WHOChestRadiographyinEpidemiologicalStudies

PartB–StudyGuidelines

Contents

IntroductionObjectives1. Personnel2. Infrastructure

2.1 Climate2.2 DepartmentRooms2.3 ConsumableStorage2.4 PowerSupply

3. EquipmentSpecifications3.1 X-rayequipment3.2 Imageprocessors3.3 Equipmentprocurement,installationandservicing

4. Identification&imagelabeling4.1 Patientidentification4.2 Imageannotations

5. ChestX-rayimagingrecommendations5.1 Patientpositioning5.2 Technicalfactors5.3 Otherrequirements5.4 Thefinalimage

6. Imagearchivingandviewingrecommendations6.1 Imagestorage6.2 Digitizingimages6.3 Imagetransportationforstudypurposes6.4 Imageviewingforstudypurposes

AcknowledgementsGlossaryReferences

IntroductionInpediatricradiographicexaminations,radiationdoseisofparticularconcern.Pediatricpatientsarerelativelymoreradiosensitivethanadultpatients(1-4).Thisisduetothecombinationofthehigherradiationsensitivityofthedevelopingorgansandthelongerlifeexpectancy,givingalongertimeframeforanyradiation-inducedcancertobeexpressed(5-7).TheaverageeffectivedoseforachestX-rayona5-year-oldpatienthasbeenquotedas0.02milli-Sieverts(mSv),whichisequivalenttoapproximatelythreedaysofnaturalbackgroundradiation(8).Furthermore,aqualitativepresentationofcancerincidenceriskforachestX-rayforpatientsat1-yearand5-yearsofagedemonstratesthattheriskisnegligible(8).ThisdataisconsideredaworldwideaverageanddespitethislowradiationdoseproducedforpediatricchestX-rays,thewidespreaduseofmedicalradiationisincreasing,particularlyinchildren.Therefore,monitoringofradiationdosestopatientsisstillpertinenttoensurethatdosesaremaintainedatacceptablelevels.Thiscanbeachievedthroughthecomparisonoflocaldosestodosereferencelevels(DRL),whichwillbediscussedindetailinPartC–QualityControl.Diagnosticimagingchallengesarisefromtheneedforimagingtobeconductedbyqualifiedand/orexperiencedpersonnelinadditiontotheuseofequipmentthathasbeenproperlyinstalledandwellmaintained.Significantchallengesarepresentwhenprovidingdiagnosticimagingtochildren,particularlyindevelopingandremotecountrieswherethereisvariableaccesstodiagnosticimaging.Forexample,inmostSub-SaharanAfricancountries,accesstoimagingfacilitiesisseverelylimited,withaclearmajorityofimagingservicesbeingavailableinurbanareas.Additionally,radiationprotectionmeasuresarerarelyenforced,sparepartsforbreakdownsareoftenrareorunaffordable,electricitysupplycanbeerraticandimagequalitysubstandard(9).Intheacquisitionofradiographsofanybodypartofanypatient,theapplicationofradiationtothepatientmustbeoptimized.Optimizationofradiationinvolvesadjustingimagingequipmentparametersandimplementingprotectivemeasuresforpatients,staffandvisitorstoensurethatthelowestradiationdoseisutilizedtoachievethedesireddiagnosticoutcome(10).Therecommendationsincludedintheseguidelinesarecomponentsthataredeemedpertinenttoachievehighqualitypediatricchestradiographs.Additionally,acountry’sradiationprotectionandsafetyinfrastructurecouldbestrengthenedbyon-goingneedsassessment,practicestandarddevelopment,policyimplementation,trainingsupportandsystemevaluation(9).Whilsttheseguidelinesareintendedforuseacrossallhealthcarefacilities,regardlessoftheirresourcelimitations,therecommendationsaretheminimumrequiredtoensurethathighqualityimagescanbeachievedforthepurposesofepidemiologicalstudies.Theaspirationhereisforhighqualityimages,yetimagesthatareconsidered‘readable’canstillbeacceptableasthereadableimagecouldbecriticaltopatientcareandsurvivalinmanysettings.Itisexpectedthatsitesinvolvedinthesestudieswillmeettheminimumstandardswithrespecttothespecificationsoutlinedintheseguidelinestoensurethatthedesiredimagesareachievable.Allsiteswillneedtobeevaluatedtodeterminetheiradherencetothespecificationsandtheleveloftechnicalsupportrequiredtomeetthestandards.Examplesofsupportmayincludeon-siteassistanceofserviceengineersforequipmentmaintenanceor

upgradeandanelectricalevaluationofthesite,aswellastrainingofstaff,provisionofsoftwareanddevelopmentoflocalprotocolsforx-raytechniques.ObjectivesTheobjectiveoftheseguidelinesistoestablisharesourceforresearchers,studystaffandcollaboratingradiologydepartments,outliningmajorissuesfacedinobtaininghighqualitypediatricchestX-rayswithafocusonremoteandunder-resourcedregions.Experiencefrompreviousstudiessuggestthatearlycollaborationbetweenradiologydepartmentsandresearchstaffwillassistinmaximizingthequalityofchestradiographs.TheseguidelinesaimtoinformthedevelopmentofprotocolsforachievingqualitychestX-raysinstudiesinvolvingchildrenaged0-59months.Theclinicalsetting,projectgoalsandneedsoftheresearcherswillvarybetweenstudies,hencetheintentofthisdocumentistoproviderecommendationsflexibletoindividualcircumstances.Eachstudywillneedtotailorthenumberanddetailofprotocolsorstandardoperatingproceduresaccordingtothescopeandcomplexityoftheproject.TheseguidelinesreviewthemajorfactorscontributingtoaqualitypediatricchestX-raywithanemphasisonissuesthataremostimportantand/oreasilyadjustedbytheresearchteam.Therecommendationsareinkeepingwithacceptedradiologicalprinciplesofjustification,optimizationandlimitation(10).Theyhavebeendevelopedfrombestpracticetechniquesaccordingtocurrentliterature,inadditiontointernationalregulationsfromtheWorldHealthOrganization(WHO),theInternationalCommissionforRadiologicalProtection(ICRP),theInternationalAtomicEnergyAgency(IAEA)andtheEuropeanCommission.MinimumrequiredstandardsareidentifiedtoensureboththatfacilitieswithresourcelimitationscanprovidequalitychestX-raysforstudypurposes,andthatthereisconsistencybetweenfacilitiesinmulti-sitestudies.Theseguidelinesdonotnecessarilyaffectasite’sexistingstandardsandprotocols,noraretheyintendedforclinicaluse.However,theirusemaybebeneficialforwiderpatientcare.Theprimaryapplicationoftheseguidelinesistooptimizechestradiographsasadiagnostictoolinepidemiologicalstudies.Asummaryoftheguidelineswithrecommendedrequirements,measuresoftherequirementsandtherationalecanbefoundinappendix1.

1.Personnel“Adequatetraininginradiationsafetyisaprerequisiteforallstaffworkinginthemedicalimagingservice.Whererecognizednationalstandardsforradiationsafetytrainingexist,thesemustbeappliedbythemedicalimagingservice.”(11)Thesignificanceofadequatetraininginchestradiography,particularlyinchildren,isimportanttoensurethathighqualityimagesareacquiredunderthesafestconditions.Additionally,theseimagesshouldbeobtainedwithminimaldistresstothepatientandparentsorcarers.Thisismorelikelytobeachievedifthoseeitheracquiringtheimagesorsupervisingthoseacquiringtheimageshavesignificantexperience(forexample,aminimumof5-years)and/oraqualificationofatleasta6-monthcertificateinradiography.Whilstthisisrecommended,thesearenotalwaysfeasiblemandatoryoptionsanditisrecognizedthattherequiredqualificationsvarygreatlyfromcountrytocountry.Eachfacilitywillthereforeneedtoconsidertheirownconstraintswhenidentifyingappropriatestaff.Thecompetenciesoffacilitystaff,alongwithotherqualityissuescanbeevaluatedusingthesampleimagesthataresenttoexperiencedradiologistsandradiographersalongwiththeassessmentsurvey(PartA).Iffacilitystaffhaveverylittleexperienceorunderstandingoftechnicalinformation,researchersshouldconsiderbudgetingforexternaladviceandtechnicalassistance.Thoseacquiringtheimages,aswellasanyotherpersonnelworkingintheX-rayexaminationroomonadailybasisareencouragedtowearradiation-monitoringbadges,forexampleThermo-luminescentdosimeters(TLD)orBerylliumOxideOpticallyStimulatedLuminescence(OSL)meters.Themonitoringbadgesarerecommendedtobeissuedandassessedbyanapprovedregulatorybodyeverythreemonths,withassessmentdatafeedbackgiventothesite,aswellasanynecessaryactionresultingfromthedata.

2.InfrastructureItisdesirablethatthelayoutandspecificationsofthedepartmentconformtonationalorinternationalregulations,whilstmaintainingcomfortforthepatient.Thiswillensurethattheradiographicexaminationscanbeconductedinamannerthatissafeandefficient,aswellasallowforthefullcapabilitiesoftheequipment.ThefollowingdepartmentspecificationsaretheminimumrequiredforthepurposesoftheseguidelinesinkeepingwiththesafeconductofchestX-rayexaminationsonchildren.2.1ClimateIndoorclimatecontrolandgoodventilation,suchaswiththeuseofairconditioners,arerequiredifindoortemperaturesbelow15degrees,above28degreesand/orahumidityofgreaterthan80%isexpected.Thiswillalsoassistintheprotectionofthesolid-statecircuitsusedforX-rayproductionandwillensurethatreliableimagequalityismaintained(11).2.2DepartmentroomsItisexpectedthatadepartmentconsistofaminimumofthreerooms(12):

• X-rayexaminationroom• Darkroomforprocessing(ifX-rayfilmprocessingisrequired)• Viewingroom(orofficewhereviewingofimagescanoccur)

2.2.1X-rayexaminationroomTherequirementsofthesizeoftheX-rayexaminationroomneedtoallowappropriateaccessforallpatients,includingthosetravellingtothedepartmentonahospitalbed.Additionally,theroomsizemustallowfortherequiredfocal-filmdistance(seesection5.2technicalfactors).ItisrecognizedthatX-rayequipmentwillvarybetweenfacilitiesduetothenumberofmanufacturersonthemarket.Theminimumroomsizewillthereforebelargelydependentonthespecificationsoftheequipment.Itisrecommendedthatthefullcapabilitiesoftheequipmentareassessedpriortostudycommencementtoensuretherequiredimagescanbeacquired.ToallowforappropriatemovementofanX-rayunit,thefloorsshouldbecompletelylevel.Thebestmaterialtoachievethisisleveledconcrete,whichiscoveredbywoodorpolyvinylchloride(PVC).(12)Windowsintheexaminationroomareacceptable,butonlyiftheyarepositionedsothatnobodyoutsideoftheroomcanbeexposedtoradiationorlookintheroom.Toensureappropriateradiationprotectiontothoseoutsideoftheexaminationroom,theWorldHealthOrganizationgenerallyrecommendsthatthewallsneedtobeconstructedofconcreteorsolidbrick(12).However,roomdesignrequirementsaregenerallynotprescriptive,rathertherequirementtomeetdoselimitsforradiationworkersandfacilityvisitorsaretobekeptwithininternationallimits,suchasthoseoutlinedbytheInternationalCommissionforRadiologicalProtection(ICRP)(12).Themethodtoachievethisrequirementisatthediscretionofthefacilityandcanbeachievedinanumberofways,suchaswarninglights,leadshieldingorphysicalrestrictiontotheexaminationroom.Additionally,chestX-raysonchildrenisconsideredalowradiationworkload,therebyreducingtheneedforstringentrestrictionsonroomconstruction.Withintheexaminationroom,ifthereareanywallsandscreensseparatingtheoperatorfromtheX-raysourcetheyshouldallowforacontinual,unobstructedviewofthepatienttoensurethatthepatientisinthecorrectpositionatthepointofimageacquisition.(12)

Allexaminationroomsshouldhaveoxygensupply,aswellassuctionforusewithpatientswhererequired.Additionally,toreducetheriskofinfection,theseroomsshouldprovideappropriateprotectiveclothingforallstaffmembers,includingwhererelevant,masks,glovesandgowns(12).2.2.2DarkroomWhenusingfilm,inordertoachievehighqualityimagestheprocessingofthefilmsarejustasimportantastheimageacquisition.Itisthereforeimperativethatthesizeandconditionsofthedarkroomareappropriateforadequatefilmprocessing.ThefollowingdarkroomrecommendationsarebaseduponthosebytheWorldHealthOrganization’squalitysystemsformedicalimagingandtheconsumerguideforthepurchaseofX-rayequipment(11,12):

• Darkroomsshould:o Beentirelylightprooffromoutsidelight,includingtheentryareao Haveanavailable60Wincandescentwhitelight.Fluorescentlightwillhave

anafterglowandmayfogthefilmo Haveasafelightforfilmprocessingconditionswithamaximumof15Wand

colouredfilter,withthecolourdependingonthetypeoffilmused.Thisshouldalsobeatleast120cmabovethebench-top

o Beproperlyventilated,withatleast15air-changesperhourallowingairtobedrawninfromoutsideandhaveanadequateextractionfanthatfunctionswheneverthedarkroomisinuse

o Allowforadequatespacefortheprocessorandconsumables,aswellasforachievingtherequiredwork.Thisis6squaremetres,withaminimumdimensionof2metresifthedarkroomservesoneX-rayexaminationroom,but,8squaremetresifthedepartmentemploysadarkroomattendant.Theceilingheightshouldnotbelessthan3metres

o Haveaslopingfloortowardsadraininggutterincaseofachemicalspillo Haveanairexchangethatconformstolocalandnationalstandardsand

providingfreshairwherepossible.2.2.3Viewingroom/officeAdequateworkingspaceforadministrativeandimage-viewingdutieswithalightboxorcomputerisaminimumof10squaremetres.Thisspacewillneedtobemuchlargerifitisalsobeingusedforfilmstorage.TheentrancetotheofficeshouldneverbethroughtheX-rayexaminationroomasthisisnotsafepractice.(12)

2.3ConsumableStorageStorageofconsumableitems,suchasunexposedfilmorunusedchemicalsrequireasignificantamountofspace,aswellasappropriateclimatecontroltoavoiddamage(11).Thefollowingarerecommendationsonstorageofunexposedfilm,unusedchemicalsandimagingcassettes:

• StorageshouldneverbeintheX-rayexaminationroomastheyareeasilydamagedinthisenvironment.

• Areasofthedepartment,suchastheviewingroom,officeordarkroomaresuitableforstorage,providedthereisadequatespacethatwillnotposeanoccupationaltrippinghazard

• Filmboxesmustbestoredasperthemanufacturerinstructions,aswellasuprightandawayfromheat,humidityandradiation.

• Imagingcassettesshouldalwaysbestoreduprighttoavoiddustsettlingonthefilm.• Onceexposedtoair,chemicalsshouldbeplacedintheappropriatesectionofthe

filmprocessorimmediatelytoavoidoxidation.Chemicalhandlingshouldbeasperthemanufacturerguidelines,ensuringthattheydonotcomeintocontactwiththeskinoreyes,andarenotinhaledoringested.Inthecaseofaccidentalchemicalsplashintotheeyes,thereshouldbeemergencyeyewashkitsineachfacility.Storageofchemicalsshouldensurethattheyareinawell-ventilatedroom,awayfromanyfilmstorage.Thestorageshouldalsoincludearotationsystemtoensurethatchemicalsdonotreachtheirexpirydate.2.4PowersupplyTherequiredpowersupplytoanX-raydepartmentlargelydependsonboththetypeofequipmentandthenumberofitemsofelectricalequipmentusedtoefficientlyrunthedepartment.Asageneralrequirement,itisexpectedthatwherepossible,thepowersupplyisconstantandreliablefortheX-rayunitsthatitissupplyingandhaveasufficientback-upsupply(forexample,anACgenerator).AstandardX-raysystemneedsasymmetrical3-phasemainswithgroundingsupply.Amulti-peakgeneratorwithenergystorageinbatteriescanusea230V,10A‘household’walloutletandstilleasilyhandletherequired30kWforchestX-rays.Thisisalsonoproblemforageneratorwithenergystorageinacapacitor(see‘equipmentspecifications’below)(12).IfthelocalmainssupplysystemdiffersfromthepermittedmainssupplysystemsforaspecificX-raysystem,atransformerforconversionwillbeneeded.Itmustbenotedherethatthesevaluesareforadultchestradiographs.Thepowerrequirementsforchildrenarethatthegeneratorisatleast80kWtoallowforshorterexposuretimesaschildrenmaybeunabletokeepstillorholdtheirbreathfortheX-ray.Iftheelectricalmainssupplyissuspectedtobeunstableorofteninterrupted,itisrecommendedthatanUninterruptiblePowerSupply(UPS)beinstalled.TheUPSisonlyusedtopowertheX-raygeneratorandassociatedimageacquisitionequipmentandwillswitchovertotheback-upsupplyautomaticallyintheeventofapoweroutage.ThemainsimpedanceistheapparentelectricalresistanceofthepowerlineandmustbelessthanorequaltothespecificationoftheX-raygeneratormainsresistance.DespitewhichX-raygeneratorisused,theimpedanceofthesupplymainsshouldbenolargerthan3ohms(Ω).However,withenergystorageintheX-raygenerator,theimpedancevalueisnotcritical(12)Ordinarylighting,darkroomlight,lightboxesandfilmmarkingequipmentwillrequireanadditional2-3kWinpower.Furthermore,anautomaticprocessorneedsaseparate,verystablemainssupplyfor3-4kW.Therefore,forelectricalsafety,allstandardelectricalwalloutletsinthedepartmentsshouldfollowlocalregulationsandshallbefor230Vand10A,mustbedouble,groundedandsuitablyprotected(12).

3.EquipmentspecificationsTheequipmentusedintheacquisitionofchestradiographsonchildrenmustadheretoaminimumstandardandcomplywithanynationalregulationsofthecountryofpracticetoensureasafe,yethighqualityimageacquisitionprocess.Thefollowingspecificationsaretheminimumrequiredtobeabletoparticipatesafelyandefficientlyinanepidemiologicalstudy.Itisexpectedthatthepersonsoperatingeachofthesepiecesofequipmenthavebeentrainedintheirdailyuseandinbasicmaintenanceandthatthemainx-rayunitusedforacquiringimagesforthepurposesofastudyisastationaryunit(12).

3.1 X-rayEquipmentTheremaybeoccasionswheretheX-rayunitorimageprocessormalfunctionsandisunabletobeusedforaperiodoftime,whichmayaffectthecollectionofdataforthestudy.Inthesecircumstancesitisexpectedthatforasitetobeincludedinastudy,equipmentrepairmustbeabletobecarriedoutwithin24-hoursofthemalfunction.Ifthisisnotpossible,analternativesourcemustbeavailabletobeused.FortheX-rayunit,thisalternativemaybeamobileX-rayunitorback-upX-rayunit.

3.1.1 GeneratorMainrequirement:A12-pulseorhighfrequencymulti-phase(alsoknownasa‘converter’)generator.Modernsystemsrequirea3-phase80kWgeneratortoallowforthelowexposuretimesrequiredforpediatricchestX-rays.Rationale:

• Enablesshortexposuretimes,whicharerequiredinpediatricimagingtoallowforacquisitionduringnormalrespirationandavoidmotionartefact.

• Allowsforhighvoltages,whichreducespatientskinentrancedose.(13)Othergeneratorrequirements:

• Tubevoltagerangeof50-120kVwithavariationconsistencyoflessthan5%(13)

• AdjustablemAssettings,withaminimumpossiblevalueoflessthanorequalto0.5mAs(13)

• SeparatedisplayofmAandtime,withtheshortestexposuretimeat1ms.(13)

• Poweroutputofastationaryormobilegeneratorshouldbegreaterthanorequalto50kWforappropriateefficiency

• Stationarygenerator(12)o Integratedenergysourceo Multi-peakinvertertechnologyo Abilitytooperatefroma‘household’mainssupplyof230Vand

10A,orfromafuel-poweredACgenerator.• Mobilegenerator(12)

o Energystorage,forexamplealead/acidbattery(notNi-cad)orlargecapacitor

o Multi-peakinvertertechnology

NotethatthepowerrequirementsfortheX-raygeneratorislargelydependentonthetypeofgenerator.Differentgeneratorswillhavedifferentpowerrequirementsandtheabilitytomeettheserequirementsshouldbeconfirmedwiththemanufactureruponpurchaseofequipmentoracceptanceofdonatedequipment.

3.1.2 StationaryX-raysystem

ThestationaryX-raysystemisonethatisusedinafixedlocationwithinabuilding.ItisanX-rayfilmbasedsystemthatuseseitheranalogue,analogue-to-digitalordigitaltechniquesforimagecaptureanddisplay.Thesystemconsistsofmodularconfigurationsthatcanbeupgradedbytheadditionofhardwareorsoftwarecomponentsoraccessories.(14)Toensureeasyandsafeacquisitionofimages,theminimumrequirements,basedontheWHOEquipmentSpecifications(14)are:

• Useahorizontal,angulatedorverticalX-raybeamtoenableimagingofthepediatricchestinboththesupineanderectposition(12)

• Separatecontrolconsoleandgeneratorallowingforasafedistanceand/orshieldingfromtheoperatorandthepatient

• DigitaldisplayofmAs,kVandelectronictimerontheconsole• AkVrangeofatleast50kVto120kV,digitallydisplayed• AmArangeofatleast25mAto600mA,digitallydisplayed• Anexposuretimeofatleast1ms• X-raytubepowerratingofatleast50kW• X-raytubewitharotatinganodeandnominalfocalspotsizelessthan

1mm(mostmodernsystemscomewithfocalspotsizesof0.6mmand1.2mm)

• Anyanti-scattergridswithintheimagereceptorholdermustbeabletoberemovedortheunitsmusthaveimagereceptorholderstoenableimagereceptorstobeplacedinfrontofthegrids

• Heatstoragecapacityoftheanodeatleast300kilo-heatunits(kHU)• Visualandaudibleexposureindicatorsontheconsole• Emergencystopcontrolsintheeventofequipmentmalfunction• Adjustablemulti-leafcollimatorsforfieldsizealterationthatare

rotatable90-degreesinbothdirectionswithaworkingpatientcenteringlightorlightbeamdiaphragm(LBD)

• Concealedcablesonthepatienttable• Source-to-imagedistancerangeofatleast90cm-125cm• FullycounterbalancedX-raytubeheadforsafeandeasymovement• TheX-raytubemustbeabletorotatedindependentlyoftheimage

receptoranditsholders• Dose-area-product(DAP)meterinstalledwherepossibletomeasureand

displaytheDAPdoseandoptionally,theDAPrateanddoserateIftheX-raysystemisadigitalsystem,thefollowingspecificationsapply(14):

• MinimumJointPhotographicsExpertGroup(JPEG)compatibleimagestorageandtransfer

• Alphanumericannotationsofimages

• Imagedisplaytobecontrastandbrightnessadjustable,withadiagonalscreensizeofatleast18inches

• Theimagestobedisplayedimmediatelyafterexposure• Thesystemtobecapableofstoringatleast3000imageswithcapacityfor

removablestorage3.1.3 MobileX-raysystemThemobileX-raysystemisonethatisusedinavarietyoflocationswithinabuilding.Itisanassemblyofdevicesthatcompriseeitheranalogue,analogue-to-digitalordigitaltechniquesforimagecaptureanddisplay.Thesystemcanoperatebybatteryandbedrivenorpushedbyanoperatortovariouslocations.(14)IfamobileX-rayunitistobeusedasatemporaryreplacementintheeventofastationaryX-raysystemmalfunction,theminimumrequirements,basedontheWHOEquipmentSpecifications(14)are:

• Useahorizontal,angulatedorverticalX-raybeamtoenableimagingofthepediatricchestinboththesupineanderectposition(12)

• AkVrangeofatleast50kVto120kV,digitallydisplayed• AmArangeofatleast0.5mAsto200mAs,digitallydisplayed• Anexposuretimerangeofleast1msto5s• X-raytuberatingofatleast50kW• X-raytubewitharotatinganodeandnominalfocalspotsizelessthan1mm• Heatstoragecapacityoftheanodeofatleast300kHU• Adjustablemulti-leafcollimators,rotatable90-degreesinbothdirectionswitha

workingpatientcenteringlightorlightbeamdiaphragm(LBD)• Aworking‘low-battery’indicator• Exposuresmadebyremotecontrol,withtheswitchonacordatleast3metres

long• X-raytubestandfullycounterbalancedforrotationinalldirections• Anarticulatedarmforimagingpatientsinanyposition• Concealedcablesinthearmsystem• Animagereceptorstoragefacility• Motorbatteryofthesealedlead-acidtype,whichcanberechargedbythemain

unitpowerconnection• Afitted,resettableovercurrentbreakeronbothliveandneutralsupplylines• Avoltagecorrector/stabilizerallowingoperationat±30%ofthelocalrelated

voltage• Capabilityofbeingstoredcontinuouslyinanambienttemperatureof0-40

degreesandrelativehumidityof15-90%,andoperatingcontinuouslyinambienttemperatureof10-30degreesandrelativehumidityof15-90%

3.2 ImageProcessorsTheWHOManualofDiagnosticImagingstatesthatimageprocessingisasimportantasimageacquisitiontoobtainthebestimagequality(15).Intheprocessingofimages,thepreferenceisforsitestoemployacomputedradiography(CR)ordigitalradiography(DR)system,duetotheoverallcostsavings,archivingabilitiesandpostprocessingmanipulationofimages.However,theimplementationofthesesystemscanbedifficult,particularlyinremoteareaswithrespecttothehighinitialcostandongoingtechnicalsupport.Consequently,theminimumprocessingrequirementsoutlinedintheseguidelinesisfortheuseofautomaticfilm(i.e.analogue)processors,whethertheyaredarkroomprocessorsordaylightprocessors.Manualdarkroomprocessingisanoldtechniquethatrequiresmoreprecisionandattentionfromdarkroomtechnicians,particularlyinsuboptimalconditions,suchashighroomtemperatureandpoorventilation(15).Imagequalityisalsomuchmorevariableanditishighlyrecommendedthatstudiesdonotusethistechnique.Theminimumrequirementsintheseguidelinesthereforeareformanualdarkroomprocessingnottobeincluded.ThefollowingspecificationsaretakenfromtheWHOEquipmentSpecifications(14)toensurethattheprocessingofimagesismaintainedatoptimumlevels:3.2.1 DarkroomAutomaticProcessor

ThedarkroomautomaticprocessorisadeviceinwhichX-rayfilmmustbemanuallyremovedfromacassetteandloadedintotheprocessorinadarkroomsetting.Theprocessorthenautomaticallytransportsthefilmthroughthedeveloping,fixing,washinganddryingstagesalongaseriesofrollers.Italsoalertstheusertothecurrentprocessstage,timetocompletionandremainingamountofreagents(14).Theminimumspecificationsforthedarkroomautomaticprocessor,basedontheWHOEquipmentSpecifications(14)are:

• Allowingforatleast100filmsofmaximumsizetobeprocessedperhour• Automaticfilmtransferandcontrolprocesses• Volumeofthestoreddeveloper,fixerandwashertobeatleast4litres

each• Allowanceofsilverreclamationfromthechemicalsused• Displaysandalertsforchemicaltemperatureandamountsremaining• Sufficientdraincapacityforcontinuousoperationatmaximumload• Automaticfilmdetectiondevice• Standbymodewhennotinuse• Thetotalweightofprocessorwithchemicalsin-situshouldbenotgreater

than250kg• Regulateddriertemperature• Adjustablewaterconsumption• Capableofbeingstoredcontinuouslyinanambienttemperatureof0-40

degreesCelsiusandrelativehumidityof15-90%,andoperatingcontinuouslyinanambienttemperatureof10-40degreesCelsiusandrelativehumidityof15-90%

• Mountedeitheronatable-toporwithafloor-mountedstand

• Aconnectiontobothahotandcoldexternalrunningwatersupplywiththeprecisewaterrequirementsaspermanufacturerrecommendationsandwatershut-offvalvessupplied.Waterconsumptionnottobegreaterthan5litresperminuteandpassedthroughafiltertoeliminateanyimpurities

• Resettablecircuitbreakersinbothliveandneutralsupplylinesforelectricalprotection

• Powermainssupplyof3-4kW

3.2.2 DaylightAutomaticProcessor

Thedaylightautomaticprocessorworksjustasadarkroomautomaticprocessor,howeverwillautomaticallyunloadX-rayfilmfromcassettesdirectlyintotheautomaticfilmprocessorportionofthesystemandreloadfreshX-rayfilmbackintothecassette(14).Thisprocessorthereforehasthesamespecificationsasdescribedforthedarkroomautomaticprocessor,withtheexceptionofthecassetteloadingandunloadingrequirements.

3.2.3 ComputedRadiographyProcessor

Unlikemanyfilm-basedsystems,CRsystemsdonotrequiretheuseofadarkroom.CRimagingplatesareknownasphosphorplatescreateanimagebyexcitingtheelectronsintheplateintoahigherenergystatewhenexposedtoX-rays,formingalatentimage.ThisisthenreadintheCRreaderwithalaserspot,wheretheelectronsabsorbthelaserenergyandemitlightastheyreturntotheirgroundstate.Thislightiscollectedbyalightguideandsenttoaphotomultipliertube,whichproducesananaloguesignalthatisconvertedtoadigitalsignal.Theplateisthenexposedtoanerasinglight,removingtheresidualradiation.Insomecases,itispossibletousethestandardfilmcassetteswithCRphosphorplates.Therearevariationsinthemethodsdescribedabovedependingonthetypeofreaderandmanufacturer.However,thefollowingminimumspecificationsforaCRsystemisrequired:

• ApanelforindicatingonlinestatusoftheCRreaderincaseofmachinemalfunction

• Thespatialresolutionofthedigitalimageis6pixels/mmormore• Theimagesizeshouldbe12-bitsorhigher• Specificpediatricalgorithmsthatareweightdependentshouldbe

establishedandbeappliedtoallpediatricchestimages.• Theabilityforpost-processingofimages,suchasannotationsandgrey

scaleoptimizations,priortoimagesbeingsentforreading.• Theabilityforsingleexposurestohavemultiplepost-processingapplied

totherawdatacreatingmultipleimagesthatcanbearchivedorfilmed• Theabilitytore-processanarchivedimagewithanewalgorithmand

thenarchivethenewimage• Recordpatientidentificationdatadirectlyontotheimage• Retrieveandreproducehighqualityimagesfromstoreddatawithoutthe

lossofimagequality

• Harddiskcapacitylargeenoughtobeabletostoreimagescommensuratewiththeworkload

• Abilitytosendimagestoanexternalsource(e.g.PACS/USB)and/orprintontohardcopy

• Powerinputtobe220-240Vat50Hzandfittedwithaplugcommensuratewithfacility’selectricaloutlets.Thereisalsotobearesettableovercurrentbreakerfittedforprotection

• Theresolutionofthephosphorscreensshouldbeintheorderof1576x1976pixelsfora24x30cmcassetteor1770x2370pixelsfora18x24cmcassette

3.2.4 DigitalRadiographySystems

DRsystemsgenerallydonotuseaphysicalmediumforwhichanimageisstored,rathersendingtheimagetoacomputerscreendirectlyafterexposure.AnothersignificantadvantageofDRoverCRisthatsimilarimagequalitycharacteristicscanbeobtainedatupto60%lowerradiationdoses.Inadditiontotheexposuresettings,theappearanceofthefinalimagedisplayedonthescreenisdependentuponthealgorithmsthathavebeenestablishedandapplied.ThefollowingspecificationsaretheminimumrequiredforaDRsystem:

• Specificpediatricalgorithmsthatareweightdependentshouldbeestablishedandbeappliedtoallpediatricchestimages.

• Theabilityforpost-processingofimages,suchasannotationsandgreyscaleoptimizations,priortoimagesbeingsentforreading.

• Theabilityforsingleexposurestohavemultiplepost-processingappliedtotherawdatacreatingmultipleimagesthatcanbearchivedorfilmed

• Theabilitytore-processanarchivedimagewithanewalgorithmandthenarchivethenewimage

• Harddiskcapacitylargeenoughtobeabletostoreimagescommensuratewiththeworkload

• Abilitytosendimagestoanexternalsource(e.g.PACS/USB)

Theimagingspecificationsfordigitalradiographyvarywidelyacrossdifferentmanufacturers.ItisthereforedifficulttoproviderecommendationsontheminimumdetectorandX-rayrequirementswhenusingdigitalradiography.However,asanexample,inapaediatricsetting,thefollowingrelevantdigitaldetectorandX-rayrequirementswouldbesufficient:• HighDoseQuantumEfficiency(DQE)CesiumIodidedetectors.Thisenables

improvedimagequalitywithlowerdoses.• Paediatricimageoptimizationsoftware• DetectorMatrixminimum

o For35x43cmdetectors–2520x3032pixelmatrixo For25x30cmdetectors–1752x2130pixelmatrixo 14bitbit-depthforacquisition,12-bitforstorageo Pixelsizeof125micrometres

Forthedisplaymonitors,thefollowingspecificationsarerecommended:

• Resolutiono 1280x1024pixels

• Visualcontrast

o 1000:1• Brightness

o 220cd/m2Asaseparaterequirementforallportabledigitaldetectors,a“highshocktolerance”isrecommendedtoavoiddamageifthedetectorisaccidentallydropped.Foranyfixeddigitalimagereceptor,thefieldsizeshouldensurethattheentirechestcanbeimagedinoneradiograph.Additionally,calibrationofthedetectorsshouldbeperformedbytheserviceengineeratthetimeofthescheduledequipmentmaintenance.

3.3.Equipmentprocurement,installationandservicing

Regularmaintenanceofequipmentisessentialtoensureaconsistentqualityofimaging.EquipmentmaintenanceprocessesthatcanbecompletedbysitepersonnelwillbediscussedindetailinPartC-QualityControl.However,itisexpectedthatforasitetoparticipateinastudy,well-trainedandqualifiedpersonnelwillservicethefollowingequipmentatleastyearly:

• X-rayunitandgenerator• UninterruptedPowerSupply(ifapplicable)• Filmprocessor• CRreader• DRimagingreceptors

Itispreferablefortheservicingpersonneltobefromthesamemanufacturerasthespecificpieceofequipment.However,thisisnotalwayspossibleandanappropriateengineer(eitherfromthesite’scountryoforiginorinternational)deemedsuitablebytheresearcherscanbeaviablealternative.Maintenanceandrepairofequipmentisfurthercomplicatedwhereequipmentisdonated.Donatingequipmentmaynotnecessarilyhavethedesiredeffectofimprovingcare(16).Forexample,almost50%ofalldonatedx-rayequipmentinthedevelopingworldisoutofserviceduetopoorinfrastructureormissingequipment(17).Furthermore,fordigitalX-rayequipment,requiredinformationtechnologyinfrastructure,suchasinternetaccesscanoftenbeoverlooked.Donationofthisequipmentshouldonlybeconsideredwhenaservicecontractfromamanufacturer’srepresentativeispurchasedalongwiththedonation.However,thecontractcostsmayexceedthatofthepurchaseofusedequipment(16).Thefollowingpointsshouldbeconsideredinthedecisiontoacceptequipmentdonations(16);

• Itisrarefordonatedequipmenttoconformtothepowersupplyrequirementsofthetargetcountryandshouldthereforebeconsideredinthepreparationofequipment

• Theequipmentshouldconformwithgovernmentpoliciesandadministrativearrangementsofthetargetcountry

• Forthequalityoftheequipmenttobeacceptableinthetargetcountry,itshouldbeacceptableinthedonorcountry

• Thereshouldbeeffectivecommunicationbetweenthedonorandrecipient.Furthermore,alldonationsshouldbemadeaccordingtoaplanagreedtobyboththedonorandrecipient.

Inthecaseswherenewequipmentisrequiredtobepurchased,considerationshouldbegiventothefollowing(inadditiontothespecificationsoutlinedabove):

• Theimagingsystemmustbeeasytouseandmaintain.Filmbasedsystemsincurlargeongoingcostsduetoconsumablesandstorage.Adigitalsystemisthereforepreferable(18)

• Digitaldevicesthataredesignedtooptimizepediatricimaging,includingtheabilitytosegregatealgorithmsintospecificpatientsizesubgroups.Usingadultsettingsinapediatricenvironmentmayunnecessarilyresultinincreasedpatientradiationdoseorpoorimagequality.

• Imagingsystemsmustbeabletoelectronicallytransferimages.JPEGorAudioVideoInterleaved(AVI)canbeused,buttheimageidentificationwouldeitherhavetobetransferredasaseparatefileorbeimbeddedwithintheimage.Additionally,aphysicalmeansofimagetransport,suchasEthernet,aUSBorWi-fiisrequired(18).

• ImplementationoftheexposureindicatorstandardbytheInternationalElectrotechnicalCommission(IEC)62494-1(19)

Whetherequipmentispurchasedordonated,allequipmentistobeinstalledbythesupplier,whoshouldalsoperformsafetyandoperationchecksbeforehandingovertothedepartment(14).Afterinstallation,appropriateinspectionshouldoccurtoensuremechanicalandelectricalsafetyaswellasproperradiationlimits(14,20).Thesupplierisalsoresponsibleforprovidingtechnicaltrainingtousersintheoperationandbasicmaintenanceoftheequipment.Alistofequipmentandproceduresrequiredforlocalcalibrationandroutinemaintenanceoftheequipment,aswellasuserandtechnicalmaintenancemanualsshallbeprovided.Thesemanualsshouldalsobeprovidedinalanguageunderstoodbytheuser(14,16).Fullrecordsofallservicing,maintenanceandanyrepairsorreplacementpartsshouldbemaintainedforeachitemofequipment(10).Theperiodofmanufacturerwarranty,ifany,shouldalsobeevidentintheservicerecords.Contactdetailsofthemanufacturerandsupplier,aswellasanylocalserviceagentsaretobeprovidedtothedepartment(14).

Furthermore,tobeincludedinastudy,sitesshouldideallyhaveservicedtheirequipmentwithin12-monthsofthebeginningofaproject.

4.IdentificationandimagelabellingTherearespecificgeneralprinciplesthatareassociatedwithgoodimagingperformance.However,someoftheseprinciplesarerequiredtoensurethatimagesareappropriatelyidentified,arematchedtotherightpatientandthatimagescontaininformationabouthowtheywereacquiredforproperanalysisandreproducibility.

4.1 PatientIdentificationAllpatientsshouldbeproperlyidentifiedpriortoimagingtoensurethatthecorrectpatientandstudymatchtherequiredimaging.Theminimumrequirementisthatpatientsareidentifiedviathefacility’susualclinicalprocedure,whichmayincludethepatientnameanddateofbirthmatchingtherequestforimaging.Anyidentificationchecksshouldberecordedonboththeimagingrequestformandstudycasereportform.

4.2 ImageannotationAllimagesmusthavethefollowinginformationpresentandlegible.Theseannotationsmustnotobscureanyanatomyandshouldbeinthesamelocationontheimageeverytime.Theyshouldalsobeeitherincludedontheradiographordigitallyinscribedontheimage.Someoftheseannotationsmaybesubsequentlyobscuredorremovedtoensurethede-identificationofpatientdataintheinterpretationofchestX-rays:

• Nameanddateofbirthofthepatient• Dateofexamination• Anatomicalsidemarker(leftorright)• Whethertheimagewasacquiredinasupineorerectposition• Nameoffacility• Exposurefactorsusedtoacquiretheimage(preferredbutnotessential)

5.ChestX-rayImagingRecommendationsIntheacquisitionofchestX-rayimagesinpediatricpatients,thereisnotonlyaneedtostandardizethex-rayequipment,butalsotheradiologictechniquestoensureoptimizationofradiationdose(21).Forexample,somepartsofthedevelopingworldusefluoroscopyunitstoobtainreal-timeimagesofthechestasadiagnostictoolforpneumonia.Thisisahighlyunreliableexaminationthatinvolvesanincreasedradiationdose(11).ItisthereforerecommendedthatastandardX-raytechniquebeusedforepidemiologicalstudies.ManypathologicalprocessesrequiretheuseofboththeAPorPAandlateralchestX-raystoassistintheirdiagnosis.ItisalsounderstoodthatfacilityprotocolmayrequirebothoftheseprojectionsforallchestX-rays.However,forthepurposesoftheepidemiologicalstudiesthattheseguidelinesarewritten,anAPorPAchestalonewillsuffice.Formanyresearchquestions,thelateralchestX-rayisnotrequired,butmaystillbeusedifclinicallyindicatedoriftheresearchquestionspecificallyrequireslateralviews.Thepurposeoftheseguidelinesistotargetstudieswithacohortofpatientsbetween0and59months.Inthesecases,theAPchestispreferredoverthePAchest.ThepositioningmethodsofpatientsinthisagegrouparemuchsimplerfortheAPchestandarelikeliertoachievepatientco-operation.Furthermore,thedifferencesinmagnificationofinternalstructuresbetweentheAPandPAchestatthisagearenegligibleduetothecylindricalshapeofthepediatricchest.

5.1 PatientPositioning

PositioningchildrenforchestX-rayexaminationsisanimportanttaskthatcanbedifficultwherepatientsareuncooperative.However,itiscrucialthattheresultantimagebeofsufficientqualitythatitisdiagnostic.Itisthereforeimperativethatthemethodofpatientpositioningisexactandindependentofthelevelofcooperationofthepatient.FortheAPchestX-rayexamination,thetwomainmethodsofacquiringtheimagearewiththepatientinthesupineorerectposition.Theerectpositionofthepatientisthemoredifficulttobeachieved,particularlyifthepersonacquiringtheimageisnotwelltrainedinthisareaordoesnotregularlyacquireimagesonthesepatients.Consequently,itisexpectedthatifthefacilityconductserectchestX-raysonchildrendaily,anerectchestX-rayshouldbeperformed.Forallotherfacilities,orwherepositioningapatientforanerectchestX-rayisdifficult,asupinechestX-raywillsuffice.TheseguidelinesdescribethepositioningmethodsforboththeerectandsupinechestX-rays.InstructionalvideosofpositioningmethodsbyTheRoyalChildren’sHospitalinMelbourne,AustraliacanalsobefoundontheWHO-CRESwebsite.ThepatientistobepositionedinatrueAPposition,withtheirshouldersandanteriorsuperioriliacspines(ASIS)equidistantfromtheimagereceptor,ensuringthattheyarenotrotated.Themid-coronalplaneofthepatientshouldbepositionedsothatitisparalleltotheimagereceptor.Intheuncooperativepatient,thearmsaretobeimmobilizedabovethepatient’sheadtoensurethatthescapulaeareclearfromthelung-fields.Thiscanbealsoachievedinthecooperativepatientbyplacingthepatient’shandsontheirthighsandbringingtheelbowsanteriorly.Mostchildrenunder5-yearswillnotcooperatewhenbeingpositionedforchestX-rays,whichwillrequirethemtobeimmobilized.Intheimmobilizationofchildrenforchest

X-raysitneedstobearelativelyeasyprocessthatisnon-traumaticforthepatient.Furthermore,whilstitneedstobeensuredthatthepatientcannotmoveandthatthebeamcanbecentered,theusefulnessofanyimmobilizationneedstobeexplainedtotheparent,asthemethodsusedcanbedistressingtoaparent.Thereareanumberofspecificallydesignedimmobilizationdevicesavailabletobepurchasedonlineatareasonablecost.However,itmustbereiteratedherethatthesemustbenon-traumatictothechildandtheymustbequickandeasytouse.Forsitesthatdonotcurrentlyuseanimmobilizationdevice,patientscanbeimmobilizedthroughtheuseofassistants.Asdiscussedabove,thevideolinkoutlineshowassistantscanbeused.Thisisalsooutlinedinthefigure1,whichisaposterthatdescribestoassistantshowtoproperlyimmobilizethepatients.EachofthesemethodsuseaspecificchairwithaVelcrostrapthathasbeenconstructedforthespecificpurposeofimmobilizingchildrenforchestX-rays.However,themethodscanbeeasilyvariedifachairsuchasthisisunavailable.Forexample,anotherassistantmaybeusedtoholdthepatientatthelevelofthefemursorpelvistoensurenorotationofthelowerhalfofthebody(15).Intheuncooperativepatient,thepersonwhoisimmobilizingthepatientbythearmsshouldholdthepatient’sarmsattheleveloftheelbowstoavoidthepatientbeingabletomovetheirarms.Slightinwardpressuretowardsthepatient’sheadshouldalsobeappliedtoensurethattheheadisimmobilized,withthepatient’schinnotoverlyingtheupperchest.

Figure1AninstructionalposterforparentsandcaregiversondisplayatTheRoyalChildren’sHospital,MelbournethatdemonstrateshowtocorrectlypositionachildforachestX-ray(Source:CreativeStudio,TheRoyalChildren’sHospital,Melbourne)

Positioning children for chest X-rayYou are your child’s best support and comfort. Please help your child and assist in getting the clearest chest X-rays by following the instructions below. Before your baby/child has their X-ray: they need to be undressed from the waist up, they need to have their hair tied up on top of their head (if they have long hair) and the child’s helper (parent/guardian/friend) will be required to put on a lead apron.

1. Seat baby on the stool with their bottom right back against the screen.

2. Baby should be straight and facing forward.

3. With baby’s legs straight forward a waist strap is tightened around baby’s lap.

4. Helper stands to the side.

5. Helper lifts the baby’s arms up as straight as possible to either side of the baby’s face and supports the baby’s head upright between their arms.

6. Hold baby in this position until X-ray is complete.

Baby who is unable to support their head

1. Seat baby on the stool with their bottom right back against the screen.

2. Baby should be straight and facing forward.

3. Then a waist strap will be tightened around baby’s lap.

4. Helper stands to the side.

5. To help secure the stool the helper may place their foot on the stool’s base.

6. Helper holds both of baby’s arms at the elbow so that the arms are straight up, at either side of baby’s head at the level of their ears.

7. Hold baby in this position until X-ray is complete.

Baby who is able to sit

1. Seat toddler on the stool with their bottom right back against the screen.

2. Toddler should be straight and facing forward.

3. Then a waist strap will be tightened around toddler’s lap.

4. Helper stands to the side.

5. To help secure the stool the helper may place their foot on the stool’s base.

6. Then helper holds both of toddler’s arms at the elbow so that the arms are straight up and at either side of toddler’s head.

7. Hold baby in this position until X-ray is complete.

Toddler

ERC 121120

1. The child sits on the stool with their bottom right back against the screen.

2. The child needs to sit facing forward and straight.

3. A waist strap is placed around the child’s lap.

4. Helper stands close by for reassurance.

5. The child is asked to put their hands on their hips and lean their back against the screen.

6. The child needs to hold this position until the X-ray is complete.

Preschooler

ItisnotidealforthepersonacquiringtheimageorotherstaffmembersofthefacilitytoholdthepatientsforchestX-rays.Thisisduetothecumulativeeffectofscatteredradiationdosethattheywouldreceiveforholdingpatientsrepetitively.Therefore,theroleofholdingthepatientshouldbegiventotheparentorcaregiverofthepatient.Whenprovidedwithproperinstructions,parentsandcaregiverscanbeveryhelpful,althoughitisimportantthattheyknowexactlywhatisrequiredofthem(22).Incaseswheretheparentorcaregiverispregnant,orwheretheparentorcaregiverareincapableofholdingthepatientthisroleshouldthenbesharedamongstthefacilitystaff.Furthermore,tominimizethescatteredradiationdosetoothers,onlythosewhoarerequiredintheexaminationroomatthetimeofexposureshouldbeintheroom.Nomatterwhoisholdingthepatient,thescatteredradiationdosetoanypersonassistinginimmobilizingthepatientduringthechestX-rayexaminationmustbebelow1mSv(23).Consequently,thispersonistobeprotectedwithastandardleadapron(11).Thethicknessoftheleadapronisselectedbaseduponconsiderationofthetypeofexamination.Forgeneralradiography,includingpediatricchestX-ray,thisleadapronistobeofatleast0.25mmleadequivalence(24).

5.2 TechnicalFactors

Therearemanyfactorsinvolvedatatechnicallevelwhenacquiringtheimagethatcanaffectboththequalityoftheimageandtheradiationsafetyofthepatient.Patientradiationdosecanvarybetweensites,aswellaswithinasiteduetodifferentequipment,filtration,techniquesandpatientcharacteristics(22).Targetsinmeetingexposureindex,alongwithfactorsofshielding,griduseandincorrectpositioningalsohighlighttheregularchallengesfaced,particularlywhenimagingchildren(25).Whilstinclinicalpractice,severalvariationsexistbetweenthesetechnicalfactors,thefollowingaretherecommendedrequirementsforchestX-raysinchildren:5.2.1 Imagereceptorandprocessing

Theimagereceptortypeandimageprocessingrequirementsarelargelydependentonwhetherfilm,CRorDRisemployed.BothCRandDRhavesignificantbenefitswhencomparedwithconventionalfilm,particularlyintheirpostprocessingcapabilitiesandimprovedcontrastresolution.Ingeneral,CRandDRhavethepotentialfordosereductionwhileimprovingimagequalityanddiagnosticaccuracy.CRandDRcancompensateforunderoroverexposuresofthepatient,coveringarangeof300-400timesthatoffilm-screensystems.Thishasamajoradvantageofreducingrepeatimaging.However,unlessthesystemisfullyoptimised,dosereductionisnotachievedandoverexposureswillgoundetected.Thisisknownasthe“exposurecreep”phenomenon.Forexample,overexposuresof5-10timesanormalexposurewillhavetheappearanceofaproperlyexposedimageduetothecompensationbyadigitaldetector.Systemoptimizationcanbeachievedwithstafftrainingandcontinuousmonitoringofparametersandpractices.

ForCRandDR,intheprocessingofimagesthenomenclaturefordigitalimageprocessingalgorithmsandexposureindicesmustbestandardizedsothattheycanbeunderstoodbyallusers.Theseimageprocessingalgorithmsincludealteringbrightness,detail,contrastandlatitudetoimprovetheoverallqualityoftheimage.Additionally,anyexposureordoseinformation,aswellasthepatientrecordshouldbeabletobesenttoanyimagestoragemediuminaccessibleform.

5.2.1.1 FilmTheuseofX-rayfilmisverycomplexastherearemanyprocessingvariablesthatcanaffectthequalityoftheimage.Theseareoutlinedasfollows:

• Eachfilmcanbecoveredinoneortwoemulsionsofsilverhalidecrystalsofvaryingshapesanddistributions.Thesefactorsinfluencetheresolutionoftheimage,withasmallercrystalsizeincreasingtheresolution.However,asmallercrystalsizewillalsodecreasethespeedatwhichanimagecanbeacquired,whichisadisadvantageinpediatricchestimagingwhereshortexposuretimesarerequired.Filmwithemulsionsofacrystalsizeof3-5micro-meters(μm)issufficientforthedetailrequiredforpediatricchestX-raysandshouldthusbeused.Thesefilmsshouldalsohaveadoubleemulsion,whicheffectivelydoublestheamountofcrystalsandincreasesthespeedatwhichtheimagecanbeacquired.

• Insidethefilmcassettesareintensifyingscreens,whichareeither

blue-sensitive(e.g.calciumtungstate)orgreen-sensitive(e.g.rareearthor“Lanex”)dependingonthelightthattheyemit.Screensarecoatedwithafluorescentmaterialcalledphosphors,whichconvertX-rayphotonenergytolight.ThepurposeofthescreensistoassistintheexposureoffilmbyemittingsmallamountsoflightontothefilmemulsionswhenexposedtoX-rays,therebydramaticallyreducingtheamountofpatientexposure.Thescreenscanvaryintheirspeed,dependingonthethicknessofthephosphors(thickerphosphors=fasterscreen).Fasterscreensareidealastheyresultinbothshorterexposuretimes,whichisidealforpediatricchestimaging,andalowerradiationexposuretothepatient.However,thisalsoresultsinalowerimageresolution.Basedonthis,thefastestpossiblescreenspeedshouldbeused,providedthereissufficientsignal-to-noiseratioandnolossofdiagnosticinformation(11).Thenominalspeedclassisthereforeaminimumof200,withamaximumof400forpediatricchestX-rays(15).Blue-sensitivescreensaretypicallyslowerandmorereadilyavailableglobally,butareavailableintheserecommendedspeeds.

Theradiationexposurerequiredtoproduceadiagnosticimagewillvarydependingonthefilmsandscreenswhenusedinconjunctionwitheachother.Forexample,twofilmsfromdifferingmanufacturersusingthesamescreenfromonemanufacturermayrequiredifferentexposurestoproducetherequireddiagnosticimage.Consequently,itishighlyrecommendedthatthefilms,screensandcassettesusedataparticular

siteareallfromthesamemanufacturerandthatthecassettesarelabeledwiththescreenspeedandfilmtype.Inmostcases,thiswillhavetheaddedbenefitofquickreplacementofpartsifrequired.Furthermore,forefficientworkflowandcontingencyplanning,itisrecommendedthatthereareatleastthreecassettesofeachscreenspeedandfilmtypeavailable.

Theopticaldensityofthefilmisameasureofthefilmdarkening.ThiscanbemeasuredwithadensitometerandisoutlinedinPartC–QualityControl.Withoutphotonexposure,allfilmshaveanopticaldensitythatisknownasthebase-foglevel.Indiagnosticradiography,thebase-fogopticaldensityshouldnotexceed0.25(13).Afterexposure,therewillbearangeofopticaldensitiesonthefilmcorrespondingthebrightanddarkareasoftheimage.Forthediagnosticareasofimaging,theopticaldensitiesshouldbeintherangeof0.5to2.2(13).However,itmustbenotedthatthejudgmentofopticaldensitiesareusuallybasedonglobalimpressionsratherthanmeasurements.Theaestheticqualityoftheimageisdeterminedbythecassettesizeused.Forchildrenlessthan5-years,acassettesizeof24x30cmissufficienttoincludeallrelevantanatomy,whilstacassettesizeof18x24cmissufficientifthepatientislessthan10kg.

5.2.1.2 ComputedRadiography

Contrarytoscreen-filmradiography,CRsystemsdonotshowanyfixedrelationbetweentheimagereceptordoseandtheopticaldensityoftheresultingfilm.Moreover,theexposureordynamicrangeofimagingplatesusedinCRismuchwiderthanconventionalfilm.Therefore,itisnotpossibletogivespeednumbersforthiskindofimagereceptor.However,cassetteswithimagingplatesshouldnotbeexposedhigherthanscreen-filmcassettesforthesamemedicalapplication,providedtheconfigurationoftheX-raysystemisthesame.Thisisevenmoreevidentwhenfilm-screencassettesandimagingplatecassettesareusedinparallel,orwhenimagingplatecassettesdirectlyreplacescreen-filmcassettesinafacility.CassettesizesforCRimagingplatesaresimilartothoseofconventionalfilm.Forsomemanufacturers,thecassettesthatareusedforfilmareapplicabletoCR.TheaestheticprinciplesforCRarethereforealsoapplicableasforfilm.Finally,theimplementationanddisplayofanyexposureindicatorvaluesisrecommendedforsufficientmonitoringofpatientdoseincomparisonwithimagequality.

5.2.1.3 DigitalRadiographyEachoftherecommendedflatpaneldetectorandmonitorspecificationsforpediatricchestradiographyusingthedigitalsystemshavebeenoutlinedinsection3.2.4under“equipmentspecifications”.Toenableoptimalimageacquisitionanddisplay,itisrecommendedthatdigitalsystemsareconfiguredtoallowtheusertoselectabodysizeoragethatisappropriatetotheindividualpatient.Forexample,thefollowingwouldbeconsideredacceptedcategories:

• Lessthan1.5kg• 1.5kgto2.5kg• Birth(greaterthan2.5kg)to1-month• 1-monthto2-years• 2-yearsto5-years

Eachofthesecategorieswouldencompassthepediatricalgorithmsdiscussedin3.2.4.Additionally,whilstnotessential,arapiddisplayofapreviewimageisrecommendedforworkflowefficiency.Viewingmonitorsshouldallowforblacksurroundingsoftheimageforeaseofviewing.AsperCR,theimplementationanddisplayofanyexposureindicatorvaluesisrecommendedforsufficientmonitoringofpatientdoseincomparisonwithimagequality.

5.2.2 Filtration

“Thequalityofx-raybeamisimportantinthereductionofradiationexposureandisaffectedbyfiltration(inherentandadded)ontheX-raytube,bytheX-raygeneratorandbytheexposuretechniqueselected.”WorldHealthOrganisation(11).

Duringimageacquisition,thelowerenergyradiationontheradiationspectrumiscompletelyabsorbedbythepatientandthusaddstotheradiationdosetothepatientandisirrelevantintheproductionoftheimage(10).Avoidanceofthisisnecessarythroughfiltrationoftheradiationbeam.Theamountoffiltrationusedmustbeenoughtoavoidthelowerenergyradiationfromreachingthepatient,butnotbetoolargethatitabsorbssomeofthehigherenergyradiationthatwouldcontributetothequalityoftheimage.RecommendedinherentfiltrationrequirementsforallX-raytubesshouldbe2mmAlforuseofexposuresabove70kVp,withallowanceforaddedfiltration(20).TheaddedfiltrationallowsforanincreasedX-raybeamenergytobeusedwithshorteravailableexposuretimes,whichwillinherentlyresultinalowerpatientdose.

Inregardstoaddedfiltration,upto1mmAlplus0.1-0.2mmCuisappropriate(notethatevery0.1mmCuisequivalentto3mmAl),andcomplieswithInternationalstandards(10).

5.2.3 Anti-scattergrid

Inradiography,theuseofagridistoassistinlimitingtheamountofscattered(secondary)radiationthatcontributestothediminishingqualityoftheimage.Thedisadvantageintheuseofagridisthatitrequiresasignificantincreaseoftheexposurefactorsusedandthustheradiationdosetothepatient.Figure2istakenfromEuropeanGuidelinesonQualityCriteriaforDiagnosticRadiographicImagesinPediatrics(13)anddemonstratestheincreaseddosetothepatient,particularlyininfants,asaresultofgriduse.

Figure2Meanentrancesurfacedose(ESD)withandwithoutagridforthechestPA/APexaminationson10-monthinfant,5yearand10-year-oldchildren.n=numberofX-rayexaminations.

Whilstthegridassistsinimprovingthecontrastoftheimage,itisnotnecessaryinpediatricchestradiographyasthereisminimalscatterduetothesmallervolumeoftissueofthepatient(21,26-28).TheomissionofthegridislinewithguidelinesfromtheInternationalAtomicEnergyAgency(IAEA)(28),theInternationalCommissionforRadiologicalProtection(10)andtheEuropeanGuidelinesonQualityCriteriaforDiagnosticRadiographicImagesinPediatrics(13)

5.2.4 AutomaticExposureControl(AEC)

TheconceptoftheAECistoensuregoodimagequalitythroughtheuseofionizationchamberspositionedbehindtheimagereceptorthatallowanamountofradiationsufficienttoproduceapre-determinedhighqualityimage.However,inpediatricexaminations,theuseoftheAECislargelyimpracticalasitreliesheavilyoncooperationofthepatientforprecisepositioningandthechambers’large,fixedsizeandshapecannotcompensateforthevariationinthesizeofthepediatricpatient(13,26).Furthermore,theirusehasthepotentialtoincreasetheexposuretime,astheyareunreliableattherequiredlowexposuretimesusedforpediatricimaging,whichincreasestheriskofmovementartefactbeingpresentontheimage(13,25).InasurveyofcontributionstoradiationdoseforpediatricchestX-rayexaminations,itwasdiscoveredthatofthefoursitesthatusedtheAECforchestexaminations,threesiteshaddeliveredthelargesteffectivedosestopatientsintheentirecohort(27).Consequently,inlinewithbothEuropeanandIAEAGuidelines(13,29)andintheinterestofoptimizingtheradiationdosetothepatient,itisrecommendedthattheAECisnotusedforpediatricchestX-rayexaminations.

5.2.5 Exposurefactors

Theexposurefactorsthatcanbesetbytheoperatorallcontributetotheimagequality,whichcanbeachievedinasafemanner.The3exposurefactorsare:

o Kilo-voltage(kV),whichdeterminestheenergyandthereforepenetratingpoweroftheX-raybeamthroughthebody

o Milli-amperes(mA),whichdeterminesthenumberofX-rayphotonsthatareproduced,directlyaffectingthebrightnessoftheimage,and

o Time(s),whichdeterminestheamountoftimetheX-rayphotonsarebeingproduced.

ThemAandtimearedirectlyrelatedandarecommonlysetasonefactor(mAs),butcanoccasionallybesetseparately.Exposurefactorsettingsvarydependingonequipmentageandcharacteristics,aswellastheimage-processingmedium.Thus,itisnotpracticaltoproviderecommendedexposuresettings,asthiswouldnottranslatetoallsites.Asaguidingprinciple,itisrecommendedthat“Theradiationdosegiventopatientsshouldbeaslowasreasonablyachievable(ALARA),whilestillprovidinganimagequalitythatisadequatetoenableanaccuratediagnosis”(7,26,30,31).However,thefollowinginformationprovidesbestpracticerecommendationsforeachoftheexposurefactorsandhowtheycontributetoimagequalityanddosetothepatient.Itisexpectedfromthisinformationthataweight-dependentexposurechartforeachsiteisdevelopedforusebythesites’operators(11).ThekVdirectlyaffectstheimagecontrast,withahighcontrastatlowersettings,However,thiscomesattheexpenseofanincreasedpatientskinentrancedose.IncreasingthekVreducesthepatientskinentrancedose,butwillalsoreducetheimagecontrast(32).Furthermore,“asbeamenergyisincreased,X-raysbecomemorepenetrating,arelesslikelytobeattenuatedwithinthepatientandaremorelikelytoreachtheimagereceptorcomparedwithlowerbeamenergies.

Thisresultsinradiationdosereductionsover50%”(32,33).Thereisthereforeabalancethatmustbereachedtoensureanappropriateimagecontrastandpatientskinentrancedose.ThekVsettingmustbehighenoughthatthelungstructureandspinecanbediscerniblebehindtheheartandmediastinum.EuropeanguidelinessuggestthattheoptimalkVrangeforpediatricchestX-raysisbetween60kVand80kV(13)anditisrecommendedthatatleast70kVisusedatthenewbornlevelthatincreasestonomorethan80kVfor5-year-oldpatients.HigherkVsettingsalsoallowforlowermAssettings,inparticularexposuretimesettings,whichreducetheriskofmotionartefactinpediatricpatients.Dependingontheageandcharacteristicsoftheequipment,at70kVsettingsaslowas0.5mAscanbeusedfornewborns.WhenestablishingthecurrentandtimesettingsforpediatricchestX-raysthereneedstobetheabilitytoalterboththemAandtimeindependentofoneanother.Itisidealthattheexposuretimeisverylow,suchaslessthan10ms,orevenlessthan4msinthenewborn.Thistakesintoaccountthenon-cooperationofthepatientandwillminimizetheriskofmovementartefact.

5.2.6 Source-to-imagedistance(SID)

Alsoknownasthefocal-film-distance(FFD),theSIDisthedistancefromtheX-raytube’sfocalspottotheimagereceptor.ForchestX-raysthisistypicallyquitelargetominimizethemagnificationfactorofinternalcheststructures,suchastheheart.Inadults,thisvalueisanywherebetween150cmand200cm.ThelongSIDisalsosuggestedbytheIAEA(26)andisthoughttoassistincontrollingthepediatricpatientradiationdosebyusingairasanaturalfilter(27).Inchildren,thesmallerthicknessofthepatientmeansthatasmallerSIDisallowableinordertoachieveasimilarmagnificationfactor.TheEuropeanguidelinessuggestthattheSIDforchestX-raysinpediatricpatientsis150cmwhenthepatientispositionederectand100cmforsupine(13).However,tostandardizetherequirementsforsimplicity,itisrecommendedthattheSIDusedforpediatricchestx-raysis125cmregardlessofwhetherthepatientispositionederectorsupine.TheSIDalsodictatesthemAsthatisusedtoachieveanappropriateimagedensity.Theintensityofthesourceofradiationisinverselyproportionaltothesquareofthedistance.Thisisknownasthe“inversesquarelaw”.Forexample,if1mAswasusedat100cmSID,4mAswouldneedtobeusedat200cmSIDinordertoachievethesameopticaldensityontheimage.ItisunderstandablethatequipmentatsomesiteswilleitherhaveafixedSIDoronethatdoesnotallowforaSIDof125cm.Inthesecases,itisexpectedthatthemAswillbealteredinaccordancewiththeinversesquarelawinordertoachieveanimagewithoptimalopticaldensityandthatthereisconsistencyfromoneimagetothenext.

5.2.7 X-raybeamposition

Withthepatientinthecorrectpositionasdescribedpreviously,theX-raybeammustnowbepositionedcorrectlyinordertoachievethedesiredimage.AsthepatientstargetedintheseguidelinesareforanAPchestX-rayonly,usinganX-raybeamthatisnotangledwillprojectthemedialendsoftheclaviclestoosuperiorlyonthelung-fields,resultinginalordoticappearanceofthechest.ThereasonforthisisduetothelargedistancebetweenthemedialendsoftheclaviclesandtheimagereceptorinconjunctionwiththedivergentgeometryoftheX-raybeam.Consequently,theX-raytubeshouldbeangled10degreesinthecaudaldirection(towardsthepatient’sfeet)inordertobeperpendiculartothepatient’ssternum.Thecentreofthebeam(centralray)istobeinthemid-sagittalplaneofthepatientatthelevelofthepatient’snipples(15).WiththeX-raybeamcentredandangledcorrectly,thebeamcanbecollimated.

5.2.8 Beamcollimation

CollimationoftheX-raybeamallowstheoperatortolimitthefieldsizetotheareaofinterest.Asspecifiedintheequipmentspecifications,thefieldsizecanbeadjustedusingtheadjustablemulti-leafcollimators.Collimationisveryimportantasitreducestheirradiationofunnecessarystructuresandlimitstheamountofscatteredradiationthatalsocontributestothepatientdoseandpoorimagecontrastandresolution(10,22,26,34).Aninappropriatefieldsizeisoneofthemostimportantfaultsinpediatricradiationtechniques.Eventheinclusionofunnecessaryanatomywithintheradiationfielddoesnotsignificantlycontributetotheclinicalgainviaincidentalfindings(25).Itisthereforeimperativethatthefieldsizeisassmallaspossible,butmaintainsalltherequiredclinicalinformationandrelevantanatomy(11,20).Inpediatricpatients,tightcollimationcanbedifficultbecauseasubstantialproportionofthesepatientsareuncooperative(21,26).Recommendedtechniquesforadultsarenotapplicabletopediatricpatientsasitcanresultinunnecessaryradiationtonon-thoracicstructures(25,35).However,thisimagecriterionspecifiestheappropriatefieldsizelimitations.Whilstsomedegreeoflatitudeisnecessarytoensurethattheentirefieldofinterestisincluded,thiscannotbeacceptedasanexcuseforrepeatedlyusingtoolargeafieldsizeinpediatricpatients.AppropriatecollimationforpediatricchestX-rayscanbedescribedasfollows:

Withthearmselevated,thesuperiorborderofthepalpableacromio-clavicular(AC)jointgenerallyliesabovethelungapexandshouldbeusedasthesuperiorcollimationborder.Inferiorly,theribscanusuallybefelt,whichissufficientfortheinferiorcollimationborder(25).Laterally,thecollimationborderscanextendto1cmlateraloftheskinedgeinneonatesto2cmforallotherchildren.

Overall,thetopofthelungstothelowerpartsofthediaphragm,includingthecostophrenicanglesshouldbeincluded.Onthefinalimage,allfourbordersofcollimationshouldbepresent.WiththeuseofbothCRandDR,itispossiblefortheoperatortoaddartificialborderstotheimageduringthepost-processingphaseafteracquisition.Whilstthiscanimprovetheoverallappearanceoftheimage,itmisrepresentstheradiationfieldthatwasusedtoexposethepatient(8,10,26).Additionally,thehistogramanalysisalgorithmsoftheCRandDRsystemswillnothaveanticipatedanyunnecessaryanatomyincludedandcontrastwillbesacrificedtoappropriatelyrepresentthisanatomy(26).5.2.9OptimizingTechnicalFactors

Relevanttothetechnologicalinformationpresentedabove,Willis(26)outlinedfivecoursesofactionin2009thatcanresultindosereductionforaradiographicprojectionthatarerelevanthere:

1. Decreasedigitalreceptordose:

Whilstthisisonlyrelevantforthosesiteswithdigitalsystems,itallowsforlowerexposurefactorstobeused.Thelowerexposurefactorswillproducesmallerdetectorsignalsandthesecanbeamplifiedbythedigitalsystem.

2. Increasereceptorefficiency:ThismaybelimitedtotheavailablesoftwareofthesystembeingusedbutisrelevanttobothCRandDRsystems.

3. Increaseradiationpenetration:Thiscanbeachievedeitherbyincreasingthebeamenergy(kV)orusingaddedbeamfiltration.Asdiscussedabove,thiscausesadecreaseinsubjectcontrastandnoiseduetolessphotonsbeingrequiredtomaintaintheexposure.

4. Decreasescatteredradiation:Anexampleofhowtodecreasethescatteredradiationistouseadequatebeamcollimation.

5. Combinenoisyimages:Notcommonlyused,butavailableinsomeCRsystems,thisisaprocesswherebystimulatedluminescencefromboththefrontandbacksidesofacomputedradiographyimagingreceptorisacquired.

5.3 OtherRequirements

Onceacquired,theresultantimageshoulddemonstratetherelevantanatomyclearlyandwithnounnecessaryartefactsthatmayinterferewiththediagnosticvalueoftheimage.Manyobjectscanbeclassifiedasunnecessaryartefacts,forexamplejewelry,patientmonitoringleadsorevenbuttonsfromclothing.Artefactscanalsobecausedduringfilmhandlingorimageprocessing,soitisimperativethatfilmhandlingandimageprocessingisperformedcorrectly.Additionally,astechnologyimproves,sotoodoestheimagedetailandthisresultsinbasicchildren’sclothingbeingsometimesvisibleontheimages.Itisthereforerecommendedthatallclothingandotherremovableartefactsthatareanticipatedtobewithinthefieldofviewareremovedpriortopositioningthepatient.

Thefinalimageshouldalsodemonstratethechestintheinspiratoryphase(15).AchestX-rayacquiredwiththepatientintheinspiratoryphaseallowssufficientcontrasttovisualizeanyfluidorothermarkingswithinthelungsduetothelowdensityofthelungs.AchestX-rayacquiredintheexpiratoryphasealsoraisesthepositionofthediaphragms,leadingtoexaggerationoftheheartsize,aswellasobscuringthelungbases.ItnoteasytoachieveachestX-rayoninspirationintheuncooperativepediatricpatient,astheycannotsuspendrespirationintheinspiratoryphaseondemand.Consequently,itisuptotheoperatortohaveanuninterruptedviewofthepatientatthepointofexposuretoensurethattheexposureismadewhilstthepatientisattheinspiratorypointoftherespiratorycycle.Pediatricpatientstendtobreatheusingtheirabdominalmusclesandexposingatthepointofinspirationisgenerallyachievedthroughobservationoftheinwardandoutwardmotionofthepatient’sabdomen.Thisisalsomoreeasilyachievedifthepatient’supperhalfisnaked.

5.4 TheFinalImage

Figure3demonstratesanexampleofanidealchestX-rayfollowingtherecommendationsdescribedabove.Itisinevitablethatvariationsinimageappearancewilloccur,howeveracertainstandardmustbemaintained.ThiswillbedescribedinmoredetailinPartC–QualityControl,alongwithrecommendationsonmaintainingthesestandardsthroughoutthestudy.Figure3An‘ideal’chestX-raythatispositionedcorrectly,withappropriatecollimationanduseofaleadsidemarker.(Source:TheRoyalChildren’sHospital,Melbourne)

6.ImageArchivingandViewingRecommendations6.1ImagestorageArchivingofimagesisanimportantfactorintheongoingcareofpatients.Imagescontributetothepermanentrecordingofapatient’smedicalhistoryandinmanyinstances,patientsreturnforrepeatstudiesthatoftenrequireacomparisonwithpreviousstudies.Successfularchivingisalsoimportanttoensurethepermanenceoftheradiographforstudypurposes,allowingforre-examinationandcomparisonasresearchquestionsareinvestigated.Imagearchivingistheresponsibilityoftheimagingdepartmentatthefacilityandimagesshouldbearchivedinawaythattheycanbeeasilyretrieveddespitethetypeofimageprocessingused(film/CR/DR).Whilstimagesmaybestoredon-siteashard-copyfilmsorasdigitalimages,allimageswillneedtobeindigitalformatforthepurposesofepidemiologicalstudies(seebelowfordigitizingspecifications).Thiswillpreventproblemsassociatedwiththepotentiallossofhardcopyimagesandincreaseefficiencyinthephysicaltransportofimages.Evenininstanceswhereplainfilmsareconsideredthepropertyofthepatientandthusnotarchived,thesefilmsshouldbedigitizedbeforebeinggiventothepatient.Studyprotocolsshouldexplainaclearprocessforthenamingofdigitalfilesthathasasystematicandconsistentapproachtofilenamesandensurethecorrectradiographisassignedtoitsrelevantcase.APictureArchivingCommunicationSystem(PACS)networkisasystemfortheelectronicstorageofimagesandallowsthemtobeviewedonanyworkstationthatisconnectedtothesystem.PACSisidealforsitesthatcurrentlystoretheirimageselectronicallyasitallowsimagestobestoredinoneplacewithoutusingamplephysicalspace.Additionally,thereisanincreasingneedforfacilitatingthecommunicationbetweenradiologistsandreferringphysiciansandthisallowsreferringphysiciansinotherareasofafacilitytobeabletoviewimagesquickly(33).APACSnetworkshouldalsoconsistofaneffectivebackupprogram,therebypreventinglossofimages.SitesthatcurrentlyhaveorareabletoestablishaPACSnetworkwillrequireastorageareanetwork(SAN)capacitythatiscommensuratewithboththeworkloadandimagingmodalitiesthatareemployedbythesite.Theywillalsorequireaccesstoasufficientbroadbandnetwork,aswellasviewingstations.PACSisnotnecessarilyanoptionforallsitesduetothecostanddatastoragerestrictions.Intheseinstances,storingimagesoncompactdiscs(CDs)onlyarenotidealastheycanoftenbehardtoretrieveshouldapatientreturnforanewstudy(36).Themostpracticalmethodistosendthedatatoanetworkgateway,suchasaninexpensivelaptopcomputerthatisconnectedtothenetworkviaacellularmodem(18).Thishasthefollowingadvantages(18);

• Studiescanbebacked-uptoCDorUSB• Itcanconnecttoanexternalantennatoincreaseitssignalandthepower

consumptionisverylow• CommunicationbetweenthegatewayandtheX-raysystemcanbeeitherwired,

suchasanEthernetcable,orwireless• Inexpensivesmallcomputersystemsmakethereplacementofsystemsabetter

optionthanrepairofthesesystems• Supportforsoftwareisavailable,albeitinformalviatheinternet

Anothersimilarmethodistostoreimagesonacomputerhard-drive,withasufficientstoragecapacitythatdoesnotaffectthequalityoftheimages,aswellasaneffectivebackupsystem.Despitethemethod,adailysystemback-upisrecommendedwiththeback-upsystemappropriatelystored(18).Anyimagesstoredforstudypurposesshouldbecentralized,easilyretrievable,andhaveadequatebackupavailable.Inthedigitalstorageandtransferofimages,theamountofdataconstitutinganimageinfluencestheamountofdigitalstoragerequirements,particularlyinfacilitieswheremanyimagesareacquired.Thisnecessitatestheneedfordigitalcompressionwherethisamountofdatacanbereduced.Thishasanaddedadvantageinthetransferofimagesasthecompressionreducesthebandwidthrequirementsfortransfer(18).Thereare2maintypesofdigitalcompression,eachwiththeirownadvantagesanddisadvantages(37-41):

• Reversiblecompressionalgorithms(lossless)o Advantage:Informationinthedigitalimageisnotalteredo Disadvantage:Onlysmallcompressionratios(3:1)arepossible(38-40)

• Irreversiblecompressionalgorithms(lossy)o Advantage:Allowsforlargecompressionratiosandthusalowsizeo Disadvantage:Altersinformationinthedigitalimage(e.g.reducedimage

sharpness(42))

Inmostcases,wherethereisaneedforcompression,theuseofreversiblecompressionalgorithmsisinefficientduetothelimitedcompressionratios.Forstorageandtransmissioncoststobesignificantlyaffected,compressionratiosintheorderof20:1orhigherarerequired(43).Withtheincreasedexpectationforaccesstoimagingdataandthusincreasesinstorageandbandwidthrequirements,irreversiblecompressioncanbejustified(40).However,usingirreversiblecompressionalgorithmshasthepotentialtoomitvitalinformationwithintheimage,dependingonthecompressionratio.Thehighertheratio,themoreimagesthatcanbestoredinaspecificarea,butthehigherthelossofinformationwithintheimage(40).Whilstthelevelofacceptableimagedegradationisinmostcasessubjective,thefollowingisaguidetosomebestpracticelevelsofdigitalcompressionanditisrecommendedthattestingforindividualapplicationsofcompressioniscarriedouttodeterminethecompressionthresholdforeachstudy.Itisalsorecommendedthatwherepossible,thecompressionratioandtypeisdisplayedandthattheseimagescannotberecompressed(40).Ithasbeendemonstratedthatirreversibledigitalcompressionmethodscanbeappliedtohighresolutionskeletalimageswithoutsacrificingimagequality(42).Furthermore,differentlossycompressionalgorithmsareavailable,someofwhichcanminimizetheeffectonimagequalitybyreducingtheamountofnoiseandnon-criticalinformationintheimage(41,43,44).Forexample,JPEGtechniquesarethemostcommonlyusedstandard.However,theysufferfromblockingartefactsthatincreaseineffectwithincreasingcompressionratio(40,43,44).Alternatively,waveletcompressionalgorithmshavebeenshowntohavenoclinicallysignificantdegradationforcompressionratiosbelow30:1andhavebeensuggestedtobeasuitablealternativetoJPEGtechniques(40,43).JPEG2000isanothertypeofcompressionalgorithmthatcanprovidehighercompressionlevelsthanJPEGimagesatanequivalentorhigherimagequality(46,47).IncomparisontoJPEGimages,theJPEG2000algorithmismoreefficientwithasingleunifiedcodingframework,cansupportregionofinterest(ROI)codingandisrobusttobiterrorsinwirelesscommunicationapplications(40,44).Usingthisalgorithm,the

CanadianAssociationofRadiologists(CAR)Guidelinessuggestthatthereisscopeforirreversiblecompressioninpeediatricchestradiographsforbothcomputedanddigitalradiographytechniques,andthatthesuggestedcompressionratioisbetween20:1and30:1(40,46).

6.2DigitizingImagesForthepurposesofepidemiologicalstudies,allimageswillneedtobepresentedtoreadersindigitalformatforinterpretation.Thereareseveralmethodsbywhichradiographscanbedigitized,suchasscanningradiographsintoadigitizerortakingdigitalphotographsoftheimages.Eachmethodcomeswithawiderangeofrequiredexpenditureandquality.Regardlessofthemethodofdigitalacquisitionfromconventionalradiograph,itiswidelyrecognizedthatthedigitizedimagewillbeinferiorinquality.Takingdigitalphotographsofhardcopyimagesisamorecost-effectivemethodofdigitizingimageswhencomparedtoadigitalfilmscanner(48).Whilstdigitalphotographyhasbeendemonstratedtobeineffectiveduetothelimitationsofspatialresolution,decreasedlatitudeandincreasedimagenoise,morerecentstudiessuggestthatthedifferenceinqualitybetweenthetwomethodsisinsignificant(41,48-51).Inonestudy,digitalphotographsofimagesweretakenwithadigitalcamerausing3.3megapixelsand6xopticalzoom,withthephotographsacquiredofimagesthatwereplaced1metreawayonafilmlightbox.Imageswererecordedwitharesolutionof2048x1536pixels,withamanualfocusofthecamerasetto1metre,ISOtoauto,picturequalitytofineandsharpnessatzero(48).

Meanwhile,imagesvisualizedfromalow-cost,flatbedcommercialscannercanproducesimilarresultstoanoriginalimage,despiteasubjectivelowerimagequality(50).Nevertheless,themainobjectiveistoensurethatanylossofimagequalityiskepttoaminimum.Itisthereforerecommendedthatimagescapturedusingananaloguetechniqueandconvertedtodigitalmustnotbecompressed(40).Itisrecommendedthattheresponsibilityofscanningfalluponasfewpeoplepersiteaspossibletoensurethatappropriatetrainingondigitizingtechniquesiseffective.Thisstaffisalsoresponsibleforensuringthatthedigitizedimageisacorrectrepresentationoftheoriginalimage,forexamplecorrectorientationandnoobviousartefactsthathaveoccurredasaresultofthedigitizationprocess.6.3ImageTransportationforStudyPurposesImagetransfermethodologywillbelargelydirectedbyspecificstudyandethicsrequirements.Hencethereisnoparticularcorrectmethodofimagetransfermentionedintheseguidelines.Thespecificformatforwhichtheimagesaretobetransferredwillalsodependonthespecificstudy.Asaminimum,itisrecommendedthattheformatbeineitheraDICOMorJPEG/TIF/Bitmapformatasthesewillensureminimumlossofqualitycomparedtootherformats.However,onlyDICOMformatsallowforzooming,panningandwindowingofimageswithoutlossofdiagnosticinformation.Despitethetransfermethodologyused,thefollowingspecificationsarerequiredtomeettherequiredobjectivesandmaintainpatientprivacyandsafety:

• Allimagesaretobede-identifiedtoensurethataspecificpatientcannotbeidentified.Imagescanthenbenamedaccordingtothestudy’simageidentificationrequirements.Astudyprotocolforfilenamingisrecommendedtoensureaconsistentprocessisfollowedfortheidentificationofeachimagetothecorrectpatientidentifier,aswellasanyadditionalfactors,suchasthenumberoftheradiographinasequenceofimages(ifmorethanonearetaken)andtheprojectionoftheimage(suchassupineorerect).

• Allimagesbeingtransferredfromasinglesiteshouldbeofsimilarsize.Imagesbeingtransferredthathavealargevariationinfilesizesindicatesthataproblemexistsinthesavingortransferalprocess.

• Forallimages,includingthosethatareacquiredinadigitalformat,itisimportantthatthereisnotanylossofimagequalityinthetransportationprocessandthattheprocessiserrorfree.

Toensurethattheelectronictransmissionofimagesismosteffective,particularlyinlowresourcedregions,thefollowingrequirementsarerecommended(18):

• Compresstheimagestolimitthecommunicationbandwidthuse• Avoidanyconstantuseofanetworkconnection.Forexample,useofthe‘cloud’

willlimittheuseofanetworkconnection• Planforfrequentperiodsofnetworkunavailabilityinkeepingwithpower

limitations.Forexample,useasoftwarepackagethatadjuststhedatapacketsizesothatsmallerpacketsaresentduringtimesofnetworkinstability

• Weighthereliabilityofvarioustransfermethodswiththeirassociatedcost.

6.5 Imageviewingforstudypurposes

Theabilityofthereadertosufficientlyreportontheimagefindingscanbeaffectedbythreeissues:

• Theimageformat,suchasDICOMversusJPEG.Asdiscussedpreviously,theseformatsaresubjectedtodifferentcompressionandadjustmentcapabilities.

• Theviewingmonitor.Differingbrightnessandresolutionfromonemonitortoanothermayaffecttheabilitytodistinguishbetweensmallchangeswithintheimage.

• Thesurroundingenvironment,forexamplethebrightnessofbackgroundlight.Thesethreeissuesaremoreimportantinstudieswhereimagesarebeingviewedinmultiplelocations.Forexample,aprogramatonefacilitymayhavetheabilityforthereadertowindowimagestothedesiredquality,whilstadifferentfacilitycanonlyviewimageswithafixedquality.Hence,thereisaneedtostandardizetheviewingconditionsandworkstationcapabilitiestominimizethisvariation.Methodsforpediatricchestradiographinterpretationinepidemiologicalstudies,suchasthatdevelopedbytheWHO,areusuallyfocusedonhighspecificityandnotintendedtoprovideadetaileddiagnosisfortheindividualpatient.Assuch,studiesdonotgenerallyrequirehighqualitysoftwareandmonitorcapabilitiesthatmightbenecessarytoinformaccuratedecisionsregardingpatientcare.Withtherecommendationthatimagesaretransportedandthereforeviewedoncomputerworkstations,theconditionsbywhichthereaderinterpretstheimagesshouldberelativelyconsistentforallworkstationlocations.Incaseswhereimagesaretobeinterpretedbymultiplereaders,imagesthatarepresentedwithnocapabilitiesfor

adjustmentofbrightness,greylevelandzoomwillminimizevaryinginterpretations.Furthermore,itisessentialthatimagesareviewedinroomswithlowambientlight.(13)

AcknowledgementsJeffSolomano–RadiographicEngineer–PhilipsAustraliaStuartBaker–BusinessDevelopmentManager–AgfaHealthcareAustraliaMitaPedersen–ChiefRadiographer–TheRoyalChildren’sHospital,MelbourneAmandaPotter–GeneralX-raySupervisor-TheRoyalChildren’sHospital,MelbourneDrThomasCherian–Coordinator,Programme&ImpactMonitoringImmunization,Vaccines&Biologicals,WorldHealthOrganization–Geneva,SwitzerlandCynthiaCowling–SessionalLecturer,MedicalImaging–MonashUniversity,MelbourneBilalOmarjee–InformationandCommunicationTechnology–TheRoyalChildren’sHospital,MelbourneSimonPase-Director,CreativeStudio–TheRoyalChildren’sHospital,MelbourneRobGrant–SeniorVideoProducer,CreativeStudio–TheRoyalChildren’sHospital,MelbourneStephenJones–BusinessManager–CarestreamAustraliaDavidHalfpenny–BusinessDevelopmentExecutiveUK–TMCTelemedicineClinicGlossaryAEC AbbreviationforAutomaticExposureControl.Ionizationchambers

positionedbehindtheimagereceptorthatallowanamountofradiationsufficienttoproduceapre-determinedgoodqualityimage

Anti-scattergrid Adeviceconsistingofalternateradiopaqueandradiolucentstrips,designedtoallowtheprimaryX-raystopassthrough,butabsorbscatteredradiation

AP Abbreviationforantero-posterior,whichdescribestheprojectionwherebythex-raybeampathtravelsfromtheanteriortoposteriorpartsofthepatient

Artefact Anartificialappearanceonaradiographthatisnotnaturalandcanbecausedbyavarietyofmeans,includingstructuresormishandlingoffilm

Base-fog Densityofaprocessedfilmwithouttheeffectsoflightorradiation,causedbythemanufacturerandstorageofthefilm

Beam(X-ray) AspatialdistributionofX-raysemanatingfromtheX-raytubeBit(binarydigit) Smallestpieceofdigitalinformationthatacomputingdevicehandles.It

representsofforon(0or1).Alldataincomputingdevicesareprocessedasbitsorstringsofbits

Bucky AcommonlyusedabbreviationofthePotter-Buckymovinggridsystem,whichisdesignedtoreducetheamountofscatteredradiationreachingthefilm

Cassette Lighttightholderthatcontainsapairofintensifyingscreens(forfilm),betweenwhichisplacedthefilm

CentralRay ThecentreoftheX-raybeam,oftenusedtodefinethedirectionoftheX-raybeamrelativetoabodypartorimagereceptor

Collimator(s) Adeviceusedtocontrolthecoverageofthex-raybeamanddeterminethex-rayfieldsize.Alsoknownasthelightbeamdiaphragm(LBD)

Compressionratio Theaveragenumberofbitsperpixel(bpp)beforeimagecompressiondividedbythenumberofbppaftercompression

Contrast Differencebetween2ormoredensitiesonafilm.Highcontrastiswheretherearefewshadesofgreybetweenthelightestanddarkestareasoftheimage

CR Abbreviationforcomputedradiography,wheretransmittedX-raysareconvertedtolightviaasolid-stateimagingdevice,suchasa

photostimulablephosphorplate,andrecoveredandprocessedusingadigitalcomputer

Darkroom LighttightroominwhichtheprocessingofradiographsiscarriedoutDensitometer Adeviceusedtomeasuretheopticaldensityonofanyspotona

radiographbymeasuringthelightthatisallowedtopassthroughitDetail(image) Theamountandqualityofinformationcontainedinaradiographicimage,

whichisdeterminedbyimagesharpness,contrastanddensity Developer Thechemicaltreatmentthatconvertsthelatentfilmimageintoavisual

imageDistortion MisrepresentationofabodypartoutlineintheimageduetochangesinX-

raybeam/bodypartalignmentorunacceptableobject-imagedistanceDose Ageneraltermdenotingthequantityofradiationorenergyabsorbedina

targetDoseQuantum AmeasureoftheinformationtransferefficiencytoadigitaldetectorthatEfficiency(DQE) isdependentontheefficientabsorptionofX-raysaswellasthe

conversiontoausefulsignalwithminimumcorruptionbyotherdetectornoisesources

DR Abbreviationfordigitalradiography,wheretransmittedX-raysareconverteddirectlyintoadigitalimageusinganarrayofsolid-statedetectors

Effectivedose Thesumoftheproductsoftheabsorbedorgandoseandtherespectivetissue-weightingfactorforeachspecifiedorganasoutlinedbytheICRP.Thesumforallorgansinthebodyshouldbe1

Emulsion Theactivelayerofchemicalcrystalssuspendedinagelatinlayeroffilm,whichissensitivetolightandradiation.Itcanalsobeusedtodescribetheradiationsensitivelayerofintensifyingscreens.

Erect TermusedtodescribetheuprightpositionofthepatientExposure TheamountofradiationproducedfromtheX-raytubebyapre-

determinedsetofexposurefactors(voltage,current,time).Theterm‘exposure’isusuallyusedtomeanexposurefactors.

ExposureCreep AphenomenonwherebytheintroductionofimagemanipulationinCRandDRhasresultedinhigherpatientexposurestoavoidimageswithquantummottle

FFD Abbreviationforfocal-film-distance,thedistancefromthefocalpoint(origin)oftheX-raybeamtotheimagereceptor.Alsoknownasthesource-image-distance(SID)

Filmdensity Degreeofblackeningonafilm.Thisincreasesasexposuretothefilmincreases.Itcanberadiographic,wherethedegreeofblackeningiscausedbythedepositofmetallicsilver,ortissue,wherethegreaterdensityofthetissuecausesmoreattenuationofthex-raybeamandthusappearslighterontheradiograph

Filter(safelight) Aspecialized,colouredglasswindow,fittedtoasafelightinadarkroomthatenablesthesafehandlingofX-rayfilm

Filter(X-ray) Asheetofmetal(usuallyaluminium)fittedtotheportofanX-raytubetofilteroutthelowwavelengthX-rayphotons

Fixer DissolvesoffallunwantedfilmemulsionandmakestheimagepermanentFocalspot TheareaontheX-raytubeanodewheretheX-raysareproducedFog Unwantedblackeningofafilm,whichiscommonlycausedbyscattered

radiationreachingtheunprocessedfilmorlightfogcausedbyunwantedwhitelightreachingtheunprocessedfilm

Grayscale Thenumberofdifferentshadesorlevelsofgraythatcanbestoredanddisplayedbyacomputersystem.Thenumberofgraylevelsisdirectly

relatedtothenumberofbitsineachpixel:6bits=64graylevels,7bits=129graylevels,8bits=256graylevels,10bits=1024graylevelsand12bits=4096graylevels.

Grid See“Anti-scattergrid”Imagereceptor AdevicethatisusedtocapturethedifferenceinX-raybeamenergies

afterpassingthroughanobjectandthenconvertingittoanimage.Itmaybeafilmandcassette,phosphorescentscreen(forCR)oraflat-paneldetector(forDR)

Intensifyingscreen Radiationsensitivescreens,placedinsideacassetteoneithersideofthefilm,whichfluorescewhenstruckbyradiation,thelightemittedsignificantlycontributingtotheblackeningeffectonthefilm

kV Abbreviationforkilo-voltage,itisanX-rayexposurefactorthatcontrolsthepenetratingpowerandthusqualityoftheX-raybeam.Italsoaffectstheimagecontrast(higherkV=lowercontrast)

Lateral Adescriptionoftheprojectionwherebythex-raybeampathtravelseitherfromthelefttorightsideorrighttoleftsideofthepatient

LosslesscompressionAcompresseddigitalimagethatisperfectlyreconstructedandnumericallyidenticaltotheoriginal.

Lossycompression Acompressedimagewheresomedataarediscarded,nevertoberecovered.Thefrequencycontenttowhichthehumaneyeisinsensitiveisremoved.Theoriginalimageisnotidenticaltothedecompressedversion

mA Abbreviationformilli-amperes,itisanX-rayexposurefactorthatcontrolstheintensityofradiationandthereforefilmdensityandpatientdose(highermA=higherfilmdensity=higherpatientdose)

mAs Abbreviationformilli-ampereseconds,itisthemultipleofthemAandtheexposuretime(inseconds)andreferstothequantityordensityofradiationtowhichthepatientisexposed.ThedensitycanbecontrolledbysettingeitherthemAsasonefactororsettingthemAandtimeseparately

Naturalbackgroundradiation Theamountofradiationtowhichapopulationisexposedfromnaturalresources,suchasterrestrialradiationresultingfromnaturallyoccurringradionuclidesinthesoilandcosmicradiationoriginatinginouterspace

Oxidation Aweakeningofthedeveloperstrengthcausedbyprolongedexposuretoair

PA Abbreviationforpostero-anterior,whichdescribestheprojectionwherebythex-raybeampathtravelsfromtheposteriortoanteriorpartsofthepatient

Penetration TheabilityoftheX-raybeamtopenetratestructures,asdeterminedbytheenergyofthebeam(controlledbykV)

Primarybeam RadiationemittedfromtheX-raytubethathasnotreachedthepatientorobjectbeingimaged

Processing ThechemicaltreatmentofanexposedX-rayfilmthatresultsintheproductionofanX-rayimage

Quality(image) Theappropriatelevelofcontrast,definitionandpatientpositioninginthedemonstrationoftherequiredbodypartsofanimagetoallowtheimagetobeappropriatelyread

Radiolucent ThepropertyofastructuretowhollyorpartiallyallowthepassageofX-rays

Radiopaque ThepropertyofastructuretowhollyorpartiallystopthepassageofX-rays

Resolution Theabilityofanimagingsystemtodifferentiatebetweenobjects

Scatter(radiation) Secondaryradiationthathasbeenchangedindirectionfromtheprimarybeam

SID Abbreviationforsource-to-imagedistance,thedistancefromthefocalpoint(origin)oftheX-raybeamtotheimagereceptor.Alsoknownasthefocal-film-distance(FFD)

Sievert Theunitofequivalentdoseandeffectivedose,equalto1J/kgintheinternationalsystemofunits

Supine Atermusedtodescribeapatientlyinghorizontalontheirback

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Appendix

1. Summaryofstudyrecommendations