nhsbsp equipment report 0802

EVALUATION AND CLINICAL ASSESSMENT OF THE AGFA CR 85-X MAMMOGRAPHY SYSTEM

NHSBSP Equipment Report 0802May 2008

Evaluation and Clinical Assessment of the Agfa CR 85-X Mammography System

EnquiriesEnquiries about this report should be addressed to:Patsy Whelehan Head of RadiographySouth East London Breast Screening ServiceKing’s College Hospital NHS Foundation TrustLondon SE5 9RSTel: 020 3299 3384Email: [email protected]

Published byNHS Cancer Screening ProgrammesFulwood HouseOld Fulwood RoadSheffieldS10 3THTel: 0114 271 1060Fax: 0114 271 1089Email: [email protected]: www.cancerscreening.nhs.uk

© NHS Cancer Screening Programmes 2008

The contents of this document may be copied for use by staff working in the public sector but may not be copied for any other purpose without prior permission from the NHS Cancer Screening Programmes.The report is available in PDF format on the NHS Cancer Screening Programmes’ website.

Typeset by Prepress Projects Ltd, Perth (www.prepress-projects.co.uk) Printed by Henry Ling Limited

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CONTENTS

ACKNOWLEDgEmENTS v

ExECuTivE SummARy vi

1. iNTRODuCTiON 1

2. OBjECTivES OF THE EvALuATiON 2

3. SySTEm DESCRiPTiON 2

3.1 Agfa CR 85-x digitiser 23.2 Agfa CR mm3.0 mammo plate 23.3 Agfa CR mm3.0 mammo cassette 23.4 Agfa Nx radiography workstation 33.5 Agfa mA3000 diagnostic workstation 33.6 Agfa Drystar 4500m hard copy imager 33.7 Agfa Drystar 5503 hard copy imager 33.8 Workflowconfiguration 3

4. ACCEPTANCE TESTiNg, COmmiSSiONiNg AND PERFORmANCE TESTiNg 4

5. ROuTiNE QuALiTy CONTROL 5

6. imAgE QuALiTy ASSESSmENT 6

7. DATA ON SCREENiNg CONDuCTED 8

7.1 Clinical dose audit 87.2 Clinic organisation and throughput 87.3 Women’s perceptions of screening 9

8. DATA ON ASSESSmENTS CONDuCTED 9

9. EQuiPmENT RELiABiLiTy 9


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10. mAmmOgRAPHERS’ COmmENTS AND OBSERvATiONS 10

10.1 Operator’s manual 1110.2 Training 1110.3 Ease of use 1110.4 Exposure times 1110.5 Time for image to appear at the acquisition workstation 1210.6 image handling and processing facilities at the acquisition workstation 1310.7 image quality at the acquisition workstation 1310.8 Transfer of images to reporting workstation and hard copy imager 13

11. RADiOLOgiSTS’/FiLm READERS’ COmmENTS AND OBSERvATiONS iNCLuDiNg ANy CONCLuSiONS RELATiNg TO THE SOFT COPy WORKSTATiON 14

12. iNFORmATiON SySTEmS 14

13. CONFiDENTiALiTy 16

14. SECuRiTy iSSuES 17

15. CONCLuSiONS AND RECOmmENDATiONS 17

REFERENCES 18

APPENDix 1: Clinical breast dose survey – Agfa CR 19

Clinicalbreastdosesurvey–KodakMin-R-EVfilm–screensystem 20


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ACKNOWLEDGEMENTS

The valuable contributions to the project of the following colleagues are gratefully acknowledged:

mr mark Hanson, medical Physics Department, East Kent Hospitals NHS Trust (the local physics service for the evaluation centre at the time of the installation).mr jim Thurston and mr james Clinch, King’s College Hospital medical Engineering and Physics Service.mr Chris Lawinski, mr Alistair mackenzie and mrs Trish Clinch, King’s Centre for the Evaluation of Radiological Equipment (KCARE).mr Adrian Bidewell and mr Tony Lake, gE Healthcare Ltd.Professor Kenneth young and Dr jenny Oduko, National Coordinating Centre for the Physics of mammography, guildford.mr john Flavell, miss Ellen Stubbe, miss Derrien Allen (now employed elsewhere), mr Walter jacobs and Dr Friedrich Wanninger and colleagues of Agfa HealthCare.Administration, radiography and radiology staff of the Breast Radiology Department of King’s College Hospital.information Technology staff of King’s College Hospital.mrs Sarah Sellars, Assistant Director, NHS Cancer Screening Programmes.


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EXECUTIVE SUMMARY

The latest Agfa CR system for mammography, incorporating CR 85-x digitiser, mm3.0 photostimulable phos-phor plates and cassettes, Nx radiography workstation and mA3000 reporting workstation, was evaluated for suitability for use in the uK NHS Breast Screening Programme. Technical evaluation had shown compliance withrelevantUKandEuropeanimagequalityanddosestandards.Theinstallationconfigurationusedfortheevaluation was limited by agreement. The system was not linked to a picture archiving and communication system (PACS) and the radiography workstation was installed in the viewing area rather than the mammo-graphyrooms.Thishadimplicationsforworkflow,whichareidentifiedwithinthebodyofthereport.

Following some initial concerns on the part of the local physics service and the engineering staff of the mam-mography equipment supplier, the system was optimised for use with two gE DmR+ mammography units to the satisfaction of all parties.

Routine quality control demonstrated a good level of stability, and subjective clinical image quality assess-ment by a panel of expert radiologists and readers indicated that image quality was similar to that of the local film–screensystem.

Althoughtheevaluationcentrehadsomedifficultyfacilitatingveryhighthroughputscreeningclinicsinthestatic site setting, a total of 608 women were screened, and it was demonstrated that the system was capable of sustaining a throughput representative of NHSBSP practice. However, the time taken for four images to appearattheradiographyworkstationexceededthattakentoprocessfourfilm–screenimages.Thismeansthat,ifusedonamobilescreeningunit,conventionalworkflowmayhavetobefollowed,withimagequalitybeing checked after completion of the clinic.

Clinical dose audit revealed that doses fell within the local and national dose reference limit. However, radia-tiondoseswereapproximately20%higherthanwiththelocalfilm–screensystem,asmeasuredbyasurveyof samples of women x-rayed on both systems.

Radiography and radiology staff had some concerns about the user friendliness of the workstations. The acquisition workstation was generally found to be well designed and some of the concerns may have been a resultofinsufficientpracticewiththesysteminalarge,rotationalworkforce.Therewasanoverallimpressionthat the operation of the mA3000 reporting workstation could have been more intuitive. The next generation reportingworkstationdesignisexpectedtoaddressthisfinding.

The evaluation has demonstrated that, in the context of a limited installation which, for example, did not include connection to PACS, the system provided an acceptable level of performance for NHS breast screening.


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1. INTRODUCTION

This user evaluation was undertaken from january to july 2007 by King’s Breast Radiology at the request of Agfa Healthcare and the NHS Breast Screening Programme (NHSBSP). The system had been included pre-viously in a comparative technical evaluation of computerised radiography (CR) systems for mammography by King’s Centre for the Evaluation of Radiological Equipment (KCARE), with a report being published in 2006.1

During the period of the evaluation, the NHSBSP Guidance Notes for Equipment Evaluation2 were being updated and the guidelines for Routine Quality Control Tests for Full Field Digital Mammography Systems3

were being written. As the project lead for this evaluation had access to the drafts, these guidelines were fol-lowed as closely as possible.

The evaluation centre is a NHSBSP unit screening approximately 22 000 women per year. The centre meets relevant national quality standards for breast screening and meets the criteria for evaluation centres outlined in the Guidance Notes for Equipment Evaluation.2 There was one respect, however, in which the evaluation setting was not ideal: the majority of screening is undertaken either on mobile units or in a static screening unit separate from the base site. The base site is primarily used for assessment, with only a small amount of screening being performed. given the staged nature of the NHSBSP user evaluation procedure, it is neces-sary to install the equipment in an assessment centre initially. For the screening phase of the evaluation, it was decided not to move the equipment to a primary screening location but to make special arrangements to achievesufficientscreeningnumbersatthebasesite.

AlimitedconfigurationsystemwasinstalledbyAgfaHealthCareonafreeloanbasisforthedurationoftheevaluation. The company agreed to indemnify the equipment for the loan period. The company also provided technicalsupportandfilmforhardcopyarchival.

The project lead was ms Patsy Whelehan, an experienced breast screening radiographer with responsibility for technical development within the evaluation centre. The centre’s clinical director, Dr michael michell, took ultimate responsibility for key clinical decisions. Both of these staff had been members of the NHSBSP steering group for digital technologies.

Commissioning tests were undertaken by the local physics services. The evaluation centre changed its physics contract during the evaluation period, so two different groups were involved in supporting the evaluation. in addition, KCARE is a hosted service within the evaluation centre’s NHS Trust. Therefore, some additional performance assessments were made by KCARE staff, who also acted in an advisory capacity during the evaluation. Staff of the National Coordinating Centre for the Physics of mammography (NCCPm) carried out further work on the system while it was installed at the evaluation centre, and subsequently published a technical evaluation.4

The cooperation of staff from gE Healthcare, working with Agfa HealthCare technical staff in respect of the installed mammography units with which the CR was used, was vital to enable optimisation of the imaging chain.


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2. OBjECTIVES OF THE EVALUATION

The overall aim of the evaluation was to assess the suitability of the Agfa CR85-x system for use in NHSBSP mammographic screening, using soft copy reporting. The following objectives were included:

to make a subjective assessment of clinical image quality by direct comparison with the standard local •film–screensystembymeansof– paired imaging of surgical breast specimens– assessmentimagingwithCRofwomenscreenedusingfilmtoevaluateeffectsonworkflowarisingfromtheinfluenceofuserinterfaces•– radiographer workstation and CR plate reader– reporting workstationto assess whether the system could accommodate typical screening appointment times of six minutes•to evaluate the reliability of the system when used for routine NHSBSP screening.•

3. SYSTEM DESCRIPTION

The components of the installed system are described below. Further details are available from Agfa Health-Care (http://www.agfa.com/en/he).

3.1 Agfa CR 85-X digitiser

The digitiser (referred to as a ‘CR reader’ by some manufacturers) has a multicassette input buffer allowing up to 10 cassettes to be deposited at a time. These are then automatically taken into the digitiser and ejected into a similar multicassette output buffer at the end of the cycle. The manufacturer’s data sheet indicates that a throughput of up to 115 plates per hour is possible, depending on size and application. in the case of mam-mography, a member of Agfa HealthCare informed the evaluation project manager that a throughput of 46 plates per hour is possible for 18 × 24 cm and 39 per hour for 24 × 30 cm. This would equate to a capacity of 10 women per hour, in line with typical NHSBSP appointment times.

The ‘spatial resolution’ of the mammography system is described as being 20 pixels per mm, giving a matrix of 3560 × 4640 for 18 × 24 cm plate size and 4760 × 5840 for 24 × 30 cm. This equates to a pixel size of 50 microns(μm).

3.2 Agfa CR MM3.0 Mammo plate

This dedicated mammography image plate has several features designed to maximise sharpness and limit noise. it is also said to have high durability but needs to be handled with care and cleaned according to the manufacturer’s instructions.

3.3 Agfa CR MM3.0 Mammo cassette

The dedicated mammography cassette has a narrow hinge designed to prevent loss of image at the chest wall edge. initialisation of the cassettes at the factory enables the digitiser to recognise them as mammography cassettes.


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3.4 Agfa NX radiography workstation

The Nx workstation incorporates software that had recently been implemented at the time of installation at the evaluation centre. The manufacturer’s information indicates that touch screen technology is available, but it was not installed for this evaluation. A single Nx radiography or ‘acquisition’ workstation was sited in the viewingroom,ratherthanoneineachx-rayroom.AnalternativeconfigurationistositeanNXworkstationin each x-ray room with an additional workstation or ‘central monitoring system’ (CmS) in a common area such as a viewing room.

3.5 Agfa MA3000 diagnostic workstation

Two mA3000 reporting workstations with impax software were provided. One was sited in the viewing room foruseduringdiagnosticassessmentclinics;theotherwassitedinascreen-readingroomalongsidethefilmmultiviewer.

3.6 Agfa Drystar 4500M hard copy imager

initially this compact hard copy imager was installed adjacent to the Nx workstation.

3.7 Agfa Drystar 5503 hard copy imager

Subsequently, this larger, higher throughput imager was installed in an adjacent room and connected via the hospital network to the Nx workstation.

3.8 Workflowconfiguration

The system was installed in the base screening and assessment department. Of three mammography rooms in the department, the machines in two were calibrated to be used with the CR. These were gE DmR+ machines. A large processing/viewing room is sited on the opposite side of the same corridor as the mammography rooms. The Nx workstation was sited in this viewing room, along with the digitiser (plate reader) and the original hard copy imager, the 4500m. Hard copy was required for archive purposes, given the uncertainty of the availability of satisfactory soft copy display for the images in the centre, if the system were to be removed following the evaluation. images were sent to the hard copy imager automatically as each examination was completed, and in busy clinics the mammographers collated them and placed them in the correct packets at the end of the clinic.

The Agfa CR system was not connected to the hospital PACS; therefore work lists could not be downloaded ontotheNXworkstation.Onsomeoccasions,mammographersenteredeachclient’sidentificationdetailsas they went along. On others, these were pre-entered into a manual work list. Radiographers had to record exposure parameters manually in the x-ray rooms. if the Nx is sited in the x-ray room, it is stated by Agfa HealthCare that it can be connected to the modality to allow download of exposure information along with thepatientandexaminationdetailswhenthecassetteisidentifiedfollowingexposure.TheNXwasnotcon-nected to the modality for the purposes of this evaluation.

Thepreferredconfiguration,basedonexperienceattheevaluationcentreaswellasadvicefromthecompany,would be to place Nx workstations in each mammography room and a CmS in the viewing room. Because theclient/patientdetailsareaddedtotheimagebyinsertingeachcassetteintoanidentificationblocksitedwiththeNXworkstation,imagescouldbeidentifiedonebyoneinthex-rayroom,increasingconvenienceandreducingthelikelihoodofincorrectviewidentification.Inasingle-roomsiteormobilescreeningtrailer,it


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may even be worthwhile to site the digitiser in the x-ray room, but this would require a relatively large room. if the Nx workstation were sited in the x-ray room, the CmS would be desirable to avoid detailed review of image quality preventing a second mammographer from undertaking the next examination promptly. This would be particularly important if mammography training was in progress, but limited availability of space maymakethisconfigurationdifficulttoimplementonamobilescreeningtrailer.ThepreferredinstallationconfigurationisshowninFigure1.

Figure 1 RecommendedAgfaCRinstallationconfiguration;diagramcourtesyofAgfaHealthCare.

4. ACCEPTANCE TESTING, COMMISSIONING AND PERFORMANCE TESTING

Following dose versus image quality optimisation procedures and subsequent inspection by the local physics service,reportsandcommentswerereceivedfromtheGEfieldengineerandseniorengineer,thelocalphysi-cist and the Agfa physicist. There were some initial concerns arising from the calibration and optimisation procedure, which are discussed below.

The gE engineer and the Agfa physicist worked together to achieve optimised calibration. Film–screen mammography would continue to be used alongside CR during the evaluation so the CR parameters were programmedintothesecond‘channel’oftheDMR+toenableswitchingbetweenfilm–screenandCRmodes.Further, the CR mode was set up to operate under ‘dose’ mode, and the ‘contrast’ and ‘standard’ modes nor-mally available became obsolete when CR was used. There were some concerns that the parameters being used could decrease x-ray tube lifespan and that long exposure times were resulting which could give rise to


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increased motion blur. However, no quantitative information was put forward to support the concerns about tube life and the view was taken that there was no major deviation from standard procedures.

The local physicist attended after the calibration had taken place, to assess dosimetry and obtain image quality tests for subsequent off-site assessment. There were concerns that the dose to the standard breast was relatively highcomparedwithfilm–screenmammography,at1.8mGyinoneroomand1.9mGyintheother.However,these doses were lower than those quoted by the Agfa physicist – 2.08 mgy and 2.12 mgy respectively. The Agfaphysicist’sfindingsfordosetothestandardbreastagreedwiththoseoftheNCCPM,whichcalculated2.14 mgy for the system.4 While the local physicist considered the reference dose to be relatively high compared withthefilm-screensysteminuseatthecentre,itdoesnotexceedtheNHSBSPremediallevelof2.5mGy.5

The use of ‘dose’ mode for all CR examinations removed the intended facility for the operator to range the DMRsystemfordifferentbreasttypesandpatientparameters.Theimagecontrastisprimarilydefinedandoptimised by the image processing and the set-up gives rise to beam qualities that will optimise the dose versus image quality balance. As a result, the radiography staff used only the fully automatic mode in the optimised set-up.

A further concern was that there was no quantitative indication of the exposure to the detector, ie no ‘exposure index’ displayed on the screen at the time of acquisition. However, it was concluded that, in the light of the careful optimisation procedure and the dose and image quality measurements available,4 the system could be trusted to provide appropriate exposure parameters.

image quality assessment results from the NCCPm were made available to the evaluation centre in the form of a draft report which showed that the system met the requirements of the NHSBSP. The report was subse-quently published as an NHSBSP Equipment Report.4 Before proceeding to image patients, a meeting was heldtodiscussthevarioustechnicalfindings.PresentwererelevantmembersofAgfastaff,membersoftheevaluation centre team, Professor Ken young from the NCCPm and the new local physicist, appointed after the testing was completed. Following consideration of all the issues, it was agreed that the evaluation could continue according to NHSBSP evaluation guidelines.2 The debate emphasised the importance of AEC set-up and dose issues. Potential users of the system would have to ensure that the system is set up correctly in order to meet image quality standards.

5. ROUTINE QUALITY CONTROL

Routine quality control (QC) was undertaken in accordance with relevant NHSBSP guidelines.3 There was some debate within the physics team on the question of whether all tests needed to be carried out using both x-ray sets, as some of the procedures in the QC guidelines3 are relevant to the CR system rather than the x-ray set. As a minimum, output and consistency tests were necessary on each x-ray set and the decision was taken to consider the whole imaging chain together and to complete all tests on each available combination. With limited automation, this was found to be fairly onerous. The QC tests were not undertaken on every day of the evaluation period because the equipment was not in constant use. Tests were carried out to ensure that QC procedures were up to date on any day that the equipment was to be used for clinical imaging.

No suitable test object was provided with the equipment, but the centre already had the required Perspex and aluminium objects to carry out signal to noise and contrast to noise tests, as well as uniformity tests up to 24×30cmfieldsize.ThedegreeofautomationwaslimitedtotheNXworkstationdisplayingthepixelvalueand calculating the standard deviation within regions of interest (ROis), which were quick and simple to apply. Further calculations, notably to derive the contrast to noise ratio, had to be carried out manually, although a


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spreadsheetcanhelpwiththis.ThedigitiserwasconfiguredsothatphysicistscoulddownloadunprocessedDiCOm format images of test objects, including the CDmAm phantom, on to a CD for analysis in their laboratories. For effective quality control it would be important to ensure that a similar facility is included in any installation.

There was some instability of results that, on investigation, was attributed to inconsistency in the size of the ROIapplied.ThesizewassetbyindividualoperatorsbecausewhentheROIfirstappearsonthemonitoritistoo big and has to be adjusted. This is partly a training issue, but it would be made easier if the ROi could be setuptodefaulttofitwithintheimageofthe1cm2 piece of aluminium so that it never needed to be manually adjusted.

Another source of apparent instability resulted from variations in mA s values, although a standard thickness of Perspex and standard compression force were used. This variation was attributed to the thickness being on the cusp of a step in the AEC set-up of the modality. The automatic kilovoltage (kvp) selection sometimes gave 28 kvp and sometimes gave 29 kvp. These variations can be attributed to the x-ray set design rather than the CR system.

Otherwise,findingsatroutinequalitycontrolwereverystable–meansignaltonoise(SNR)andcontrasttonoise(CNR)ratiosbeingwithin±10%ofthemeanatalltimes.KeyfindingsareshowninTable1.

6. IMAGE QUALITY ASSESSMENT

image quality was monitored as part of the routine QC regime using the Leeds TORmAm test object. The images were scored using full resolution (one pixel to one pixel) display on the mA3000 workstation and ensuring very low ambient light levels. it was noted by the project manager that some surprisingly low scores were being recorded. given the well recognised problem of observer variability in mammography phantom scoring, and the fact that the two quality assurance radiographers were new to the role, two physicists from KCARE were asked to rescore the TORmAm images. The mean score across a sample of eight TORmAm images rescored by KCARE was 71. The images were read at window settings of around 11 000 and level settingsaround17000.TheTORMAMscoreswereagainnotinlinewithpreviousKCAREfindings.1 This

Table 1 Summaryofmainroutinequalitycontrolfindings

Room 1 Room 2

mean SNR (4 cm PmmA) 80.10 79.88

SNR range (4 cm PmmA) 75.46–84.32 72.58–84.23

mean CNR

2 cm PmmA 16.03 17.10

4 cm PmmA 13.10 13.60

7 cm PmmA 11.21 10.99


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may be related to the fact that the published score of 85 (± 5)1 was obtained using a molybdenum anode and filter,whilethescoresintheevaluationwereobtainedwithamolybdenumanodeandrhodiumfilter.

Following the staged approach advocated in the NHSBSP evaluation guidelines,2 comparative clinical image qualitywasevaluatedinitiallybyimagingexcisionormastectomyspecimenswithbothfilm–screenandCRmammography.Subsequently,equivalentimagesofwomenscreenedwithfilmandassessedwithCRwerecompared.Sevendifferentobserverscommented,includingconsultantradiologistsandradiographerfilmread-ers. There was a mixture of independent and consensus scoring. The template form provided by the NHSBSP2 wasfoundtobeunwieldy,andasimplifiedversionwasdevelopedwhichaskedobserverstoclassifytheCRimagesasthe‘same’,‘better’or‘worse’overallthanthefilmimages.ObserverswereaskedtoviewalltheCR images at full resolution.

Arangeoflesionswasimaged,includingmicrocalcificationandlowdensitymasses.Thereweresomedif-ferences of opinion on the relative image quality. Some observers considered the CR images to be inferior tofilm–screenimages,includingdecreasedconspicuityofsomemalignantmasses.However,thetwomostexperienced radiologists found that, in 28 of 28 assessment cases, the diagnostic quality was either equivalent orbetterintheCRimagecomparedwithfilm.CombinedopinionsofallcasesshowCRimagesbetterin43cases,equivalentin56andworsethanfilmin28.Itmustbeemphasisedthatthesearesubjectivefindingsandcannotbeconsideredscientificallyrobust.Nostatisticalanalysiswasattempted.

Theopinionsofradiologistsandfilmreadersontheclinicalimagequalityofasampleofthefullfieldscreen-ing images were also collected. Six observers commented and the results are shown in Figure 2.

Excellent Good Satisfactory Poor

Visibility of skin edge

Visibility of dense glandulartissue

Visibility ofmicrocalcifications

Visibility of masses

Contrast

Figure 2 Subjective clinical opinions of screening image quality.


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7. DATA ON SCREENING CONDUCTED

7.1 Clinical dose audit

Theexposuredatafromthefirst100womenscreenedwereenteredintotheNCCPMdosesurveysoftware(available at http://www.nccpm.org/). The results are shown in Appendix 1. The mean mean glandular dose (mgD) was 2.09 mgy for the craniocaudal (CC) view, for a mean thickness of 48 mm, and 2.49 mgy for the mediolateral oblique (mLO) view, for a mean thickness of 53 mm. The mean mgD for the 50–60 mm breast was 2.45 mgy, for a mean thickness of 55 mm. The evaluation centre has adopted the national dose reference level (DRL) of 3.5 mgy per image for the 50–60 mm breast,8sothesurveyfindingsconfirmcompliancewiththe DRL. The mean mgD per examination for a two view mammogram was 4.51 mgy.

AcomparativeclinicaldosesurveyusingtheKodakMin-REVfilm–screencombination(CarestreamHealthInc.,Rochester,NY,USA)wascarriedoutbytheevaluationcentre.Thefilmdensityfor40mmPMMAwas1.69. The mean mgD for the CC view was 1.76 mgy, for a mean thickness of 52 mm, and the mean mgD for the mLO view was 1.96 mgy, for a mean thickness of 55 mm. The mean mgD for the 50–60 mm breast was 1.96 mgy, for a mean thickness of 55 mm, and the mean mgD for a two view mammogram was 3.70 mgy. Thus,theincreaseindoseforCRcomparedwiththelocalfilm–screencombination,inthedefinedsample,was 22%.

7.2 Clinic organisation and throughput

There was considerable discussion on whether to move the equipment, following the initial phases of the evaluation, either to the static screening site nearby or to a mobile screening unit. The staged approach to a clinical evaluation of mammography equipment is that the initial stages require the type of work that is done at an assessment centre but the later stages require high throughput screening. The two types of work do not necessarily exist in the same location, and in this evaluation centre the vast majority of primary screening is carried out away from the base location. it was decided that, rather than incurring the disruption and expense of relocating the equipment, dedicated screening clinics for the evaluation would be set up at the assessment centre.Theotherdifficultyatthisevaluationcentreistherelativelylowuptakeforscreening,associatedwiththe nature of the population served. in order to test the system at high intensity screening rates, some clinics were booked with very short appointment times – three minutes – to compensate for the low uptake. The number of clients who would attend a clinic was nevertheless unpredictable.

The total number of women screened during the evaluation was 608. The highest number of women screened within a one hour period was nine. There was also one instance when eight women were screened in an hour but the number of images was 42. This shows that screening at appointment times of six minutes with at least a 90% attendance rate can be accommodated using the Agfa CR 85-x.

The throughput, in terms of time taken to digitise the images following the examination, is discussed fur-ther in section 10. in most clinics, two mammography rooms were available. This was necessary in order to maximise the rate of examinations to be processed through the Nx and the CR 85-x. The examination times in the mammography rooms were limited by the physical environment and the need to record exposure parameters manually. it would not have been meaningful to investigate examination times within the x-ray room because they are not affected by the introduction of CR equipment. Overall throughput in the system configurationusedattheevaluationcentrecouldhavebeenaffectedbymammographersnotbeingreadytore-enter the x-ray room because they were still engaged at the Nx workstation. However, careful teamwork andindividualworkflowmanagement,egperforminganotherexaminationwhiletheprevioussetofcassettesis in the digitiser, minimises this effect.


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We cannot comment authoritatively on the capacity of this system in a one-roomed department or a mobile screeningunitaswehavenothadthatexperience.Withtherecommendedconfiguration,wewouldexpectthat typical screening appointment times of six minutes could be supported in a one-roomed static depart-mentwithtwomammographers.However,itisdifficulttoseehowthiswouldbepossibleonamobiletrailerunlesstherewereasuitablelocationandsufficientspacefortheadditionofaCMSoutsidethex-rayroom.ItisthereforesuggestedthatatraditionalNHSBSPfilm–screenworkflowmayberequired,wherebyimagesare not checked for quality before the woman leaves the mobile facility and anyone requiring repeat imaging for technical reasons is recalled to a further appointment.

7.3 Women’s perceptions of screening

Women’s perceptions of the mammography examination would not be expected to be affected by the introduc-tion of CR and were therefore not investigated. No relevant comments were elicited through the radiography questionnaires.

8. DATA ON ASSESSMENTS CONDUCTED

Thetotalnumberofassessmentcasesexaminedwas69.Aproportionoftheseincludedmagnificationviews.Wheresuitable,thatiswhereafullfieldstandardviewwasrepeatedatassessment,imagesfromtheassessmentsconducted were used for direct clinical image quality comparisons (see section 7). The assessment procedures were unaffected by the use of CR because the x-ray equipment is unchanged. usual practice was followed intermsoftheviewsperformedatassessment.Therewasnoattempttoreducethenumberofmagnificationviewsperformedandsubstituteelectronicmagnificationoffullfieldviews.

Therewassomedebateaboutwhethertheoptimisedautomaticexposureregimesetupforfullfieldexamina-tionswasalsosuitableformagnificationexaminationsbuttheequipmentwasusedinthesamemodeandtheresults did not reveal any clinically detectable issues.

NostereotacticprocedureswerecarriedoutusingCRbecausethedepartmentisequippedwithasmallfielddirect digital prone stereotactic system.

9. EQUIPMENT RELIABILITY

The equipment was generally reliable. it was not meaningful to quantify uptime as a proportion of that expected because the equipment was used sporadically and in the event of downtime the women could be screened using film–screenmammography.Therefore,whendowntimedidoccur,repairsmaynothavebeenundertakenasurgently as they otherwise would.

Oneapparentfaultwasinfactaresultofusererror:itwasreportedthattheidentificationtabletlocatedwiththe Nx was refusing to identify cassettes. This was because it was not switched on. it has a separate switch from the computer and the monitor of the Nx.


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There were two problems with cassettes entering the digitiser. On one occasion the cassette became jammed in the inward track. The radiographer opened the doors of the digitiser, removed the cassette, which had not opened, and restarted the procedure. On the second occasion, a cassette was stuck in the digitiser at several attempts. The imaging plate was not removed. On inspection, the cassette had two broken corners. The cause is unknown. The cassette was withdrawn from use.

Amoresignificantproblemwiththedigitiser–asingleinstance–wasa‘digitisernotready’fault.Thiscauseddowntime and required replacement of a circuit board.

A routine physics check revealed that a monitor of the mA3000 workstation in the viewing area needed recalibra-tion of the luminance level. This was carried out by the Agfa engineer and the monitors were then re-examined by the physicist. The following is an excerpt from the physicist’s report, following the engineer’s visit:

Quality assurance tests were performed on this medical display device after recalibration of both monitors had been performed by the engineer.

The performance of this display was outside the recommended tolerances for primary classification. We would recommend it is NOT used for the interpretation of medical images (e.g. radiologist reporting), until the following issues have been resolved:

• The luminance response of the left hand monitor compared to the greyscale standard display function is outside the recommended tolerance limit. After some discussion it has been decided that the engineer will arrange a replacement for this monitor. Please contact King’s Radiation Protection Service when the new monitor has been installed so we can ensure that this has been effective while the engineer is still on site.

• The right hand monitor is now within the recommended limits and suitable for use.• Specular reflections on the monitors can only be avoided when the room is in darkness with all doors shut,

window blinds drawn and light boxes and other computer screens switched off. Otherwise, reflections visible on the monitor screens can interfere with viewing the displayed images.

• The ambient light levels only reach a satisfactory level when the room is in darkness as described above. When the above issues have been rectified, it is recommended that these monitors are only used for the interpretation of medical images when these conditions are in place. Due to the positioning of these monitors in a busy processing room, this may be difficult to achieve satisfactorily.

The defect was accepted because the workstation was not in use for screen reading.

There was one fault with the 4500m printer. it had been set up to print automatically when a case was closed at the Nx workstation. Normally, it would do this only once, not every time the case was opened and closed subsequently, but this aspect failed and multiple copies were produced. The problem was resolved by replace-ment of a part.

10. MAMMOGRAPHERS’ COMMENTS AND OBSERVATIONS

mammographers’ opinions were collected using the relevant form from the NHSBSP equipment evaluation guidelines.2 many of the questions are not relevant to CR, only to direct digital mammography. The results should be treated with a degree of caution for several reasons. Firstly, 11 of 15 questionnaires were returned andsomefieldswithinthesewerenotcompleted.Secondly,theequipmentwasusedonlyfortheminimum


NHSBSP May 2008 11


number of examinations required in the evaluation protocol.2 This meant that mammographers received less practice with the equipment than they would have done in a non-evaluation condition. The low levels of usage andstaffrotationtootherscreeningsitesmeantthatitwasdifficultformammographerstobecomeproficientinusingtheequipment,whichmayhaveledtoalackofconfidenceandthereforetomorenegativeimpres-sionsthanwouldotherwisehavebeenthecase.Asummaryofthemammographers’findingsandtheprojectmanager’s observations are presented below.

10.1 Operator’s manual

Theoperator’smanualwasprovidedinelectronicformat.Itwasalarge,detailedandcomprehensivefile.Thispresentedpracticaldifficultiesforthemammographersbecauseitwasnotconvenienttoclosetheexamina-tion screen at the Nx workstation during use in order to open the manual through microsoft Windows. There were separate computers available in the vicinity but, as Trust policy dictates that users should log off when notattheworkstation,eachuserwouldhavehadtoinstalltheCDunderherownuserprofileandlogineachtime she wished to view the manual. The team would have preferred a hard copy manual containing concise and relevant operating instructions. A brief ‘get started’ guide to the Nx workstation was printed, but this contained only very basic information.

10.2 Training

Not all mammographers answered this question because not all received training directly from the Agfa staff. Those who did comment found the training satisfactory (4) or poor (3). The Agfa staff concerned were kind and helpful and as accommodating as possible. Conditions for training were not always ideal because of the environment and the logistics of the department. it is suggested, however, that the applications specialists might adopt an approach whereby, rather than spending the majority of the training time demonstrating, they encourage the trainees to undertake the tasks themselves from an early stage whilst receiving close instruction and supervision. This approach was prevented on occasions because too many mammographers attended for training at a time. in addition, the staged approach of an evaluation impedes training because mammographers have to be trained before they can start using the system but, because they are not able to carry out full mam-mographic examinations until comparative imaging has been completed, they do not get enough practical experience of using the system in the period immediately after the training session.

10.3 Ease of use

Thiswasclassifiedasgood(3),satisfactory(6)orpoor(2).Onemammographercommentedthatshesufferedundue fatigue if the clinic was busy and another that there were sometimes too many steps in simple processes attheNXworkstation.CRismoreakintofilm–screenmammographythandirectdigitalmammographyintermsofthepotentialformusculoskeletalstrain,sonosignificanteffectswereapparentinthisregard.Itis,however, important to site the Nx workstation on a suitable piece of furniture and in a suitable location to avoid awkward body positions being adopted when using the mouse and keypad.

10.4 Exposure times

The question of exposure times has been discussed in section 5, but the radiographers considered that they were either satisfactory or good. One radiographer expressed concern about radiation doses being higher than forfilm–screenimages.


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10.5 Time for image to appear at the acquisition workstation

This was categorised as satisfactory (4) or poor (7). measurements were taken to ascertain the validity of these impressions. A representative sequence is shown below (Table 2). This sequence is for 18 × 24 cm cassettes. The 24 × 30 cm cassettes take slightly longer to digitise – approximately one minute longer per set of four cassettes. it is also expected that the network infrastructure may have a bearing on time taken for images to appear on the workstation. it must be borne in mind that if the Nx workstation was in the x-ray room, the cassetteswouldbeidentifiedduringtheexaminationtimeintheroom,addingnothingtotheexaminationtimecomparedwithidentifyingfilmcassettesinalightmarkerorDataFlash (Carestream Health). in the evaluationsetting,theradiographerbroughtallcassettesoutoftheroomtotheworkstationtobeidentifiedand digitised. The radiographers developed systems to ensure that the correct cassette was assigned the cor-rectviewidentification.

The information in Table 2 shows that the digitisation cycle can be carried out within a typical six minute screening time; in other words, while one radiographer is carrying out a mammogram in the x-ray room, another would have time to digitise and check her images from the previous client. if the Nx were in the x-ray room,thetotaltimewouldbelessthaninTable2becauseeachcassettewouldbeidentifiedasitwereremovedfromthemammographymachine,inmuchthesamewayasfilmcassettesareenteredintoanunloaderonamobile unit.

Incomparisonwithfilmprocessing,thetimetakenforanindividualimagetoappearontheNXdisplayisless than a typical two and a half minute processing cycle, but the interval between one image and the next becomingavailableislongerthanwithfilm.

All mammographers who completed questionnaires reported that they felt that the system limited patient throughput. One recognised that this was a result of congestion at the Nx workstation, largely a result of the agreedlimitedinstallationconfiguration.Itwasclearthatthemammographersfeltthattheywerewaitingalongtimeforimagestoappear.Alongwiththesuboptimalinstallationconfigurationemployedintheevaluationcentre,itseemsthatthetimebetweenoneimageappearingandthenextisthemostsignificantfactoringivingrisetothemammographers’impressions,asthisiswherethereisadelaycomparedwithfilmprocessing.

Table 2 Process time for digitisation cycle in screening clinic

Action Elapsed time

Select client from the work list 0 min 0 s

Identifyfirstcassette 0 min 23 s

identify second cassette 0 min 29 s

identify third cassette 0 min 37 s

identify fourth cassette 0 min 45 s

image 1 appears on Nx display 1 min 36 s




Last cassette exits CR 85-x into output buffer 6 min


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10.6 Image handling and processing facilities at the acquisition workstation

Thesewereclassifiedasexcellent(1),good(2),satisfactory(6)orpoor(1).Therewasvariabilityinusageof the tools available, according to the mammographer. it was rarely necessary to perform any manipulation of the image of the breast itself and mammographers were encouraged to send the images to the reporting workstation without undue manipulation beforehand. Techniques such as blackening the background in coned viewimageswereuseful.Theradiographershadlittledifficultyinchangingtheviewassignedtotheimagein the event of a mistake at the time of identifying the cassette.

10.7 Image quality at the acquisition workstation

Thiswasclassifiedsubjectivelyasgood(6),satisfactory(4)andpoor(2).Therewasoneknowninstanceofblur being overlooked by the person checking the images, but this could have been operator error rather than thelimitationsofthedisplay.SomeradiographerspreferredtocarryoutafinalcheckofimagequalityatthemA3000 reporting workstation. As one of these was sited in the same viewing area as the Nx, this was fea-sibleandindeedcouldhelpwithworkflowwheretherewereseveralmammographerstryingtousetheNXat a time. However, checking image quality on the mA3000 would not always be an option and we have no evidence to suggest that it is necessary.

There was one instance of a horizontal white line artefact on an image, believed to be attributable to dust in the digitiser.

Three radiographers, including the project manager, gained the impression that there was image cut-off, com-paredwithwhatwasexpectedonperformingtheexaminationtobeincludedattheedgesofthefield.Thiswas raised with Agfa staff and also investigated by a KCARE physicist. it was noted that the image plate was identicalinareatoamammographyfilm.Bytakingcomparisonimagesofascale(ruler)withleadmarkers,usingtheCRandthefilm–screensystems,itwasdemonstratedthattherewasastripupto5mmmissingonone or other side of the image area on both 18 × 24 and 24 × 30 cm formats.

The Agfa physicist was able to explain this observation:

It is correct that film and CR plate dimensions are identical (within measurement and manufacturing tolerance; there is no standard for CR plate size as there is with film). For the 18 × 24 format, the pixel matrix is 4640 for the long side of the cassette; with 50 µm pixel width this gives 232.0 mm effective length of the digital image. If you compare to the nominal value of 238 mm (film dimension), a gap of 3 mm on each side laterally can be expected. The reason for this is that the plate is not completely scanned to the very edge of the image plate to make sure no edge effects appear in the clinical image.

it is perhaps surprising that such a small loss should be noticeable to the mammographers clinically, but their impression was vindicated by the above tests and explanation. Clearly, this effect is not a problem where the breastfitscomfortablywithinthefieldbut,incaseswherethereislittletolerance,themammographersneedto allow a larger margin for error and have a lower threshold for changing to large format.

10.8 Transfer of images to reporting workstation and hard copy imager

Thiswasclassifiedasexcellent(1),good(7),satisfactory(1)andpoor(1).Onselecting‘CloseandSend’attheNXattheendofanexamination,theimagesweresenttotheprinterbydefault,andtothefirstMA3000workstation. However, it was not possible to have the images sent to both mA3000 workstations automatically, so at the end of each clinic the operator had to send all the examinations to the second mA3000. This could,


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however, be done by whole clinic, rather than by individual examination, so was not too onerous. However, there was a hitch in the software of the second mA3000 whereby an error message repeatedly appeared on the screen when images were being received. This required anyone using this workstation to click ‘OK’ to remove the message each time it appeared. if the system had been integrated into PACS, the second step would not have been necessary as the images would have been retrieved from the PACS when required and not stored on the mA3000.

in busy clinics it was not feasible for mammographers to wait for images to be printed before proceeding to the next examination, because of the time taken to print. This did not pose serious problems, however, as images could be collated during a clinic hiatus or at the end of the clinic. Printing was an issue only because the system was not integrated into the PACS.

11. RADIOLOGISTS’/FILM READERS’ COMMENTS AND OBSERVATIONS INCLUDING ANY CONCLUSIONS RELATING TO THE SOFT COPY WORKSTATION

The standard evaluation form (#9)2wasusedtocollecttheviewsofradiologistsandfilmreadersregardingthe mA3000 reporting workstation. Five questionnaires were returned. There was considerable variation in the responses, with one of the questionnaires being more favourable than the other four. The overall levels of satisfaction with the workstation were good (1), satisfactory (2) and poor (2). Combined responses are shown in Table 3. Not all respondents answered all questions.

The radiologists and readers suffered from the recognised problems that arise from comparing soft-copy imageswithpriorfilmimages.Priorimageswerenotdigitisedbutweremountedonamultivieweradjacenttothesoftcopyworkstation.Thisresultedinergonomicandambientlightdifficultiesthatwerenotthefaultof the Agfa system. No new solution to the problem was found.

Following the evaluation project, members of the Agfa team visited the centre to demonstrate the next genera-tion reporting workstation design. This is not yet available to purchase but it was found to address a number ofthe‘userfriendliness’issuesidentifiedabove.Thereactionoftheradiologistsandfilmreaderstothenewdesign features was generally favourable.

12. INFORMATION SYSTEMS

There were some information systems issues associated with this evaluation because the equipment was not integrated into the hospital PACS. The National Breast Screening System (NBSS), the database for the NHSBSP, does not operate as a fully functional radiology information system (RiS) and at the beginning of the project had not been adapted to interface routinely with a PACS.


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Table 3 Summary of responses – evaluation form 9

Excellent Good Satisfactory Poor Comments(includeallspecificdifficulties)

How good was the operator’s manual? (State if N/A) No hard copy manual available

How good was the training provided by the supplier? 2 3

How easy is it to adjust the height and angle of the reporting monitors to suit the user?

3 1

How easy is it to adjust the height and angle of the database monitor to suit the user?

N/A

How do you rate the ease of use of the workstation controls? (Complete any applicable.)

Slow

(a) mouse 1 1 3

(b) keyboard 1 1 3

(c) keypadN/A, although a keypad was added near the end of the evaluation, after questionnaires had been completed

How do you rate the image handling tools (zoom, etc.)? 1 1 3 Not very instinctive; symbols

unusual

Rate visibility and usability of on-screen icons separately 1 2 2 Not very instinctive; symbols

unusual

How do you rate the post-processing image manipulation (window and level)? 1 2 2 Particularlydifficultfor

microcalcification

How do your rate the reading/reporting flowpattern? 1 2 2

if there was a choice of hanging protocols, how easy was it to set these? 1 2 2

Within a hanging protocol, how easy was it to display a different choice of image, ie images performed beyond the standard four?

1 1 3

How do you rate the time taken between an image being selected and appearing on the screen?

1 3 1

(a) new patient selection 2 3

(b) in-examination change 4 1


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Excellent Good Satisfactory Poor Comments(includeallspecificdifficulties)

Did the database or PACS software allowforrecordingfindingsunderNHSBSP reading protocols?

N/AThe workstation was designed to be used with PACS but was not integrated. Results were input to NBSS using ADE.

Howeasywasittorecordfindings?List any specific difficulties in the comments section.

N/A

How much of a problem was light from the database screen raising ambient lighting around the reporting monitors?

NBSS screen for ADE caused a light probleminopinionofoneoffive.

Did you identify any hazards associated with the workstation or its use? yES or NO Nohazardsidentified

Describe any additional or unusual features or quirks of the system.

Not very user friendly compared with other systems.if images were sent to second workstation while reading in progress, error message requiring ‘click OK’ very irritating (see section 10.8)

What is your overall level of satisfaction with the reporting workstation? 1 2 2

Table 3 continued

it was necessary to connect the Nx workstation, the CR 85-x digitiser, the hard copy imagers and the mA3000 workstations via the hospital network. The local Agfa installation and service engineer was familiar with work-ing with the Trust information technology (iT) department, as he regularly supported the Agfa CR system in the general radiology department. The engineer installed a networking hub to enable all the components to beconnectedintheabsenceofsufficientpointsbeinginplace.ThiswascontrarytoTrustITprotocols.Itistherefore important that breast imaging management staff are fully informed and take responsibility for all aspects of equipment installation, including networking.

Thenetworkappearedtocopewellwiththemammographytrafficandtherewasonlyoneepisodewhennet-workcommunicationbetweentheNXandtheprinterbrokedown.Thiswaspromptlyrectifiedbyamemberof the Trust iT department.

13. CONFIDENTIALITY

PatientInformationAdvisoryGroup(PIAG)Section60confidentialityanddisclosurepolicymustbecare-fullyfollowedduringauserevaluation.EachmemberofAgfastaffwhohadcontactwithpatientidentifiableinformation was asked to read the local policy and sign the PiAg agreement.


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14. SECURITY ISSUES

There were several aspects to security issues in relation to this evaluation. Data security in terms of prevent-inglossofimagesfromtheworkstationswasnotasignificantissuebecausehardcopywascreatedforallexaminations. There was an understanding by the project lead that no images would be automatically deleted from the mA3000 computer. However, this proved not to be the case and the earliest images had started to disappear from the system by the end of the evaluation period. This could have been avoided by changing the relevant settings. The problem appeared to be one of communication between members of the team, rather than a technical issue. Clearly, if the system was integrated with a PACS, the security issues would be different.

A security issue of secondary importance that arose during the evaluation was the fact that the viewing area where the Nx and one mA3000 workstation were sited was not routinely locked at night. The desirability ofthenewcomputersincludingthepairof5megapixelmonitorsledtoanewlockbeingfittedandtheroombeing locked.

15. CONCLUSIONS AND RECOMMENDATIONS

Close cooperation between Agfa technical staff, mammography equipment engineers and local physicists enabled the CR system in combination with the mammography units to be optimised and initial local con-cerns to be resolved. Technical assessment by the NCCPm showed that relevant national and European dose and image quality standards were met. Clinical dose audit demonstrated that radiation dose reference levels werenotexceeded,althoughdosecomparisonwiththelocalfilm–screensystemshowedanincreaseindoseof about 22%. The dose settings were selected by Agfa to ensure that the required image quality levels were achieved.

Theequipmentwasmostlystableandreliable,withonlyonebreakdownthatcausedsignificantdowntime.

Expertopinion indicated thatclinical imageswereof satisfactoryquality incomparisonwithfilm-screenmammography.

in the context of this limited installation, there was a range of perceptions among radiographic and radiologi-cal staff concerning the user friendliness of the system. On balance, they found the workstations acceptable but with room for improvement on a number of points. A next generation workstation should address these points but is not yet available.

it was shown to be feasible to screen at intensive rates representative of NHSBSP practice in a setting with several rooms and more than one mammographer per x-ray room but the production of four ready to view imagesfollowingtheexaminationtooklongerthanwithfilmprocessing.Itisdifficulttosee,althoughthiswas not directly tested, how screening with Agfa CR on a one-roomed mobile unit would enable images to be quality checked at the time of the examination within a schedule where appointments are at the six minute intervals typical of the NHSBSP. This would not preclude the use of Agfa CR on mobile units but would meanthatonepotentialbenefitofdigitalimagingintermsofavoidingrecallfortechnicalreasonscouldnotbe realised.


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Overall, this system performed to acceptable levels in all respects and could be used in the NHSBSP. While ingeneraltermsthereareclearlyadvantagesofCRmammographyversusfilm–screen,egadigitalimagecanbe manipulated, transmitted and stored electronically, there are also general disadvantages of CR systems. in ouropinion,inthisevaluation,patientdoseandtimetakentoobtainfinishedimageswerethemostsignificantdisadvantages.

REFERENCES

1. Lawinski CP, Honey i, Blake P, mackenzie A, Cole H, Emerton D. Computed Radiography (CR) Systems for Mammography – A Comparative Technical Report. Centre for Evidence-based Purchasing, 2006 (Report 06047; Edition 2).

2. Guidance Notes for Equipment Evaluation: Protocol for User Evaluation of Imaging Equipment for Mammographic Screening and Assessment. NHS Cancer Screening Programmes, 2007 (NHSBSP Equipment Report 0703).

3. Routine Quality Control Tests for Full Field Digital Mammography Systems. NHS Cancer Screening Programmes, 2007 (NHSBSP Equipment Report 0702).

4. young KC, Oduko jm. Technical Evaluation of the Agfa CR 85-X Mammography System. NHS Cancer Screening Programmes, 2007 (NHSBSP Equipment Report 0707).

5. Commissioning and Routine Testing of Full Field Digital Mammography Systems, version 2. NHS Cancer Screening Programmes 2006 (NHSBSP Equipment Report 0604).


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APPENDIX 1:

Clinical breast dose survey – Agfa CR


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Clinicalbreastdosesurvey–KodakMin-R-EVfilm–screensystem

nhsbsp equipment report 0802

Documents

routine quality

kings college

national coordinating

hard copy

local physics

ma3000 reporting

agfa cr system

nhsbsp evaluation