醫(yī)學影像物理學05數字X射線成像技術

DigitalX-rayImagingTechnologyDSA——Digitalsubtractionangiography數字化攝影CR——computedradiographDR——Digitalradiography(DDRandIDR)DSI——DigitalSportImagingDF——DigitalfluorographyDigitizetheX-rayimagingandadoptdigitaltechnologytodoprocessionofimage.1DigitalSubtractionAngiographyDSAInterventionaltherapyincardiologyInterventionalradiologytherapyInterventionalmedicineinneurologyvasculardiseaseDigitalsubtractionangiographyisakindofdigitalX-rayimagingtechnologyusedtoresearchvascularsystem.ByitwecansubtractunnecessaryportionfromanX-rayimageofvascular.Observethepositionofcatheterinvascular,controlthemotionofcathetertoreleasedrugordoalittleoperation(suchassettlebracketinnarrowvessels.2Whatisimagesubtraction

PixeltoPixel456787893713735059852567876935135150576520000020020022000220——==3PrincipleofDSAA:Imagewithoutcontrastagent(Mask)B:ImagewithcontrastagentC:Imageofsubtraction4物理含義TheimageafterDSisdeterminedbytheabsorptioncoefficientofcontrastagentandlength,isindependentwithboneandsofttissues.5MethodofDSATimesubtractionEnergysubtractionMixedsubtractionLocationandanchorpoint圖像配準與運動偽影6TimesubtractionConcentrationTakesuccessiveshotsSuccessivesubtract得到的是圖像序列7Energysubtraction/能量減影/雙能減影/K緣減影IodineX-ray33KeV(tubevoltage:70KVand120KV)Image(70KV,beequivalenttobackground)——Image(120KV,beequivalenttocontrastagentimage)Advantage:GoodmethodintheoryDisadvantage:DemandspecialX-raydevices(switchtubevoltageinhighspeed)；BoneandSofttissue

imagedifferentlyintwotubevoltage

8Reason在無血管情況下:通過調整系數,可以減少其中一種組織的影響.9MixedsubtractionDo2kindsofsubtractionimaginginsametime.DoThreetimesofSubtractionDothefirstenergysubtractionbeforecontrastagentinjection,thesecondafterinjection,dothelastwiththetworesult.(對比劑到達前后都做雙能減影,消除軟組織,再利用結果做時間減影,消除骨組織)10DSA缺陷的彌補:圖像配準11AdvantageofDigitalX-rayImagingTechnologyContrastresolvingpowerSmallRadiationDoseProcessionofimageConveniencestorageHighsensitvitytodetectX-rayandLowDoseHighdynamicrangePACSPowerfulfunctiontodoprocessionandanalysisButthespatialresolvingpowerisnotasgoodasX-rayphotographyinfilm.Expensive12ScanMethodinDigitalX-rayImagingTechnologycone-shapeSectorbeamDotbeam13CR:computedradiography影像板取代膠片ReplaceX-rayfilmwithIP(Imageplate).激光掃描激發(fā)讀出圖像EquipcomputertocontrolaLaser(lightamplificationbystimulatedemissionofradiation)scansystem,whichcanreadtheimagefromIP數字化成像的優(yōu)點14IP-ImageplateXtubeBodyImageplateProtectionlayerPSLlayerSupportinglayerBackProtectionlayerWhentheX-raysabsorbbyIP,theatomsinphotostimulatedluminescencesubstance(PSLlayer)willchangeitsenergylevelsinsemistabilitystate.Thelatentimagecomesintobeing.IftheseatomsisexcitedbyLaser,visuallightwillemitted,Imageisformed.15PrincipleofIP光致發(fā)光現象：光照->能量儲存->二次激發(fā)光->熒光發(fā)出一般PSL物質熒光非常弱，選擇參銪離子的氟溴化鋇在比較寬的范圍內，X射線照射量與PSL物質二次激發(fā)熒光光強成線性關系激發(fā)波長與發(fā)射波長excitationspectrum600nm(helium-neonlaser)Emissionspectrum390-400nm，易于區(qū)分，信噪比高16ThestructureofCRsystemX-rayTubeBodySSP/IPLaserScansystemComputerImageProcessionDigital-AnalogConversionMemorizer/StorePhotographsystemImageScreenCentercomputer17Readingoutdevices18CharacterofIP讀出速度：0.8us，高掃描速度Effectiveperiod8hourDynamicrangedirectproportionalRepeatable19AdvantagesofCR與膠片攝影相比擬的成像質量暴光量少，劑量低，寬容度大數字成像的優(yōu)點操作相對簡潔方便缺點：動態(tài)不足，價格昂貴，過度產品2021DigitalizedRadiographyIDROnthebaseofX-rayTVX-rayScanner掃描放射成像DDRDirectlyimagingbyX-raydetectorarrayDRD與FPD22ThestructureofIDRX-rayTubeBodyImageIntensifierOpticsystemMemorizer/StoreDisplayVideoCameraA/D(analogtodigital)conversionComputerprocession23ThestructureofDDRX-rayTubeBodyX-raydetectorarrayComputerImageProcessionMemorizer/StoreImageDisplayNetwork24X-raydetectorarray(FPD)非晶態(tài)硒平板探測器（直接X射線攝影探測器）非晶態(tài)硅平板探測器（間接平板探測器）氣體（多絲正比）電離室/低劑量X射線探測器(LDRD)CCD:ChargeCoupleDevice25非晶態(tài)硒型平板探測器（直接X射線攝影探測器）組成：X射線轉換單元(Se)探測器陣列單元(TFT)高速信號處理單元數字影像傳輸單元26TFT(thinfilmtransistor)WhenX-rayphotonenterSe-layer,cavity-electronpairsgenerate,underKVvoltage,positivechargeandnegativechargeappearonbothsidesoflayer,thecapacitorischargedup,dischargethecapacitorbyaFET,measurethecurrent,canknowthequantityofelectriccharge,socanknowtheintensityofX-raybeamSe，硒（非晶硒），一種光電材料。FET，場效應晶體管27TFTArray用薄膜晶體管技術在一玻璃基質上組裝幾百萬個探測元陣列，每個探測元包括一個電容和一個FET，對應于一個圖像像素。像素排成二維陣列，按行設門控線，按列設圖像信號輸出線。按行同時讀出。高速DSP控制，讀出后信號放大經A/D轉換。28非晶態(tài)硅型平板探測器（間接平板探測器）ScintillatingCrystal:常采用CsI（銫）閃爍體。閃爍體是一種吸收X射線并把能量轉換為可見光的化合物。銫，高原子序數，對X射線良好的吸收。CsI摻雜質晶體，發(fā)射光譜550nm，是非晶光譜靈敏度峰值，匹配性能好。2930IFPDArrayCsI晶體成管狀，厚度約1mm，保持良好的分辨率。光電二極管在外部反向電壓作用下，此處相當于TFT中的電容。31電子暗盒32CCD型Mos電容器，當光線進入，形成電子—空穴對在外電場作用下，電子和空穴向電極兩端移動，產生光生電荷，存儲在電極下方的勢阱中33ApplicationDF，DSA