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1、ComponentsofImageQuality&RadiographicArtifactsRadiologicTechnologyASpring2010nX-rayExposureFactorsnRadiographicDensity&ContrastnComponentsofImageQualitynRadiographicArtifactsReviewChapter7nPrimaryradiationexitsthetubenInteractswithvariousdensitiesinthebodynPhotonsmaybeabsorbednSca
2、tterednPassedthroughwithoutanyinterferencetothecassetteorimagereceptor(IR)HowwellwecanseesomethingontheimageImagedetailisaffectedby:PhotographicpropertiesandGeometricpropertiesPhotographicProperties–__________–__________X-rayExposureFactorsnTECHNIQUESELECTION:nRadiographerselectst
3、henKilovoltagepeak(kVp)nMilliamperage(mA)&time(s)nMilliamperagextime=mAs(milliamperagemultipliedbyasettimemeasuredinseconds)KilovoltagePeaknkVpnOnekilovolt=1000voltsnTheamountof________selectedforthex-raytube.nRange30to150kVpnkVpcontrols__________?MilliamperagenOnemilliampere(mA)=
4、onethousandthofanampere.nTheamountof____________suppliedtothex-raytubenHow______________x-rayswillbeproducednRange10to1200mATimenInsecondsnHowlongx-rayswillbeproducedn0.001to6secondsMilliampereSecondsnTechnologiststhinkintermsofmAsnCalculatedbymAxsecondsnEx:100mAX0.2s=20mAsnHowman
5、yx-rayswillbeproducedandforhowlong.nModernx-raymachinesonlyallowcontrolofnmAscontrols_______________?FactorsAffectingDensitynPrimarycontrolfactor–mA–Time(seconds)nInfluencingfactors–kVp–Grids–Beamrestriction–Bodystructures(sizeofpt,pathology–Processing–SID&OID–FilmScreencombinatio
6、nsPrimaryControllingFactorofDensitynmAsnmA=___________ofelectronssentacrossthetubecombinedwithTIME(S)=mAsnmAscontrols________onradiographnprimaryfunctionofmAsisDENSITYImaginethis…nIfthemAstationischangedfrom200to400mA,twiceasmanyelectronswillflowfromthecathodetotheanode.nFrom10mAt
7、o1000mA=100xmorenmAcontrolshowmanyelectronsarecomingatthetargetnmAsisacombinationofhowmanyandforhowlong(seconds)ChangingMas–ChangesDensity+25%+50%masInfluencingFactoronDensity:kVp???kVpmoreenergy=morephotonspassingthoughtissue&strikingtheimageá15%kVp=doublingofexposuretothefilma15
8、%kVp=halvingofexposuretothefilm15
