Medical-Physics

WhatdoPhysicistsdoin…“REALLIFE”ManyworkwithdoctorsinthefieldofMedicineDoctorsoftenneedtolookinsideourbodieswithoutcuttingthemopen….Someyoumayhaveheardof…X-rays…..CTscans…..MRIscansAndnewonesyoumaynothaveheardofyet….PETscans…..MEGareessentialinthedevelopmentofmanyscanningtechnologiesHereisyourchanceto…FindoutthebasicsofhowthesescansworkSeehowimportantphysicsistomodernmedicine.X-raysVerylittleordinarylightcanpassthroughskin.It’seitherabsorbedatthesurfaceorreflectedback…..To“see”insideweneedakindof“light”withmoreenergy…SkinOrdinaryLightXraysTaking“Xrays”ThepatientisplacedinfrontofasourceofXRAYSXrayTubeAphotographicplateisplacedontheothersideofthepatientMostoftheXrayspassthroughthepatient’sbody…….X-raysareabsorbedbybonebutcanpassthroughskinandsofttissueboneSofttissuePhotographicplateXraysthatareabsorbedinthephotographicplatecausechemicalchanges.Theseshowasdarkenedareaswhentheplateisdeveloped.X-raysarealsopartlyabsorbedbysometissuesinthebodythiscreatesamoresubtlepicture.boneSofttissuePhotographicplateWhatpartofthebodydotheseXRaysshow?Answer:AkneeAdvantagesofBasicXrayImagingXraysareeasytoproduceXraymachinesarerelativelycheapIncontrolleddosesXrayimagesaresafetothepatientDisadvantagesofXrayImagingInlargedosesXrayscanbeharmfultohealthImagesareonly“shadowprints”inone“plane”…..no3DinformationImagingofsofttissuesandorgansisnotalwaysverydetailed.TrueorFalseChallenge…1.Xraysaremadeofthesame“stuff”asvisiblelight.Theyarebothformsof“electromagneticradiation”.2.Xrayswerediscoveredcompletelybyaccidentduringaphysicsexperimentcarriedoutin1965.3.Xrayscandamagehealthytissues.CTScansCTor“CAT”scanstakeXrayimagingto“C”standsfor“Computed”“T”standsfor“Tomography”Inshort….CTscannersarecomplexXraymachinesattachedtoveryclevercomputersusingcomplicatedmathematicstobuildupimagesofourinsides.ThepatientisplacedonabedThescanner(Xraymachine)istheshapeofaringThepatientisslowlymovedthroughtheringasthescantakesplace…Lookingendon….XraytubeXraydetectorPatientXRaysareproducedinanXraytube,passthroughthepatientandaredetectedbythedetectorThescannerrotatestheXraytubeanddetectorsothepatientisscannedfromallanglesTherearenophotographicplatesinCTscanners.Allimagesarecreatedbycomputersusingtheinformationtheyreceivefromthex-raydetectorTheimageproducedislikea“slice”throughthebody.ribsspineAdvantagesofCTscansImagesarelike“slices”Comparedotherscanners(MRIandPET)CTmachinesarequitecheap.DisadvantagesofCTStilluseXraysthatcandamagehealthytissues(inlargedoses).Imagingofsofttissuesisimprovedbutstillnotalwaysasdetailedasdoctorsrequire.TrueorFalseChallenge…4.CTstandsforComplexTomography.5.CTscansmakeimagesofyourinsidesinslices.Computerscannowtaketheseslicesandmakea3Dpictureofyourinsides.6.WithCTscansthepatientreceivesalowerdoseofxraysthanwithastandardXraymachine.MRIWhatdothelettersstandfor?M………..MagneticR…………ResonanceI………….ImagingMRIscannersdonotuseXrays.MRIExplained...Yoursciencestudieshaveshownyouthatyourbodyismadeupoflivingcells…Whicharemadeupofmolecules…WhicharemadeupofatomselectronneutronprotonThesimplestatomis…Hydrogen1electron1protonIt’snucleuscontainsjustoneprotonInthe1940’sphysicistsdiscoveredthatthenucleiofsomeatomshaveapropertycalled“SPIN”…….Likeawobblingspinningtop.Thiscausesthenucleusactlikeatinymagnet….NSAftermanyyearsofinvestigationphysicistsfoundtheycouldaffectthetinynuclearmagnetsofhydrogenatomsusingverystrongmagnetsandradiowaves…Bringinthemagnets….SNNote:ThenuclearmagnetscanlineupintwopossibledirectionsApulseofradiowavescancausesomeofthenuclearmagnetsabsorbenergyand“flip”Thishighenergysituationcannotbesustainedforlong.Manywill“flip”back….Whenthishappensenergyisreleasedasatinypulseofradiowaves!!!….watchhowthemagneticfieldaffectsthetinynuclearmagnetsThistinypulseofradiowavesthatcanbedetectedandanalysed.Thetiming,andtheenergyofthesesignals,revealsinformationabouttheHydrogenatomsandwhattypesofmoleculestheyareattachedto.Sowhathasallthisgottodowithlookinginsideyourbody?Whatisyourbodymostlymadeof?Whatisthechemicalnameofwater?H2OHydrogeninthemostabundantelementinyourbody(approx63%ofalltheatomsareH)OrganicmoleculesthatmakeuptissueslikeFATMUSCLETENDONSetc.containalargenumberofHydrogenatomsIttookphysicistsover40yearstoturntheirdiscoveryofnuclearmagnetsintoimagesofthehumanbody.Buttheresultsareamazing…Allthisfrommanipulatingthemagneticpropertiesofhydrogennuclei!Thepatientisplacedonabedandthenmovedintoalargehollowtube.Thetubecontainsaverypowerfulmagnet….UsinganMRIScanner…MostMRIscannersusemagnetsAnelectriccurrentpassesthroughamassivecoilmadeofaspecial“superconducting”materialThiscreatesaverystrongmagnet(x20000timesstrongerthanearthsmagneticfield)Thismayseemlikeareallyeasywaytocreateastrongmagnetbutthereisacatch……Superconductingmaterialsonlyworkcorrectlywhentheyarereallycold…..Butnotjustcoldlikefreezertemperatures….Canyouguesshowcold?degreesCelsiusThat’scolderthanonthesurfaceofPluto!Toachievethesetemperaturesthesuperconductingcoilsneedtositinacontainerfilledwith…Thankfullythepatientisinsulatedfromthisextremelylowtemperaturewhilstinsidethemagnet.Themag