate,this problem o

87、ught to ideally be addressed immediately.If it is not possible or practical(e.g.without major purchases)to make these improvements with CR plate technology,it is recommended that the facility consider switching to DDM as part of the solution to achieving high quality.(c)If the current imaging qualit

88、y is compatible with recognized guidelines such as those of the AAPM 10,ACR 11,EUREF 6 or the IAEA 2 and workload demands can be accommodated,then it is reasonable to continue with the existing CRM system.If the mammography equipment is due for replacement,purchase of a DDM system is recommended.2.1

89、.5.Tertiary care hospital with breast imagingDDM is recommended in the case of a tertiary care hospital with a dedicated breast imaging service that includes multiple mammography units,several mammography medical radiation technologists,an adequate number of breast radiologists,and access to CQMPs a

90、nd qualified service engineers.Although DDM systems can offer the highest quality images from a technical point of view,this quality is possible only if the DDM system is operating properly and 9is being used correctly by appropriately trained personnel.Therefore,attention to QC and training standar

91、ds is essential.3.RESOURCES AND NEEDSIn this section,the resources and needs for different mammography technologies are described in detail.3.1.PROJECT MANAGEMENTFigure 7 shows the overall project management process in the establishment of a mammography facility.In developing the work plan,advice fr

92、om a professionally trained radiologist,medical radiation technologist and CQMP,with experience in mammography,would be invaluable.3.2.CORE CONSIDERATIONS3.2.1.Needs analysisNeeds analysis is the first step in project management.The needs analysis ought to be carried out on the basis of existing dem

93、ands as well as a realistic forecast.If an SFM is to be replaced by a DDM system,advice from experienced users would be useful.If local experience is not available,models from a similar health institution in the same country,or in a neighbouring country with similar socioeconomic structures,ought to

94、 be sought 8.The following points ought to be considered during needs analysis:Clinical need for breast imaging.For example,breast cancer is a significant problem,or its incidence is increasing rapidly in the region.Available clinical infrastructure for diagnosis and treatment of breast cancers.This

95、 includes the access to means of pathological diagnosis and access to treatments.Appropriate expertise to perform mammography diagnosis and screening.There ought to be an adequate number of qualified radiologists and medical radiation technologists to carry out routine mammography services.If local

96、10expertise(i.e.breast radiologist)is not available,telemammography may be considered.Financial resources to purchase the mammography equipment,support maintenance costs,replace expensive components at the end of their life and meet routine QC costs.11FIG.7.Overall project management process to esta

97、blish a mammography facility.Personnel to perform equipment maintenance,QC tests(daily tests by a medical radiation technologist and comprehensive tests by a CQMP)and professional advice and support from CQMP or information technology(IT)specialist.Expected patient volume or number of examinations p

98、er day.Possibility of lesion localization procedures.Possibility of advanced breast imaging techniques(e.g.tomosynthesis).Other breast imaging techniques(e.g.ultrasound)locally available.3.2.2.Facility designOnce the needs analysis is completed and needs are clearly identified,then discussion on the

99、 design of the facility will be initiated.More specifically,the following items can be investigated:Physical space:Based on the examination volume and the mix of procedures,the required amount of equipment and rooms can be determined.Personnel:Based on the workload,this includes breast radiologists,

100、medical radiation technologists,CQMPs and access to a qualified service engineer,administrative staff,IT support staff(if a digital system is chosen),etc.Workflow:The reception area,changing room,mammography equipment room,image processing area(e.g.darkroom for SFM,CR reader for CRM,digital workstat

101、ion,etc.),image display and radiologists reporting room,etc.ought to be located adjacent to each other for a better workflow.Supporting units such as IT and engineering services ought to be accessible or within the vicinity.Image and data management:Depending on the systems to be installed(SFM,CRM o

102、r DDM,either fixed or mobile),identify the storage requirements for images and data.Local regulations will dictate the minimum period of time they must be retained before they can be discarded.For digital data storage(cloud computing or a local server),it is necessary to comply with Health Level 7 s

103、tandards.1 Logistics:The mammography facility is usually located within an imaging department/centre so that the supporting services such as administration,scheduling,finance,etc.can be shared with other imaging services.1 http:/www.hl7.org123.2.3.Infrastructure and room When planning any medical X

104、ray imaging facility,it is necessary to ensure that nearby staff and public are not exposed to levels of radiation that exceed the current regulatory exposure limits 13.A mammography room may be smaller in size than other X ray rooms because of the smaller dimensions of the equipment.The room shield

105、ing requirements are also reduced due to the low X ray energies used.Because of this,normal building materials such as gypsum wallboard may provide sufficient attenuation.However,if this approach is used,it is important to remember that recalculation of the shielding will be required if the room is

106、used for other radiological purposes in the future 13.Depending on the design of the equipment,techniques used and total workload,radiation shielding requirements ought to be properly calculated by qualified personnel such as CQMPs or radiation protection experts and approved by the regulatory bodie

107、s 13.Details of the shielding calculation methods are described in Refs 1417.A typical mammography facility consists of the following structures(Fig.8):Reception area;Waiting areas(at least one for casual clothing and the other for gowned individuals);Changing room(s)either inside or adjacent to the

108、 mammography equipment room;Equipment room large enough for the mammography system and acquisition computer workstation(if applicable)with private access for the patient and staff;Darkroom(for SFM)or space for a CR plate reader(if applicable)close to the mammography unit;Radiologists interpretation

109、and reading room with appropriate viewing conditions(e.g.low ambient light level);Space allocated to additional service needs,if possible,such as medical physics,IT and engineering equipment;Spaces for professional training and meetings,if possible,with appropriate technology including computers,sof

110、tware,Internet access,online resources,etc.In addition,mammography equipment rooms require:Adequate power supply for uninterrupted function of the system without significant fluctuations.In all systems,an uninterruptable power supply(UPS)is recommended,while at least a simple surge protector ought t

111、o be 13added in the system when needed.Modern X ray generators can generally handle 5 second power outages,but not longer.Computers can be provided with a UPS,but normally the 10 to 30 minute range is the longest practical length of time for which these provide power.Temperature and humidity control

112、 to meet the needs of the imaging system.See the special needs of DDM systems in Section 3.3 both for image storage and operation.Dust control.Secure Internet access for software upgrades and possibly remote monitoring.Appropriate authorization(for the premises and the practices)according to the app

113、licable legislation,which includes radiation protection.3.2.4.EquipmentEquipment specifications need to be prepared by technical experts such as CQMPs,taking into consideration input from medical radiation technologists and radiologists,with full knowledge of the clinical needs and operational condi

114、tions,as well as regulatory requirements.Equipment specifications provided to the vendors ought to indicate the layout,the type of equipment/system needed,and the types of clinical procedures intended to be performed as well as a list of system components and description of the design,construction a

115、nd performance features of each component.Any electrical,mechanical and environmental conditions which may affect the performance of the equipment ought to also be included 13,18.14FIG.8.Sample mammography facility layout.The main components of a mammography system(Fig.9)include:X ray source(generat

116、or and tube)and gantry including compression paddle;X ray detector;Image processor(for an SFM or CRM system);Image display for interpretation;Data archive;Quality control tools and materials;UPS.As the designs and characteristics of the equipment depend strongly on the type of technology used,these

117、will be described in more detail in Sections 3.33.5.3.2.5.Authorization needsOnce the initial needs analysis is completed and discussion of the facility design is initiated,the authorization needs ought to be identified.These need to follow local or national legislation and regulatory bodies require

118、ments.This involves at least authorization by the regulatory body for radiation protection and by the health authority to carry out clinical practice.The authorization for radiation protection may be a two stage process of an initial application to build 15FIG.9.Main components of typical mammograph

119、y X ray equipment.a facility(submitted before construction begins)followed by a full review and assessment by the regulatory body,leading to granting of authorization 13.If the mammography system will be used for screening,additional justification and authorization might be needed.3.2.6.Staff Hiring

120、 and training of the dedicated staff to provide mammography services(including radiologists,medical radiation technologists and CQMPs)ought to be identified.In certain cases,when on-site staff cannot be available,access(e.g.through a contract)to adequate professional services is required.It is impor

121、tant to budget staff costs including training during the initial planning.3.2.7.Staff trainingIt is considered necessary for all staff members to have the certification required by local or national legislation to practice in the field of mammography.More information on the elements of the training

122、required for the imaging staff is discussed in Appendix VI.People with adequate training who are licensed to operate in a mammography facility ought to include the following staff:Radiologists;Medical radiation technologists;CQMPs;Administrative staff.Continuing education is important for radiology

123、professionals including those working in mammography.There are various methods(vendor videos,professional organizations,for-profit courses)to continually update knowledge in breast imaging.Most professional organizations recommend 15 hours of continuing education every three years,including the topi

124、c of radiation protection and medical exposure(justification and optimization).3.2.8.ProcurementOnce all of the above issues are addressed,then equipment procurement can be planned.Tender processes are usually applied in most centres to invite submission of quotations and technical specifications fr

125、om multiple vendors.The specifications need to be thoroughly reviewed to ensure that the qualified vendors have addressed all the identified needs of the equipment and facility.The quotation ought to also include a fully comprehensive maintenance and service 16contract,such as installation and calib

126、ration of the equipment,warrantees,delivery time,maintenance plans,QC tools,staff training and all other criteria as listed in the purchasers specifications.A purchase contract that sets out all items and conditions of the purchase as agreed by both the purchaser and the assigned vendor is recommend

127、ed.The contract ought to also include actions to be taken if conditions for acceptance are not met.A detailed and concise purchase contract will ensure the delivery of equipment in a timely and cost effective manner 18.3.2.9.Site-specific trainingThe training of all related staff on-site is vital fo

128、r the successful implementation of a mammography programme.This is particularly important for medical radiation technologists and radiologists.Plans for continuing education ought to also be identified.In developing the work plan,advice from professionally trained radiologists,medical radiation tech

129、nologists and CQMPs with experience in mammography would be valuable.The training programmes ought to include:Acceptance testing and commissioning of the equipment by a qualified CQMP;Implementation of a QAP;Breast screening and/or diagnostic workflow.3.2.10.Quality Every facility ought to develop a

130、nd put in place a relevant QAP with the participation of all professionals involved under the supervision of a CQMP.This is explained in more detail in Appendix V,but in terms of major quality needs,the QAP ought to include the following:(a)Preparation of relevant approval documents of the equipment

131、 for mammography use,as well as ensuring required approvals for electrical safety and radiation safety;(b)An organized QAP compatible with international or national recommendations that includes:(i)Acceptance test performed by a CQMP,with system adjustments until the system passes all the required p

132、hysico-technical tests.(ii)Approval of the clinical image quality by the radiologist team.(iii)Regular QC testing.Although it is very difficult to develop a technical QC test that correlates completely with clinical imaging performance,it is known that,to detect cancer,it is necessary to visualize s

133、ubtle 17changes in tissue for very small objects(e.g.microcalcifications)with a sufficiently high signal to noise ratio.It is desirable to do this at the lowest radiation dose compatible with such a task.There are various physical QC tests such as those developed and described as part of the program

134、mes from the AAPM 10,EUREF 6,the European Federation of Organisations for Medical Physics 19 and the IAEA 2,5.Tests of this sort ought to be used as part of the QC.Details of the testing are discussed in Appendix V.3.2.11.MaintenanceEvery facility ought to assure that maintenance is provided at leas

135、t yearly or in accordance with the recommendations of the manufacturer if that is more often 13.Maintenance for the first year after purchase is normally included as part of the purchase price and is called a warranty.Maintenance packages for subsequent services can be purchased after the end of the

136、 warranty.It is important for the facility to determine at the time of purchase precisely what is and what is not covered by such packages,as the details can vary tremendously.It is possible that details of these packages are negotiable,but this is usually done before the facility commits to purchas

137、ing the equipment.There are very expensive components,such as the X ray tube,X ray detector and high resolution monitors.If the cost of replacing such components is not included in the package,then funds to cover replacement cost need to be secured.Having a maintenance package may also guarantee a f

138、aster response by the service group in repairing system problems.Maintenance ought to be done by qualified personnel trained by the manufacturer.The equipment logbook ought to also be kept up to date with all maintenance details and notes.3.3.SPECIFIC NEEDS FOR DDMThe specific needs for a DDM facili

139、ty are discussed in this section.Figure 10 shows the typical workflow in a DDM facility.With the advantages of digital technology,the mammographic image and data can be viewed and analysed immediately once acquired,conveniently stored,printed and transmitted to the picture archiving and communicatio

140、n system(PACS).183.3.1.DDM equipmentImportantly,all mammography equipment ought to comply with relevant standards for mammography 9 as minimum requirements to ensure suitability for clinical use.A clinical DDM system includes the following:X ray source(X ray generator and X ray tube);Digital detecto

141、r;Acquisition workstation/operating console;UPS;Image processing and diagnosis workstation;Applicable software.Table 1 shows the recommended minimum specifications for a modern DDM system.Optionally,the system could be upgradeable to one with contrast-enhanced digital mammography(CEDM)and digital br

142、east tomosynthesis(DBT).Figure 11 shows the typical layout of a DDM equipment room while Fig.12 illustrates the main components of DDM X ray equipment.19FIG.10.Typical workflow in a DDM facility.Once the digital image is acquired,it can be shared instantly with the image processing software(puter ai

143、ded diagnosis),radiologists workstation and PACS server for evaluation.The image can either be stored digitally or printed in hard copy.(Images courtesy of Hospital Sungai Buloh,University of Malaya Medical Centre and Bin Zheng,Malaysia.)20TABLE 1.RECOMMENDED MINIMUM SPECIFICATIONS FOR A MODERN DDM

144、SYSTEM 2,6,11,2022 X ray generatorPower5.0 kWTube voltage range 2435 kVp(maximum 1 kVp step)Tube load rangeAt least 5400 mAsAECManual and automated selection of kVp,mAs,filterExposure time rangeAt least 30 ms to 2 sAnode and filter materialMaterials need to allow for low dose/high penetration spectr

145、a,even for thick or dense breasts.Examples of appropriate target materials are,for X rays:molybdenum(Mo),rhodium(Rh),tungsten(W)and for beam filter(s):Mo,Rh,aluminium(Al),silver(Ag)Focal spotTwo(approximately 0.3 mm and 0.1 mm);with both manual and automated selection of the focal spot availableAnod

146、e heat capacityAt least 200 000 HUX ray tube and gantryCollimators Fully automated adjustment for different paddles,sizes and magnificationMovementsMotorized vertical and rotating movementArm locking systemElectromechanical brakes or equivalentArm moving systemMotorizedControl buttons for vertical a

147、nd rotational movementOn both sides of C-armFocal spot to image detection distance(SID)65 cmPatient face shieldProvided for 2-D imaging21TABLE 1.RECOMMENDED MINIMUM SPECIFICATIONS FOR A MODERN DDM SYSTEM 2,6,11,2022 (cont.)Breast compression Manual and automated breast compression Maximum force when

148、 automated is between 150 N and 200 N Emergency release Automatic decompression after exposureDigital numerical indicator,both sides For C-arm rotation angle and compression forceMemorizable mediolateral oblique(MLO)angleC-arm that can stop automatically at contralateral angleScatter rejectionAntisc

149、atter grid(or equivalent technology)Magnification views At least one magnification view(with magnification stand)Magnification ratio provided,display providedAntiscatter grid removalAutomatic,motorized for magnification viewsBreast compression paddlesSeveral sizes(e.g.18 cm 24 cm and 24 cm 30 cm)wit

150、h small breast,spot and magnification paddles includedDigital detectorDetector typePreferably direct conversion flat panel detector(amorphous selenium(a-Se)or similar)Effective field sizeAt least equivalent to 24 cm 29 cmPixel size100 mDead pixel mapProvidedImage depthAt least 12 bitSystem spatial r

151、esolution7 lp/mmAcquisition workstationGeneral A separate workstation for image positioning and patient demographic data22TABLE 1.RECOMMENDED MINIMUM SPECIFICATIONS FOR A MODERN DDM SYSTEM 2,6,11,2022 (cont.)Operator controlsBoth detector and generator controls integrated in the same consoleExposure

152、 parameters settingBoth manual and fully automaticStandard clinical protocolsDocumented on a chart and/or preprogrammed within the systemComputer systemLatest technology(processor generation/type/speed,RAM or operating memory,hard disk,storage systems,etc.)Storage capacityAccording to the facilitys

153、need(e.g.minimum 5000 patients,both projections,both breasts)MonitorAt least 3 MP high resolution flat panelTime between sequential acquisitions30 sTime between acquisition and workstation preview60 cm31TABLE 3.RECOMMENDED MINIMUM SPECIFICATIONS FOR A CRM SYSTEM 2,28,29 (cont.)Patient face shieldPro

154、videdBreast compression Manual and automated breast compression Maximum automated force between 150 N and 200 N Emergency release Automatic decompression after exposureDigital numerical both sides indicatorFor C-arm rotation angle and compression forceMemorizable MLO angleC-arm that can stop automat

155、ically at a contralateral angleScatter rejectionAntiscatter grid(or equivalent technology)Magnification viewsAt least one magnification view(with magnification stand)as specified;magnification ratio needs to be providedAntiscatter grid removalAutomatic,motorized for magnification viewsBreast compres

156、sion paddlesSeveral sizes available(e.g.18 cm 24 cm and 24 cm 30 cm)with small breast,spot and magnification paddles includedCassette holder and buckyAvailable to hold different cassette sizes(i.e.18 cm 24 cm and 24 cm 30 cm)and a large bucky if appropriate to the populationAcquisition workstationGe

157、neral A separate workstation for image positioning and patient demographic dataOperator controlsGenerator controls integrated in the same consoleExposure parameters settingBoth manual and fully automaticStandard clinical protocolsDocumented on a chart and/or preprogrammed within the system32TABLE 3.

158、RECOMMENDED MINIMUM SPECIFICATIONS FOR A CRM SYSTEM 2,28,29 (cont.)Computer systemLatest technology(processor generation/type/speed,RAM,hard disk,storage systems,etc.)Storage capacityAccording to the facilitys needs(e.g.minimum 5000 patients,both projections,both breasts)MonitorAt least 3 MP high re

159、solution flat panelDICOM functionality and connectivityDICOM compatible(e.g.DICOM 3.0)Image processingImage analysis tools(e.g.mean,standard deviation,and region of interest tool with adjustable size and shape)Additional capabilities Ability to perform repeat/reject analyses Special processing for i

160、mplants Ability to add comments to an imageHand/foot switchesDouble hand switch for the exposure and double foot switch for breast compression/arm movements Radiation protection barrier dimensionsAdequate for operator protection(as calculated by the qualified personnel)Dimensions need to be provided

161、Radiation protection barrier thickness Adequate thickness to protect the operator(as calculated by the qualified personnel)Lead equivalence(mmPb)needs to be providedComputed radiography detector(imaging plate)Detector typeReusable photostimulable storage phosphor imaging plate stored in a cassetteEf

162、fective field size Commonly available in two sizes:18 cm 24 cm and 24 cm 30 cmPixel size50 mImage depthAt least 12 bit33TABLE 3.RECOMMENDED MINIMUM SPECIFICATIONS FOR A CRM SYSTEM 2,28,29 (cont.)System spatial resolution10 lp/mmNumber of imaging plate recommendedAt least two of each size;preferably

163、at least four of each sizeComputed radiography readerLaser spot size 50 m(modern reader)100 m(conventional reader)Readout time 50 s for a 18 cm 24 cm imaging plate 60 s for a 24 cm 30 cm imaging plateTransition time for digital image to be displayed on the workstation3060 sErasure time1020 sTotal cy

164、cle time(insert,read,remove and insert next cassette)6090 s(depending on the imaging plate size and signal density on the plate)Image processing and diagnosis workstationWorkstation System of the latest technology workstation class hardware(processor generation/type/speed,RAM,hard disk,storage syste

165、ms,etc.)MonitorsAt least two approved diagnostic mammography monitors of at least 5 MP and 53.5 cm(21 inches),with automated self-calibrationDisplay graphic cardHigh end medical gradeStorage capacityAs required(e.g.at least 1.5 TB)Workstation capabilities Display of multiple images and priors for co

166、mparison purposesMultimodality viewer capability for display of ultrasound,X ray,digital mammography,MRI,PET,CT on a third colour monitor34TABLE 3.RECOMMENDED MINIMUM SPECIFICATIONS FOR A CRM SYSTEM 2,28,29 (cont.)Mouse,keypadDedicated keypad for mammography,common keypad,mouseSoftware and interconn

167、ectivitySoftwareDedicated breast imaging software with at least the following functions:Magnification Zoom Pan Windowing Brightness adjustment Contrast adjustment Distance measurement Histogram display Contrast enhancementDisplay capabilitiesOne-to-one image display:One pixel on detector correspondi

168、ng to one pixel on monitorInterconnectivity Full DICOM compatibility(e.g.DICOM 3.0);Media export/import Automated transfer of the image acquisition parameters(e.g.kV,target and filter material,breast thickness,compression force,projection,L/R)for each exposure into the DICOM header Capability to exp

169、ort unprocessed and processed DICOM imagesPower supplyUPSDedicated on-line UPS(for all workstations and accessories)for a minimum backup time of approximately 30 minutesFigure 16 shows the main components in a CRM equipment room and Fig.17 illustrates the structure of a CRM cassette/imaging plate.35

170、36FIG.16.Typical layout of a CRM equipment room.(Image courtesy of CPD Projects,Australia.)FIG.17.Inner structure of a mammography CR cassette.3.4.2.Computed radiography readerThe CR reader can be used exclusively for mammography imaging plates or can be shared with other radiography plates.Ideally

171、it needs to be optimized for mammography use with the specific imaging plate technology that is present.The readers are available in different designs(Fig.18)to suit the local needs.The reader needs to be equipped with a computer and a display to register the patient,identify the plate and review or

172、 check the image.It ought to be capable of dedicated image processing for a breast and of producing DICOM compatible image formats.It is desirable for technical data such as exposure parameters,compression force and mean glandular dose(MGD)to be automatically transferred to the appropriate tags in t

173、he DICOM header to allow tracking.Alternatively,these can be manually registered,although this can be time consuming.The reader needs to be connected to PACS or to another storage device,whereby it ought to permit the export of images to other digital media,and appropriate software licences to do th

174、is need to be in place.It ought to be possible to export DICOM for processing images for QC purposes too.3.4.3.Review workstationThe review workstation requirements for a CRM facility are in general similar to those of a DDM 2.Also in CRM,two high resolution monitors of at least 5 MP are required.If

175、 it is not possible to purchase two monitors,software ought to be available to allow side by side viewing of images on a single high 37FIG.18.Samples CR readers:(a)tabletop;(b)single slot;and(c)multiple slots.resolution monitor.As with DDM,the monitor(s)are calibrated according to the Grayscale Stan

176、dard Display Function and tested regularly 2,25 using the standard Society of Motion Picture and Television Engineers test pattern(Fig.19)25.3.4.4.Data archivingIdeally,the system will be connected to a PACS system in the facility.Otherwise,some other form of adequate digital storage is required tha

177、t is appropriate for the workload of the facility.Approximately 40 MB is required for each examination that uses CR plates,assuming lossless compression.38FIG.19.Standardized Society of Motion Picture and Television Engineers test pattern,one type of test pattern that may be provided with the medica

178、l diagnostic monitor for quality control.3.4.5.Image printingIdeally,image interpretation will be done on a workstation with high resolution monitors so that the image can be manipulated interactively while viewing.If this is not feasible,images can be printed on a high resolution film printer.This

179、ought to be done at full size(1:1,one pixel printed for one pixel in the image)so that information is not lost.If interpretation is done from films(printed images),suitable film viewers(view boxes)are required.3.4.6.Quality The quality needs are as stated in Section 3.2.10,with the following additio

180、ns:A comprehensive QAP for CRM needs to be in place,as described in international guidelines 2,6,7.Test objects,software tools and dosimetry equipment ought to be available for QC of the CRM system.It is recommended to include such equipment in the procurement plan of new installations to minimize o

181、r optimize costs and avoid subsequent unanticipated expenses.System optimization to detect small,subtle structures in the breast.Because CRM is less dose efficient than DDM,the main task is to get the best performance it can deliver.This is often quantified by achieving at least a specified value of

182、 the signal difference to noise ratio(SDNR)as a ratio to dose.3.4.7.MaintenanceAlthough CR plates are part of the digital imaging component of the system,they are considered consumables and they need to be replaced when their performance is suspected to have deteriorated below set quality limits.Thi

183、s is a cost that needs to be foreseen in the planning of new practices and will depend on the workload of the department.The lifespan of a CR plate is typically hundreds or thousands of exposurereadouterase cycles,determined primarily by the care in handling and environmental conditions.During their

184、 lifespan it is important that the CR cassettes and screens be kept in good working condition,and one staff member(usually the medical radiation technologist)ought to have the responsibility for their regular maintenance,such as cleaning,removing from service and requesting replacement of those cass

185、ettes that have degraded or cannot be cleaned.Maintenance ought to be done by personnel qualified and trained by the manufacturer.Maintenance logbooks need to be kept up to date.393.4.8.Staff trainingTransition from film to CRM is a challenging task and requires adequate competencies for all involve

186、d professionals.Some of the required additional skills for radiologists,medical radiation technologists and CQMPs are shown in Table 4.TABLE 4.ADDITIONAL SKILLS REQUIRED IN CRM FOR A RADIOLOGIST,MEDICAL RADIATION TECHNOLOGIST AND CQMP PersonnelAdditional skillsRadiologist Basic principles of CRM Bas

187、ic understanding of the modality and technique Reading/reviewing the modality(or telemammography)Basic computer skills especially related to digital image postprocessing Accommodation to the different,possibly unfamiliar appearance of digital images Judgement of clinical image quality In-depth train

188、ing on optimal use of the modality,including image presentation,storage and retrieval(to and from PACS and other media)Basics of DICOM and PACS Image windowing How to evaluate quality(i.e.images acquired by medical radiation technologists,image processing and QC tests by the CQMPs)Use of additional

189、features,if available(computer aided detection,etc.)Creation of databases,especially for teaching purposes,if applicableMedical radiation technologist Basic principles of CRM Basic understanding of the modality and technical specifications Positioning and compression for breast imaging(including tra

190、ining specific to CRM,e.g.when using new plate sizes)In-depth training on optimal use of the modality,including image presentation,storage and retrieval(to and from PACS and other media),DICOM knowledge,AEC functionality,image windowing,dose indexes interpretation and recording,etc.Computer skills N

191、ew QA/QC procedures,including identification of artefacts from both QC and patient images Cleaning and handling of the CR image plates40TABLE 4.ADDITIONAL SKILLS REQUIRED IN CRM FOR A RADIOLOGIST,MEDICAL RADIATION TECHNOLOGIST AND CQMP (cont.)PersonnelAdditional skillsCQMP Physical principles of CRM

192、 Advanced knowledge on the technical specifications of the modality Quality assurance protocols and interpretation for CRM In-depth knowledge of image quality and dose optimization in CRM Advanced computer skills(in handling DICOM images)Knowledge of basic image processing Basics of networking(to su

193、pport PACS)3.5.SPECIFIC NEEDS FOR AN SFMAn SFM can provide excellent image quality,but quality tends to be reduced for dense breasts.In addition,it provides less flexibility than DDM or CRM,and image quality can be lower than DDM in the case of suboptimal film processing.There are challenges and cos

194、t implications associated with the acquisition and storage of film as well as the use and disposal of chemicals.Figure 20 shows the typical workflow of an SFM facility.Multiple steps and lengthy processes are involved to acquire,process,view and store an X ray film.As well,many of the costs,expertis

195、e needs,QC and QA activities would be centralized.3.5.1.SFM equipmentAll equipment complies with relevant standards for mammography equipment(e.g.IEC 9)at minimum,to ensure suitability for clinical use.A clinical SFM system would ideally include the following:X ray source(X ray generator and X ray t

196、ube);Acquisition/operating console;Screen-film combination image receptor(Fig.21);Darkroom for film processing(Fig.22);Film viewing and display room.Table 5 shows the recommended specifications for an SFM system.4142FIG.20.Typical workflow in an SFM facility.(Images courtesy of Konstatopoulio Genera

197、l Hospital,Greece and Hospital Sungai Buloh,University of Malaya Medical Centre,Malaysia.)FIG.21.Construction of a mammography screen-film system(single-emulsion single-screen combination).TABLE 5.RECOMMENDED MINIMUM SPECIFICATIONS FOR AN SFM SYSTEM 5,6,28,3032 X ray generatorPower5.0 kWTube voltage

198、 range 2435 kVp(maximum 1 kVp step)Tube load rangeAt least 5400 mAsAECManual and automated selection of kVp,mAs,filterAEC sensor(phototimer)Located underneath the screen-film cassette,with position adjustable below appropriate region of the breastExposure time rangeAt least 30 ms to 2 sAnode and fil

199、ter materialAppropriate target material(s)for X ray(e.g.Mo,Rh,W)and beam filter(s)(e.g.Mo,Rh,Al,Ag)Focal spotTwo:approximately 0.3 mm usually used for contact mammography and 0.1 mm primarily used for magnificationAnode heat capacityAt least 200 000 HUX ray tube and gantry43FIG.22.Typical darkroom l

200、ayout.(Image courtesy of Chan Lai Kuan,Malaysia.)TABLE 5.RECOMMENDED MINIMUM SPECIFICATIONS FOR AN SFM SYSTEM 5,6,28,3032 (cont.)Collimators Fully automated adjustment for different paddles,sizes and magnificationMovementsMotorized vertical and rotating movementArm locking systemElectromechanical br

201、akes or equivalentArm moving systemMotorizedControl buttons for vertical and rotational movementOn both sides of C-armFocal spot to image detection distance(SID)60 cmPatient face shieldProvidedBreast compression Manual and automated breast compression Maximum automated force between 150 N and 200 N

202、Emergency release Automatic decompression after exposureMemorizable MLO angleC-arm that can stop automatically at a contralateral angleMagnification viewsAt least one magnification view(with magnification stand).Magnification ratio needs to be providedAntiscatter grid Moving antiscatter grid with gr

203、id ratio between 3.5:1 and 5:1,for each image receptor size that is removable for magnifications viewsBreast compression paddlesAvailable in different sizes(i.e.18 cm 24 cm and 24 cm 30 cm).Small breast,spot and magnification paddles need to also be includedFilm cassette holder and buckyAvailable to

204、 hold different cassette sizes(e.g.18 cm 24 cm and 24 cm 30 cm)and a large bucky if appropriate to the population Operating console44TABLE 5.RECOMMENDED MINIMUM SPECIFICATIONS FOR AN SFM SYSTEM 5,6,28,3032 (cont.)General A separate workstation for image positioning and patient demographic data is re

205、quiredOperator controlsGenerator controls integrated in the same consoleExposure parameters settingBoth manual and fully automaticStandard clinical protocolsDocumented on a chart and/or preprogrammed within the systemHand/foot switchesDouble hand switch for the exposure and double foot switch for br

206、east compression/arm movements Radiation protection barrier dimensionsAdequate for operator protection(as calculated by the qualified personnel)Dimensions need to be providedRadiation protection barrier thickness Adequate thickness to protect the operator(as calculated by the qualified personnel)Lea

207、d equivalence(mmPb)needs to be providedScreen-film image receptorDetector typeSingle back intensifying screens used with single-emulsion radiographic film enclosed in a lightproof cassette.All cassettes used in the department need to be identicalIntensifying screenCommonly available in two sizes:18

208、cm 24 cm and 24 cm 30 cm(paired with the mammographic films)Quantum detection efficiency60%for a typical screen thickness and X ray spectrumX ray to light conversion efficiency10%Mammographic film typeFilms need to be of the same type(manufacturer,sensitivity rating,etc.)and be compatible with the p

209、hosphor screens and cassettes45TABLE 5.RECOMMENDED MINIMUM SPECIFICATIONS FOR AN SFM SYSTEM 5,6,28,3032 (cont.)Film size18 cm 24 cm and 24 cm 30 cm(compatible with the phosphor screen and cassette)Film emulsionMatched to be sensitive to the spectrum of light emitted from the phosphor screenTarget op

210、tical density1.51.9Film sensitivity(speed)Compatible with the phosphor screenScreen-film combination speedRelative speed 150200System spatial resolution11 lp/mmDarkroom for film processing 5LocationAdjacent to the mammography roomBackground radiation Acceptable level is 5 cm)or spread to skin of the

211、 breast or chest wall or spread to lymph nodes even above the collar bone.Stage IV In this stage,cancer cells have spread to and established residence in other organs and tissues including the brain,liver,lung or bone.I.2.INCIDENCEOnce a disease mainly associated with wealthier countries,breast canc

212、er incidence is now increasing in Asia and Africa.Because of large populations,among the highest number of breast cancers appearing annually occur in Asia.When expressed as rates per 100 000 population,there is a twentyfold difference between countries with the highest breast cancer incidence(204/10

213、0 000 in Belgium)and those with the lowest incidence(15/100 000 in Bangladesh and 10/100 000 in Tanzania)4.While the highest incidence rates are still observed in Europe,Australia and New Zealand and North America,the rates are rising quite slowly over time.Conversely,rates are rising most quickly i

214、n countries that have low and middle incomes,such as Uganda and China.I.3.BREAST CANCER MORTALITYIn terms of mortality,patterns are similar,with the number of breast cancer deaths being highest in Asia,although age standardized mortality rates tend to vary less.A much higher proportion of women who

215、are diagnosed with breast cancer die of the disease in countries that have a low human development index.Santucci et al.studied trends over time between 2000 and 2016 in France,Germany,Italy,Japan,United Kingdom and the United States of America and found that breast 70cancer mortality fell 1.0%to 2.

216、5%on average per year in every country except in Japan where there was an annual increase of 1.4%73.Incidence increased in most of these countries at annual relative rates of between 0.3%and 1.0%.Japan,however,showed the highest rate of increase in incidence over this period of 5.2%per year,although

217、 the values of both incidence and mortality themselves are the lowest among these countries.Santucci et al.also observed an increase in survival over the period in all the countries studied although survival rates varied considerably,being lowest in the UK and highest in Japan 73.When the mortality

218、rates are graphed versus incidence rates(Fig.30),there is an overall positive correlation between the two among different countries.Examples of countries with high incidence,in which mortality is in the middle of the cluster are Argentina,Lebanon,Singapore and Jordan.It is instructive,however,to con

219、sider the outliers.In some countries with medium and high reported incidence rates,mortality is markedly lower than the trend line.Examples of these countries are Australia,Canada,Finland,Republic of Korea,Malta,Norway,Portugal,Spain,Switzerland and the United States of America.This is likely due to

220、 a combination of earlier detection,relatively prompt and effective treatment and thorough,efficient reporting through cancer registries.Also seen are countries where reported incidence is relatively low,but mortality is disproportionately high.These include the Central African Republic,Equatorial G

221、uinea,Fiji,Niger and Somalia.One possibility is that the actual incidence is higher than recorded due to incomplete incidence reporting.Another possibility is that,in the absence of screening programmes,breast cancer is detected only when it is symptomatic and access to high quality treatment is ver

222、y limited.In their study of breast cancer outcomes in India,Mallath et al.identified that the ratio of mortality to incidence is negatively correlated with the human development index 74.I.4.BREAST CANCER SURVIVAL RATESIn the comprehensive study known as CONCORD-3,Allemani and colleagues analysed th

223、e 5-year survival rates of over 6.4 million women from 66 countries who were diagnosed with invasive breast cancer between the years 2000 and 2014 75.They found that the current 5-year survival rate for breast cancer stands at 89.5%in Australia and 90.2%in the United States,yet there are considerabl

224、e international variations,with rates as low as 66.1%in India 75.The researchers observed that survival rates ranged from 70%to 79%in 12 countries,which included Cuba and Ecuador;Kuwait and Mongolia;and eight European nations(Estonia and Lithuania from Northern Europe;Croatia from Southern Europe;as

225、 well as Bulgaria,Poland,Romania Cluj,Russia and 71Slovakia from Eastern Europe)75.While there was a general improvement in breast cancer survival rates between 2000 and 2014,significant differences in the rate of progress persist among countries,with many Eastern European countries still experienci

226、ng low survival rates.An excellent overview of the international patterns of breast cancer incidence and mortality,and projections of these into the future for countries at different levels of development is provided by the International Agency for Research on Cancer 76.It is predicted that in the m

227、ost developed countries,breast cancer incidence will increase by 16%between 2012 and 2025 while deaths will increase by 24%.In countries with the lowest human development indices,it is expected that incidence will increase by 47%and deaths by 57%.I.5.STAGE AT DETECTIONIn jurisdictions where earlier

228、detection or screening programmes do not exist,breast cancer tends to be detected when tumours are larger and at a more advanced stage.In Mexico,a 2017 publication indicates that 49%of breast cancers are diagnosed at Stage III/IV 77.In a 2002 report from Chennai,72FIG.30.Mortality due to breast canc

229、er compared to its incidence in various countries 4.Note:North America contains data from USA and Canada,whereas the Americas include data from both North and South America.India,only 1.0%of cancers were detected at Stage I,23%at Stage II and three quarters at Stage III or IV 78.Jedy-Agba et al.carr

230、ied out a systematic review of data on diagnosis of breast cancer in sub-Saharan Africa and found that 74.7%(median value)of breast cancers were found at Stage III or IV 79.There was wide heterogeneity between different regions(30100%)in the proportion of cancers diagnosed at a later stage,with the

231、percentage being higher in Black women than in women who are not Black,and higher in rural than urban areas.In some of the reports listed,these later stage cancers accounted for over 90%of the cancers diagnosed.Furthermore,in sub-Saharan Africa most of the breast cancers were diagnosed in women aged

232、 3549.The percentage of late-stage cancers fell gradually between 1980 and 2000,but both the rates and the rate of decline continue to be much higher than in most of Europe and North America.The authors compared these data with the USA,where between 1973 and 2011 the percentage of Stage III/IV cance

233、rs fell from 60%to 27%in White women and fell from 60%to 32%in Black women,while rates in Black women in sub-Saharan Africa are still well over 60%.Kim et al.surveyed regional variations of breast cancer outcomes in Asia and found that the proportion of Stage III/IV cancers among breast cancers diag

234、nosed was highest in the Philippines(42%)and Jordan(35%),intermediate in China(26%)and Israel(Jewish population)(23%)and lowest in Japan(12%),Hong Kong,China(18%)and the Republic of Korea(19%)80.In Canada,Davidson et al.demonstrated a marked downward shift in stage at diagnosis associated with parti

235、cipating in an organized screening programme;9%of cancers were found at Stage III/IV in participants versus 21%in non-participants 81.I.6.BREAST CANCER SCREENINGScreening is the routine examination of asymptomatic individuals for the purpose of detecting a disease earlier,before it presents symptoms

236、.It has been demonstrated in randomized controlled trials,case-control studies and observational studies of real-world screening programmes that regular high quality screening with X ray mammography can contribute to marked reductions in mortality from breast cancer 8286.Through earlier detection,sc

237、reening can often also make it possible to treat smaller cancers at an earlier stage,allowing less harsh therapies to be used:breast conserving surgery rather than mastectomy,avoidance of axillary dissection and chemotherapy 8791.While breast cancer screening can be effective,it is not an efficient

238、process in that typically only between 2 and 10 cancers will be detected per 1000 examinations.In addition,depending on how screening is 73practised,between 3%and 15%of women will have at least slightly suspicious findings upon initial examination,prompting the need for further imaging.If results re

239、main positive,definitive diagnosis of cancer is then obtained by biopsy,currently often performed using a core needle method.Typically,between one third and one half of the biopsies performed are positive for a diagnosis of cancer.Screening,therefore,requires considerable resources:a mechanism to in

240、vite women to have their regular examinations and to convey results back to them,imaging equipment,a medical radiation technologist to perform the exam by positioning the breast and acquiring the images,a radiologist to interpret the examinations,access to biopsy,pathology to provide the diagnosis,a

241、nd surgical,medical or radiation therapy as well as maintenance and QC of the imaging equipment.Before attempting to implement a screening programme,all these factors ought to be considered.Providing these necessary components may be extremely challenging.Anderson et al.argued that earlier detection

242、 of symptomatic cancer needs to be in place before embarking on screening and they proposed a sequential action plan for moving in this direction,particularly in LMICs:“1)promote the empowerment of women to obtain health care,2)develop infrastructure for the diagnosis and treatment of breast cancer,

243、3)begin early detection efforts through breast cancer education and awareness,and 4)when resources permit,expand early detection efforts to include mammographic screening.Public education and awareness can promote earlier diagnosis,and these goals can be achieved in simple and cost-effective ways,su

244、ch as dissemination of messages through mass media.All women have the right to education about breast cancer,but it must be culturally appropriate and targeted and tailored to the specific population”78.Several documents have been developed to provide guidance on the decision regarding implementing

245、screening and on the design of screening programmes 9295.While the principles in these documents continue to apply,some of the documents are old,and both technology for breast cancer detection and treatment options continue to advance.It is important to keep this in mind when referring to these reso

246、urces.74Appendix II MAMMOGRAPHY TECHNOLOGYMammography is the leading technique for breast cancer diagnosis and the only imaging method that,when used for screening,has been demonstrated to contribute to reduced breast cancer mortality.It is the first line diagnostic test for non-palpable breast lesi

247、ons.Breast cancer screening programmes(discussed in Appendix I)are well established in many countries worldwide,but there are significant variations in the quality of tests and time intervals between examinations.These vary from mammograms performed every year to one examination every three years.Cu

248、rrently,many LMICs have not invested in screening programmes and preventive medicine because of limited financial resources and health care infrastructure.It ought to also be emphasized that the reliability and sustainability of any screening programmes require strict QA of imaging procedures,from t

249、echnical issues(e.g.positioning of the breast during imaging,choice of image acquisition parameters,image quality and calibration of the X ray equipment)to interpretation of the images(e.g.viewing conditions,review of previous images,double reading),evaluation of early recalls,feedback information,m

250、ultidisciplinary conferences,diagnostic performance indicators and continuing education.Mammography requires adequate competence and training of dedicated personnel(discussed in Appendix VI)in order to guarantee high quality diagnostic information(high sensitivity and specificity in detecting cancer

251、,thereby minimizing the chances of missed cancers and reducing unnecessary recalls in the case of undetermined findings).It is desirable that a mammography facility provide a short waiting time for appointments and a friendly and inviting atmosphere.The role of the medical radiation technologist nee

252、ds to be highlighted at this point,especially in terms of personal communication and interaction with the patient.As the medical radiation technologist is usually the only health professional the patient will meet,it is important to have adequate training,skills and competencies to deal with this se

253、nsitive situation.The diagnostic accuracy(especially sensitivity)of mammography is suboptimal in subjects with so-called dense breasts;sensitivity can be as low as 65%in dense breasts,compared to 8590%in mainly fatty breasts.Doubtful cases can be clarified by other imaging modalities such as ultraso

254、und,MRI and mammoscintigraphy(the latter being used much less commonly).75II.1.BREAST IMAGING WITH MAMMOGRAPHYMammography is an X ray examination of the breast.Images are acquired at relatively low X ray energy with the breast placed between an image receptor(recording device)and a compression plate

255、 which is used to reduce the thickness of the breast to improve image quality and decrease the dose to the patient.Although mammography plays an important role in the early detection of breast cancer,it has been demonstrated that when the quality of the mammograms is not sufficiently high,the abilit

256、y to detect cancers earlier is impaired 96.In breast cancer screening(Appendix I),reduced accuracy of mammography is associated with worse outcomes of the screening programme.A high quality mammography image is one that has the following properties:The breast is properly positioned;There is excellen

257、t contrast over as much of the breast as possible;There is adequate sharpness(spatial resolution)throughout the breast area;There is no excessive noise that can degrade the imaging of the anatomical structures;There are no disturbing artefacts that can resemble pathological findings or obscure prope

258、r diagnosis;The imaging examination delivers as low a radiation dose as low as possible,consistent with the required image quality,keeping in mind that the examination can be performed on healthy women without any symptoms.Image quality is associated with the performance of the equipment as well as

259、with the manner in which it is used.Equipment performance depends on its design and manufacturer but also on whether it is properly maintained and adjusted over time.Figure 31 shows an example of a mammogram acquired in MLO projection.II.2.OVERVIEW OF MAMMOGRAPHY X RAY TECHNOLOGIESII.2.1.Components

260、of a mammography systemMammography X ray technology has improved remarkably since the turn of the 21st century.When purchasing a new or used mammography machine,one ought to expect the system to have a high frequency power supply to energize the X ray tube,capable of delivering tube voltages up to 4

261、9 kV.The tube needs to have a design specifically for mammography that includes a molybdenum,rhodium or tungsten target with two sizes of focal spot to permit both contact 76and magnification imaging.The X ray field ought to be able to cover the entire breast with a single exposure.Appropriate metal

262、lic beam filters matched to the available target materials need to be in place.The system ought to provide collimation to define the X ray field for exposure and have an integrated optically transparent compression plate 77FIG.31.Example of a mammogram acquired in an MLO projection.Characteristic be

263、nign calcifications(in red circle)are seen in this mammogram.(Image adapted from 28.)with a mechanism for controlled compression of breast thickness and a safety mechanism to avoid overpressure.An antiscatter grid,with either a motion mechanism to blur grid lines or a dedicated stationary grid with

264、sufficiently high pitch so that grid lines do not interfere with the image,also need to be integral to the system.An AEC device which senses the amount of radiation transmitted through the breast to reach the image receptor is essential.Other desirable features include readout of breast compression

265、thickness and force or pressure and automatic selection of exposure parameters such as target/filter combination and kilovoltage on the basis of information about the breast gathered from a short low dose pre-exposure and the readout of compression thickness.Figure 32 illustrates the main components

266、 of typical mammography X ray equipment.II.2.2.DDM technologyDigital mammography,introduced commercially in 2000,is able to overcome many of the technical limitations of screen-film mammography.In digital mammography,image acquisition produces a digital image that can then be further processed,displ

267、ayed and stored independently,allowing for optimization of each step.Acquisition is carried out using low-noise X ray detectors with a 78FIG.32.Main components of a typical mammography X ray equipment.broad dynamic range.The resultant image can be digitally stored and displayed with a contrast that

268、does not depend on detector characteristics but is determined by the specific imaging task requirements.A variety of helpful image processing techniques can be conveniently applied before displaying the image.These techniques may include anything from straightforward contrast improvement to altering

269、 the histogram and spatial frequency filtering to enhance image sharpness or minimize noise.The hurdles in developing a digital mammography system with enhanced performance largely revolve around the X ray detector and the display apparatus.The detector exhibits the following features:Efficient abso

270、rption of the incoming radiation beam;A response that is linear or logarithmic across a broad spectrum of incident radiation intensity;Minimal inherent noise and virtually no fixed pattern noise,to ensure that images are X ray quantum noise limited;A limiting spatial resolution on the scale of 5 to

271、10 cycles/mm(50 to 100 m sampling);It can handle a field size of at least 18 24 cm and ideally a 24 30 cm;It has the capability to image immediately adjacent to the chest wall;A satisfactory image capture duration and heat handling capacity of the X ray tube(for instance,in detectors that ideally re

272、quire scanning to image the entire breast).There are two main approaches in detector development area detectors and scanning detectors(Fig.33).Most commercial systems adhere to the initial method where the complete image is captured all at once.In contrast,scanning systems acquire only a fragment of

273、 the image at a time,and the entire image is compiled by moving the X ray beam and detector across the breast.Area detectors provide quick image acquisition and can be utilized with traditional X ray machines equipped with a grid to minimize scatter.On the other hand,scanning systems have extended a

274、cquisition durations and are mechanically more intricate,but employ relatively uncomplicated detectors and exhibit superior inherent scatter rejection 28.Various detector technologies are employed in DDM systems.In so-called indirect detectors(Fig.34),each del(detector element)includes both a light

275、sensitive photodiode(i.e.amorphous silicon(or a-Si)and a thin film transistor switch.The array is covered with a phosphor layer,typically made of thallium activated CsI(caesium iodide(CsI:Tl).X rays transmitted by the breast are absorbed by the phosphor and the light produced is converted in the pho

276、todiode to charge,which is stored on its capacitance.The array in 79question is coated with a phosphor layer,usually comprising thallium-activated CsI(caesium iodide,CsI:Tl).X rays passing through the breast are absorbed by the phosphor,which then emits light.This light is transformed into electrica

277、l charge by the photodiode,and this charge is stored in its capacitance.Following the X ray exposure,signals are sent along each row one by one,triggering the corresponding switches.This process moves the charge down the columns towards readout amplifiers and multiplexers,where it is subsequently di

278、gitized to create the image.This reading system enables the extraction of signals from the dels in a very short time.The needle-like crystals of CsI,which behave a bit like fibre optics,direct the light to the photodiodes with less sideways dispersion than granular phosphors would cause.This propert

279、y allows for a thicker phosphor layer compared to a granular one,enhancing the detectors X ray detection efficiency without significantly sacrificing spatial resolution.Direct detectors employ a similar readout strategy but,instead of a phosphor,employ an X ray absorber composed of amorphous seleniu

280、m(a-Se),which is a photoconductor.In these detectors:“the energy of the absorbed X rays causes the liberation of electron hole pairs in the selenium.The charged particles are drawn to the opposite faces of the detector by an externally applied electric field.To collect the signal,an array of electro

281、de pads(rather than photodiodes)forms the dels.Unlike the phosphor based detectors,the electric field can be tailored to collect the charge with minimal lateral spread.This allows the use of a relatively thick detector to achieve excellent QDE efficiency without significant reduction in resolution a

282、t near normal incidence(Fig.35)28.”80FIG.33.Comparison of(a)a scanning detectors system and(b)an area detector system of a typical DDM system.II.2.3.CRM technologyA different type of detector technology employed in CRM involves a lightproof cassette containing a plate composed of photostimulable pho

283、sphor material.This plate gets excited by electrons when exposed to X rays,and the resulting captured electrons are proportional to the amount of X ray energy absorbed in a specific area of the detector.Following exposure,the plate is placed in a reading device(known as the computed radiography plat

284、es reader(Fig.36)and is scanned with a red HeNe laser beam 28.The laser lights energy triggers the release of electrons from the traps,causing them to transition through energy levels within the phosphor crystal,which in turn generates blue light.An effective optical system collects this light,measu

285、res it using a photomultiplier tube,and converts it into digital signals.By matching the signals measurement time to the scanned laser beams location,the signal can be assigned to a specific image pixel.In CRM,image resolution depends on various factors such as the size of the scanning laser beam,th

286、e scatter of the readout laser light in the phosphor and the sample measurements distance.81FIG.34.Basic principles of an indirect conversion flat panel detector.Thallium activated caesium iodide(CsI:Tl)phosphor converts X rays into lights and then they are converted into charges by the amorphous si

287、licon(a-Si)photodiode.The charges are stored in individual thin film transistors and then transferred to readout amplifiers and multiplexers to form a digital image.In mammography photostimulable phosphor systems,several differences exist in comparison to general radiography photostimulable phosphor

288、 systems.These mammography systems have been designed to achieve higher spatial resolution,necessitating the use of thinner phosphor materials,and finer sampling 82FIG.35.Comparison of(a)indirect conversion and(b)direct conversion flat panel detector used in DDM systems.FIG.36.Basic operations of a

289、CR plates reader.pitch,usually around 50 m.These factors contribute to reduced signal per pixel,which has been addressed by several innovative techniques.These techniques include using dual-sided readout of the phosphor plates and the use of needle-like phosphors that permit the use of thicker detec

290、tors with superior performance.Overall,these adaptations enable the production of high quality images with improved resolution and better sensitivity.Thus far,the detector systems examined have been acquiring images by aggregating the signal from a number of X ray quanta that get absorbed in the det

291、ector,which then undergoes digitization.The noise present in these images is influenced by both the Poisson X ray quantum fluctuations arising from X ray absorption,and additional noise sources related to the production of the electronic signal.These noise sources may emerge from the variation in th

292、e amount of light produced by a phosphor after absorbing an X ray with a specific energy level or from the X ray spectrum itself,where different quantities of signal occur as X ray quanta of differing energies interact with the detector material.Alternatively,one could directly tally the interacting

293、 quanta,sidestepping the extra noise sources in the process.Quantum counting detectors,usually designed as multiline devices,commonly utilize a set-up where the X ray beam is collimated into a single or multiple slits.This beam is then systematically moved across the breast to gather the necessary i

294、maging data.The detectors basis could be either a solid-state method,which generates electron hole pairs in a substance such as crystalline silicon,or a pressurized gas method where the signal is constituted by ions formed within the gas.Regardless of the method,the charge signals collection and sui

295、table amplification result in a pulse for each X ray quantum interaction.These pulses are then simply tallied to form the signal.Another characteristic of these detectors is their collimation of the beam to only expose a section of the breast at a time.This reduces the scatter to primary ratio(SPR)w

296、ithout requiring a grid,thereby enhancing the systems dose efficiency 28.II.2.4.Comparison among mammography technologiesThere are two general forms of mammography technology currently in use:analogue systems like SFM and digital systems.Digital systems are further subdivided into two types:CRM and

297、DDM systems.In SFM systems,X rays transmitted through the breast are absorbed by a fluorescent screen,producing a pattern of light representing the relative transmission of the X rays through different areas of the breast(Fig.37).A sheet of photographic film pressed tightly against the screen record

298、s that light pattern.The screen and film are contained in a lightproof cassette.After the X ray exposure,the film is transferred to a processor where chemicals are used to 83render a pattern of varying dark areas on the film.When placed on a brightly illuminated surface(of a viewing box)the light tr

299、ansmitted through the film forms the mammographic image that is viewed and interpreted by a radiologist.In CRM,a fluorescent screen in a cassette is used as in an SFM set-up and no film is required.The construction of a CR imaging plate is shown in Fig.37.Rather than the phosphor emitting the light

300、during exposure,the phosphor is photostimulable in that the energy from the absorbed X rays forms a pattern of trapped electrons in the phosphor,the density of electrons being proportional to the number of X rays absorbed.This latent image pattern is stored in the traps until the cassette and plate

301、are moved to a reader(Fig.38)where the latter is raster scanned by a fine red laser beam and the electrons are released from the traps to emit blue light.The intensity of the emitted light is recorded digitally and,when plotted versus the x-y coordinates of the point on the plate from which the ligh

302、t was emitted,produces the digital image.In DDM systems,a detector is integrated into the mammography system.This detector absorbs the X rays transmitted by the breast,converts their energy into a pattern of electrons,records the associated signal on very small 84FIG.37.Construction of a mammographi

303、c screen-film system.A single emulsion-single screen is used in mammography to preserve high spatial resolution.The image receptor is positioned such that X rays travel through the cassette cover and film before interacting with the intensifying screen.As X rays are more likely to interact near the

304、screen phosphor surface,which is closest to the film emulsion,this configuration reduces the distance between light photons and film emulsion and minimizes the diffusion path of the light to preserve high spatial resolution.discrete elements of the detector and allows readout along wires in the dete

305、ctor for digitization.Even though SFM,CRM and DDM systems are the three broad categories that represent different technologies of imaging,it has to be highlighted that even within each category one can identify large variations in the technical design(e.g.powder versus needle detectors for CRM,direc

306、t versus indirect X ray conversion in DDM).Selecting the proper technology requires care,as the implications for the resulting image quality,radiation dose and cost of the equipment can be significant.Film based imaging was the reference standard for many years.It is relatively inexpensive,but it is

307、 now gradually being replaced by digital technologies because it can overcome inherent limitations of film based technologies,including the necessity of film processing and inability to control the brightness,contrast and other image display properties while viewing images.The advantages and limitat

308、ions of film compared to digital imaging are summarized in Table 8.An important factor that distinguishes the performance of SFM,CRM and DDM systems is associated with point to point non-uniformities in the image that are unrelated to the breast,such as spatial variations in the X ray beam intensity

309、 or variations in the sensitivity of the detector.These are spatial variations that are constant,at least over periods of days or more.In CRM,these variations will be displayed in the image and can reduce its quality.They are often termed fixed pattern noise(e.g.screen artefacts).85FIG.38.Constructi

310、on of a CR imaging plate 28,97.The photostimulable storage phosphor is doped with a small number of impurities(e.g.europium,Eu),which alter the physical properties of its crystalline structure.When X ray energy is absorbed by the phosphor,the absorbed energy excites electrons associated with the eur

311、opium atoms and enables them to enter the conduction band.Some electrons return immediately to the valence band,but others remain trapped in the forbidden zone(so-called F-centre)between the two bands.The F-centre traps these electrons in a higher energy,metastable state where they can remain for da

312、ys to weeks,with some fading over time.The number of trapped electrons per area unit is proportional to the amount of radiation incident at each location during the exposure 32.86TABLE 8.ADVANTAGES AND LIMITATIONS OF FILM BASED IMAGING AND DIGITAL IMAGINGAdvantagesLimitationsFilm based imaging Low c

313、ost High spatial resolution Less sensitive to scattered radiation Multiple sizes of image receptors Ease of display Well established technique Requires special rooms(darkroom)and physical storage of films pre-and post-irradiation Requires the use of chemicals,wet processing,well controlled processin

314、g conditions and special drainage or waste facilities Limited dynamic range Characteristics of recorded image(e.g.contrast,brightness)cannot be adjusted Cannot be transmitted without the loss of information through scanning May require a higher dose to the breast than digital systemsDigital imaging

315、Efficient information dissemination and increased access to images Wider dynamic range Improved reliability,error free retrieval of images without information loss Improved workflow and patient throughput Potential for multimodality,composite imaging Simultaneous transmission and display of images t

316、o multiple locations Image manipulation and postprocessing,feature extraction and enhancement High initial cost Generally poorer limiting spatial resolution compared to screen-film Susceptible to artefacts due to the imaging plate(for CRM)or image processing algorithms Increased sensitivity to scatt

317、ered radiation Loss of instantaneous feedback on over-or underexposure Requires some basic knowledge of digital image processing and viewing Requires IT support for interconnectivityIn DDM systems they can be removed by imaging a uniform field(such as a slab of plastic)and performing corrections on

318、the recorded image to make it virtually uniform.The mask or gain map describing those corrections is stored digitally and used to correct all subsequent images,essentially removing the fixed pattern noise.The manufacturers specify the number of non-uniformities that can be corrected.Because the plat

319、es in CRM are not integral to the system but are removed for processing and interchanged,it is much more complex to perform such a correction on CRM images and this is not done on commercial systems.Therefore,CRM images are much more subject to the effects of fixed pattern noise.CRM systems are cons

320、idered a relatively inexpensive solution(see Table 7)compared to DDM systems.CRM technology is often considered to be a natural step when moving away from film technologies,as it offers increased flexibility on the choice or reuse of X ray equipment and the ability to be used with more than one X ra

321、y system.Nevertheless,the following considerations should be kept in mind:The ease of transition is sometimes misleading and,if an effective intercommunication between the X ray and CRM is not provided,as is sometimes the case,this can lead to misuse and suboptimal performance.The spatial resolution

322、 is limited for the demanding application of mammography.The efficiency of using the radiation to form the image is limited:radiation doses(and exposure times)are higher than in DDM systems and occasionally even higher than in SFM systems 26,27.87TABLE 8.ADVANTAGES AND LIMITATIONS OF FILM BASED IMAG

323、ING AND DIGITAL IMAGING(cont.)AdvantagesLimitations Immediately available to authorized viewers after image acquisition(for DDM)or reading(for CRM)Eliminates environmental problems caused by film based imaging Eliminates darkrooms and physical storage space Phosphor plates have a limited lifespan,an

324、d their performance has to be evaluated frequently.The need to physically move imaging plates is labour intensive,reduces productivity and causes wear and tear.It ought to be mentioned,however,that retrofit detectors may be a cost effective alternative to CR plate detectors:they can be used in combi

325、nation with existing X ray devices and have an intrinsic quality compatible with typical digital technology detectors 12.DDM systems offer all of the digital advantages already described as well as improved spatial resolution compared to CRM.They efficiently detect incident radiation,offering signif

326、icantly lower doses compared to SFM and CRM systems.However,they are more expensive,requiring substantial capital investment.The need for proper implementation,use and maintenance of a mammography imaging system cannot be highlighted enough.Poorly installed,maintained or supervised systems pose obvi

327、ous problems.However,the probability and extent of these problems increases when:The system has increased complexity and handling needs,such as in the case of film processing.The system is composed of disparate components that are not properly matched or adjusted to form an optimized configuration.T

328、his could occur,for example,when an existing mammography machine is upgraded to digital with the procurement of a CRM system and cassettes without proper re-commissioning and maintenance.II.3.DIGITAL BREAST TOMOSYNTHESISDBT is an X ray technique in which the X ray tube moves over a limited angle(bet

329、ween 7 and 30)around the breast to acquire multiple projections(typically 9 to 25)28(Fig.39)which are then used to reconstruct a 3-D stack of planar image slices.This allows radiologists to view breast images in planes parallel to the detector and overcomes much of the tissue overlap that is charact

330、eristic of normal projection imaging.The benefit of DBT in comparison to 2-D mammography has been demonstrated for the detection of masses,while its performance in detecting microcalcifications is a topic of ongoing investigation 98100.DBT was approved by the US Food and Drug Administration(FDA)in 2

331、011 as a diagnostic technique and for screening in adjunct to DDM systems.More recently it was also approved as a stand-alone technique.Several clinical 88trials have also evaluated this new modality within the framework of screening.These found increases in cancer detection of typically 30%,as well

332、 as a decrease in false positive recall rate.Today,however,there is not yet a proven impact on the interval cancer rate or on mortality,probably due to limited data so far.The combined application of mammography and DBT increases the dose to the breast for a complete exam by up to 160%.Other practic

333、al issues influencing the uptake of DBT for screening are the increased reading time required of a radiologist,the large data volumes affecting speed of access and 89FIG.39.Basic principle of DBT.The X ray tube moves over a limited angle(to+)around the breast to acquire multiple projections.These projections are then reconstructed to produce a series of images in closely spaced focal planes parall