Peak kilovoltage - Wikipedia

Peak kilovoltage (kVp) refers to the maximum high voltage applied across an X-ray tube to produce the X-rays. During X-ray generation, surface electrons are ... Peakkilovoltage FromWikipedia,thefreeencyclopedia Jumptonavigation Jumptosearch Thisarticleneedsadditionalcitationsforverification.Pleasehelpimprovethisarticlebyaddingcitationstoreliablesources.Unsourcedmaterialmaybechallengedandremoved.Findsources: "Peakkilovoltage" – news ·newspapers ·books ·scholar ·JSTOR(December2017)(Learnhowandwhentoremovethistemplatemessage) PeakvoltageacrossanX-raytube Peakkilovoltage(kVp)referstothemaximumhighvoltageappliedacrossanX-raytubetoproducetheX-rays.DuringX-raygeneration,surfaceelectronsarereleasedfromaheatedcathodebythermionicemission.Theappliedvoltage(kV)acceleratestheseelectronstowardananodetarget,ultimatelyproducingX-rayswhentheelectronsarestoppedintheanode.Thus,thekVpcorrespondstothehighestkineticenergyoftheelectronsstrikingthetarget,andisproportionaltothemaximumenergyoftheresultingX-rayemissionspectrum.[1]InearlyandbasicX-rayequipment,theappliedvoltagevariescyclically,withone,two,ormorepulsespermainsACpowercycle.OnestandardwaytomeasurepulsatingDCisitspeakamplitude,hencekVp.MostmodernX-raygeneratorsapplyaconstantpotentialacrosstheX-raytube;insuchsystems,thekVpandthesteady-statekVareidentical. kVpcontrolsthepropertycalled"radiographiccontrast"ofanX-rayimage(theratiooftransmittedradiationthroughregionsofdifferentthicknessordensity).EachbodypartcontainsacertaintypeofcellularcompositionwhichrequiresanX-raybeamwithacertainkVptopenetrateit.Thebodypartissaidtohave"subjectcontrast"(thatis,differentcellularmakeup:somedense,somenotsodensetissuesallwithinaspecificbodypart).Forexample:bonetomuscletoairratiosintheabdomendifferfromthoseofthechestarea.Sothesubjectcontrastissaidtobehigherinthechestthanintheabdomen.Inordertoimagethebodysothatthemaximuminformationwillresult,highersubjectcontrastareasrequireahigherkVpsoastoresultinalowradiographiccontrastimage,andviceversa. Althoughtheproductoftubecurrentandexposuretime,measuredinmilliampere-seconds(mA·s),istheprimarycontrollingfactorofradiographicdensity,kVpalsoaffectstheradiographicdensityindirectly.Astheenergy(whichisproportionaltothepeakvoltage)ofthestreamofelectronsintheX-raytubeincreases,theX-rayphotonscreatedfromthoseelectronsaremorelikelytopenetratethecellsofthebodyandreachtheimagereceptor(filmorplate),resultinginincreasedfilmdensity(comparedtolowerenergybeamsthatmaybeabsorbedinthebodyontheirwaytotheimagereceptor).However,scatteredX-raysalsocontributetoincreasedfilmdensity:thehigherthekVpofthebeam,themorescatterwillbeproduced.Scatteraddsunwanteddensity(thatis,densitythatdoesnotbringpertinentinformationtotheimagereceptor).ThisiswhykVpisnotprimarilyusedtocontrolfilmdensity–asthedensityresultingfromincreasingkVpexceedswhatisneededtopenetrateabodypart,itonlyaddsuselessphotonstotheimage. IncreasingmAscausesmorephotons(radiation)oftheparticularkVpenergytobeproduced.Thisishelpfulwhenlargerbodypartsareimaged,becausetheyrequiremorephotons.Themorephotonsthatpassthroughaparticulartissuetype(whosekVpisinteractingatthecellularlevel),themorephotonsreachtheimagereceptor.Themorephotonsthatpassthroughapartandreachtheimagereceptorwithpertinentinformation,themoreusefulthefilmdensityontheresultingimage.Conversely,lowermAscreatesfewerphotons,whichwilldecreasefilmdensity,butishelpfulwhenyouimagesmallerparts.ThemeasurementofkVpisdonebykVmeter.ThequalityofX-raytubedependsuponthekVappliedacrossthefilamentatthetarget.AslightchangeinkVaffectstheimagesignificantly.Therefore,itisnecessarytomeasurekVappliedtotubeaccurately. References[edit] ^K.,Thayalan(30May2014).ThePhysicsofRadiologyandImaging.Ravichandran,Ramamoorthy(First ed.).NewDelhi,India.ISBN 9789351521716.OCLC 871508499. Retrievedfrom"https://en.wikipedia.org/w/index.php?title=Peak_kilovoltage&oldid=1042655239" Categories:RadiographyRadiologyHiddencategories:ArticlesneedingadditionalreferencesfromDecember2017AllarticlesneedingadditionalreferencesArticleswithshortdescriptionShortdescriptionmatchesWikidata Navigationmenu Personaltools NotloggedinTalkContributionsCreateaccountLogin Namespaces ArticleTalk Variants expanded collapsed Views ReadEditViewhistory More expanded collapsed Search Navigation MainpageContentsCurrenteventsRandomarticleAboutWikipediaContactusDonate Contribute HelpLearntoeditCommunityportalRecentchangesUploadfile Tools WhatlinkshereRelatedchangesUploadfileSpecialpagesPermanentlinkPageinformationCitethispageWikidataitem Print/export DownloadasPDFPrintableversion Languages العربية Editlinks