ct imaging system prestudyWord格式.docx
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ct imaging system prestudyWord格式.docx
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gantrycomponents3.1
position3.2
projections3.4
raysums3.8
thex-raysource3.9
thex-raybeam3.13
geometricshaping3.13
spectralshaping3.16
measuringthex-rays3.17
thedetectors3.17
analog-to-digitalconversion3.18
dataintervaltiming3.20
datatransfer3.22
datapreprocessing3.26
chapter4-imagereconstruction
backprojection4.1
backprojection-agraphicalview4.6
backprojection-amathematicalview4.7
theproblemswithbackprojection4.7
conditioningtherawscandata4.14
offsetcorrection4.14
aircalibration4.16
dynamiccalibration418
dynamicreferencing4.20
spectrumcorrection4.21
detectorcorrection4.23
refanning4.24
convolution4.25
chapter-5-imagedisplay
imagestorage5.2
displayinganimage5.4
thevideomonitor5.4
thevideographicsgenerator5.7
imagemanipulation5.11
displayingattenuationcoefficients5.11
windowcontrol5.13
linearandareameasurements5.15
annotation5.16
zoom5.18
multipleviews5.19
imagearchiving5.20
hardcopy5.21
chapter6-factoraffectingimagequality
factorsaffectingspatialresolution6.1
focalspotsize6.2
samplingrate6.3
detectoraperture6.5
reconstructionfiltering6.8
pixelarraysize6.9
factorsaffectingcontrastresolution6.9
channelresolution6.10
videoresolution6.11
signal-to-noiseratio6.12
otherfactorsaffectingimagequality6.14
chapter7-control
controlcomponents7.1
software7.2
bootstrapping7.3
theoperatingsystem7.3
chapter8-patientpositioning
thecouch-verticalmotion8.1
thecouch-horizontalmotion8.2
manualpositioning8.2
indexing8.5
pilotscanmotion8.6
gantrytilt8.6
pilotscanning8.7
chapter9-iqintroduction9.1
chapter10contentsoftheiq
thegantry10.2
thepatientsupport10.9
theconsole10.11
chapter11-iqdataflow
systempowerup11.2
settingupascan11.2
scandataflow11.4
chapter12-appendicies
appendixa-motorolamicroprocessorsa1
appendixb-multibusllb1
appendixc-iqspecificationsc1
appendixd-bibliographyd1
appendixe-glossarye1
appendixf-commentsf1
hapter1-introduction
figure1.1actlmage1.3
figure1.1blocationofcrosssectionalslice1.4
figure1.2conventionalradiograph1.5
figure1.3aschematicofchest
figure1,3bradiographofschematicofchest
figure1.4typicalheadstudy1.8
figure1.5ctblockdiagram1.9
figure1.6patientpositioning1.10
hapter2-howactworks,afirstpass
figure2.1typicalctsystem2.1
figure2.2tiltedgantry2.3
figure2.3fields2.4
figure2.412lnchwaterphantom2,7
figure2.58lnchwater/contrastphantom2.8
figure2,6quarterfieldspatialresolutiophantom2.10
figure2.7slicethicknessphantom2.11
figure28patientandpixels2.12
figure2.9attenuationcoefficient2.13
figure2.10grayscale/level&
width2.15
figure2.11grayscale/lncreasedwidth2.16
hapter3-collectingdata
figure3.1rotation3.2
figure3.2gantrycomponents3.3
figure3.3position3.4
figure3.4projections3.6
figure3,5fieldsizes3.7
figure3.6raysum3.9
figure37voxel'
sviewofprojection3.10
figure3.8x-raytube3.11
figure3.9rotatinganode3.14
figure3.10geometriccollimation3.15
figure311x-raybeamfiltering3.16
chapter1-introduction
yourformaltrainingonpickercomputedtomography(ct)systemsassumesyouknowwhatact
systemdoes,andhowitdoesit,whichisexplainedandillustratedthroughoutthisdocument
the11chaptersfolowingthisintroductionexplaingenericctoperationtheexplanationis
limited,however,tothestationarydetectorconfigurationusedbypicker.chapters2thru8
explainhowascnismadeandthecriteriaforproducingagoodimage.chapters9thru11
explainbasicconceptsofpicker'
siqsystem.finally,theappendixsomeimportantadditional
information,includingaglossaryofthemanynewtermsandanindex.
whenyoufinishthisprestudyyoushouldknowhowactsystemcollectsdatafromthe
patent,reconstructsthosedataintoanimage,anddisplaystheimage,inaddition,youshould
knowwhatacomputermustdotocontrolthesystemandhowapatientispositionedto
optimizetheimage.aquizwillbegivenatthebeginningofclass,youmustpassthisquizto
attendtheremainderoftheclass.samplequestionsintheprestudy'
sappendiceswillhelp
youprepareforthequiz.
contentsofthisprestudy
thisprestudycontains10chapters:
thisiswhatyouarereaing.lnadditiontointroducingct,italsotellsyou
whatisinthisprestudyandhowtoreadit.
chapter2-howactworks,afirstpass
anoverviewofhowanimageismadeandthedefinitionsofcommonlyusedctjargon.
chapter3-collectingrawscandata
tomakeanimageofthepatientthesystemmustcollectdatafromthepatient.thisisthe
primaryfunctionofthegantryandtheprlmarytopicofthischapter
chapter4imagereconstruction,makinganimage
abriefexplanationofhowrawscandatabecomesimagedata.
howtoreadthisprestudy
thisprestudybeginswithatableofcontents,listingthestartingpageforall
headings,andatableofgraphics,listingthepageonwhichtheyarefound.
theprestudyisorganizedintochaptersandheadingsofvariuslevels.thelevelsare
notedbyboldfacedandunderlinedtype,suchas:
firstlevelheading
secondlevelheading
thirdlevelheading
fourthlevelheading
allnewterms,whenfirstused,appearinboldfacedtype.thesetermsarealsodefined
intheglossaryinchapter12.termsbeingcontrastedorcomparedareunderlined
purposeofcomputedtomography
computedtomography(ct)makescrosssectionalimagesofobjects,typicallythehuman
headorbody,figure1.1aistheimageofahumanhead,figure1.1bshowswherethecross
sectionwastaken.
scannedctheadimage
figure1.1blocationofcrosssectionalslice
ctusesx-rayabsorptiontocreatetheimageand,assuch,imagesonlywhatabsorbs
xrays.ctshowsanatomicaldetails,thelnternalstructuresoftheobjectlikethelocationof
bone,muscle,organs;
itcannotshowphysiologicalprocesses(THECHEMICALPROCESSOFlife)
butdoesdepictstructuralchangescausedbyphysiologicalmalfunctions.forexample,poor
bloodflowcanweakenoforkilltissue;
ctdoesnotdirectlyshowtheinadequate
metabolismbutdoesimagethedamagedtissue.
Aconventionalradiographicfilm(e.g.achestx-rayorthefilmofabrokenboneasshown
infigure1.2)isashadowoftheinternalstructuresofanobject,itisanegativeimage-
whitewheretheshadowiscast,blackelsewhere.tomakeaconventionalradiograph,anx-ray
tubegeneratesx-rayswhichpassthroughthepatient(seefigure1.3a,aschematicofa
chest).boneabsorbsmostofthex-rayspassingthroughittherefore,thefilmundertheribs
andspineislightlyexposedtox-raysand,whendeveloped,willbewhite(seefigure1.3b).
softtissue,suchasmuscleororgans,absorbslessofthex-rays;
thefilmunderitgets
exposedanddevelopstoshadesofgray.inotherwords,lightershadesofgrayimplymore
beyondthepatient'
sbodyisdirectlyexposedtox-rays(theypassonlythruair)and
developsblack.
scannedchestx-ray
figure1.2conventionalradiograph
unfortunately,boneabsorbssomuchofthex-raysthatfewareleftforsofttissue
absorption;
thesofttissuecannotbeseenthroughthewhiteimageofthebone.assuch
conventionalradiographssufferfromthesuperimposition(coveringup)ofinternal
structures.thissuperpositionofboneoversofttissueisparticularlytroublesomeinthe
head,whereadenselayerofprotectivebone(theskull)completelysurroundsthebrain.
ctovercomessuperpositionbyimagingacrosssectionalsliceoftheobject(again,see
figure1.1b),theslicethicknessistypically10mm,althoughsomectsystemscansliceas
thinas1mm.therefore,superpositionoccursonlyoninternalstructureslessthantheslice
thickness.
Asseeninfigure1.1a,eventheskullcannotdisturbtheimage,itisimagedonlyasawhite
perimeteraroundthebrain.notsurprising,ctwasfirstusedinneurologytoimagethebrain
althoughnowitcommonlyimagesallpartsofthebodywheninternaldetailsmustbe
distinguishedfromsurroundingtissues.
air
liver
spine
lung
patient
foraradiologisttomakeadiagnosis,severalslicesaremade.thistypicalheadstudy
consistsof8to12slices,eachhavingaslicethicknessof5mm(seefigure1.4).thepatient
isscannedonceperslice;
ascanispasssingx-raysthruthepatientandcollectingthe
data.betweenscans,thecttypicallythedistanceisequaltotheslicethickness,indexing
positionsthepatientforscanningthenextslice,thusastudycontainsimagesofthevolume
ofthepatientbetweenthefirstandlastslices
contentsofacomputedtomographysystem
figure1.5showsthemajorsectionslfactsystem,thepathofdatafrompatientthrough
thefinalimage
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