X-rays - National Institute of Biomedical Imaging and ...

X-rays are a form of electromagnetic radiation, similar to visible light. Unlike light, however, x-rays have higher energy and can pass through most objects ... Skiptomaincontent scienceeducation ScienceTopics X-rays X-rays Share:   ScienceEducation Whataremedicalx-rays? Howdomedicalx-rayswork? Whenaremedicalx-raysused? Arethererisks? WhatareNIBIB-fundedresearchersdevelopinginthefieldofx-raytechnology? Whataremedicalx-rays? X-raysareaformofelectromagneticradiation,similartovisiblelight.Unlikelight,however,x-rayshavehigherenergyandcanpassthroughmostobjects,includingthebody.Medicalx-raysareusedtogenerateimagesoftissuesandstructuresinsidethebody.Ifx-raystravellingthroughthebodyalsopassthroughanx-raydetectorontheothersideofthepatient,animagewillbeformedthatrepresentsthe“shadows”formedbytheobjectsinsidethebody. HowDoX-raysWork? Onetypeofx-raydetectorisphotographicfilm,buttherearemanyothertypesofdetectorsthatareusedtoproducedigitalimages.Thex-rayimagesthatresultfromthisprocessarecalledradiographs. Howdomedicalx-rayswork? Tocreatearadiograph,apatientispositionedsothatthepartofthebodybeingimagedislocatedbetweenanx-raysourceandanx-raydetector.Whenthemachineisturnedon,x-raystravelthroughthebodyandareabsorbedindifferentamountsbydifferenttissues,dependingontheradiologicaldensityofthetissuestheypassthrough.Radiologicaldensityisdeterminedbyboththedensityandtheatomicnumber(thenumberofprotonsinanatom’snucleus)ofthematerialsbeingimaged.Forexample,structuressuchasbonecontaincalcium,whichhasahigheratomicnumberthanmosttissues.Becauseofthisproperty,bonesreadilyabsorbx-raysand,thus,producehighcontrastonthex-raydetector.Asaresult,bonystructuresappearwhiterthanothertissuesagainsttheblackbackgroundofaradiograph.Conversely,x-raystravelmoreeasilythroughlessradiologicallydensetissuessuchasfatandmuscle,aswellasthroughair-filledcavitiessuchasthelungs.Thesestructuresaredisplayedinshadesofgrayonaradiograph. Whenaremedicalx-raysused? Listedbelowareexamplesofexaminationsandproceduresthatusex-raytechnologytoeitherdiagnoseortreatdisease: Diagnostic X-rayradiography:Detectsbonefractures,certaintumorsandotherabnormalmasses,pneumonia,sometypesofinjuries,calcifications,foreignobjects,dentalproblems,etc. Mammography:Aradiographofthebreastthatisusedforcancerdetectionanddiagnosis.Tumorstendtoappearasregularorirregular-shapedmassesthataresomewhatbrighterthanthebackgroundontheradiograph(i.e.,whiteronablackbackgroundorblackeronawhitebackground).Mammogramscanalsodetecttinybitsofcalcium,calledmicrocalcifications,whichshowupasverybrightspecksonamammogram.Whileusuallybenign,microcalcificationsmayoccasionallyindicatethepresenceofaspecifictypeofcancer. CT(computedtomography):Combinestraditionalx-raytechnologywithcomputerprocessingtogenerateaseriesofcross-sectionalimagesofthebodythatcanlaterbecombinedtoformathree-dimensionalx-rayimage.CTimagesaremoredetailedthanplainradiographsandgivedoctorstheabilitytoviewstructureswithinthebodyfrommanydifferentangles. Fluoroscopy:Usesx-raysandafluorescentscreentoobtainreal-timeimagesofmovementwithinthebodyortoviewdiagnosticprocesses,suchasfollowingthepathofaninjectedorswallowedcontrastagent.Forexample,fluoroscopyisusedtoviewthemovementofthebeatingheart,and,withtheaidofradiographiccontrastagents,toviewbloodflowtotheheartmuscleaswellasthroughbloodvesselsandorgans.Thistechnologyisalsousedwitharadiographiccontrastagenttoguideaninternallythreadedcatheterduringcardiacangioplasty,whichisaminimallyinvasiveprocedureforopeningcloggedarteriesthatsupplybloodtotheheart. Therapeutic Radiationtherapyincancertreatment:X-raysandothertypesofhigh-energyradiationcanbeusedtodestroycanceroustumorsandcellsbydamagingtheirDNA.Theradiationdoseusedfortreatingcancerismuchhigherthantheradiationdoseusedfordiagnosticimaging.Therapeuticradiationcancomefromamachineoutsideofthebodyorfromaradioactivematerialthatisplacedinthebody,insideorneartumorcells,orinjectedintothebloodstream.Clickhereformoreinformationonradiationtherapyforcancer. Arethererisks? Whenusedappropriately,thediagnosticbenefitsofx-rayscanssignificantlyoutweightherisks.X-rayscanscandiagnosepossiblylife-threateningconditionssuchasblockedbloodvessels,bonecancer,andinfections.However,x-raysproduceionizingradiation—aformofradiationthathasthepotentialtoharmlivingtissue.Thisisariskthatincreaseswiththenumberofexposuresaddedupoverthelifeoftheindividual.However,theriskofdevelopingcancerfromradiationexposureisgenerallysmall. Anx-rayinapregnantwomanposesnoknownriskstothebabyiftheareaofthebodybeingimagedisn’ttheabdomenorpelvis.Ingeneral,ifimagingoftheabdomenandpelvisisneeded,doctorsprefertouseexamsthatdonotuseradiation,suchasMRIorultrasound.However,ifneitherofthosecanprovidetheanswersneeded,orthereisanemergencyorothertimeconstraint,anx-raymaybeanacceptablealternativeimagingoption. Childrenaremoresensitivetoionizingradiationandhavealongerlifeexpectancyand,thus,ahigherrelativeriskfordevelopingcancerthanadults.Parentsmaywanttoaskthetechnologistordoctoriftheirmachinesettingshavebeenadjustedforchildren. Clickonthefollowinglinksforinformationaboutrisksforspecificprocedures: Mammography CT(computedtomography) WhatareNIBIB-fundedresearchersdevelopinginthefieldofx-raytechnology? Currentresearchofx-raytechnologyfocusesonwaystoreduce radiation dose,improveimageresolution,andenhancecontrastmaterialsandmethods. Fordetailedexamplesofresearchadvancementsforspecificimagingprocedures,clickonthelinksbelow: Mammography CT(computedtomography) Thumbnail XRay-SciEdLanding ViewandDownloadScienceTopicFactSheets(PDFs) ExploreMore ThereissomuchmoretoexploreatNIBIB. HealthTopicsBoneDiseaseBreastCancerCancerCardiovascularDiseaseDigestiveDiseasesHeartDiseaseInjuryRespiratoryDisease ResearchTopicsDiagnosticsX-ray ProgramAreasX-ray,Electron,andIonBeam