X線攝影條件

exposurefactorX線攝影條件(exposurefactor)攝影電壓：KV(仟伏）(PhotographicVoltage)攝影電流：mA（毫安）(PhotographicCurrent)攝影時間：S（秒）(Photographictime)距離：FFD（厘米）(Distances)

要獲得一張優(yōu)質(zhì)的X線照片，除擺好正確的攝影位置，還需要掌握好X線攝影條件，照片受X線管焦點、被照體、影像轉(zhuǎn)換介質(zhì)、照片沖洗、激光照相機等多種因素的影響Toobtainahigh-qualityX-rayphotographs,inadditiontogracefullycorrectshootingposition,youalsoneedthepalmgoodgripX-rayphotographicconditions,photographsbyX-raytubefocus,thebody,theimagetransfermedium,photoprinting,lasercamerasandotherfactors感光效應Vn．i．t．s．f．zE=k

d.Z.ρ.r2

V：管電壓，i：管電流，t：攝影時間，s：增感率，f：感光度，z：靶物質(zhì)原子序數(shù)，d：被照體的厚度，Z：被照體的有效原子序數(shù)，ρ：被照體的密度，r：攝影距離，k：常數(shù)PhotographiceffectsVn．i．t．s．f．zE=k

d.Z.ρ.r2

V:tubevoltage,i:tubecurrent,t:photographytime,s:sensitizationrate,f:sensitivity,z:atomictargetsubstanceordinal,d:thicknessoftheilluminatedbody,Z:accordingtothebodyoftheeffectiveatomicnumber,ρ:densityoftheilluminatedbody,r:shootingdistance,k:constant1．管電壓管電壓(tubevoltage)是影響照片密度值、對比度、層次及信息量多少的重要因素。管電壓的作用主要有二個方面：①在X線攝影中，管電壓代表著X線的穿透能力，高的管電壓可以穿透更厚和更高密度的結(jié)構(gòu)；②管電壓代表X線光子的能量，管電壓越高，感光量越多。1.TubevoltageThetubevoltage(tubevoltage)thataffectthephotodensityvalues,Contrast,thelevelandamountofinformationthatmanyimportantfactors.Thetubevoltageappliedmainlytwoaspects:①IntheX-rayphotography,representingtheX-raytubevoltageofwearthroughcapacity,hightubevoltagecanpenetratethickerandhigherdensitystructure;②X-raytubevoltagerepresentativeofthephotonenergy,thehighertubevoltage,themoreamountoflight.VariouspartsofthebodyselectedreferencetubevoltagevaluetubevoltagePhotographypartsBreastThyroidFourlimbsshoulderJointCervicalvertebraMastoidChest(Bedside)SkullThoracicLumbarAbdomenChestcardiacandlargevessel2．管電流量管電流量代表X線量的多少，因而管電流量的大小直接影響探測器感光量的多少。管電流量增加探測器感光量增加，影像的量子斑點減少。但是對于屏-片組合而言，管電流量過高會使照片黑化度（光學密度）太大，組織結(jié)構(gòu)不易觀察。2.TubecurrentamountThetubecurrentamountrepresentstheamountofX-rays,andthusthethesizeoftubecurrentdirectlyaffectsthetheamountofthephotosensitivedetector.Whentheamountofcurrentdetectortubeincreases,theamountoflightincreasestoo,butthenumberofquantumdotdecreases.Butforscreen-filmportfolio,theoverhighamountofcurrentisleadtolargephotoblacktubedegree(Opticaldensity),anditisdifficulttoobservetheorganizationalstructure.3．攝影距離焦點至探測器的距離稱為攝影距離，或稱源像距（source-imagedistance,SID）焦點至膠片的距離，簡稱為焦-片距（focus-filmdistance；FFD）。在感光量計算公式中SID就是r。在攝影的有效范圍內(nèi)，探測器上得到的感光量與SID的平方成反比。3.PhotographyDistanceThedistancefromfocustodetectoriscalledphotographydistance,orthesource-imagedistance(source-imagedistance,SID)Thedistancefromfocustofilm,iscalledfocus-filmdistance(Focus-filmdistance;FFD).IntheamountoflightSIDistheformulaforcalculatingr.Intheeffectiverangeofphotography,theamountoflightonthedetectorisinverselyproportionaltoSIDsquare.4．成像探測器（1）屏-片組合（2）影像增強器-電視系統(tǒng)（3）成像板（4）平板探測器4.Imagingdetector(1)screen-filmportfolio(2)imageintensifier-televisionsystem(3)theimagingplate(4)flatpaneldetector（1）屏-片組合1）膠片（?。┓N類①一般攝影用X線膠片②多幅相機和激光打印機成像膠片結(jié)構(gòu)（ⅱ）結(jié)構(gòu)：主要由感光乳劑層、片基、保護層和底層構(gòu)成。（ⅲ）感光特性：感光材料中直接決定和影響影像質(zhì)量的因素統(tǒng)稱為照相性能。包括：感光性能、物理性能、成像性能(1)screen-filmportfolio.1)Film.(Ⅰ)category.①generalphotographywithX-rayfilm.②multiplecamerasandlaserprinterimagingfilmstructure.(Ⅱ)Structure:Mainlycomposedbyaphotosensitiveemulsionlayer,afilmbase,aprotectivelayerandabottom..(Ⅲ)PhotographicFeatures:photosensitivematerialdirectlydetermineandshadowfactorsthataffecttheimagequalityreferredtoasphotographicproperties.Including:photographicproperties,physicalproperties,imagingperformance2）增感屏增感屏(intensifyingscreen)是X線攝影的重要器材之一。在X線攝影中，利用X線激發(fā)增感屏的熒光體所產(chǎn)生的熒光對膠片增加感光作用，大大減少X線曝光量。（?。┓N類：增感屏的種類根據(jù)其構(gòu)成及用途分成三大類：①鎢酸鈣屏②稀土增感屏③特殊增感屏2)IntensifyingscreenIntensifyingscreenisoneoftheimportantequipmentinX-rayphotography.IntheX-rayphotography,theuseofX-rayexcitationphosphorintensifyingscreentorubberfluorescencegeneratedphotosensitivesheetincreaseseffect,greatlyreducingX-rayexposure.(Ⅰ)Type:thetypeofintensifyingscreenaccordingtoitscompositionandusesdividedintothreecategories:①calciumtungstatescreens②earthintensifyingscreen③specialintensifyingscreen（ⅱ）增感屏結(jié)構(gòu)：主要有四層組成：①基層②熒光體層③保護層④反射層或吸收層（ⅲ）性能：增感屏的性能有二個方面：①增感率②對影像效果的影響(Ⅱ)intensifyingscreensstructure:Therearefourmaincomponents:①grassroots②phosphorlayer③protectivelayer④reflectororabsorberlayer(Ⅲ)Performance:Theperformanceoftheintensifyingscreenhastwoaspects:①sensitizationrate②effectontheimage暗盒背面觀Tubeside

病人Screen–filmcombination膠片沖洗機照片X線管X-raytubepatientFilmProcessorPhoto3）屏-片組合屏-片組合成像性能的優(yōu)劣表現(xiàn)在X線照片影像與輸入的X線信息影像的差別上，差別越小，屏-片組合的信息傳遞功能就越好。屏-片組合的信息傳遞功能通過MTF的測定來客觀評價。3)Screen-filmportfolioScreen-filmportfolioperformanceimagingperformancemeritsaccordingtotheX-rayfilmX-rayimagesandtheinputinformationonthedifferenceimage,thesmallerdifferencesinscreen-filmportfoliothebettermessagingfeaturepossibility.Screen-slicethroughacombinationofmessagingfeaturesMTFmeasurementtoobjectivelyevaluate.（2）影像增強器-電視系統(tǒng)影像增強器-電視（II-TV）攝像機系統(tǒng)中，增強器將X線轉(zhuǎn)換成可見光，并將其強度增強放大數(shù)千倍，再用TV攝像機內(nèi)轉(zhuǎn)換為電子信號，影像用陰極射線管（CRT）顯示?，F(xiàn)代的系統(tǒng)已將輸出信號數(shù)字化，影像可用陰極射線管或液晶屏顯示。(2)imageintensifier-televisionsystemIntheimageintensifier-television(II-TV)CameraSystemtheX-rayintensifierconvertedintovisiblelight,anditsintensityamplifiedthousandsoftimes,andthenintheTVcameramachineconvertedtoelectronicsignals,imagesaredisplayedbyacathoderaytube(CRT).Modernsystemsmaketheoutputsignaldigitized,theimagecanbedisplayedbyacathoderaytubeorliquidcrystalscreen.Imageintensifierandmonitor(CRT)FocuselectrodePhotocathodeAnodeIncidentonthephosphorscreenIncidentplanesubstrateX-rayIncidentsurfaceFocusPowerFluorescentimageOpticalimageCathodepowersupply影像增強器（imageintensifier）數(shù)字遙控透視DigitalremoteperspectiveWhat’sthis?（3）成像板1）成像板結(jié)構(gòu)①表面保護層②PSL物質(zhì)層③基板④背面保護層2）特性：IP主要結(jié)構(gòu)是熒光物質(zhì)層，它對放射線、紫外線的敏感度遠高于普通X線膠片。(3)theimagingplate1)Imagingplatestructure①surfaceprotectivelayer②PSLmateriallayer③substrate④backoftheprotectivelayer2)Features:IPmainstructureisafluorescentmateriallayer,whichtoradiation,ultravioletsensitivityismuchhigherthannormalX-rayfilm.保護層支持層成像層背襯層氟鹵化鋇ProtectivelayerSupportinglayerImaginglayerBackinglayerHalogenatedbariumfluoride激光源強度控制線束偏導裝置線束成型光學裝置傳輸環(huán)節(jié)集光器光學濾波器光電探測器模擬電子器件模數(shù)轉(zhuǎn)化器圖像緩沖器IP具有以下特性：（?。┌l(fā)射與激發(fā)光譜（ⅱ）時間響應特征（ⅲ）動態(tài)范圍（ⅳ）存儲信息的消退（ⅴ）天然輻射的影響IPhasthefollowingfeatures:(Ⅰ)emissionandexcitationspectra(Ⅱ)timeresponsecharacteristics(Ⅲ)DynamicRange(Ⅳ)Storinginformationregression(Ⅴ)Effectofnaturalradiation（4）平板探測器1）直接型平板探測器（?。┙M成：主要由導電層、電介層、Se(硒)層、頂層電極、集電矩陣層、玻璃襯底、保護層，以及高壓電源和輸入輸出電路組成。頂電極a-Se轉(zhuǎn)換層TFT陣列(4)flatpaneldetector1)Direct-typeflatpaneldetector(Ⅰ)components:mainlycomposedbyconductivelayer,adielectriclayer,Se(selenium)layer,thetopelectrode,acollectormatrixlayer,aglassSubstrate,aprotectivelayer,andahighvoltagepowersupplyandinputandoutputcircuit.Topelectrodea-SeconversionlayerTFTarray（ⅱ）特性：①直接光電轉(zhuǎn)換②直接讀出X線曝光過程中的電荷分布③量子檢測效率（DQE）④曝光寬容度大⑤X線敏感度和響應特性⑥空間分辨力⑦調(diào)制傳遞函數(shù)（MTF）(Ⅱ)Features:①directphotoelectricconversion②directlyreadouttheX-rayexposureprocessoftheelectricalchargedistribution③detectivequantumefficiency(DQE)④exposurelatitude⑤Xlinesensitivityandresponsecharacteristics⑥spatialresolution⑦modulationtransferfunction(MTF)2）間接型FPD：是一種以a-Si（非晶硅）光電二極管陣列為核心的X線影像間接型FPD。（?。┗窘M成：a-SiFPD基本組成是由CsI閃爍體（cesiumiodidescintillator）層、a-Si光電二極管陣列、行驅(qū)動電路、列讀取電路以及圖像信號讀取電路等部分構(gòu)成。2)IndirectFPD:isakindofa-Si(amorphoussilicon)PhotodiodewiththecoreofX-rayimagesindirectFPD.(Ⅰ)basiccomponents:a-SiFPDbasiccompositionisCsI??scintillator(cesiumiodidescintillator)layer,a-Siphotodiodearray,thelinedrivercircuit,column,readcircuitaswellasotherpartsoftheimagesignalreadcircuit.閃爍體非晶硅傳感器讀出電路外殼驅(qū)動電路DrivecircuitShellAmorphoussiliconsensorReadoutcircuitScintillator（ⅱ）性能參數(shù)：①調(diào)制傳遞函數(shù)（MTF）較高。②FPD的噪聲主要來源于X線量子噪聲、探測器電子學噪聲。在普通條件下，電子學噪聲要遠小于量子噪聲。③量子檢測效率（DQE）也較高。④其他品質(zhì)因素，有靈敏度、線性、記憶效應、探測器圖像獲取時間、探測器的溫度穩(wěn)定性（stability）等。(Ⅱ)Performanceparameters:①modulationtransferfunction(MTF)ishigher.②FPDnoisecomesmainlyfromtheX-rayquantumnoise,detectorelectronicnoise.Innormalconditions,detectorelectronicnoiseisfarlessthanthequantumnoise.③detectivequantumefficiency(DQE)ishigher.④otherqualityfactors,thereissensitivity,linearity,memoryeffect,theprobeimageacquisitiontime,thedetectortemperaturestability(stability)andsoon.3）電離型探測器：電離型DR系統(tǒng)的成像探測器為線狀結(jié)構(gòu)，采用動態(tài)線掃描技術(shù)直接接收X射線光子。有兩種形式：①多絲正比室②電離室3)Ionizationdetector:IonizingimagingdetectortypeDRsystemislinearjunctionstructure,theuseofdynamiclinescantechnologytodirectlyreceiveX-Rayphoton.Therearetwoforms:①multi-wireproportionalchamber②ionizationchamber碘化銫/非晶硅與非晶硒的比較電荷收集電極E-----++TOP電極絕緣層Selenlum硒X線半導體電子阻斷層偏壓電場

讀出電路

+_X-Ray光子碘化銫閃爍體(CsI)可見光不定型硅陣列電信號數(shù)字信號讀出電路X-Ray光子數(shù)字信號Cesiumiodide/amorphoussiliconandamorphousseleniumcomparisonChargecollectionelectrodesE-----++TOPelectrodeInsulatinglayerSelenlum硒X-raysemiconductorElectronblockinglayerBiaselectricfieldReadoutcircuit

+_X-RayphotonsCesiumiodidescintillator(CsI)VisiblelightAmorphoussiliconarraysElectricsignalDigitalsignalReadoutcircuit

X-RayphotonsDigitalsignal碘化銫/非晶硅與非晶硒的比較

Cesiumiodide/amorphoussiliconandamorphousseleniumcomparison間接（碘化銫）轉(zhuǎn)換方式Indirect(CsI)conversion高純度非晶硒絕緣片HV直接轉(zhuǎn)換（非結(jié)晶硒）方式Directconversion(non-crystallineselenium)mode+-a-SiPhotoDiodeCsILightIncidentX-raysOutput碘化銫

非晶硅光電二極管可見光碘化銫/非晶硅與非晶硒的比較非晶態(tài)硒CR傳統(tǒng)膠片非晶態(tài)硅(143微米)碘化銫/非晶硅與非晶硒的比較量子捕獲效率高（DQE）刷新速度快照射劑量低應用設備廣泛（DR，DSA等）平板生產(chǎn)商

GE（整板）

TRIXELL（四塊拼接）設備生產(chǎn)商

GE，SIEMENS，PHILIPS……量子捕獲效率較低（DQE）刷新速度慢照射劑量高在DR上應用平板生產(chǎn)商

HOLOGIC設備生產(chǎn)商

KODAK，友通Cesiumiodide/amorphoussiliconandamorphousseleniumcomparisonHighquantumcaptureefficiency（DQE）HignrefreshspeedLowdoseApplicationequipmentiswide（DR，DSA

edc）Theflat-panelmanufacturers

GE（fullboard）

TRIXELL（fourstitching）Theequipmentmanufacturer

GE，SIEMENS，PHILIPS……Lowquantumcaptureefficiency（DQE）LowrefreshspeedHighdoseIntheapplicationofDRTheflat-panelmanufacturers

HOLOGICTheequipmentmanufacturer

KODAK，DFI5．濾線柵X線攝影時，被照體產(chǎn)生散射線，使照片影像上形成灰霧（fog），使影像的對比度減小，減少散射線到達膠片最有效的方法是利用濾線柵(grid)。一般認為肢體厚度超過10cm就應用濾線柵。濾線柵不僅吸收了散射線，而且還吸收掉一部分原發(fā)X線。因此，在制定攝影條件時，必須考慮到濾線柵的曝光系數(shù)B5.GridsX-rayphotography,thescatteredradiationproducedaccordingtothebody,makephotoImageformingfog(fog),sothattheimagecontrastdegreeofreduction,reducingthescatteredradiationreachingthefilmthemosteffective.Methodistheuseofgrids(grid).Generallybelievedlimbthickerthan10cmontheapplicationofgrids.Gridsnotonlyabsorbedthescatteredradiation,butalsoabsorboutpartoftheprimaryX-ray.Therefore,informulatingphotographingpiecesmustbetakenintoaccountgridsexposurefactorBFocusX-raytubeTheprimaryX-rayThespecimenScatteredradiationpassthroughX-rayOrganicintermediatefillerParallelFocusGridsstructure散射線原發(fā)射線Originalemissionlines濾線柵的作用散射線Scatteredradiation照片密度大

照片密度小高柵比低柵比tightloose6.照射野通過X線管窗口的X線束(X-raybean)入射于被照體的曝光面的大小稱為照射野（radiationfield）。照射野的大小，與X線照片的對比度、影像密度都有很重要的關(guān)系。6RadiationfieldSizeofexposureinthesurfaceofthebodycausedbyX-raybeanwhichpassthroughX-raytubewindowcalledirradiationfield(radiationfield).Thesizeoftheradiationfield,hasimportantrelashionshipwiththeX-rayphotographandimagedensity.據(jù)研究照射野在100cm2～200cm2以上時，散射線(scatteredradiation)含有率急劇增加。照射野在600cm2～700cm2時，散射線含有率趨于飽和。X線攝影時，應將X線的照射野的大小減少到能包含被照部位最小程度，以起到對患者和工作人員的輻射防護(radiationprotection)作用及提高照片的清晰度。Accordingtostudytheradiationfieldin100cm2~200cm2ormore,scatteredradiation(scatteredradiation)contenturgentincreasesharply.Radiationfieldin600cm2~700cm2,thebulkraycontentsaturated.WhenX-rayphotography,X-rayradiationfieldshouldreducetothesizeoftheleastpartthatilluminatedportioncancontaintoplayforpatientsandstaffradiationprotection(radiationprotection)foruseandenhanceyourphotos.照射野和膠片大小相同照射野大于膠片散射線7．其他因素當使用傳統(tǒng)的屏-片組合進行攝影時，膠片處理條件影響著照片的密度值，顯影液就是影響感光效應的重要因素。顯影液的性能取決于顯影液的配方、pH值、顯影時間和顯影溫度。一般講，顯影液濃度高、pH值高、溫度高相對感度高。在激光打印技術(shù)中，照片的密度與照射激光的強度有正相關(guān)關(guān)系。7.OtherfactorsWhenusingconventionalscreen-filmportfoliophotography,plasticwaferprocessingconditionsaffectthedensityofthepicture,thedevelopingliquidisanimportantfactoraffectingthephotosensitiveeffect.Developmentperformancedependsonthedeveloperliquidformulations,pH,developmenttimeanddevelopmenttemperature.Generallyspeaking,thedeveloperconcentration,pHvalue,temperatureandhighrelativesensitivity.Inlaserprintingtechnology,thepicturedensityandirradiationintensityofthelaserhasapositivecorrelation.X線影像的形成X線成像的途徑X線對比度光學密度光學對比度X-rayimageformationX-rayimagingapproachXlinecontrastTheopticaldensityOpticalContrastX線成像的途徑X線被照體X線對比度增強器、熒光屏、熒光板顯定影照片觀片燈

IP影像板（或平板探測器）光學對比度人眼人腦加以判斷X-rayimagingapproachX-ray

body

X-raycontrast

booster、screen、board

fuser

photo

light

IP

board（flatpaneldetector）Opticalcontrast

eyes

DeterminebythebrainX線X線對比度1.X線對比度KXX線穿過被照體兩部分產(chǎn)生不同線量之比

II0KX=I′II′X-raycontrast1.X-raycontrastKXTheratiooftheX-raypassthroughtwodifferentparts

II0KX=I′II′X-raycontrast

X線對比度2.四種狀態(tài)下產(chǎn)生的X線對比度⑴.被照體的衰減系數(shù)和厚度均不同

II0e－μdKX===eμ′d

′－μdI′I0e－μ′d′⑵.被照體的衰減系數(shù)相同,厚度不同

II0e－μdKX===eμ(d

′－d)I′I0e－μd′2.FourstatesarisingundertheX-raycontrast⑴.attenuationcoefficientandthicknessaredifferent

II0e－μdKX===eμ′d

′－μdI′I0e－μ′d′⑵.sameattenuationcoefficientdifferentthickness

II0e－μdKX===eμ(d

′－d)I′I0e－μd′⑶.被照體的衰減系數(shù)不同,厚度相同

II0e－μdKX===ed(μ

′－μ)I′I0e－μ′d⑷被照體內(nèi)部含有不同衰減系數(shù)的物質(zhì)

II0e－μdKX===ed

′(μ′－μ)I′I0e－μ(d－d′)－μ′d′⑶.Different

attenuationcoefficientsamethickness

II0e－μdKX===ed(μ

′－μ)I′I0e－μ′d⑷containsubstancewithDifferentattenuationcoefficient

II0e－μdKX===ed

′(μ′－μ)I′I0e－μ(d－d′)－μ′d′三、對比度指數(shù)1.μ值的大小

μ值的大小與物質(zhì)的成分有關(guān)

μ=bZ4λ3

骨骼:μb=2.09λ3+0.342

肌肉:μm=2.2λ3+0.18

脂肪:μf=1.692λ3+0.1692

空氣:μa=0.00338λ3+0.000234Third、thecontrastindex1.μ

size

sizeofμhasrelationshipof

compositionoftherelevantmaterial

μ=bZ4λ3bones:μb=2.09λ3+0.342mucles:μm=2.2λ3+0.18fatty:μf=1.692λ3+0.1692air:μa=0.00338λ3+0.000234Contrastindexandtubevoltagerelationship

對比度指數(shù)與管電壓的關(guān)系2.對比度指數(shù)

X線攝影中常見

KX=ed

′(μ′－μ)

μ′－μ為被照體內(nèi)的衰減系數(shù)之差叫對比度指數(shù)。隨電壓升高，對比度指數(shù)下降2.Contrastindex

commoninX-rayphotography

KX=ed

′(μ′－μ)

μ′－μistheattenuationcoefficientoftheilluminatedbodycalledthedifferencecontrastindex.Withthevoltageincreases,thecontrastindexdeclines四、X線對比度觀察法1.透視法①.X線被照體熒光板影像

(淺淡、須在暗房)②.X線被照體倍增管監(jiān)視器影像(明亮)

Four、X-raycontrastobservation1.Perspective①.X-ray

body

board

image

(lightshouldbeinthedark)②.X-ray

body

tube

Supervise

image

(bright)2.攝影法①.直接攝影法

X線熒光物質(zhì)照片②.間接攝影法

X線倍增管光學成像系統(tǒng)照片(35、70、100mm）2.PhotographyFrance①.DirectphotographicmethodX-ray

fluorescencesubstance

photos②.IndirectphotographicmethodX-ray

tubeopticalimagingsystem

photos(35、70、100mm）五、影響X線對比度的因素1.被照體的原子序數(shù)Z2.被照體的密度ρ3.X線的波長λ4.被照體的厚度d5.散射效應Fifth、thefactorsthataffecttheX-raycontrast1AccordingtothebodyoftheatomicnumberZ2Beaccordingtothedensityρ3X-linewavelengthλ4Accordingtothebodythicknessd5Scatteringeffect光學密度透光率阻光率光學密度OpticalDensityTransmittanceLightratioOpticalDensity一、透光率透過光與入射光之比，表示物體的透光程度

入射光

I透過光

T=I0I0IFirst、thetransmittanceTheratiooftheincidentandtransmittedlight,whichmeanstheobjectlightdegree

IIncidenttransmitted

T=I0

I0I二、阻光率入射光與透光之比，表示物體的吸光能力

I01O==IT

當O接近1時，即I≈I0，表示物體的吸收光的能力很小，對于照片來說，此處顯得幾乎為透明，則所接受的X線曝光量就越小Second、thelight-blockingratioTheratioofthetransmittedandincidentlight，whichrepresenttheabilityoflightabsorption

I01O==ITWhenOiscloseto1,I≈I0，meanstheabilityoflightabsorptionislow，tophotos,thispartisalmosttransparent，thenthereceivedX-rayexposureissmall三、光學密度1.光學密度D

光學密度D是阻光率的對數(shù)

D=lgO

特點:

①.O=I0/I是阻光率，是一個不變的比值，D不隨入射光的變化而變化②.D是無量綱的Third、theopticaldensity1.OpticaldensityDOpticaldensityDisthelogarithmofthelight-blockingrate

D=lgOFeatures:①.O=I0/Iisthelight-blockingratioisaconstantratio,Ddoesnotchangewiththeincidentlight②.D

isdimensionless2.密度、黑化度光學密度又稱黑化度、簡稱密度∑D=D1+D2+D3+……+Dn照片密度=片基本底灰度+兩面藥膜密度3.光學密度的測量

直射密度D"①.透射式密度計漫射密度D#

2.Density,degreeofblackeningOpticaldensityisalsoknownasblackdegree,referredtoasdensity∑D=D1+D2+D3+……+DnThephotoDensity=gray+sidesofthebottompieceofbasicmembranedensity3.Opticaldensitymeasurement

DirectdensityD"①.Transmissiondensitymeter

DiffusedensityD#D"Q=D#

Q是Callier系數(shù),與照片的銀粒子大小有關(guān)，極小時為1，否則都大于1測量直徑：1～3mm（光電式）D"Q=D#QisCalliercoefficient,whichrefertothesizeofthesilverparticlesinthephotos,extremelysmallas1orgreaterthan1Measuringdiameter：1～3mm（photoelectric）②.顯微密度計帶微機處理，打印系統(tǒng)

測量直徑：

5～200μm應用：屏膠系統(tǒng)調(diào)制傳遞函數(shù)MTF(modulationtransferfunction)的測試焦點的MTF的測試照片的顆粒度(graininess)MRS的測試觀測者操作特性曲線ROC的曲線②.MicroscopicdensitymeterWithcomputerprocessing,theprintingsystemMeasuringdiameter:5~200μmApplication:TestofscreendispensingsystemmodulationtransferfunctionMTF(modulationtransferfunction).FocusMTFtestThephotooftheparticlesize(graininess)MRStestObserveroperatingcharacteristiccurveROCcurve光學對比度光學對比度影響光學對比度的因素Opticalcontrast

OpticalcontrastFactorsaffectingopticalcontrast一、光學對比度1.光學對比度K

照片上相鄰兩處的密度值之差稱為光學對比度

K=D1－D2I0I0I2

=lg－lg=lgI1I2I1

First、theopticalcontrast1.KopticalcontrastThephotoonthedensityvalueofthetwoadjacentdifferenceiscalledopticalcontrast

K=D1－D2I0I0I2

=lg－lg=lgI1I2I1

2.照片上的光學對比度(opticalcontrastinphotos)

D1－D2ν=lgI2－lg

I1

K=D1－D2I1=νlgI2

=lgKX

=ν（μ2d2－μ1d1）

Formationofopticalcontrast

光學對比度的形成

Opticalcontrastonfilm

膠片上的光學對比度二、影響光學對比度的因素1.膠片反差系數(shù)ν值的影響

ν值大，照片對比度好

ν值小，照片對比度差

應用：腹部用ν值大的膠片胸部用ν值小的膠片

Second、thefactorsthataffecttheopticalcontrast1FilmgammavalueofνΝvalueislarge,goodcontrastphotosΝvalueissmall,poorcontrastphotoApplication:AbdominalfilmwithalargevalueνThechestfilmwithasmallvalueνDifferentgammacontrasteffectsonthephotofilm

不同反差系數(shù)膠片對照片對比度的影響2.線質(zhì)的影響低KV時，照片對比度好高KV時，照片對比度差高KV,ν值小膠片特性曲線在直線部分低KV,ν值大膠片特性曲線在肩部或趾部

為了獲得良好的對比度，可采用不同管電壓進行攝影

軟組織攝影：25～35KVp

普通攝影：40～100KVp

高仟伏攝影：100KVp以上2LinequalitativeimpactLowKV,thephotogoodcontrastHighKV,picturespoorcontrastHighKV,νissmallpartofthefilmcharacteristiccurveinastraightlineLowKV,νislargerfilmcharacteristiccurveintheshoulderortoeInordertoobtaingoodcontrast,canbephotographedindifferenttubevoltageSofttissuePhotography:25~35KVpGeneralphotography:40~100KVpHighkVPhotography:100KVpmoreDifferentlinequalitativeimpactonthefilmcontrast

不同線質(zhì)對膠片對比度的影響3.線量的影響

mAS對X線照片對比度沒有直接的影響，但線量增加了，使低密度區(qū)增高，影像密度值在特性曲線的直線部分，使這部分影像可以辨認3TheamountoflineMAScontrasthavenodirectlyeffecttotheX-rayphotographs,butthelinecapacityincreased,thedensityareaincreased,theimagedensityvalues??ofthecharacteristiccurveSsraightsection,sothatyoucanidentifywhichpartoftheimageEffectsofradiationqualityinvariantlineamounttocontrastratio

線質(zhì)不變線量對

對比度的影響4.灰霧的影響Fogeffects片基灰霧Filmbasefog乳劑灰霧引起照片對比度下降Emulsionfogcausedcontrastdegradation散射灰霧Scatteringfog優(yōu)質(zhì)X線照片影像銳利度影像分辨率優(yōu)質(zhì)X線照片的條件High-qualityX-rayphotographImagesharpnessImageresolutionHigh-qualityX-rayphotographoftheconditions一、影像銳利度表示閱片時的難易程度，照片上指相鄰兩個器官組織影像清楚的程度

KS=HS是一個模糊數(shù)學概念，與對比度K成正比，與模糊值H成反比，是衡量照片質(zhì)量的一個模糊概念First、theimagesharpnessExpressesthedegreeofdifficultyreadingfilms,photographsontheadjacentfingertwoimagesclearlytheextentoforganandtissue

KS=HSisafuzzyconcept,withapositivecontrastKandinverselyproportionalwiththefuzzyvalueH,isafuzzymeasureofpicturequalityImagesharpness

影像銳利度二、影像分辨率當半影H=2d時，照片對比度為0，影像消失，這時R=1/2d，稱為極限分辨率多個成像單元組成的成像系統(tǒng)的影像分辨率

1R=1111+++……+R1R2R3RnSecond、theimageresolutionWhenH=2dpenumbra,thepicturecontrastis0,theimageeliminationmissing,thenR=1/2d,calledlimitingresolutionApluralityofimageformingunitsoftheimageoftheimagingsystemresolution

1R=1111+++……+R1R2R3RnImageresolution

影像分辨率例：用1.0mm焦點的X線管，10cm的肢－片距，焦－片距FFD為110cm的條件攝影時，焦點所產(chǎn)生的半影為：

10H=F×=0.1(mm)