55469809-computed n Digital-Radiography.ppt

Digital Radography

1. DIGITAL RADIOGRAPHY
Moderator:
Mr. Ram Singh (Lecturer)
Deptt. of Radio-Diagnosis & Imaging
PGIMER, Chandigarh-160012
Presented By:
Debendra Prasad Gupta
M. Sc. Med. Tech. (Radiodiagnosis) –1
st
Year Student
Deptt. of Radio-Diagnosis & Imaging
PGIMER, Chandigarh-160012
12
th
September, 2009
1

2. DIGITAL RADIOGRAPHY:
Definition:-
Itisdefinedastheimagedataacquiredfrom
thenumericvaluei.e.indiscretebinarydigits
byuseofcomputers.
WhereasinConventionalRadiography
informationisrepresentedintheanalogor
continuousformratherthanadiscrete
fashion.
2

3. History:-
In1980researchersat“FujiLaboratories”
developedanerasableX-rayimagingdevice
basedonthex-rayexcitationofaphosphorlayer
andsubsequentreadingofthestoredimagedata
withthehelpofinfraredlaser(i.e.
PhotostimulableLuminescence).
Resultsshowedthattheimagingplatewasmore
sensitivethanconventionalX-rayFilmwith
intensifyingscreens.
3

4. Sincetheclinicaluseofx-raysin1895,majorityof
radiographicexaminationshavebeencarriedoutbythe
conventionalmethod.
Thebeamisprojectedthroughthepatientandthetransmitted
beam,whichhasinformationaboutthebodystructures,is
madetostrikethecassettecontainingthefilmandthe
intensifyingscreens.Thiswaythelatentimageisproducedon
thefilm.
Thelatentimagecanbemadevisibleandpermanentby
processingitwithsuitablechemicals.
Thisconventionalmethodofobtainingradiographshas
dominatedthefieldofradiographyformanyyears.Butnow,it
hasbeenrealizedthattheFSsystemhasitsownlimitations.
INTRODUCTION:
4

5. LIMITATIONS OF FS:
1.Afterthefilmhasbeenexposed,theinformationcontents
cannotbeenhanced.
2.Iftheradiographistoodark(Over-Exposed)ortoolight
(Under-Exposed)eitherbyExposureFactor,FilmFaultor
ProcessingFaults,ithastoberepeatedi.e.NoPost-
Processingoptionwhichresultsinextraexposuretothe
patient.
3.Thecompletionoftheexaminationisdelayedasthefilm
hastobeprocessedtoconvertthelatentimageintoa
permanentone.
4.Amagnifyingglassmayberequiredtoseeverysmall
structuresindetaili.e.NoZooming&PanningOption.
5

6. 5.Copiedradiographsareofinferiorqualitythanoriginalones.
6.Thefilmisaphysicalobjectandsoitrequiresconsiderable
morespaceforstoragei.e.Storage&RetrievalCost.
7.Filmscanonlybeinoneplaceatatimeandtheyalsoget
deterioratedwithpassageoftime.
8.Filmcannotbestoredforlongertimewhenrequired.
9.Dynamicrangeofx-rayfilmislimited(i.e.0.2–3).
Theselimitationscanbeovercomebytheincorporationof
computertechnologyintothediagnosticx-rayimaging.
WithDRsystemconventionalanaloginformationisconverted
intodigitalform,processingthedigitaldataanddisplayingthe
imageonthemonitorthatsurprisinglylookslikeaconventional
image.
Cont…
6

7. MILESTONE IN DIGITAL
RADIOGRAPHY:
Year Development: -
1980Scan Projection Radiography (SPR).
1983Computed Radiography (CR), Storage Phosphors.
1990Charge-Coupled Device (CCD) Slot-Scan Direct
Radiography (DR).
1994Selenium Drum Direct Radiography (DR).
1995Amorphous Silicon -Based–Cesium Iodide ( Scintillator )
Flat-Panel Detector in Indirect DR.
1995Selenium-Based Flat-Panel Detector in Direct DR.
1997Amorphous Silicon-Based -Gadolinium ( Scintillator ) Flat-
Panel Detector in Indirect DR.
2001Dynamic Flat-Panel Detector for Digital Fluoroscopy in
DSA.
7

8. Digital Radiography (DR)
SPR
NaI –Scintillator
Photodiode
Indirect
Conversion
Storage Phosphor
Plate (IP)
BaFX:Eu
+2
CR
Indirect Conversion Direct Conversion
DR
Photoconductor +
TFT (a:Se-DFPD)
Selenium Drum
Scintillator + Photodiode
(a:Si) + TFT (IFPD)
Scintillator + CCD
CsI:Tl or CsI:Na &
Gd
2O
2S:Tb
3+
Accordingtothenature,designandfunctionofthedetectorthe
Digitalradiographycanbedividedmainlyinthefollowingway:-
8

9. SCAN PROJECTION SYSTEM:
EarlierScanprojectionradiography(SPR)was
performedonacomputertomographyCTsystemby
translatingthepatientthroughtheCTgantry
aperture.
ItisbasedonCT–Technology,anotherprojection
radiographytechniquewasdevelopedusinga
narrowfanbeamofX-Raysinterceptedbylinear
arrayofdetectorscalled“ScanProjection
Radiography”.
Basically,SPRinvolvestheuseoftheexistingCT-
Gantry&Computertogenerateanimagethatlooks
surprisinglylikeConventionalRadiography.
9

10. TheX-raybeamisshapedintoafanby
collimatorsthatconfinethebeamtoa2-10
mmthicknessthroughonarchof30
0
–45
0
.
Therearetwocollimators:-
1)Thepre-patientcollimatorswhichshapethebeam,
reducedscatterradiation&controlpatientdose.
2)Thepost-patientcollimatorswhichfurtherreduce
thescatterradiationrejection.
SPR Cont…
10

11. PRINCIPLE OF S.P.R.:
X-Raybeamafterpassingthroughpatientis
detectedbydetectorarray.Thesignalhave
beenimageinformationofthebodypartsare
transferredtothecomputerwheretheyget
digitized&processedtoreconstructthe
image.
Toobtainacompleteimageofthebodypart,
X-Raytube&detectorassemblyremains
stationary&thepatientistranslatedthrough
theX-raybeamoralternativelypatient
remainsstationary,whiletheX-Raytube-
detectorassemblytranslates.
SPR Cont…
11

12. COMPONENTS OF S.P.R. SYSTEM:
1.X-Ray Tube.
2.Pre-Patient Collimator.
3.Post-Patient Collimator.
4.Detector Array.
SPR Cont…
12

13. X-RAY TUBE ASSEMBLY:
X-Raytubeofhighheatloadingcapacity
usuallyabove1MHuisrequiredbecauseof
longimagingtime.Usually20–50cm
bodypartofpatientisimagedata
translationspeedof1–20cm/s.
Twotypesofdetectorcanbeused:-
1.AGasFilled.
2.ScintillationDetectorscouplewithSolid
StatePhotodiode,i.e.CCD.
SPR Cont…
13

14. Advantage:-
InSPRX-raybeamiscollimatedinafanx-raybeambyPre-
Patient&Post-PatientCollimators.i.e.:-
1.High Amount of Associated Scatter Rejection.
2.High Radiographic Image Contrast.
3.High Dynamic Range (i.e. Low Contrast Detectibility).
4.Image Manipulation.
Disadvantages: -
1.Scanning Time is More.
2.Poor Spatial Resolution &
3.More Radiation Dose to the patient.
SPR Cont…
14

15. ADVANCEMENT:
Atthepresenttime,SPRisre-emergingwith
somemodificationasapromisingadjunctto
DigitalMammography Tomosynthesis
(DMT).
ThepurposeofallformsofTomographyis
toimproveimagecontrast,andi.e.thegoal
ofDigitalMammographyTomosynthesis
(DMT).
15

16. COMPUTED RADIOGRAPHY:
Definition:-
DigitalwayofdoingGeneralRadiographywith
ConventionalX-raymachinesexceptConventional
Screen/FilmanddarkroomisknownasComputed
Radiography.
Principle:-
ItisbaseduponPhotostimulatedLuminescencein
whichtheradiographicdataiscapturedfroma
conventionalX-raymachineandprocessedthedata
digitallytoproducecrispandhighquality
radiographicimages.
16

17. TheCRCassetteisexposedwithtransmittedx-raysbeaminasimilar
fashionastheconventionalcassette.
ThelatentimageisformedinthephosphorlayeroftheImagingPlateinthe
formofElectricalCharge.
Thenthelatentimageismadevisibleonmonitorbyprocessingorscanned
andreadthatexposedimagingplatebyalaserscanningdevicecalledImage
Reader.
Theoutputsignalfromtheimagereaderisfedtoanimagearrayprocessor
wherethedigitalgray–scaleimageisformed.
Thedigitalimagegeneratedbytheimagereaderisstoredtemporarilyona
localharddiskwhichisprocesseda/ctoneedandtheresultingimagecan
bedisplayedeitherassoft(VideoDisplay)copyonmonitororsendit
directlytolaserprinterthatmakehard(Film)copiesofthedigitalimage.
Thedigitalimagecanthenbestoredonanopticalormagneticdiskforlong
termarchivingorconnectedtothePACSthroughDICOMforTele-
radiology.
Working:
17

18. 18

19. 19

20. COMPONENTS OF THE C.R.
SYSTEM:
3.) Image Reader: -
4.) Image Processor: -
Cassette With Imaging Plate
2.) Image Recorder: -
1.) General X-ray Equipment: -
20

21. Material: -
•Body: -ABS ( Acrylonitrylbutadiene styrene).
•Corners: -PUR (Polyurethane rubber).
•Hinges: -PP (Polypropylene).
•Inner lining: -Felt.
Sizes: -
•Same as that of conventional cassette.
Identification: -
•Embedded memory chip.
•Contactless RF identification.
Backscatter Protection: -
•150 μmlead.
CASSETTE:
21

22. THE IMAGING PLATE (IP):
TheImagingPlate(IP)isalsoknownasComputed
Radiography(CR)PlateorStoragePhosphorScreen
(SPS)orPhotostimulablePhosphor(PSP)detectorto
recordtheradiographicimageinplaceofthe
conventionalfilm/screencassette.
Theimagingplateishousedinaruggedcassette&
appearssimilartoascreen/filmcassette.
Itisavailableinthesamesizesasconventional
cassettes.
Itishandledinthesamemannerasascreen/film
cassette.
22

23. Itisnotloaded&unloadedinadarkroom.Rather,it
ishandledinthemannerofascreen/filmdaylight
loader.
AtypicalIPcanstorealatentimageforaconsiderable
periodoftime.However,itwillloseabout25%ofthe
storedsignalb/w10min.to8hrsafteranexposure
resultinginthelossofenergythroughspontaneous
phosphorescence.
Itretainstheimagefor24hours,butsomedegradation
mayoccurwithpassageoftime.
Imagingplateshowsalinearresponsetotheintensity
ofx-rayexposureoverabroadrange.
Cont…
23

24. CONSTRUCTION OF IMAGING
PLATE (IP):
PROTECTIVE LAYER
PHOSPHOR LAYER
ANTI-HALO & REFLECTIVE LAYER
BASE
BACKING LAYER
Protective layer: -
-Fluorinated Polymer Material
Phosphor Layer: -
-Ba FX: Eu
+2
, 0.4mm thick.
Anti-halo Layer + Reflecting Layer
-Prevent laser light from passing through.
Base:-
-PET-Polyethylene teraphtalate
Backing Layer: -
-Protects the base from damage &
reduces back scatter X-rays.
-150 μm lead.
24

25. THE IMAGING PLATE:
AProtectiveLayercomposedof“FluorinatedPolymer”
whichmakeresistanttotheabrasion,damaged&scratches
causedontheIPduringstorageandtransfer.
ThePhosphorLayerconsistofafamilyofPhotostimulable
Phosphorcrystalsi.e.BrFX:Eu
2+
whereXcanbeanyof
halogensi.e.Chlorine(Cl),Bromine(Br)orIodine(I)oran
arbitarymixtureofthem.
AtypicalPhosphorLayercomposedofabout85%-BaFBr
&15%-BaFI,activatedwithaverysmallquantityof
Europium(Eu)asactivatorincrystal.
ThisEuropiumactivationprocedure,alsocalleddoping,
createsdefectsintheBaFBrcrystalsthatallowelectronsto
trappedmoreefficientlyi.e.increasesmoreDQEofcrystal.
TeReflectingLayerliesb/wphosphor&baselayer.which
preventsthereflectionoflightisalsoapplied. 25

26. TheBaseLayercomposedof“Polyethylene
TeraphtalateResign”overwhichalayerof
photostimulablephosphor(EuropiumdopedBarium
FluoroBromidecrystals-BaFBr:Eu
+2
)iscoated.
ThenextisBackingLayercomposedof“Lead”
whichpreventsthebasefromdamage&reducesback
scatterX-rays.
ThelastistheBar-CodeLabelwhichcontainsthe
numberassignedtotheimagingplate.
ThisBar-Codeprovidesamechanismforassociating
eachimagingplatewithPatientidentification,
Relatedexamination&PositioningInformation.
Theimagingplateisflexibleandlessthan1mm
thick.
Cont…
26

27. LATENT IMAGE FORMATION IN IP:
Topreparetheimagingplatforanx-rayexposure,the
plateisexposedtotheintenselighttoeraseany
previousimage.
ForX-rayimaging,theIPisplacedinacassetteandis
usedjustlikeafilm/screencassettewithstandard
radiographicequipment.
WhenexposedtoX-ray,theEuropiumatomsinthe
phosphorcrystallinelatticeareionized&converted
fromEu
2+
-Eu
3+
bylibratingaValanceElectron:
Eu
2+
-X-rayIrradiation-Eu
3+
+e
-
TheseelectronareraisedtoHigherEnergystateinthe
ConductionBandwheretheycanmovedthroughout
thecrystallattice. 27

28. Thepresenceofimpurities(e.gBromine)introduceenergy
levelintheForbiddenZonecalledF–centre.
OnceintheConductionBand,theelectrontravelfreely
untiltheytrappedintheF–centreintheMetastableState
withanenergylevelslightlybelowthatofConduction
BandbuthigherthanthatofValanceBand.
Theno.oftrappedelectronisproportionaltotheamount
ofX-rayabsorbedlocally.
Thetrappedelectronintheformofmetastablestate
constitutetheLatentImage.
Duetothermalmotionelectronwillslowlybeliberated
fromtraps,andtheLatentImageshouldthereforberead
withouttoomuchdelay.
Atroomtemp,theimageshould,however,bereadableup
to8hrs.afterexposure.
Cont…
28

29. LIFETIME OF THE IP: -
OneofthemajoradvantagesofCRisthattheimaging
plateisreusableandthousandsofexposurescanbe
madeonit.However,thereareanumberoffactorsthat
mayaffectthelifetimeofanimagingplate:-
Theplatesaresubjectedtonormalwearandtearfrom
scratches,scuffs,cracks,andcontaminationwithdust
anddirt,whichmayinterferewiththeproductionofa
goodimage.
Theestablishmentofawellorganisedqualitycontrol
programwillplayanimportantroleinassessingthe
clinicalqualityoftheimagingplate.Thismayeasily
becarriedoutbyartefactassessmentanduniformity
evaluationacrosstheplate.
29

30. DustanddirtbuilduponCRphosphor
plates,leadingtoimageartifacts.To
avoidthis,platesneedcleaningat
regularintervals.
Solvent:Ethanol-99.7%.
Additives:CatanacSN(Cyastat
SN50)-0.3%.
SafetyPrecautions:-
-Highlyflammable.
-Keepcontainerclosed.
-Keepawayfromsourcesof
ignition.
IMAGING PLATE CLEANER:
30

31. TheCRimagereaderisalso
knownasAnalogtoDigital
Converter(ADC).
Definition:-
Itisadevicewhichconvertsthe
ContinuousAnalogImageof
ImagingPlateintotheDigital
Image.
Construction:-
Itisconsistsofthreeparts:-
1.MechanicalFeature.
2.OpticalFeature&
3.ComputerControl.
IMAGE READER:
31

32. What Happens to the Plate in the Reader?
1.Cassetteisenterthereader.
2.Imageplateisremovedfrom
cassette
3.Latentimageisscannedbylaser
4.Imageplateiserasedwithhigh
intensitylight.
5.Imageplateisreturnedtocassette
andejected.
32

33. Afterexposurethecassetteisfeededintoimagereadersystem.
Wherethecassetteisopenedautomaticallyandtheimaging
plateisremovedfromthecassetteinsidethereader.
ThentheIPismovedalongitslongaxisandscanned
sequentially(Horizontally)byaMonochromaticInfraredLaser
BeamofHelium-Neon(He-Ne)GasorSolidStateLaserof
intensity≈633nm.
Thelaserlightstimulatesthetrappedelectronmovingthemup
totheconductionbandwheretheymaketheirexitreturningto
thelowerenergyValanceBand.
ThismovementinvolvesthetransformationofEuropiumfrom
theEu
3+
-Eu
2+
i.e.MetastableStatetoGroundStateby
emissionofenergyintheformoflight(Blue&Green)havinga
wavelengthlowerthanthatofthestimulatedlaserlight.
Eu
3+
+e
-
→(InfluencedbyIRLaserof633nm)→Eu
2+
+hf(400nm).
FUNCTION ORREADING PROCESS:
33

34. Theintensityoftheemittedlightisproportionaltothe
amountofx-rayenergyabsorbedinthePSP–layer.
ByusingaOpticalFilter,thatabsorbsredlightbutis
transparenttoBlue&Greenlight
ThisemittedlightiscollectedusingaLightGuide&is
fedtoaPhotomultiplierTubewherethelightis
convertedtoanElectricalSignalwhichisamplifiedto
anElectricOutputSignal.
TheElectricOutputSignalisconvertedintoDigitized
ImageSignalbyADC&storedinacomputerasa
DigitalMatrix.
Cont…
34

35. TheDigitizedImageSignalisprocessedbycomputer&
convertedintoagaininElectricOutputSignalbyDAC
whichisdisplayedonthemonitor.
Thewholereadoutprocessfora14”X17”imaging
platetakesabout30–40sec.thus,amaximumworkload
of90–120imagingplatesperhrs.istheoretically
possible.
But,practicallyCRsystemcanreadonly65–70IP/hrs
acceptingmixedcassettesize&thetimefromcassette
exposuretoimagepresentationcanbelessthan90sec.
Thereforeonereadercanserveseveralradiographic
roomsandthedatainputisstoredonaneasyimage
workstation.
Cont…
35

36. 36

37. Erasing Process: -
Itisnecessarytoreusetheimagingplateagain.
BecauseresidualLatentImageelectronsarestill
trappedonhigherenergylevelafterreadout.
Ifresiduallatentimageremained,ghostingcould
appearonsubsequentuseoftheIPinthenextexam.
Thisenergyiserasedafterthereadoutprocessusinga
highintensitywhitelightfromabankofspecially
designedFluorescentLampssourcethatflushesthe
trapswithoutreintroducingelectronfromtheground
energylevel.
Cont…
37

38. WORKSTATION:
HereRadiographicTechnologistcanbeprocessed
thedigitalimageinavarietyofwaysdependingupon
theclinicalapplication&thefinalimagecanbe
recordedasahardcopythroughMultiFormat
CameraorLaserImager.Intheformofanalog
image.
Heredigitaldataisstoredontheharddiskofawork
stationfromwhereitcanbeprocessed,viewed,
printedthroughordistributedviaalocalnetworkto
peripheralstations.
TheworkstationprovidesaDICOMcompliantoutput
whichmaybedirectedtoalaserPrinterforhard
copies,ornetworkedtootherviewingstationsor
archivedinPACSforTeleradiology.
38

39. ADVANTAGES OF C.R. SYSTEM:
Nospecialequipmentisrequired.
NohandlingofProcessingChemicals.
TheExposureLatitudeiswideri.e.HighDynamicRange
(1:10,000)whichleadstoreducedratesoffailedx-ray
exposuresoinasingleradiographlargedensitiesvariation
canbeobtained.
FewerRepeatexaminationsshouldbeneededdueto
exposurefactorsbecauseofthewideexposureLatitude.
TheCRsystemarecassettebased,theycaneasilybe
integratedintoexistingradiographicdevicesarehighly
mobilesoalltypesofRadiographicExaminationi.e.
Mobile,Portable(Bedside),Trauma,DentalRadiography
arepossiblewiththeC.R.system.
39

40. IfasingleImagingPlateshowsdefects,itcaneasily
bereplacedbytheradiographerhimselfwithnoneed
forspecializedequipmentorserviceperson.
Theimagedisplayedonthemonitorcanbe
manipulatedinavarietyofways:contrast
enhancement,edgeenhancement,black/white
reversal,zooming&panningetc(i.ePostProcessing).
Theprocessofstoringtheimagesdoesnotrequire
separateroomsandisrelativelyeasier.
Costeffectiveroutetodigitalradiography.
Theacquiredimagecanbetransferredtomany
monitors,differentplacesforviewingtolargeno.of
person.
Increasedcapabilityforconsultationmadepossibleby
electronictransmissionofdigitalimagesthrough
PACS&Teleradiology(i.e.networkingsystem).
Cont…
40

41. LIMITATIONS OF THE C.R. SYSTEM:
ThetechniqueisTime&LaborIntensivelikeFSR.
Imagereadertakestimebeforetheimagecanbedisplayedso
thetimetakenissameasthatrequiredforFSR.
Lesserspatialresolutionascomparedtoconventional
radiography.
SpeedClassof100-200issimilartothatofMediumSpeedFSR
systemsothatradiationdoserequiredissameormorethan
FSR.
Radiologicaltechnologistsreceivenodirectfeedbackonthe
accuracyoftheirselectionofexposurefactorsastheresultant
imagesareofconsistentqualityregardlessoftheexposure.This
mayleadtoundesirableandundetectedoverexposuretothe
patient.
41

42. INNOVATIONS & NEWER
APPLICATIONS IN CR:
SomeofthedrawbacksofCRsystem,
namely:
-CassettesHandling.
-LongReadOutTimeofPSPPlates.
-LowDQE&
-PoorResolution
havebeenaddressedbynewerinnovations&
technologicaladvances.
42

43. AUTOMATED CRSYSTEM WITH
FAST READOUT:
CRsystemefficiencyhasbeenrecently
improvedbyreducingthereadouttime&by
removingthestepofcassettehandling.
AutomatedCRsystemachievethisbyline–
scanlasers&photodiodedetectorsthat
reducethereadouttimeofaPSPplatetoless
than10s.
Inthesesystemthereisnocassettehandling,
leadingtototallyautomaticimagedata
acquisition.
43

44. NEWER PHOSPHORS FOR IP:
CommerciallyavailableIPhaveunstructured
phosphorlikeRubidiumChloride(RbCl)orBaFX:Eu
Thesearescannedinarasterpattern.
Aneedle–shapedphosphorRbI,CsBr,hasbeen
newly;introduced,e.g.KonicaMinolta’sRegius370
UprightDR&isconsideredmoreefficientduetoits
structuralconfigurationofcrystals.
Thiscrystalstructurereduceslaterallightdiffusion
becauseoftheneedleshapedconfigurationthatacts
aslightguide.
Inadditionthenewerphosphorsaremoreefficient
withanincreasedDQE.
44

45. Cont…
45

46. MOBILE CRSYSTEM:
Bedsideradiographyofcriticallyillpatientswithconventional
CRinvolvesphysicaltransportofthecassettestotheCR
reader,oftenlocatedfaraway.
Thesituationgetsworseastheno.of‘portable‘filmsincrease.
TosaveLabor,Time&ImproveWorkflow,portablecompact
CRsystemhavebeenintroducedinlate2007,withFugiFilm
(FCRCarbonXLCRReader)&CarestreamHealthInc
(Pointof–CAreCR-ITX560)machines.
ThesesystembasicallyhaveamobileX-rayunitwithan
integratedCRreader.
So,theyareeasytouse&offerquickimageavailabilityinless
than25sec.
46

47. 47

48. DUAL-ENERGY IMAGING:
Itisdonebytwomethods:-
1.)SubtractionTechnique&
2.)DoubleExposeTechnique.
1.)SubtractionTechnique:-
Inthismethod,x-rayenergiesareseparatedbytheinsertion
ofacopperfilterb/wtwoimageplateswhicharethengiven
asingleexposure.
thelowenergyimageisrecordedonthefrontimageplate&
ahighenergyimageisrecordedontheback.
OwingtothedifferenceinenergytheabsorptionratioofX-
raythroughbone&softtissuewilldifferforthetwoimages.
Bysubtractingthesetwoimagesusingweightedfactors,
boneorsofttissuedetailcanbeselectivelydisplayed.
48

49. 2.).DoubleExposeTechnique:-
Inthismethod,byusingahigh&lowKVp,twoimagesare
createdinthetwodifferentimageplates.
Softtissue&bonescanbeseparatelydepictedbythis
method.
Dual–energytechniquearemosteffectivewhenboth
imagesareacquiredsimultaneously.
Similarresultsareobtainedwithtwoexposurewithinavery
shortperiodoftime.
Uses:-
InChestRadiography,particularlyfortheevaluationof
partiallycalcifiednodules&pleuralplaques.
Cont…
49

50. AUTOMATIC IMAGE STICHING:
Thisisusefulindeterminingprecisemeasurementinlengthy
anatomicalregionslike-wholespine,lowerlimbsorupper
limbinaskeletalsurvey.
Nowadays,thelargestflatpanelDRplatesareavailablein
43X43cm.
Usingthesedetectors,onlyalimitedportionofthebodypart
canbeimagedatatimeinasingleexposure,thusmaking
thesedetectorsinadequateforstudyingthewholespineorthe
entirelowerlimb.
Toovercomethisproblem,multiplesequentialexposuresat
differentpatientpositionsareacquiredinastillpatient.
Automaticstitchingisthenperformedtoreconstructalarger
compositeimage.
Thisspecialsoftwareenablespixelshiftandoverlap.
50

51. WiththerecentapprovaloftheClearViewdigital
mammographyproducts,FUJIFILMMedicalSystemsUSA
(Stamford,Conn)becomesthefirstvendortoofferafull-field
digitalmammography(FFDM)systembasedonCRtechnology
intheUnitedStates.
CRformammographyusesimagingplates(IPs)madewith
photostimulablephosphortoconvertx-raysintodigital
information.Existingglass,flat-panelFFDMsystemsrelyon
solid-statedetectors.
CR-BASED FFDM
51

52. TheCRReader,theClearViewCSM,hasauniquedual-sidereading
capabilitythatpermitsthecaptureofx-rayinformationfrombothsidesof
theImagingPlate(IP)simultaneously.The50-µmlaserexcitesthe
phosphor,whichhasathickercoatingcomparedtostandardCRIPs.Light
isemittedfrombothsidesduetoaclearbaseandiscapturedwithdual
lightguides.
52

53. SLOT SCAN SYSTEM:
ThissystemusesnarrowfanbeamX-rayofabout5
mm&linearCCDarraydetectorsystem.
Ithasmechanicallylinkedx-raytube&collimator
oppositethenarrowCCDarraywithfewrowsof
detectorandscanalongthelongaxisofthepatient
anatomy.
Ithastwopreciselyalignedmovingslitcollimators,
oneoneithersideofthepatient.
Duetowhichthissystemprovidestheultimatein
scatterrejection&detectorefficiency.
53

54. Cont…
Thususeofaradiographicgridisnotnecessary,
significantlyusingtheradiationdose.
Therearedifferentpossiblemovementofmechanical
linkedsystem&patientcouchmovement.
Theexposuretimetothepatientisabout20msec.&
readoutprocesstimetakesabout1-3sec.
Scantimedependsontheareacoveredi.e.2–30
seconds.
Becauseoftheneedforfixedinstallation,SlotScan
DRsystemisdedicatedtoChestradiography,
Mammography,orDentalRadiography.
54

55. CCD Slot Scan Direct Radiography
55

56. ADVANTAGES:
Scatterradiationalmosttotallyabsent.
Nogridisrequired.
Radiationdoseisreducedasgridnorequired.
Detectorefficiencyismorewithlowerimagenoise.
Longer&largeanatomicalregionsarewellcovered.
DISADVANTAGES :
Highinitialcost.
Longeracquisitiontimeduetonarrowfanbeam.
So,requirementofequipmentwithhighratingof
generator&X-raytubes.i.e.hightubeloading.
PoorSpatialResolution,duetoPatientmotionwhich
degradeimagequalityduringscanning.
Itisafixedmodalitymethodwithbulkydesign.
BedsideRadiographyisnotpossible. 56

57. Rotatingselenium-dotteddrum,whichhasapositiveelectricalsurfacecharge,is
exposedtox-rays.Duringexposure,achargepatternproportionaltothatofthe
incidentx-raysisgeneratedonthedrumsurfaceandisrecordedduringrotation
byananalog-to-digitalconverter.
SELENIUM DRUM DR SYSTEM:
Advantage:-
Itprovidegoodimagequalitythatis
superiortothatprovidedbyscreen-
filmorCRsystems.
Disadvantage:-
Becauseoftheirmechanicaldesign,
seleniumdrumdetectorsarededicated
forcheststandsystemsonlywithno
mobilityatall.
57

58. Indirect Conversion Direct Conversion
Direct Radiography (DR)
Photoconductor (a:Se)
+ TFT (DFPD)
Selenium Drum
Scintillator +
Photodiode (a:Si) +
TFT (IFPD)
Scintillator + CCD
CsI:Tl or CsI:Na &
Gd
2O
2S:Tb
3+
DIRECT RADIOGRAPHY (DR):
DRtechnologyconvertsx-raysintoelectricalchargesby
meansofadirectreadoutprocessusingCCD/TFTarrays.
58

59. INDIRECT DR:
Inthiscase,X-rayenergyisfirstconvertedinto
lightphotonsbyanphosphorscintillator(CsI:Tl,
Gd
2
o
2
S:Tb).
Thenthelightphotonsareconvertedinelectric
chargebyPhotodiodePhosphor(a:Si).
Theelectricchargeisconvertedinelectrical
signalbyCCD/TFTwhichisdigitizedbyADC
indigitalsignal&storedincomputer.
Thestoreddigitalsignalincomputerisprocessed
andconvertedinanalogsignalbyDACtoseeon
themonitor.
Thewholeprocesswilltakeonly1.3–3sec.
59

60. Cont…
ConvertX-raysintolightphoton
afterthenelectronicsignalsfor
digitalimageformation.
Uses 3 step process : -
X –rays
Visible Light
Electronic Signals
Image formation
CsI:Tl, Gd
2
o
2
S:Tb
a:Si
TFT & ADC
60

61. DIRECT DR:
Inthiscasewedonotusethephosphorcoatingscintillator
layer,thuseliminatingtheintermediatelightproducing
step.
Hencea:Sedirectlyactsasthex-raydetector.
Thex-raybeamdirectlyinteractswithathinlayerofa:Se
creatingelectron-holepairs,whichbeingcharged,travel
directlytotheTFT.
FromTFT,thechargepatternisreadoutbycharge
amplifier&digitizedbyADCindigitalsignal&storedin
computer.
Thestoreddigitalsignalincomputerisprocessedand
convertedinanalogsignalbyDACtoseeonthemonitor.
Thewholeprocesswilltake<1.3sec. 61

62. ConvertX-raysintoelectronic
signalsfordigitalimageformation
Uses 3 step process : -
X –rays
Electronic Signals
Image formation
Cont…
a:Si
TFT & ADC
62

63. 63

64. 64

65. CONSTRUCTION & WORKING
OF FPD SYSTEM:
Thephysicaldimensionsofthedetectorarrayare40x
50x4cmswith2560x3072pixelmatrix.
Thematrixiscoveredwithascintillatorlayerof
CsI:TlorGd
2O
2S:TbincaseofIndirectFPDonly.
Thematrixarrayconsistsofaglasssubstrateonto
whichalayerofa:Siisevaporatedinthecaseof
IndirectFPD&a:SeincaseofDirectFPD.
Thea:Siora:Seisstructuredinamatrixofindividual
photosensorsandswitchingelements,eitheraTFTor
aCCDwhichallowstheconnectionsofthesensor
withthereadoutlineincolumndirection.
65

66. TFTorCCDarecontrolledviaaddresslinesinthe
horizontaldirection,inordertoreadoutthesingle
chargevaluesofphotodiodes.
Thesesignalsaremultiplexedandconvertedinto
digitalsignalsbyanA.D.C.insidethedetector
housing.
The2-Ddigitalimagedataisdirectlytransferredto
theimageprocessingcomputerviaanopticfiber
link.
Sotheimageisavailableindigitalformshortly
aftertheexposurehasbeenmade.
Cont…
66

67. ADVANTAGES of DRSYSTEM:
IncreasingWorkflowEfficiency,SavingTime&Labor.
IntegratinghighpowerX-raysystemof30–1000KWRating,very
ShortExposureTime,EliminatingMotionBlur.
VariableSpeedAcquisitionpossible(speedclass100–800)
dependingonacceptableSNR.
MostDRsystemhavepresetsavailableforvariousanatomicalstudies
includingoptimizedpostprocessinge.g.chest,spineetc.
Automatictubedetectorpositioningforselectedstudy.
Autoselectionfilter&FocalSpotSizea/ctotheanatomicalpart.
Automatictrackingforeasypositioning.
ImmediateavailabilityofimageforQualityCheck&Diagnosis.
Theexaminationbecomesquickasnocassetteshavetobefetched
fromthestoragearea,takentotheexaminationsite,ortothe
processingunitafterexposure.
Radiographyaswellasfluoroscopycanbeperformed.
Postprocessingcanbedone. 67

68. DISADVANTAGES OF DR
SYSTEMS:
Highinitialcost.
Someradiographicviewaredifficulttoobtainas
thedetectorsaregenerallynotfreetobeplacedin
anyposition.
Carefulhandlingisrequiredduetofragilenature
ofmostdetectors.
Duetoitsinflexibility,portableorward
radiographyisnotpossible.
Differentequipmentisrequiredfordifferent
kindsofwork.
68

69. DIGITAL FLUOROSCOPY:
ItprovidesRealTimeImagingofanatomic
structures.Asmaximumimagedetailis
required,soimagebrightnessmustbehigh.
Imageintensifierwasdevelopedtoreplace
theconventionalfluoroscopicscreen.
Withtheintroductionofcomputer
technologyintofluoroscopy,digitalimages
withbetterdetailcanbeobtained.
69

70. EQUIPMENT:
D.F.requiresthesamefluoroscopy
equipmentinadditiontoacomputer,2video
monitors,andamorecomplexoperating
console.
Ahighvoltagegenerator.
Avideosystem.
Achargecoupledevice.
70

71. ADVANTAGES:
Lessradiationdoseascomparedtothe
I.I.T.V.system.
Betterimagequality.
71

72. DEVELOPMENTS IN D.F. :
FlatpaneldetectorsystemhasreplacedtheI.I.T.V.
system.
X-rayspassingthroughthepatientareconvertedinto
electricalsignalsbytheF.P.D.Thesearethenpassed
throughtheamplifierandADCwheretheyareconverted
intodigitalsignals.
Thedigitalimagedataisdirectlytransferredtoanimage
storagePCviaanopticfiberlinkattherateof30f/s
Thissystempermitshighspeeddigitalimageacquisition,
processinganddisplay.
Imagesareofexcellentresolution.
72

73. DYNAMIC FPDFLUOROSCOPY:
Dynamic Detector 73

74. INNOVATIONS & NEWER
APPLICATIONS IN DR:
DigitalRadiographyiswitnessingrapid
innovationsinhardwareaswellassoftware
applications.
Clinicalutility&thetruepotentialofthese
applicationswillbeunderstoodbetterinthe
yearsahead.
Fewoftheexcitingapplicationsare:
74

75. PHOTON COUNTING TYPE DRSYSTEM:
ItissimilartoSlotScanningTypesystembutusesa
differenttypesofmultislitdetectormadeupof
CrystallineSilicon(Si)whichissomewhatsimilarto
theoneusedindirecttypeofFlatPanelDetectors
System.
Avoltageofabout100voltsisappliedacrossthe
arrayofthin(50µm)Sicrystals.
AbsorbedX-rayproduceelectrons&holes.Eachof
theseeventiscountedinatimermeterwithtime
correspondingtothespatiallocationalongthe
directionofX-rayfanbeamsweep.
75

76. EachabsorbedX-rayphotonresultsinaunitcount
regardlessofthephotonenergy.
Astheelectricalpulsegeneratedismuchhigherthan
theelectronicnoise,thistypeofDRsystemproduce
imageswithhighSNR.
Uses:-
1)Mammography(Sectramicrodose).
2)IngaseousmicrostripdetectorsforBiplaneWhole
BodyImaginginerectweightbearingpositionwith
excellentresult(EOSofBiospacemed).
Cont…
76

77. 77

78. Advantages:-
Radiationdoseisreducedasgridisnotrequired.
HighsystemDQE.
HighSNRduetominimalelectronicnoise.
Noghostimage(Previousexposureisresidue).
Highcontrast&detailresolution.
Disadvantages:-
Exposuretimeislong.
Patientsmotionmaydegradeimagequality.
Requirementofequipmentwithhighratingofgenerators
&X-raytubes.
78

79. DIGITAL TOMOSYNTHESIS:
Inthistechniquemultiplelowdoseexposureare
givenfromvariousangleswhilethex-raytube
movesinanarc&thedetectorremainsstationary.
Multipleimageswithdifferentfocalzonesare
possibletobecreatedbyadditionoftheselowdose
imagesafterpixelshift.
Itemphasizecontrastinaparticularlayerofaregion
ofbody.
Generatedimagescanbeviewedsinglyorasacine
loop.
ItisalsoconsideredtousefulinMammography,
Chest,IVUstudies.
79

80. DIGITAL MAMMOGRAPHY
TOMOSYNTHESIS (DMT):
Itisarecentadvancedapplicationof
DM.
Inthistechnique,anareaX-ray
beaminteractswiththedigital
mammographicimagereceptor,
producingadigitalmammogram.
Thisdigitalmammogramisrepeated
severaltimesatdifferentangles.
Eachimagesisavailableindigital
form&canbereconstructedasa3D
Matrixofvalues,eachrepresentinga
Voxel.
Withthesedigitaldataavailable,a
tomographicsectioncanbe
reconstructedwithenhancedimage
contrastatacceptablepatient
radiationdose.
80

81. MOBILE /PORTABLE DR:
Nowadaysflatpaneldetectorportableradiography
isalsopossible.
ThismethodwasfirstinventedbyCanon.
TheFPDareavailablein17”X17”withacablefor
portable/mobileradiography.
AsageneralaFPDconnectedbyacabletoamobile
orportableunithavingamonitor.
TheuseofportableDRsystemhamperedbythe
fragilityoftheFPDs&thehighcosts.
AportableDRsystem,whencomparedwithanFSR
system,avoidsallproblemsrelatedtothe
availability,storage,transportation,disposedof
films&chemicals. 81

82. WIRELESS FPDs:
WiththeintroductionofthemodelPixium3543fromThales,
wirelessportableDRsystemisnowareality.
Afterexposure,itwirelesslytransferimagedatatotheDR
system.
AlternativelytheimagedatacanbetransferredtoDR
consoleviaanEthernetcable.
Ithasnocables&doesnotinterferewithsurrounding
machines.So,itiseasytohandleasaCRcassettes.
Typicallya17”X14”imagesizeismadeavailablewithin
3s.
Itisparticularlywellsuitedforusewithimmobilized
patients,inoperatingrooms,intensivecareunits,emergency
situations,androomsforexamsrequiringdifficultorunusual
X-rayprojections.
82

83. WIRELESS FPDSYSTEM:
X-Ray Generator
Power supply
Pixium Portable
Docking Station
WiFi (or back-up cable)
Pixium Portable 3543
Ethernet
Cable
Acquisition
board
Ethernet
Board
RS 232Optical Fiber
Power supply
Pixium RAD 4600
PixRad software
PC
83

84. FLUOROSCOPY:
Real–timedigitalimaginginDRispossiblewith
theinventionPixiumRF4343,fromThales.
Itfacilitateshigh-qualityradiography&
fluoroscopy(upto30images/sec.)
Thisfluoroscopyfeatureisusein
Gastroenterology,Urology& Vascular
applications.
NewerFPDslikePixium4700&Pixium4800
fromThalesareusedforVascular&
CardiovascularDSAapplicationsbypermitting
low–dosefluoroscopy.
84

85. Integris Allura Flat Dynamic
Detector for Cardio
Scintillator Photodiodearray Refresh light
85

86. IMAGE QUALITY PARAMETERS:
Pixel Size, Matrix & Detector Size.
Dynamic Range & Contrast.
Spatial Resolution.
Limiting Spatial Resolution (LSR).
Signal to Noise Ratio (SNR).
Modulation Transfer Function (MTF).
Detective Quantum Efficiency (DQE).
86

87. DYNAMIC RANGE & CONTRAST:
Contrastlevelsorfilm
densitiesgeneratedovera
rangeofx-rayexposurelevels.
Dynamicrangeisameasure
ofthesignalresponseofa
detectorthatisexposedtox-
rays.
Narrow Dynamic Range
Image Brightness
Toe Part
Shoulder
Straight
X-ray Detected
Wide Dynamic Range
Shoulder
Straight
Toe Part
X-ray Detected
Image Brightness
87

88. Film-Screen
Detector
Low Contrast
High Contrast
Cont…
88

89. LIMITING SPATIAL RESOLUTION
(LSR):
SpatialResolutionreferstotheminimumresolvable
separationbetweenhigh-contrastobjects.
InDigitalDetectors,SpatialResolutionisdefined
andlimitedbytheminimumPixelSize.
89

90. Decreasing Noise
Increasing Contrast
High SNR Low SNR
Noise
Signal
Contrast Ratio
QuantumMottle(QM):-Itisanappearanceofnoisein
theradiographicimageduetolowSNRofthe
informationreachingtheimagerecordingsystem.
SIGNAL TO NOISE RATIO (SNR):
90

91. IMPACT OF NOISE:
QuantumandElectronicnoiseareunavoidableina
digitalimagingchain.Theeffect,oftenexpressedas
Signal-to-NoiseRatio(SNR),canvarywidelyfrom
systemtosystem.
Signal Useful Image Formation
-------------= ------------------------------------
Noise Erratic (Unwanted) Information
1:1 SNR 2:1 SNR 5:1 SNR
91

92. MODULATION TRANSFER
FUNCTION (MTF).
Modulationtransferfunction(MTF)isthecapacityofthe
detectortotransferthemodulationoftheinputsignalata
givenspatialfrequencytoitsoutput.
Light Photons
Gd
2O
2S:Tb + a:Si
High Scattering
Low MTF
CsI:Tl + a:Si
Low Scattering
Good MTF
Electron
a:Se
No Scattering “Perfect”
MTF
Light Photons
X-Ray Photons:
92

93. DEECTIVE QUANTUM EFFICIENCY ( DQE):
DetectiveQuantumEfficiency(DQE)isoneofthe
fundamentalphysicalvariablesrelatedtoimage
qualityinradiography&referstotheefficiencyofa
detectorinconvergingincidentX-rayenergyintoan
imagesignal.
Itdependson:-
-RadiationExposure.
-SpatialFrequency.
-MTF.
-DetectorMaterial.
-Qualityoftheradiationapplied(Voltage&Current).
93

94. 1 Digital Radiographic Room = 2.6
Conventional Screen/Film Room !
ImagingTechnique Average Exam time
Conventional Screen Film Radiography 6:05 Minutes
Computed Radiography 7:02 Minutes
Direct Capture Radiography 2:18 Minutes
94

95. Feature  X-ray
Converter
Readout Detector
size
Pixel SizeMatrix Size
Screen FilmGd2O2S Film 14x17 Grain Size
2
………..
Storage
Phosphor
BaFBr:EuLASER 14x17 100 -200
µm
1760x2140
Slot scan
CCD
CsI:Tl CCD 17x17 162 µm 2736x2736
Direct FPDa:Se Active Se
Matrix
14x17 139 µm 2560x3072
Indirect FPD
Gd2O2S:TbActive a:Si
Matrix
17x17 160 µm 2688x2688
CsI:Tl Active a:Si
Matrix
17x17 143 µm 3121x3121
Technical Features Of Various DRSystem:
95

96. IMAGE RECEPTOR COMPARISION:
FEATURE FILM/SCREENCR (PSP) DR
RADIATION DOSE Higher Lower Lower
GENERATION OF
VISIBLE IMAGE
Chemical, Wet
Processing
Laser Scanner, ComputerComputer
IMAGE VIEWING Delayed, View box
Transillumination
Delayed, Computer
Monitor
In few seconds, Computer
Monitor
RESOLUTION 16-20 lp/mm 6-8 lp/mm 8-10 lp/mm
CONSTRUCTION Thin, Flexible Thin, Flexible Thick, Rigid & Robust
LIFE SPAN Single Use Reusable after ErasureReusable (Unlimited)
IMAGE
ENHANCEMENT
Fixed Unchangeable
Image
Multiple Operations: -
Contrast, Density,
Magnification,
Positive/Negative,
Measurement
Multiple Operations: -
Contrast, Density,
Magnification,
Positive/Negative,
Measurement
STORAGE Patient Record,
Huge Space required
Variety of Archiving
Method: -Server, Zip,
OMD, MOD, CD, DVD,
PACS
Variety of Archiving
Method: -Server, Zip, OMD,
MOD, CD, DVD, PACS
96

97. Physical Design: -
-Compatible in size with Film Cassette.
-Immediate Readout.
-Robust.
-Cost Effective.
Image Capture: -
-High Quantum efficiency.
-Low Dose.
Image Quality: -
-Spatial & Contrast Resolution as good
as Film/Screen System.
-Wide Dynamic Range.
-DICOM Compatible.
IDEAL DRSYSTEM:
97

98. CONCLUSION:
Withtheadventofcomputedradiographydiagnostic
radiologyisadvancingtowardsafilmlesssystem.
Thereplacementoffilmbydetectorsandstorage
deviceseliminatedseveralinherentdrawbacksof
conventionalradiographyanddecreasestheradiation
exposuretothepatientandradiographer.
Verysoondigitalimagingwillbecomemorecommon
andaffordableforallaspectofradiography.
WiththedevelopmentofDigitalRadiography,the
RadiographicExaminationbecomesmoreeasy,handy
andlesstimeconsumingmethodwithgoodqualityof
image. 98

99. References:-
1.http://www.google.com
2.http://www.wikipedia.com’
3.http://www.xray2000.co.uk
4.http://www.radiologyinfo.com
5.http://www.amersham,health.com
6.Indian Radiology Journal
7.American College of Radiology Journal
99

100. 100