X-ray - Wikipedia

X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. In many languages, X-radiation is referred to as Röntgen ... X-ray FromWikipedia,thefreeencyclopedia Jumptonavigation Jumptosearch Formofshort-wavelengthelectromagneticradiation Thisarticleisaboutthenature,production,andusesoftheradiation.Forthemethodofimaging,seeRadiography.Forthemedicalspecialty,seeRadiology.Forothermeanings,seeX-ray(disambiguation). NottobeconfusedwithX-waveorX-band. X-raysarepartoftheelectromagneticspectrum,withwavelengthsshorterthanUVlight.DifferentapplicationsusedifferentpartsoftheX-rayspectrum. X-rayimageofhumanlungs AnX-ray,or,muchlesscommonly,X-radiation,isapenetratingformofhigh-energyelectromagneticradiation.MostX-rayshaveawavelengthrangingfrom10 picometersto10 nanometers,correspondingtofrequenciesintherange30 petahertzto30 exahertz(30×1015 Hzto30×1018 Hz)andenergiesintherange124 eVto124 keV.X-raywavelengthsareshorterthanthoseofUVraysandtypicallylongerthanthoseofgammarays.Inmanylanguages,X-radiationisreferredtoasRöntgenradiation,aftertheGermanscientistWilhelmConradRöntgen,whodiscovereditonNovember8,1895.[1]HenameditX-radiationtosignifyanunknowntypeofradiation.[2]SpellingsofX-ray(s)inEnglishincludethevariantsx-ray(s),xray(s),andXray(s).[3] Contents 1History 1.1Pre-Röntgenobservationsandresearch 1.2DiscoverybyRöntgen 1.3Advancesinradiology 1.4Hazardsdiscovered 1.520thcenturyandbeyond 2Energyranges 2.1SoftandhardX-rays 2.2Gammarays 3Properties 4Interactionwithmatter 4.1Photoelectricabsorption 4.2Comptonscattering 4.3Rayleighscattering 5Production 5.1Productionbyelectrons 5.2Productionbyfastpositiveions 5.3Productioninlightningandlaboratorydischarges 6Detectors 7Medicaluses 7.1Projectionalradiographs 7.2Computedtomography 7.3Fluoroscopy 7.4Radiotherapy 8Adverseeffects 9Otheruses 10Visibility 11Unitsofmeasureandexposure 12Seealso 13References 14Externallinks History[edit] Pre-Röntgenobservationsandresearch[edit] ExampleofaCrookestube,atypeofdischargetubethatemittedX-rays Beforetheirdiscoveryin1895,X-rayswerejustatypeofunidentifiedradiationemanatingfromexperimentaldischargetubes.Theywerenoticedbyscientistsinvestigatingcathoderaysproducedbysuchtubes,whichareenergeticelectronbeamsthatwerefirstobservedin1869.ManyoftheearlyCrookestubes(inventedaround1875)undoubtedlyradiatedX-rays,becauseearlyresearchersnoticedeffectsthatwereattributabletothem,asdetailedbelow.CrookestubescreatedfreeelectronsbyionizationoftheresidualairinthetubebyahighDCvoltageofanywherebetweenafewkilovoltsand100 kV.ThisvoltageacceleratedtheelectronscomingfromthecathodetoahighenoughvelocitythattheycreatedX-rayswhentheystrucktheanodeortheglasswallofthetube.[4] Theearliestexperimenterthoughttohave(unknowingly)producedX-rayswasactuallyWilliamMorgan.In1785,hepresentedapapertotheRoyalSocietyofLondondescribingtheeffectsofpassingelectricalcurrentsthroughapartiallyevacuatedglasstube,producingaglowcreatedbyX-rays.[5][6]ThisworkwasfurtherexploredbyHumphryDavyandhisassistantMichaelFaraday. WhenStanfordUniversityphysicsprofessorFernandoSanfordcreatedhis"electricphotography",healsounknowinglygeneratedanddetectedX-rays.From1886to1888,hehadstudiedintheHermannHelmholtzlaboratoryinBerlin,wherehebecamefamiliarwiththecathoderaysgeneratedinvacuumtubeswhenavoltagewasappliedacrossseparateelectrodes,aspreviouslystudiedbyHeinrichHertzandPhilippLenard.HisletterofJanuary6,1893(describinghisdiscoveryas"electricphotography")toThePhysicalReviewwasdulypublishedandanarticleentitledWithoutLensorLight,PhotographsTakenWithPlateandObjectinDarknessappearedintheSanFranciscoExaminer.[7] Startingin1888,PhilippLenardconductedexperimentstoseewhethercathoderayscouldpassoutoftheCrookestubeintotheair.HebuiltaCrookestubewitha"window"attheendmadeofthinaluminium,facingthecathodesothecathoderayswouldstrikeit(latercalleda"Lenardtube").Hefoundthatsomethingcamethrough,thatwouldexposephotographicplatesandcausefluorescence.Hemeasuredthepenetratingpoweroftheseraysthroughvariousmaterials.Ithasbeensuggestedthatatleastsomeofthese"Lenardrays"wereactuallyX-rays.[8] In1889,Ukrainian-bornIvanPuluj,alecturerinexperimentalphysicsatthePraguePolytechnicwhosince1877hadbeenconstructingvariousdesignsofgas-filledtubestoinvestigatetheirproperties,publishedapaperonhowsealedphotographicplatesbecamedarkwhenexposedtotheemanationsfromthetubes.[9] HermannvonHelmholtzformulatedmathematicalequationsforX-rays.HepostulatedadispersiontheorybeforeRöntgenmadehisdiscoveryandannouncement.Hebaseditontheelectromagnetictheoryoflight.[10][fullcitationneeded]However,hedidnotworkwithactualX-rays. In1894,NikolaTeslanoticeddamagedfilminhislabthatseemedtobeassociatedwithCrookestubeexperimentsandbeganinvestigatingthisinvisible,radiantenergy.[11][12]AfterRöntgenidentifiedtheX-ray,TeslabeganmakingX-rayimagesofhisownusinghighvoltagesandtubesofhisowndesign,[13]aswellasCrookestubes. DiscoverybyRöntgen[edit] WilhelmRöntgen OnNovember8,1895,GermanphysicsprofessorWilhelmRöntgenstumbledonX-rayswhileexperimentingwithLenardtubesandCrookestubesandbeganstudyingthem.Hewroteaninitialreport"Onanewkindofray:Apreliminarycommunication"andonDecember28,1895,submittedittoWürzburg'sPhysical-MedicalSocietyjournal.[14]ThiswasthefirstpaperwrittenonX-rays.Röntgenreferredtotheradiationas"X",toindicatethatitwasanunknowntypeofradiation.Thenamestuck,although(overRöntgen'sgreatobjections)manyofhiscolleaguessuggestedcallingthemRöntgenrays.Theyarestillreferredtoassuchinmanylanguages,includingGerman,Hungarian,Ukrainian,Danish,Polish,Bulgarian,Swedish,Finnish,Estonian,Turkish,Russian,Latvian,Lithuanian,Japanese,Dutch,Georgian,Hebrew,andNorwegian.RöntgenreceivedthefirstNobelPrizeinPhysicsforhisdiscovery.[15] ThereareconflictingaccountsofhisdiscoverybecauseRöntgenhadhislabnotesburnedafterhisdeath,butthisisalikelyreconstructionbyhisbiographers:[16][17]RöntgenwasinvestigatingcathoderaysfromaCrookestubewhichhehadwrappedinblackcardboardsothatthevisiblelightfromthetubewouldnotinterfere,usingafluorescentscreenpaintedwithbariumplatinocyanide.Henoticedafaintgreenglowfromthescreen,about1meter(3.3 ft)away.Röntgenrealizedsomeinvisiblerayscomingfromthetubewerepassingthroughthecardboardtomakethescreenglow.Hefoundtheycouldalsopassthroughbooksandpapersonhisdesk.Röntgenthrewhimselfintoinvestigatingtheseunknownrayssystematically.Twomonthsafterhisinitialdiscovery,hepublishedhispaper.[18] HandmitRingen(HandwithRings):printofWilhelmRöntgen'sfirst"medical"X-ray,ofhiswife'shand,takenon22December1895andpresentedtoLudwigZehnderofthePhysikInstitut,UniversityofFreiburg,on1January1896[19][20] Röntgendiscoveredtheirmedicalusewhenhemadeapictureofhiswife'shandonaphotographicplateformedduetoX-rays.Thephotographofhiswife'shandwasthefirstphotographofahumanbodypartusingX-rays.Whenshesawthepicture,shesaid"Ihaveseenmydeath."[21] ThediscoveryofX-raysstimulatedaveritablesensation.Röntgen'sbiographerOttoGlasserestimatedthat,in1896alone,asmanyas49essaysand1044articlesaboutthenewrayswerepublished.[22]Thiswasprobablyaconservativeestimate,ifoneconsidersthatnearlyeverypaperaroundtheworldextensivelyreportedaboutthenewdiscovery,withamagazinesuchasSciencededicatingasmanyas23articlestoitinthatyearalone.[23]Sensationalistreactionstothenewdiscoveryincludedpublicationslinkingthenewkindofraystooccultandparanormaltheories,suchastelepathy.[24][25] Advancesinradiology[edit] TakinganX-rayimagewithearlyCrookestubeapparatus,late1800s.TheCrookestubeisvisibleincenter.Thestandingmanisviewinghishandwithafluoroscopescreen.Theseatedmanistakingaradiographofhishandbyplacingitonaphotographicplate.Noprecautionsagainstradiationexposurearetaken;itshazardswerenotknownatthetime. SurgicalremovalofabulletwhoselocationwasdiagnosedwithX-rays(seeinset)in1897 RöntgenimmediatelynoticedX-rayscouldhavemedicalapplications.Alongwithhis28DecemberPhysical-MedicalSocietysubmission,hesentalettertophysiciansheknewaroundEurope(January1,1896).[26]News(andthecreationof"shadowgrams")spreadrapidlywithScottishelectricalengineerAlanArchibaldCampbell-SwintonbeingthefirstafterRöntgentocreateanX-ray(ofahand).ThroughFebruary,therewere46experimenterstakingupthetechniqueinNorthAmericaalone.[26] ThefirstuseofX-raysunderclinicalconditionswasbyJohnHall-EdwardsinBirmingham,Englandon11January1896,whenheradiographedaneedlestuckinthehandofanassociate.OnFebruary14,1896,Hall-EdwardswasalsothefirsttouseX-raysinasurgicaloperation.[27] ImagesbyJamesGreen,from"SciagraphsofBritishBatrachiansandReptiles"(1897),featuring(fromleft)Ranaesculenta(nowPelophylaxlessonae),Lacertavivipara(nowZootocavivipara),andLacertaagilis Inearly1896,severalweeksafterRöntgen'sdiscovery,IvanRomanovichTarkhanovirradiatedfrogsandinsectswithX-rays,concludingthattherays"notonlyphotograph,butalsoaffectthelivingfunction".[28]Ataroundthesametime,thezoologicalillustratorJamesGreenbegantouseX-raystoexaminefragilespecimens.GeorgeAlbertBoulengerfirstmentionedthisworkinapaperhedeliveredbeforetheZoologicalSocietyofLondoninMay1896.ThebookSciagraphsofBritishBatrachiansandReptiles(sciagraphisanobsoletenameforanX-rayphotograph),byGreenandJamesH.Gardiner,withaforewordbyBoulenger,waspublishedin1897.[29][30] ThefirstmedicalX-raymadeintheUnitedStateswasobtainedusingadischargetubeofPului'sdesign.InJanuary1896,onreadingofRöntgen'sdiscovery,FrankAustinofDartmouthCollegetestedallofthedischargetubesinthephysicslaboratoryandfoundthatonlythePuluitubeproducedX-rays.ThiswasaresultofPului'sinclusionofanoblique"target"ofmica,usedforholdingsamplesoffluorescentmaterial,withinthetube.On3February1896,GilmanFrost,professorofmedicineatthecollege,andhisbrotherEdwinFrost,professorofphysics,exposedthewristofEddieMcCarthy,whomGilmanhadtreatedsomeweeksearlierforafracture,totheX-raysandcollectedtheresultingimageofthebrokenboneongelatinphotographicplatesobtainedfromHowardLangill,alocalphotographeralsointerestedinRöntgen'swork.[31] 1896plaquepublishedin"NouvelleIconographiedelaSalpetrière",amedicaljournal.Intheleftahanddeformity,intherightsamehandseenusingradiography.TheauthorsnamedthetechniqueRöntgenphotography. Manyexperimenters,includingRöntgenhimselfinhisoriginalexperiments,cameupwithmethodstoviewX-rayimages"live"usingsomeformofluminescentscreen.[26]Röntgenusedascreencoatedwithbariumplatinocyanide.OnFebruary5,1896,liveimagingdevicesweredevelopedbybothItalianscientistEnricoSalvioni(his"cryptoscope")andProfessorMcGieofPrincetonUniversity(his"Skiascope"),bothusingbariumplatinocyanide.AmericaninventorThomasEdisonstartedresearchsoonafterRöntgen'sdiscoveryandinvestigatedmaterials'abilitytofluorescewhenexposedtoX-rays,findingthatcalciumtungstatewasthemosteffectivesubstance.InMay1896,hedevelopedthefirstmass-producedliveimagingdevice,his"Vitascope",latercalledthefluoroscope,whichbecamethestandardformedicalX-rayexaminations.[26]EdisondroppedX-rayresearcharound1903,beforethedeathofClarenceMadisonDally,oneofhisglassblowers.DallyhadahabitoftestingX-raytubesonhisownhands,developingacancerinthemsotenaciousthatbotharmswereamputatedinafutileattempttosavehislife;in1904,hebecamethefirstknowndeathattributedtoX-rayexposure.[26]Duringthetimethefluoroscopewasbeingdeveloped,SerbianAmericanphysicistMihajloPupin,usingacalciumtungstatescreendevelopedbyEdison,foundthatusingafluorescentscreendecreasedtheexposuretimeittooktocreateanX-rayformedicalimagingfromanhourtoafewminutes.[32][26] In1901,U.S.PresidentWilliamMcKinleywasshottwiceinanassassinationattempt.Whileonebulletonlygrazedhissternum,anotherhadlodgedsomewheredeepinsidehisabdomenandcouldnotbefound.AworriedMcKinleyaidesentwordtoinventorThomasEdisontorushanX-raymachinetoBuffalotofindthestraybullet.Itarrivedbutwasnotused.Whiletheshootingitselfhadnotbeenlethal,gangrenehaddevelopedalongthepathofthebullet,andMcKinleydiedofsepticshockduetobacterialinfectionsixdayslater.[33] Hazardsdiscovered[edit] WiththewidespreadexperimentationwithX‑raysaftertheirdiscoveryin1895byscientists,physicians,andinventorscamemanystoriesofburns,hairloss,andworseintechnicaljournalsofthetime.InFebruary1896,ProfessorJohnDanielandDr.WilliamLoflandDudleyofVanderbiltUniversityreportedhairlossafterDr.DudleywasX-rayed.AchildwhohadbeenshotintheheadwasbroughttotheVanderbiltlaboratoryin1896.Beforetryingtofindthebullet,anexperimentwasattempted,forwhichDudley"withhischaracteristicdevotiontoscience"[34][35][36]volunteered.Danielreportedthat21daysaftertakingapictureofDudley'sskull(withanexposuretimeofonehour),henoticedabaldspot5centimeters(2 in)indiameteronthepartofhisheadnearesttheX-raytube:"Aplateholderwiththeplatestowardsthesideoftheskullwasfastenedandacoinplacedbetweentheskullandthehead.Thetubewasfastenedattheothersideatadistanceofone-halfinch[1.3 cm]fromthehair."[37] InAugust1896,Dr.HD.Hawks,agraduateofColumbiaCollege,sufferedseverehandandchestburnsfromanX-raydemonstration.ItwasreportedinElectricalReviewandledtomanyotherreportsofproblemsassociatedwithX-raysbeingsentintothepublication.[38]ManyexperimentersincludingElihuThomsonatEdison'slab,WilliamJ.Morton,andNikolaTeslaalsoreportedburns.ElihuThomsondeliberatelyexposedafingertoanX-raytubeoveraperiodoftimeandsufferedpain,swelling,andblistering.[39]Othereffectsweresometimesblamedforthedamageincludingultravioletraysand(accordingtoTesla)ozone.[40]ManyphysiciansclaimedtherewerenoeffectsfromX-rayexposureatall.[39]OnAugust3,1905,inSanFrancisco,California,ElizabethFleischman,anAmericanX-raypioneer,diedfromcomplicationsasaresultofherworkwithX-rays.[41][42][43] Hall-Edwardsdevelopedacancer(thencalledX-raydermatitis)sufficientlyadvancedby1904tocausehimtowritepapersandgivepublicaddressesonthedangersofX-rays.Helosthispersonalbattleandhisleftarmhadtobeamputatedattheelbowin1908,[44]andfourfingersonhisrightarmsoonthereafter,leavingonlyathumb.Hediedofcancerin1926.HislefthandiskeptatBirminghamUniversity. 20thcenturyandbeyond[edit] Apatientbeingexaminedwithathoracicfluoroscopein1940,whichdisplayedcontinuousmovingimages.ThisimagewasusedtoarguethatradiationexposureduringtheX-rayprocedurewouldbenegligible. ThemanyapplicationsofX-raysimmediatelygeneratedenormousinterest.WorkshopsbeganmakingspecializedversionsofCrookestubesforgeneratingX-raysandthesefirst-generationcoldcathodeorCrookesX-raytubeswereuseduntilabout1920. Atypicalearly20thcenturymedicalX-raysystemconsistedofaRuhmkorffcoilconnectedtoacoldcathodeCrookesX-raytube.Asparkgapwastypicallyconnectedtothehighvoltagesideinparalleltothetubeandusedfordiagnosticpurposes.[45]Thesparkgapalloweddetectingthepolarityofthesparks,measuringvoltagebythelengthofthesparksthusdeterminingthe"hardness"ofthevacuumofthetube,anditprovidedaloadintheeventtheX-raytubewasdisconnected.Todetectthehardnessofthetube,thesparkgapwasinitiallyopenedtothewidestsetting.Whilethecoilwasoperating,theoperatorreducedthegapuntilsparksbegantoappear.Atubeinwhichthesparkgapbegantosparkataround6.4centimeters(2.5 in)wasconsideredsoft(lowvacuum)andsuitableforthinbodypartssuchashandsandarms.A13-centimeter(5 in)sparkindicatedthetubewassuitableforshouldersandknees.An18-to-23-centimeter(7to9 in)sparkwouldindicateahighervacuumsuitableforimagingtheabdomenoflargerindividuals.Sincethesparkgapwasconnectedinparalleltothetube,thesparkgaphadtobeopeneduntilthesparkingceasedinordertooperatethetubeforimaging.Exposuretimeforphotographicplateswasaroundhalfaminuteforahandtoacoupleofminutesforathorax.Theplatesmayhaveasmalladditionoffluorescentsalttoreduceexposuretimes.[45] Crookestubeswereunreliable.Theyhadtocontainasmallquantityofgas(invariablyair)asacurrentwillnotflowinsuchatubeiftheyarefullyevacuated.However,astimepassed,theX-rayscausedtheglasstoabsorbthegas,causingthetubetogenerate"harder"X-raysuntilitsoonstoppedoperating.Largerandmorefrequentlyusedtubeswereprovidedwithdevicesforrestoringtheair,knownas"softeners".Theseoftentooktheformofasmallsidetubethatcontainedasmallpieceofmica,amineralthattrapsrelativelylargequantitiesofairwithinitsstructure.Asmallelectricalheaterheatedthemica,causingittoreleaseasmallamountofair,thusrestoringthetube'sefficiency.However,themicahadalimitedlife,andtherestorationprocesswasdifficulttocontrol. In1904,JohnAmbroseFleminginventedthethermionicdiode,thefirstkindofvacuumtube.Thisusedahotcathodethatcausedanelectriccurrenttoflowinavacuum.ThisideawasquicklyappliedtoX-raytubes,andhenceheated-cathodeX-raytubes,called"Coolidgetubes",completelyreplacedthetroublesomecoldcathodetubesbyabout1920. Inabout1906,thephysicistCharlesBarkladiscoveredthatX-rayscouldbescatteredbygases,andthateachelementhadacharacteristicX-rayspectrum.Hewonthe1917NobelPrizeinPhysicsforthisdiscovery. In1912,MaxvonLaue,PaulKnipping,andWalterFriedrichfirstobservedthediffractionofX-raysbycrystals.Thisdiscovery,alongwiththeearlyworkofPaulPeterEwald,WilliamHenryBragg,andWilliamLawrenceBragg,gavebirthtothefieldofX-raycrystallography. In1913,HenryMoseleyperformedcrystallographyexperimentswithX-raysemanatingfromvariousmetalsandformulatedMoseley'slawwhichrelatesthefrequencyoftheX-raystotheatomicnumberofthemetal. TheCoolidgeX-raytubewasinventedthesameyearbyWilliamD.Coolidge.ItmadepossiblethecontinuousemissionsofX-rays.ModernX-raytubesarebasedonthisdesign,oftenemployingtheuseofrotatingtargetswhichallowforsignificantlyhigherheatdissipationthanstatictargets,furtherallowinghigherquantityX-rayoutputforuseinhighpoweredapplicationssuchasrotationalCTscanners. Chandra'simageofthegalaxyclusterAbell2125revealsacomplexofseveralmassivemultimillion-degree-Celsiusgascloudsintheprocessofmerging. TheuseofX-raysformedicalpurposes(whichdevelopedintothefieldofradiationtherapy)waspioneeredbyMajorJohnHall-EdwardsinBirmingham,England.Thenin1908,hehadtohavehisleftarmamputatedbecauseofthespreadofX-raydermatitisonhisarm.[46] Medicalsciencealsousedthemotionpicturetostudyhumanphysiology.In1913,amotionpicturewasmadeinDetroitshowingahard-boiledegginsideahumanstomach.ThisearlyX-raymoviewasrecordedatarateofonestillimageeveryfourseconds.[47]DrLewisGregoryColeofNewYorkwasapioneerofthetechnique,whichhecalled"serialradiography".[48][49]In1918,X-rayswereusedinassociationwithmotionpicturecamerastocapturethehumanskeletoninmotion.[50][51][52]In1920,itwasusedtorecordthemovementsoftongueandteethinthestudyoflanguagesbytheInstituteofPhoneticsinEngland.[53] In1914,MarieCuriedevelopedradiologicalcarstosupportsoldiersinjuredinWorldWarI.ThecarswouldallowforrapidX-rayimagingofwoundedsoldierssobattlefieldsurgeonscouldquicklyandmoreaccuratelyoperate.[54] Fromtheearly1920sthroughtothe1950s,X-raymachinesweredevelopedtoassistinthefittingofshoes[55]andweresoldtocommercialshoestores.[56][57][58]Concernsregardingtheimpactoffrequentorpoorlycontrolledusewereexpressedinthe1950s,[59][60]leadingtothepractice'seventualendthatdecade.[61] TheX-raymicroscopewasdevelopedduringthe1950s. TheChandraX-rayObservatory,launchedonJuly23,1999,hasbeenallowingtheexplorationoftheveryviolentprocessesintheuniversewhichproduceX-rays.Unlikevisiblelight,whichgivesarelativelystableviewoftheuniverse,theX-rayuniverseisunstable.Itfeaturesstarsbeingtornapartbyblackholes,galacticcollisions,andnovae,andneutronstarsthatbuilduplayersofplasmathatthenexplodeintospace. AnX-raylaserdevicewasproposedaspartoftheReaganAdministration'sStrategicDefenseInitiativeinthe1980s,buttheonlytestofthedevice(asortoflaser"blaster"ordeathray,poweredbyathermonuclearexplosion)gaveinconclusiveresults.Fortechnicalandpoliticalreasons,theoverallproject(includingtheX-raylaser)wasdefunded(thoughwaslaterrevivedbythesecondBushAdministrationasNationalMissileDefenseusingdifferenttechnologies). Doghipxrayposteriorview Phase-contrastX-rayimageofspider Phase-contrastX-rayimagingreferstoavarietyoftechniquesthatusephaseinformationofacoherentX-raybeamtoimagesofttissues.Ithasbecomeanimportantmethodforvisualizingcellularandhistologicalstructuresinawiderangeofbiologicalandmedicalstudies.ThereareseveraltechnologiesbeingusedforX-rayphase-contrastimaging,allutilizingdifferentprinciplestoconvertphasevariationsintheX-raysemergingfromanobjectintointensityvariations.[62][63]Theseincludepropagation-basedphasecontrast,[64]Talbotinterferometry,[63]refraction-enhancedimaging,[65]andX-rayinterferometry.[66]Thesemethodsprovidehighercontrastcomparedtonormalabsorption-contrastX-rayimaging,makingitpossibletoseesmallerdetails.Adisadvantageisthatthesemethodsrequiremoresophisticatedequipment,suchassynchrotronormicrofocusX-raysources,X-rayoptics,andhighresolutionX-raydetectors. Energyranges[edit] SoftandhardX-rays[edit] X-rayswithhighphotonenergiesabove5–10 keV(below0.2–0.1 nmwavelength)arecalledhardX-rays,whilethosewithlowerenergy(andlongerwavelength)arecalledsoftX-rays.[67]TheintermediaterangewithphotonenergiesofseveralkeVisoftenreferredtoastenderX-rays.Duetotheirpenetratingability,hardX-raysarewidelyusedtoimagetheinsideofobjects,e.g.,inmedicalradiographyandairportsecurity.ThetermX-rayismetonymicallyusedtorefertoaradiographicimageproducedusingthismethod,inadditiontothemethoditself.SincethewavelengthsofhardX-raysaresimilartothesizeofatoms,theyarealsousefulfordeterminingcrystalstructuresbyX-raycrystallography.Bycontrast,softX-raysareeasilyabsorbedinair;theattenuationlengthof600 eV(~2 nm)X-raysinwaterislessthan1 micrometer.[68] Gammarays[edit] ThereisnoconsensusforadefinitiondistinguishingbetweenX-raysandgammarays.Onecommonpracticeistodistinguishbetweenthetwotypesofradiationbasedontheirsource:X-raysareemittedbyelectrons,whilegammaraysareemittedbytheatomicnucleus.[69][70][71][72]Thisdefinitionhasseveralproblems:otherprocessesalsocangeneratethesehigh-energyphotons,orsometimesthemethodofgenerationisnotknown.OnecommonalternativeistodistinguishX-andgammaradiationonthebasisofwavelength(or,equivalently,frequencyorphotonenergy),withradiationshorterthansomearbitrarywavelength,suchas10−11 m(0.1 Å),definedasgammaradiation.[73]Thiscriterionassignsaphotontoanunambiguouscategory,butisonlypossibleifwavelengthisknown.(Somemeasurementtechniquesdonotdistinguishbetweendetectedwavelengths.)However,thesetwodefinitionsoftencoincidesincetheelectromagneticradiationemittedbyX-raytubesgenerallyhasalongerwavelengthandlowerphotonenergythantheradiationemittedbyradioactivenuclei.[69]Occasionally,onetermortheotherisusedinspecificcontextsduetohistoricalprecedent,basedonmeasurement(detection)technique,orbasedontheirintendeduseratherthantheirwavelengthorsource. Thus,gamma-raysgeneratedformedicalandindustrialuses,forexampleradiotherapy,intherangesof6–20 MeV,caninthiscontextalsobereferredtoasX-rays.[74] Properties[edit] Ionizingradiationhazardsymbol X-rayphotonscarryenoughenergytoionizeatomsanddisruptmolecularbonds.Thismakesitatypeofionizingradiation,andthereforeharmfultolivingtissue.Averyhighradiationdoseoverashortperiodoftimecausesradiationsickness,whilelowerdosescangiveanincreasedriskofradiation-inducedcancer.Inmedicalimaging,thisincreasedcancerriskisgenerallygreatlyoutweighedbythebenefitsoftheexamination.TheionizingcapabilityofX-rayscanbeutilizedincancertreatmenttokillmalignantcellsusingradiationtherapy.ItisalsousedformaterialcharacterizationusingX-rayspectroscopy. AttenuationlengthofX-raysinwatershowingtheoxygenabsorptionedgeat540eV,theenergy−3dependenceofphotoabsorption,aswellasalevelingoffathigherphotonenergiesduetoComptonscattering.TheattenuationlengthisaboutfourordersofmagnitudelongerforhardX-rays(righthalf)comparedtosoftX-rays(lefthalf). HardX-rayscantraverserelativelythickobjectswithoutbeingmuchabsorbedorscattered.Forthisreason,X-raysarewidelyusedtoimagetheinsideofvisuallyopaqueobjects.Themostoftenseenapplicationsareinmedicalradiographyandairportsecurityscanners,butsimilartechniquesarealsoimportantinindustry(e.g.,industrialradiographyandindustrialCTscanning)andresearch(e.g.,smallanimalCT).ThepenetrationdepthvarieswithseveralordersofmagnitudeovertheX-rayspectrum.Thisallowsthephotonenergytobeadjustedfortheapplicationsoastogivesufficienttransmissionthroughtheobjectandatthesametimeprovidegoodcontrastintheimage. X-rayshavemuchshorterwavelengthsthanvisiblelight,whichmakesitpossibletoprobestructuresmuchsmallerthancanbeseenusinganormalmicroscope.ThispropertyisusedinX-raymicroscopytoacquirehigh-resolutionimages,andalsoinX-raycrystallographytodeterminethepositionsofatomsincrystals. Interactionwithmatter[edit] X-raysinteractwithmatterinthreemainways,throughphotoabsorption,Comptonscattering,andRayleighscattering.ThestrengthoftheseinteractionsdependsontheenergyoftheX-raysandtheelementalcompositionofthematerial,butnotmuchonchemicalproperties,sincetheX-rayphotonenergyismuchhigherthanchemicalbindingenergies.PhotoabsorptionorphotoelectricabsorptionisthedominantinteractionmechanisminthesoftX-rayregimeandforthelowerhardX-rayenergies.Athigherenergies,Comptonscatteringdominates. Photoelectricabsorption[edit] TheprobabilityofaphotoelectricabsorptionperunitmassisapproximatelyproportionaltoZ3/E3,whereZistheatomicnumberandEistheenergyoftheincidentphoton.[75]Thisruleisnotvalidclosetoinnershellelectronbindingenergieswherethereareabruptchangesininteractionprobability,socalledabsorptionedges.However,thegeneraltrendofhighabsorptioncoefficientsandthusshortpenetrationdepthsforlowphotonenergiesandhighatomicnumbersisverystrong.Forsofttissue,photoabsorptiondominatesuptoabout26 keVphotonenergywhereComptonscatteringtakesover.Forhigheratomicnumbersubstances,thislimitishigher.Thehighamountofcalcium(Z = 20)inbones,togetherwiththeirhighdensity,iswhatmakesthemshowupsoclearlyonmedicalradiographs. Aphotoabsorbedphotontransfersallitsenergytotheelectronwithwhichitinteracts,thusionizingtheatomtowhichtheelectronwasboundandproducingaphotoelectronthatislikelytoionizemoreatomsinitspath.AnouterelectronwillfillthevacantelectronpositionandproduceeitheracharacteristicX-rayoranAugerelectron.TheseeffectscanbeusedforelementaldetectionthroughX-rayspectroscopyorAugerelectronspectroscopy. Comptonscattering[edit] ComptonscatteringisthepredominantinteractionbetweenX-raysandsofttissueinmedicalimaging.[76]ComptonscatteringisaninelasticscatteringoftheX-rayphotonbyanoutershellelectron.Partoftheenergyofthephotonistransferredtothescatteringelectron,therebyionizingtheatomandincreasingthewavelengthoftheX-ray.Thescatteredphotoncangoinanydirection,butadirectionsimilartotheoriginaldirectionismorelikely,especiallyforhigh-energyX-rays.TheprobabilityfordifferentscatteringanglesisdescribedbytheKlein–Nishinaformula.Thetransferredenergycanbedirectlyobtainedfromthescatteringanglefromtheconservationofenergyandmomentum. Rayleighscattering[edit] RayleighscatteringisthedominantelasticscatteringmechanismintheX-rayregime.[77]Inelasticforwardscatteringgivesrisetotherefractiveindex,whichforX-raysisonlyslightlybelow1.[78] Production[edit] Wheneverchargedparticles(electronsorions)ofsufficientenergyhitamaterial,X-raysareproduced. Productionbyelectrons[edit] CharacteristicX-rayemissionlinesforsomecommonanodematerials.[79][80] Anodematerial Atomicnumber Photonenergy[keV] Wavelength[nm] Kα1 Kβ1 Kα1 Kβ1 W 74 59.3 67.2 0.0209 0.0184 Mo 42 17.5 19.6 0.0709 0.0632 Cu 29 8.05 8.91 0.154 0.139 Ag 47 22.2 24.9 0.0559 0.0497 Ga 31 9.25 10.26 0.134 0.121 In 49 24.2 27.3 0.0512 0.455 SpectrumoftheX-raysemittedbyanX-raytubewitharhodiumtarget,operatedat60kV.Thesmooth,continuouscurveisduetobremsstrahlung,andthespikesarecharacteristicKlinesforrhodiumatoms. X-rayscanbegeneratedbyanX-raytube,avacuumtubethatusesahighvoltagetoacceleratetheelectronsreleasedbyahotcathodetoahighvelocity.Thehighvelocityelectronscollidewithametaltarget,theanode,creatingtheX-rays.[81]InmedicalX-raytubesthetargetisusuallytungstenoramorecrack-resistantalloyofrhenium(5%)andtungsten(95%),butsometimesmolybdenumformorespecializedapplications,suchaswhensofterX-raysareneededasinmammography.Incrystallography,acoppertargetismostcommon,withcobaltoftenbeingusedwhenfluorescencefromironcontentinthesamplemightotherwisepresentaproblem. ThemaximumenergyoftheproducedX-rayphotonislimitedbytheenergyoftheincidentelectron,whichisequaltothevoltageonthetubetimestheelectroncharge,soan80 kVtubecannotcreateX-rayswithanenergygreaterthan80 keV.Whentheelectronshitthetarget,X-raysarecreatedbytwodifferentatomicprocesses: CharacteristicX-rayemission(X-rayelectroluminescence):Iftheelectronhasenoughenergy,itcanknockanorbitalelectronoutoftheinnerelectronshellofthetargetatom.Afterthat,electronsfromhigherenergylevelsfillthevacancies,andX-rayphotonsareemitted.ThisprocessproducesanemissionspectrumofX-raysatafewdiscretefrequencies,sometimesreferredtoasspectrallines.Usually,thesearetransitionsfromtheuppershellstotheKshell(calledKlines),totheLshell(calledLlines)andsoon.Ifthetransitionisfrom2pto1s,itiscalledKα,whileifitisfrom3pto1sitisKβ.Thefrequenciesoftheselinesdependonthematerialofthetargetandarethereforecalledcharacteristiclines.TheKαlineusuallyhasgreaterintensitythantheKβoneandismoredesirableindiffractionexperiments.ThustheKβlineisfilteredoutbyafilter.Thefilterisusuallymadeofametalhavingoneprotonlessthantheanodematerial(e.g.,NifilterforCuanodeorNbfilterforMoanode). Bremsstrahlung:Thisisradiationgivenoffbytheelectronsastheyarescatteredbythestrongelectricfieldnearthehigh-Z(protonnumber)nuclei.TheseX-rayshaveacontinuousspectrum.Thefrequencyofbremsstrahlungislimitedbytheenergyofincidentelectrons. So,theresultingoutputofatubeconsistsofacontinuousbremsstrahlungspectrumfallingofftozeroatthetubevoltage,plusseveralspikesatthecharacteristiclines.ThevoltagesusedindiagnosticX-raytubesrangefromroughly20 kVto150 kVandthusthehighestenergiesoftheX-rayphotonsrangefromroughly20 keVto150 keV.[82] BothoftheseX-rayproductionprocessesareinefficient,withonlyaboutonepercentoftheelectricalenergyusedbythetubeconvertedintoX-rays,andthusmostoftheelectricpowerconsumedbythetubeisreleasedaswasteheat.WhenproducingausablefluxofX-rays,theX-raytubemustbedesignedtodissipatetheexcessheat. AspecializedsourceofX-rayswhichisbecomingwidelyusedinresearchissynchrotronradiation,whichisgeneratedbyparticleaccelerators.ItsuniquefeaturesareX-rayoutputsmanyordersofmagnitudegreaterthanthoseofX-raytubes,wideX-rayspectra,excellentcollimation,andlinearpolarization.[83] ShortnanosecondburstsofX-rayspeakingat15 keVinenergymaybereliablyproducedbypeelingpressure-sensitiveadhesivetapefromitsbackinginamoderatevacuum.Thisislikelytobetheresultofrecombinationofelectricalchargesproducedbytriboelectriccharging.TheintensityofX-raytriboluminescenceissufficientforittobeusedasasourceforX-rayimaging.[84] Productionbyfastpositiveions[edit] X-rayscanalsobeproducedbyfastprotonsorotherpositiveions.Theproton-inducedX-rayemissionorparticle-inducedX-rayemissioniswidelyusedasananalyticalprocedure.Forhighenergies,theproductioncrosssectionisproportionaltoZ12Z2−4,whereZ1referstotheatomicnumberoftheion,Z2referstothatofthetargetatom.[85]Anoverviewofthesecrosssectionsisgiveninthesamereference. Productioninlightningandlaboratorydischarges[edit] X-raysarealsoproducedinlightningaccompanyingterrestrialgamma-rayflashes.TheunderlyingmechanismistheaccelerationofelectronsinlightningrelatedelectricfieldsandthesubsequentproductionofphotonsthroughBremsstrahlung.[86]ThisproducesphotonswithenergiesofsomefewkeVandseveraltensofMeV.[87]Inlaboratorydischargeswithagapsizeofapproximately1 meterlengthandapeakvoltageof1 MV,X-rayswithacharacteristicenergyof160 keVareobserved.[88]Apossibleexplanationistheencounteroftwostreamersandtheproductionofhigh-energyrun-awayelectrons;[89]however,microscopicsimulationshaveshownthatthedurationofelectricfieldenhancementbetweentwostreamersistooshorttoproduceasignificantnumberofrun-awayelectrons.[90]Recently,ithasbeenproposedthatairperturbationsinthevicinityofstreamerscanfacilitatetheproductionofrun-awayelectronsandhenceofX-raysfromdischarges.[91][92] Detectors[edit] Mainarticle:X-raydetector X-raydetectorsvaryinshapeandfunctiondependingontheirpurpose.Imagingdetectorssuchasthoseusedforradiographywereoriginallybasedonphotographicplatesandlaterphotographicfilm,butarenowmostlyreplacedbyvariousdigitaldetectortypessuchasimageplatesandflatpaneldetectors.Forradiationprotectiondirectexposurehazardisoftenevaluatedusingionizationchambers,whiledosimetersareusedtomeasuretheradiationdoseapersonhasbeenexposedto.X-rayspectracanbemeasuredeitherbyenergydispersiveorwavelengthdispersivespectrometers.ForX-raydiffractionapplications,suchasX-raycrystallography,hybridphotoncountingdetectorsarewidelyused.[93] Medicaluses[edit] Thissectionneedsadditionalcitationsforverification.Pleasehelpimprovethisarticlebyaddingcitationstoreliablesources.Unsourcedmaterialmaybechallengedandremoved.Findsources: "X-ray" – news ·newspapers ·books ·scholar ·JSTOR(November2017)(Learnhowandwhentoremovethistemplatemessage) X-ray. Achestradiographofafemale,demonstratingahiatalhernia SinceRöntgen'sdiscoverythatX-rayscanidentifybonestructures,X-rayshavebeenusedformedicalimaging.[94]Thefirstmedicalusewaslessthanamonthafterhispaperonthesubject.[31]Upto2010,five billionmedicalimagingexaminationshadbeenconductedworldwide.[95]Radiationexposurefrommedicalimagingin2006madeupabout50%oftotalionizingradiationexposureintheUnitedStates.[96] Projectionalradiographs[edit] Mainarticle:Projectionalradiography Plainradiographoftherightknee Projectionalradiographyisthepracticeofproducingtwo-dimensionalimagesusingX-rayradiation.Bonescontainahighconcentrationofcalcium,which,duetoitsrelativelyhighatomicnumber,absorbsX-raysefficiently.ThisreducestheamountofX-raysreachingthedetectorintheshadowofthebones,makingthemclearlyvisibleontheradiograph.Thelungsandtrappedgasalsoshowupclearlybecauseoflowerabsorptioncomparedtotissue,whiledifferencesbetweentissuetypesarehardertosee. Projectionalradiographsareusefulinthedetectionofpathologyoftheskeletalsystemaswellasfordetectingsomediseaseprocessesinsofttissue.SomenotableexamplesaretheverycommonchestX-ray,whichcanbeusedtoidentifylungdiseasessuchaspneumonia,lungcancer,orpulmonaryedema,andtheabdominalx-ray,whichcandetectbowel(orintestinal)obstruction,freeair(fromvisceralperforations),andfreefluid(inascites).X-raysmayalsobeusedtodetectpathologysuchasgallstones(whicharerarelyradiopaque)orkidneystoneswhichareoften(butnotalways)visible.TraditionalplainX-raysarelessusefulintheimagingofsofttissuessuchasthebrainormuscle.Oneareawhereprojectionalradiographsareusedextensivelyisinevaluatinghowanorthopedicimplant,suchasaknee,hiporshoulderreplacement,issituatedinthebodywithrespecttothesurroundingbone.Thiscanbeassessedintwodimensionsfromplainradiographs,oritcanbeassessedinthreedimensionsifatechniquecalled'2Dto3Dregistration'isused.Thistechniquepurportedlynegatesprojectionerrorsassociatedwithevaluatingimplantpositionfromplainradiographs.[97][98] Dentalradiographyiscommonlyusedinthediagnosesofcommonoralproblems,suchascavities. Inmedicaldiagnosticapplications,thelowenergy(soft)X-raysareunwanted,sincetheyaretotallyabsorbedbythebody,increasingtheradiationdosewithoutcontributingtotheimage.Hence,athinmetalsheet,oftenofaluminium,calledanX-rayfilter,isusuallyplacedoverthewindowoftheX-raytube,absorbingthelowenergypartinthespectrum.Thisiscalledhardeningthebeamsinceitshiftsthecenterofthespectrumtowardshigherenergy(orharder)X-rays. Togenerateanimageofthecardiovascularsystem,includingthearteriesandveins(angiography)aninitialimageistakenoftheanatomicalregionofinterest.Asecondimageisthentakenofthesameregionafteraniodinatedcontrastagenthasbeeninjectedintothebloodvesselswithinthisarea.Thesetwoimagesarethendigitallysubtracted,leavinganimageofonlytheiodinatedcontrastoutliningthebloodvessels.Theradiologistorsurgeonthencomparestheimageobtainedtonormalanatomicalimagestodeterminewhetherthereisanydamageorblockageofthevessel. Computedtomography[edit] Mainarticle:CTscan HeadCTscan(transverseplane)slice–amodernapplicationofmedicalradiography Computedtomography(CTscanning)isamedicalimagingmodalitywheretomographicimagesorslicesofspecificareasofthebodyareobtainedfromalargeseriesoftwo-dimensionalX-rayimagestakenindifferentdirections.[99]Thesecross-sectionalimagescanbecombinedintoathree-dimensionalimageoftheinsideofthebodyandusedfordiagnosticandtherapeuticpurposesinvariousmedicaldisciplines. Fluoroscopy[edit] Mainarticle:Fluoroscopy Fluoroscopyisanimagingtechniquecommonlyusedbyphysiciansorradiationtherapiststoobtainreal-timemovingimagesoftheinternalstructuresofapatientthroughtheuseofafluoroscope.Initssimplestform,afluoroscopeconsistsofanX-raysourceandafluorescentscreen,betweenwhichapatientisplaced.However,modernfluoroscopescouplethescreentoanX-rayimageintensifierandCCDvideocameraallowingtheimagestoberecordedandplayedonamonitor.Thismethodmayuseacontrastmaterial.Examplesincludecardiaccatheterization(toexamineforcoronaryarteryblockages)andbariumswallow(toexamineforesophagealdisordersandswallowingdisorders). Radiotherapy[edit] TheuseofX-raysasatreatmentisknownasradiationtherapyandislargelyusedforthemanagement(includingpalliation)ofcancer;itrequireshigherradiationdosesthanthosereceivedforimagingalone.X-raysbeamsareusedfortreatingskincancersusinglowerenergyX-raybeamswhilehigherenergybeamsareusedfortreatingcancerswithinthebodysuchasbrain,lung,prostate,andbreast.[100][101] Adverseeffects[edit] Abdominalradiographofapregnantwoman,aprocedurethatshouldbeperformedonlyafterproperassessmentofbenefitversusrisk DiagnosticX-rays(primarilyfromCTscansduetothelargedoseused)increasetheriskofdevelopmentalproblemsandcancerinthoseexposed.[102][103][104]X-raysareclassifiedasacarcinogenbyboththeWorldHealthOrganization'sInternationalAgencyforResearchonCancerandtheU.S.government.[95][105]Itisestimatedthat0.4%ofcurrentcancersintheUnitedStatesareduetocomputedtomography(CTscans)performedinthepastandthatthismayincreasetoashighas1.5–2%with2007ratesofCTusage.[106] Experimentalandepidemiologicaldatacurrentlydonotsupportthepropositionthatthereisathresholddoseofradiationbelowwhichthereisnoincreasedriskofcancer.[107]However,thisisunderincreasingdoubt.[108]ItisestimatedthattheadditionalradiationfromdiagnosticX-rayswillincreasetheaverageperson'scumulativeriskofgettingcancerbyage75by0.6–3.0%.[109]TheamountofabsorbedradiationdependsuponthetypeofX-raytestandthebodypartinvolved.[110]CTandfluoroscopyentailhigherdosesofradiationthandoplainX-rays. Toplacetheincreasedriskinperspective,aplainchestX-raywillexposeapersontothesameamountfrombackgroundradiationthatpeopleareexposedto(dependinguponlocation)everydayover10days,whileexposurefromadentalX-rayisapproximatelyequivalentto1dayofenvironmentalbackgroundradiation.[111]EachsuchX-raywouldaddlessthan1per1,000,000tothelifetimecancerrisk.AnabdominalorchestCTwouldbetheequivalentto2–3yearsofbackgroundradiationtothewholebody,or4–5yearstotheabdomenorchest,increasingthelifetimecancerriskbetween1per1,000to1per10,000.[111]Thisiscomparedtotheroughly40%chanceofaUScitizendevelopingcancerduringtheirlifetime.[112]Forinstance,theeffectivedosetothetorsofromaCTscanofthechestisabout5 mSv,andtheabsorbeddoseisabout14 mGy.[113]AheadCTscan(1.5 mSv,64 mGy)[114]thatisperformedoncewithandoncewithoutcontrastagent,wouldbeequivalentto40yearsofbackgroundradiationtothehead.AccurateestimationofeffectivedosesduetoCTisdifficultwiththeestimationuncertaintyrangeofabout±19%to±32%foradultheadscansdependinguponthemethodused.[115] Theriskofradiationisgreatertoafetus,soinpregnantpatients,thebenefitsoftheinvestigation(X-ray)shouldbebalancedwiththepotentialhazardstothefetus.[116][117]IntheUS,thereareanestimated62 millionCTscansperformedannually,includingmorethan4 milliononchildren.[110]AvoidingunnecessaryX-rays(especiallyCTscans)reducesradiationdoseandanyassociatedcancerrisk.[118] MedicalX-raysareasignificantsourceofhuman-maderadiationexposure.In1987,theyaccountedfor58%ofexposurefromhuman-madesourcesintheUnitedStates.Sincehuman-madesourcesaccountedforonly18%ofthetotalradiationexposure,mostofwhichcamefromnaturalsources(82%),medicalX-raysonlyaccountedfor10%oftotalAmericanradiationexposure;medicalproceduresasawhole(includingnuclearmedicine)accountedfor14%oftotalradiationexposure.By2006,however,medicalproceduresintheUnitedStateswerecontributingmuchmoreionizingradiationthanwasthecaseintheearly1980s.In2006,medicalexposureconstitutednearlyhalfofthetotalradiationexposureoftheU.S.populationfromallsources.Theincreaseistraceabletothegrowthintheuseofmedicalimagingprocedures,inparticularcomputedtomography(CT),andtothegrowthintheuseofnuclearmedicine.[96][119] DosageduetodentalX-raysvariessignificantlydependingontheprocedureandthetechnology(filmordigital).Dependingontheprocedureandthetechnology,asingledentalX-rayofahumanresultsinanexposureof0.5to4 mrem.AfullmouthseriesofX-raysmayresultinanexposureofupto6(digital)to18(film)mrem,forayearlyaverageofupto40 mrem.[120][121][122][123][124][125][126] FinancialincentiveshavebeenshowntohaveasignificantimpactonX-rayusewithdoctorswhoarepaidaseparatefeeforeachX-rayprovidingmoreX-rays.[127] EarlyphotontomographyorEPT[128](asof2015)alongwithothertechniques[129]arebeingresearchedaspotentialalternativestoX-raysforimagingapplications. Otheruses[edit] OthernotableusesofX-raysinclude: Eachdot,calledareflection,inthisdiffractionpatternformsfromtheconstructiveinterferenceofscatteredX-rayspassingthroughacrystal.Thedatacanbeusedtodeterminethecrystallinestructure. X-raycrystallographyinwhichthepatternproducedbythediffractionofX-raysthroughthecloselyspacedlatticeofatomsinacrystalisrecordedandthenanalysedtorevealthenatureofthatlattice.Arelatedtechnique,fiberdiffraction,wasusedbyRosalindFranklintodiscoverthedoublehelicalstructureofDNA.[130] X-rayastronomy,whichisanobservationalbranchofastronomy,whichdealswiththestudyofX-rayemissionfromcelestialobjects. X-raymicroscopicanalysis,whichuseselectromagneticradiationinthesoftX-raybandtoproduceimagesofverysmallobjects. X-rayfluorescence,atechniqueinwhichX-raysaregeneratedwithinaspecimenanddetected.TheoutgoingenergyoftheX-raycanbeusedtoidentifythecompositionofthesample. IndustrialradiographyusesX-raysforinspectionofindustrialparts,particularlywelds. Radiographyofculturalobjects,mostoftenx-raysofpaintingstorevealunderdrawing,pentimentialterationsinthecourseofpaintingorbylaterrestorers,andsometimespreviouspaintingsonthesupport.Manypigmentssuchasleadwhiteshowwellinradiographs. X-rayspectromicroscopyhasbeenusedtoanalysethereactionsofpigmentsinpaintings.Forexample,inanalysingcolourdegradationinthepaintingsofvanGogh.[131] UsingX-rayforinspectionandqualitycontrol:thedifferencesinthestructuresofthedieandbondwiresrevealtheleftchiptobecounterfeit.[132] Authenticationandqualitycontrolofpackageditems. IndustrialCT(computedtomography),aprocessthatusesX-rayequipmenttoproducethree-dimensionalrepresentationsofcomponentsbothexternallyandinternally.Thisisaccomplishedthroughcomputerprocessingofprojectionimagesofthescannedobjectinmanydirections. AirportsecurityluggagescannersuseX-raysforinspectingtheinteriorofluggageforsecuritythreatsbeforeloadingonaircraft. BordercontroltruckscannersanddomesticpolicedepartmentsuseX-raysforinspectingtheinterioroftrucks. X-rayfineartphotographyofneedlefishbyPeterDazeley X-rayartandfineartphotography,artisticuseofX-rays,forexampletheworksbyStaneJagodič X-rayhairremoval,amethodpopularinthe1920sbutnowbannedbytheFDA.[133] Shoe-fittingfluoroscopeswerepopularizedinthe1920s,bannedintheUSinthe1960s,intheUKinthe1970s,andlaterincontinentalEurope. Roentgenstereophotogrammetryisusedtotrackmovementofbonesbasedontheimplantationofmarkers X-rayphotoelectronspectroscopyisachemicalanalysistechniquerelyingonthephotoelectriceffect,usuallyemployedinsurfacescience. RadiationimplosionistheuseofhighenergyX-raysgeneratedfromafissionexplosion(anA-bomb)tocompressnuclearfueltothepointoffusionignition(anH-bomb). Visibility[edit] Whilegenerallyconsideredinvisibletothehumaneye,inspecialcircumstancesX-rayscanbevisible.Brandes,inanexperimentashorttimeafterRöntgen'slandmark1895paper,reportedafterdarkadaptationandplacinghiseyeclosetoanX-raytube,seeingafaint"blue-gray"glowwhichseemedtooriginatewithintheeyeitself.[134]Uponhearingthis,Röntgenreviewedhisrecordbooksandfoundhetoohadseentheeffect.WhenplacinganX-raytubeontheoppositesideofawoodendoorRöntgenhadnotedthesameblueglow,seemingtoemanatefromtheeyeitself,butthoughthisobservationstobespuriousbecauseheonlysawtheeffectwhenheusedonetypeoftube.Laterherealizedthatthetubewhichhadcreatedtheeffectwastheonlyonepowerfulenoughtomaketheglowplainlyvisibleandtheexperimentwasthereafterreadilyrepeatable.TheknowledgethatX-raysareactuallyfaintlyvisibletothedark-adaptednakedeyehaslargelybeenforgottentoday;thisisprobablyduetothedesirenottorepeatwhatwouldnowbeseenasarecklesslydangerousandpotentiallyharmfulexperimentwithionizingradiation.Itisnotknownwhatexactmechanismintheeyeproducesthevisibility:itcouldbeduetoconventionaldetection(excitationofrhodopsinmoleculesintheretina),directexcitationofretinalnervecells,orsecondarydetectionvia,forinstance,X-rayinductionofphosphorescenceintheeyeballwithconventionalretinaldetectionofthesecondarilyproducedvisiblelight. ThoughX-raysareotherwiseinvisible,itispossibletoseetheionizationoftheairmoleculesiftheintensityoftheX-raybeamishighenough.ThebeamlinefromthewigglerattheID11attheEuropeanSynchrotronRadiationFacilityisoneexampleofsuchhighintensity.[135] Unitsofmeasureandexposure[edit] ThemeasureofX-raysionizingabilityiscalledtheexposure: Thecoulombperkilogram(C/kg)istheSIunitofionizingradiationexposure,anditistheamountofradiationrequiredtocreateonecoulombofchargeofeachpolarityinonekilogramofmatter. Theroentgen(R)isanobsoletetraditionalunitofexposure,whichrepresentedtheamountofradiationrequiredtocreateoneelectrostaticunitofchargeofeachpolarityinonecubiccentimeterofdryair.1 roentgen = 2.58×10−4 C/kg. However,theeffectofionizingradiationonmatter(especiallylivingtissue)ismorecloselyrelatedtotheamountofenergydepositedintothemratherthanthechargegenerated.Thismeasureofenergyabsorbediscalledtheabsorbeddose: Thegray(Gy),whichhasunitsof(joules/kilogram),istheSIunitofabsorbeddose,anditistheamountofradiationrequiredtodepositonejouleofenergyinonekilogramofanykindofmatter. Theradisthe(obsolete)correspondingtraditionalunit,equalto10 millijoulesofenergydepositedperkilogram.100 rad = 1 gray. Theequivalentdoseisthemeasureofthebiologicaleffectofradiationonhumantissue.ForX-raysitisequaltotheabsorbeddose. TheRoentgenequivalentman(rem)isthetraditionalunitofequivalentdose.ForX-raysitisequaltotherad,or,inotherwords,10 millijoulesofenergydepositedperkilogram.100 rem = 1 Sv. Thesievert(Sv)istheSIunitofequivalentdose,andalsoofeffectivedose.ForX-raysthe"equivalentdose"isnumericallyequaltoaGray(Gy).1 Sv = 1 Gy.Forthe"effectivedose"ofX-rays,itisusuallynotequaltotheGray(Gy). Ionizingradiationrelatedquantitiesview ‧ talk ‧ edit Quantity Unit Symbol Derivation Year SIequivalence Activity(A) becquerel Bq s−1 1974 SIunit curie Ci 3.7×1010s−1 1953 3.7×1010 Bq rutherford Rd 106s−1 1946 1,000,000 Bq Exposure(X) coulombperkilogram C/kg C⋅kg−1ofair 1974 SIunit röntgen R esu/0.001293gofair 1928 2.58×10−4C/kg Absorbeddose(D) gray Gy J⋅kg−1 1974 SIunit ergpergram erg/g erg⋅g−1 1950 1.0×10−4Gy rad rad 100erg⋅g−1 1953 0.010 Gy Equivalentdose(H) sievert Sv J⋅kg−1×WR 1977 SIunit röntgenequivalentman rem 100erg⋅g−1xWR 1971 0.010 Sv Effectivedose(E) sievert Sv J⋅kg−1×WR×WT 1977 SIunit röntgenequivalentman rem 100erg⋅g−1×WR×WT 1971 0.010 Sv Seealso[edit]  Medicalportal Physicsportal BackscatterX-ray Detectivequantumefficiency High-energyX-rays Macintyre'sX-RayFilm–1896documentaryradiographyfilm Nray Neutronradiation NuSTAR Radiographer Reflection(physics) ResonantinelasticX-rayscattering(RIXS) Small-angleX-rayscattering(SAXS) TheX-Rays–1897Britishshortsilentcomedyfilm 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Externallinks[edit] WikimediaCommonshasmediarelatedtoX-ray. Lookupx-rayinWiktionary,thefreedictionary. "OnaNewKindofRays".Nature.53(1369):274–276.January1896.doi:10.1038/053274b0. "IonX-Raytubes".TheCathodeRayTubesite. "IndexofEarlyBremsstrahlungArticles".ShadeTreePhysics.12Apr2010. Samuel,Jean-Jacques(20October2013)."LadécouvertedesrayonsXparRöntgen".BibnumEducation(inFrench).Röntgen’sdiscoveryofX-rays(Englishtranslation) vteElectromagneticspectrum Gammarays X-rays Ultraviolet Visible Infrared Microwave Radio←higherfrequencies       longerwavelengths→ X-rays softX-ray hardX-ray Ultraviolet Extremeultraviolet Vacuumultraviolet Lyman-alpha FUV MUV NUV UVC UVB UVA Visible(optical) Violet Blue Cyan Green Yellow Orange Red Infrared NIR SWIR MWIR LWIR FIR Microwaves Wband Vband Qband Kaband Kband Kuband Xband Cband Sband Lband Radio THF EHF SHF UHF VHF HF MF LF VLF ULF SLF ELF Wavelengthtypes Microwave Shortwave Mediumwave Longwave vteNucleartechnologyScience Chemistry Engineering Physics Atomicnucleus Fission Fusion Radiation ionizing braking Fuel Tritium Deuterium Helium-3 Fertilematerial Fissilematerial Isotopeseparation Nuclearmaterial Uranium enriched depleted Plutonium Thorium Neutron Activation Capture Poison Crosssection Generator Radiation Reflector 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