X-ray dose detector based on color changing of light-emitting polymer–metal complex hybrid material.

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SensorsandActuatorsBxxx (2012) xxx–xxx

ContentslistsavailableatSciVerseScienceDirect

Sensors

and

Actuators

B:

Chemical

j o u r n al hom e p a g e :w w w . e l s e v i e r . c o m / l o c a t e / s n b

X-ray

dose

detector

based

on

color

changing

of

light-emitting

polymer–metal

complex

hybrid

material

T. Schimitberger

a

_,

_G.R.

_Ferreira

a

_,

_M.F.

_Saraiva

b

_,

_A.G.C.

_Bianchi

a

_,

_R.F.

_Bianchi

a,∗

a_Laboratory_of_Polymers_and_Electronic_Properties_of_Materials,_Department_of_Physics,_Federal_University_of_Ouro_Preto,_Ouro_Preto_–_MG,_35400-000,_Brazil b_Cancer_Hospital_of_Muriae,_Cristiano_Varella_Foundation,_Muriaé_–_MG,_36880-000,_Brazil

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received14September2011

Receivedinrevisedform29February2012 Accepted23March2012 Available online xxx Keywords: Radiotherapy Semiconductingpolymer Organicdevice Dosimeter Opticalsensor

a

b

s

t

r

a

c

t

Wereport on the design, fabrication and performanceof a poly(2-methoxy-5(2 -ethylhexyloxy)-p-phenylenevinylene)/tris-(8-hydroxyquinoline)aluminum (MEH-PPV/Alq3) X-ray dose detector for

improvingsafetyforcancerpatientsshortlybeforeradiationtherapy.Thedetectorconsistsofan inexpen-sive(<US$1)organicdevicethatisirreversiblycolorchangingfromred,toyellow,togreenandmeasures thedelivereddosefromtheradiationbeamsofalinearaccelerator(6MV)intherangeof0–40Gy.The effectofradiationontheopticalpropertiesofMEH-PPV/Alq3wasdescribedandweobservedastrong

correlationbetweenthephotoemissionspectrumofAlq3andthephotoemissionandabsorptionspectra

ofMEH-PPVdegradedbyradiation.Aseriesoftestswasconductedontheperformanceoftheorganic detectorinmeasuringdepth-dosedistributionofphotonbeamsinawaterphantomanddemonstrating linearityintheshiftofPLandabsorptionasfunctionsofthedose.Theseresultshaveenabledthe qual-itativeandquantitativeanalysisofhowtheradiationinstabilityofopticalpropertiesofMEH-PPV/Alq3

canbeusedtodevelopaninnovativeorganicdeviceforradiationtherapy.

1. Introduction

Radiationtherapyhasbeenusedforseveraldecadesinthe treat-mentofoncologypatients,usingradiationorparticlestodamage anddestroycancercells[1].Itisshownthatthisﬁeldhasundergone enormousprogressoverthelastfewdecadesandmodern radi-ationtherapiesrangefromplanningcapacitiestoreducepatient set-uperrorsinclinicalpracticestostandarddosimetric method-ologyformeasuringsinglescandoseproﬁlesanddosedelivered tothetumor,aswellasdepthandcumulativedose,forthebest possibletherapy [2].Thisproposed treatmentaims toimprove canceroustumorcontrol,thusreducingsideandlong-termeffects ofradiationtherapy.Themainradiationtherapymodalityisthe externalbeamradiotherapy,orteletherapytreatment,inwhichthe radiationsourceisplacedoutsidethebodyandtheemittedbeam penetratesthetissuesinteractingwithnormalandcancerouscells [2–4].Amongtheradiationoncologyequipmentavailable,someof themostpopularforthetreatmentofdeepseatedtumorsisthe LinearAccelerator(LINAC),inwhichtheexternalbeamradiation therapyisdeliveredbymeansofhighenergyX-rays(6MV)[5]. LINACisthestandardmethodforproducingphotonsandelectrons deliveredtothetumorwithextremeaccuracysuchasbeam qual-ity,direction,andintensity.Itisprogrammedtosendprecisedoses

∗ Correspondingauthor.Tel.:+553135591667;fax:+553135591667. E-mailaddress:bianchi@iceb.ufop.br(R.F.Bianchi).

ofradiationdirectlytocancercellsinaverytargetedwaythrougha state-of-the-arttherapycalledIntensityModulatedRadiation Ther-apy.Themajorityoftumorsrequiredosesintherangeof8–70Gy, fractionatedindosesof1.8–2.0Gyonceaday,ﬁvetimesaweekfor 5–7weeks.

Wehaveperformedaninvestigationofseveralstudiesonthe impactofradiationoncancertreatments,whichhasbeen summa-rizedinrecentreviewedarticlesbyAbdelazizandBiggs[6,7].Most oftheseworks,however,aimtoallowdoctorstoattacktumors moreprecisely,ratherthanidentifyingradiationinjuriescaused by softwareflaws and faulty programmingonindividualcases, which canbedifficulttocontroldue toLINAC’s complexity[8]. Theseflawshaveaseriousimpactonpatienttreatment,asseen inseveralreportedtreatmenterrorsandincidents[8].Whenthese mistakesoccur,theycanbefatal;itiscriticaltopreventsucherrors inthisextremelyimportantfield.PreviousworkbytheAmerican AssociationofPhysicistsinMedicineandtheAmericanSocietyof RadiationOncologysupportstheviewthat“errorreporting sys-tems shouldbedeveloped in radiationtherapy”to“protectthe safetyofeachandeverypatient”[8–11].Fromthispointofview, aneasy-to-use,easy-to-readandlow-costdosimeter,thatisalso moreaccessibletopeopleinplaceswithlimitedresources,may ensurethateverytreatmentwillbeassafeaspossible.Henceit is aninnovativeproposal forthe psychologicalcomfort of can-cerpatientsas it ensures properfunctioning of LINACs. In this case,eachpatientwillbeabletopersonallymonitortheresponse of the radiation detector shortly before being irradiated and 0925-4005/$–seefrontmatter © 2012 Elsevier B.V. All rights reserved.

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thereforemakingsurethattheprescribeddosefor theircancer treatment will be administered properly, avoiding fatal radia-tion overdose or underdose caused by software problems and poorqualitycontrolforradiationdeliveryinmanyhospitals. Con-comitantly, a notable advance in the development of personal dosimeters for gamma ray detection [12] and blue-light sen-sors[13–15]wasrecentlydemonstratedbysomeoftheauthors thatusestheradiationstabilityoftheopticalpropertiesof tris-(8-hydroxyquinoline)aluminum – Alq3 in chloroform solution

combinedwiththeradiationinstabilityofpoly(2-methoxy-5(2 -ethylhexyloxy)-p-phenylenevinylene) – MEH-PPV to yield an opticallyintegratedandmultifunctionalmaterial.Theresults pre-sentedinthesepapersdemonstratethepotentialuseofMEH-PPV andMEH-PPV/Alq3assmartsystemsforionizingandnon-ionizing

radiationdetectorswhosecumulativedoseiseasilyindicatedbya multicoloredchangeassociatedwiththeradiation-induced degra-dationprocessesofMEH-PPV.Theseresultsreveal,ontheonehand, thepotentialuseofaluminescentpolymerasanactivematerialfor ionizingradiationdetectorsand,ontheotherhand,reﬂect,forthe ﬁrsttime,thescopeofusingthecombinationofalight-emitting polymerandametalcomplexwithadifferenceinopticalemission andintheirdegradationratesinducedbyradiationtoforma poten-tialhybridsystemwhicharerarelyseentogether.Inviewofthe growinginterestinimprovingpatientsafetyinradiationoncology [8,9],itthusappearspromisingtousethishybridsystemasactive materialforhighenergyX-raydetectors.Theinitialmotivationfor thisworkontheevaluationofahigh-energyX-raydoseradiation detectorwastoattempttodevelopasmart,easy-to-read,and inex-pensivereferenceradiationmonitoringorganicdevicebasedonthe substantialdependenceoftheopticalpropertiesofMEH-PPV/Alq3

onX-raydose.Thisdeviceisthuscapableofrecordingthetotal dosedeliveredtotheoncologypatientshortlybeforeaLINAC-based treatment.

2. Experimentalprocedures

Poly(2-methoxy-5(2-ethylhexyloxy)-p-phenylenevinylene)– MEH-PPV and tris-(8-hydroxyquinoline)aluminum – Alq3 were

purchasedfromSigmaAldrichanddissolvedinchloroformat MEH-PPV/Alq3wt/wtsolutionsequalto1/2asdescribedelsewhere[13].

Thesolutionsweretransferredtoglassampouleswhichwerethen ﬂame-sealedtoavoidsolventevaporation.Thespeciﬁcationsfor theampoulesareas follows: nominalvolume,diameter, exter-nalthicknessandwallthicknessof1.25ml,10mm,8.0mmand 0.50mm,respectively. Theirradiation ofthesamplesby X-rays wasperformedin thedark atthe RadiotherapyCenterof Cris-tianoVarellaFoundation,Braziltoevaluatetheeffectofionizing radiationintherangeof0–40Gyontheopticalpropertiesof MEH-PPV/Alq3hybridmaterial.Inthepresentstudy,VarianClinac600C

LINACcomputer-controlledequipmentwithaconventionalX-ray sourcewasused.Thismachinegeneratesa6MVX-raybeamwith rectangularsymmetricﬁelds[11]anddeliverstheexactprescribed dosetothepatientinthelowestnumberofmonitoringunits.The irradiationofsampleswasperformedinawaterphantom accord-ingtoIAEATRS398dosimetryprotocols[16]atasource-surface distanceof100cmwitha(30×30)cm2_ﬁeld_in_order_to_maintain

thechiefconditionsofcancertreatment.Computertomographyof theorganicsystemswasalsoperformedbyusingthesameVarian Clinac600CLINACtoobtainthephysicaldoseparameters describ-ingthedosedistributioninthetargetsamples.Thephotoemission (PL) spectraof MEH-PPV/Alq3 systems wererecorded using an

USB2000OceanOpticsspectrophotometer,whileanInGaNlaser (405nm,5mW)wasusedastheexcitationsource.Finally,UV–vis absorptionspectrawerecarriedoutinthe300–800nmrangeusing theShimadzuUV1650equipment,andthecolorcoordinatesofCIE

Fig.1.UV–visabsorptionandphotoemission(PL)spectraobtainedfrom(a) MEH-PPVand(b)Alq3solutionsexposedto0,20and40GyofhighenergyX-rays(6MV).

Thevisibleelectromagneticspectrumshownontopofthegraphicisintendedto guidetheeyesandshowsthecolor-changingofMEH-PPVinducedbyradiation. (Forinterpretationofthereferencestocolorinthetext,thereaderisreferredtothe webversionofthearticle.)

(1931)chromaticitydiagramwereobtainedusingthePLspectra oforganicsolutionsandtheColorCalculatorFreesoftwarefrom RadiantImaging.Allmeasurementswereperformedatroom tem-perature.

3. Experimentalresults

Fig.1displaystheeffect ofradiationdose(0,20 and 40Gy) deliveredbyLINAConthevariationofUV–visabsorptionand pho-toemission(PL)propertiesofMEH-PPV(Fig.1a)andAlq3(Fig.1b)

solutions.Itshouldbenotedthatdosechangeshavelargerand irreversibleeffectsontheopticalpropertiesofMEH-PPV,buthave littleeffectonthesamepropertiesofAlq3.Itcanbeseenfromthese

resultsthatincreaseddoseradiationresultsintheUV–vis absorp-tionandPLpeaksofMEH-PPVshiftingtowardslowerwavelengths anddecreasinginintensity,whiletheUV–vis absorptionandPL peaksofAlq3areslightlyalteredbytheradiation.Assuggestedby

thepreviousworkofsomeoftheauthorsontheeffectofionizing andnon-ionizingradiationofconjugatedpolymers[12–15,17],we assumethattheblueshiftintheUV–visabsorptionandPLpeak positionsofMEH-PPVresultfromthedecreaseoftheeffective con-jugationlength,andperhapsalsofromthefreeradicalformedas theprimaryproductsduringCHCl3degradationcausedbyionizing

radiationexposure[18].Sincemostfreeradicalsareveryreactive andhaveashortlifetime,theycansufferanaccelerationofseveral stepsinthedegradationprocessofMEH-PPVinducedbythe irra-diationprocess,butdonotinﬂuencetheopticalpropertiesofAlq3.

Inordertoconﬁrmthesecondassumption,theuseofother sol-vents,suchastoluene,insteadofchlorinated-solventsisunderway

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Fig.2. UV–visabsorptionandPLspectraobtainedfromMEH-PPV/Alq3hybrid

mate-rialafterexposuretodosesof0,2.5,5.0,7.5,10.0,12.5,15.0,20.0and40Gy.The visibleelectromagneticspectrumshownontopofthegraphicisintendedtoguide theeyesandshowstheblue-shiftinUV–visabsorptionandPLspectraof MEH-PPV/Alq3inducedbyradiation.(Forinterpretationofthereferencestocolorinthis

ﬁgurelegend,thereaderisreferredtothewebversionofthearticle.)

Fig.3. ChromaticdiagramofMEH-PPV/Alq3chloroformsolutionsafterexposure

todosesof0,2.5,5.0,7.5,10.0,12.5,15.0,20.0and40Gy.Theright-toppicture showsred,yellowandgreenMEH-PPV/Alq3solutionsafterexposuretodosesof0,

20and40Gy,respectively.(Forinterpretationofthereferencestocolorinthisﬁgure legend,thereaderisreferredtothewebversionofthearticle.)

[18].However,theforegoingarguments,althoughinfavorofhow theopticalpropertiesofMEH-PPVareaffectedbyradiation,alone cannotexplain themechanismsinvolved inthecolorchangeof MEH-PPVinCHCl3duringtheradiationprocess,andthusitis

spec-ulatedherethatClradicalscanbeformedduringirradiationand reactwiththepolymerleadingtoadecreaseintheeffective con-jugationlengthofMEH-PPV[18].HereitisestablishedthatCHCl2•

andCl•areproductsofCHCl3exposedtoradiation.Theseradicals

caninitiateoxidationreactionsinthepolymericchainofMEH-PPV. SincetheopticalspectraofAlq3werenotshiftedwiththeradiation

exposure,weassumethattheradiationandthepresenceofradicals didnotcausechangesinthemolecule.Thechemicalreactionsinthe MEH-PPVchainandAlq3moleculewillbeexplainedinfuturework

bytheNMRandFTIRspectroscopiesandGPCchromatography[18]. ThephenomenonofmulticoloredMEH-PPVshowninFig.1a hasnotonlyrevealedtheirreversiblechangesofMEH-PPVfrom redtolight yellowthatoccurduringtheradiation process,but also provided a sensitive and convenientprobe for monitoring andevaluatingtheradiationdoseintherangeof0–40Gy. More-over,aspectraloverlapoftheAlq3greenemission(Fig.1b)with

thepristineandradiationdamagedMEH-PPVabsorption(Fig.1a) is observed.As doseincreases,theoverlapping gradually tends towards zero.The MEH-PPV degradationand theAlq3 stability

under irradiation are the key to develop an irreversible color-changefromredtoyellow,andthentogreen,inorganicradiation detector.

InFig.2itisdisplayedtheeffectofX-rayradiationontheoptical propertiesofMEH-PPV/Alq3system.Specialcarewastakentosee

whethertheAlq3andX-rayplayedanypartinthechangesinthe

UV–visabsorptionandPLspectraofthehybridmaterial.

ThereisacommonpatterninFigs.1and2.Consideringthe ini-tialopticalpropertiesofMEH-PPV/Alq3,itispossibletodistinguish

betweenthecontributionsofMEH-PPV(Fig.1a)andAlq3(Fig.1b)

inthepronouncedspectraloverlapobservedintheUV–vis absorp-tionandPLspectraofthehybridmaterial(Fig.2a).Inaddition,the

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Fig.4. WavelengthsofthemostintenseUV–visabsorption(ABS

max)andPL(PLmax)of

MEH-PPV/Alq3chloroformsolutionsobtainedfromthespectraofFig.2asafunction

oftheradiationdose.Thefulllinesdenotethelinearregressionlines.

opticalcharacteristicsofpristineMEH-PPV/Alq3 (Fig.2a)arenot

related(atleast,directly)tothevariationsofchemicalstructure ofMEH-PPVandAlq3.However,themajorfeatures tonotice in

Fig.2a–earetheprogressiveionizingradiation-induced degrada-tionofMEH-PPVwhichleadstoemissioncolorofMEH-PPV/Alq3

tuningfromredtogreenwiththeincreaseinradiationdose.This isalsoillustratedbythepicturesandinthechromaticitydiagrams ofpristineandirradiatedhybridmaterialshowninFig.3,anditis clearfromthisevidencethatcolorwasusedtoguidethesearch foracolor-indicatordosimeter.Moreover,theUV–visabsorption andPL spectraof theMEH-PPV/Alq3 afterexposuretodoses of

40Gy(Fig.2e) arethesameofAlq3 withoneemissionpeak at

around380nmand515nm(Fig.1b),respectively.Finally,thecolor changeofthehybridmaterialisconsistentwiththereplacement ofthevinylgroupbycarbonylgroupsontheMEH-PPVbackbone [17,19,20]mainlybecauseofdegradationprocessesinducedby X-rays.Itreducestheaverageeffectivepolymerconjugationlength andusuallyactsasaquenchingcenterforexcitonicemission.

Realtimemonitoringdosimetersrequirefastandprecise oper-ation.Oneobservation,whichfollowsregardlessofthechoiceof color-changeofthehybridmaterial,isthatthetuningfromred toanycolor,shownontheCIEchromaticdiagram (Fig.3), that occursduringtheirradiationprocessisirreversibleandtheﬁnal colorisstableforatleastthreemonthswhentheorganicsolutions arestoredinthedarkatroomtemperature.Ourtasknowisto identifythelinearityandsensitivityofthesensorresponse.Firstof all,werestrictedconsiderationtothesetof27ampoulesﬁlledwith

Fig.5. (a)Setof10× 10sealedglassampoulesﬁlledwithMEH-PPV/Alq3chloroform

solutions.(b)Schematicrepresentationofthesetupusedinthedepth-dose simu-lations.(c)Computedtomographicimageofthelocationoftheampoules(isodose analysis).

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Fig.6. Sealedglass ampoulesﬁlled with MEH-PPV/Alq3 chloroform solutions

arrangedalongthex-axesandafterexposuretodosesof18.8Gy,17.8Gy,13.6Gy and12.2Gy.Thetoprightpictureshowsthequadraticarrangementidentiﬁedwith analyzed(blackcircles,blacksquaresandblacktriangles)andnon-analyzed(gray circles)samples.Dosevaluesweredeterminedbyusingtheisodosesshownin Fig.5c.

pristineMEH-PPV/Alq3solutionfollowingtheproceduredescribed

inSection2.Fromthissetofampoules,allthreeofthemwere irra-diatedwiththesamedose(0,2.5,5.0,7.5,10.0,12.5, 15.0,20.0 or40.0Gy).Thisprocedureachievesreasonableagreementwith experimentalresultsshowninFig.2(andthereforetheyarenot showninthispaper),guaranteedreproducibilityinthe prepara-tionprocess,andalsothehighopticalperformanceoftheorganic solution.

Fig. 7.Sealedglass ampoulesﬁlled with MEH-PPV/Alq3 chloroform solutions

arrangedalongthey-axesandafterexposuretodosesof18.8,17.0Gy,15.2Gy, 13.6Gy and 12.2Gy. Thetop right pictureshows the quadraticarrangement identiﬁedwithanalyzed(blackcircles,blacksquaresandblacktriangles)and non-analyzed(graycircles)samples.Dosevaluesweredeterminedbyusingtheisodoses showninFig.5c.

Inordertoobtainthelinearityofthesensorresponse,we consid-eredthewavelengthsofthemostintenseUV–visabsorption(ABS

max)

andPL(PL

max)spectra,butreasonablypracticalparameters,inFig.3.

Fig.4showsthelinearradiation-dosedependenceofABS

maxandPLmax,

andalsothelinearregressionofABS

maxandPLmaxondose(fulllines).

Italowestpercentageerrorisobtainedsomewherearound1%and alargerlinearitycoveringawiderangeofcharacteristicradiation doseavailableatRadiotherapyCenters.

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Fig.8. Sealedglass ampoulesﬁlled with MEH-PPV/Alq3 chloroform solutions

arranged(a)alongthey-axesafterexposuretodosesrangingfrom12.2to18.8Gy, and(b)alongthex-axesafterexposureto15.2Gy.Therightpicturesonthese graph-icsshowthequadraticarrangement(Fig.5b)identiﬁedwithanalyzed(blackcircles, blacksquaresandblacktriangles)andnon-analyzed(graycircles)samples.Dose valuesweredeterminedbyusingtheisodosesshowninFig.5c.Theinsetﬁgure showsthelinearradiation-dosedependenceoftherelationbetweentheabsorption intensitiesat400nmandat475nm.

Inordertodeterminethesensitivityofthesensor response, 100sealedglassampoulesﬁlledwithpristineMEH-PPV/Alq3

solu-tionsplacedinaquadraticarrangement(10×10ampoules)were exposedtoX-raysinawater phantomfordeterminationofthe dynamicbeamisodose.Bearingthesepointsinmind,wefoundthat thedesignprocedurerequiresstraightforwarddepth-dose simu-lationwithComputedTomographic(CT)imagesoftheampoules insidethewaterphantom(isodoseanalysis).

Fig.5showsthequadraticarrangement(Fig.5a),theschematic representationof thesetupusedin thedepth-dosesimulations (Fig.5b),andtheCTimageofampoules(Fig.5c).Straightforward calculationsshowunavoidablepracticalimperfectionsinthe iso-dosedeterminationforeach ampouledue tothelargediameter ofthissystem(=10mm)ifcomparedtothedepth-dosevariation inthesamescale.Thus,it mayintroduce anewsourceoferror intheinduced-radiationeffectontheopticalpropertiesof MEH-PPV/Alq3.Inconsequence,weassumedthattheorganicsolution

willreceiveanaveragedoseperampoule,whichisproportionalto theisodosecalculatedatthecentralaxisoftheampoules.

Figs.6–8showtheUV–visandPLspectraofseveralsamples exposed toX-ray as shown in the schematic representation of Fig.5b.Theinsetintheseﬁguresshowtherelativepositionbetween theampoulesﬁlledwiththeMEH-PPV/Alq3(darkcircles,triangles

andsquares)usedtotracktheprogressontheopticalproperties ofthehybridmaterialinducedbydifferentradiationdoses.The quadraticarrangement wasfoundtobevery usefulfor investi-gatingisodosesonwater phantoms,since theorganicsolutions exposedtoanisodosecurve(alongthex-axis,Figs.6and8a)show

similarUV–vis andPLcurves,whilethosedistributedalong dif-ferentisodoses (alongy-axis,Figs.7and 8b)showconsiderable changethatemphasizesthatthevariationsofthesecurvesaremore pronouncedthehigherthedifferencebetweentheisodosesis. Nev-ertheless,ifoneestimatesanaverageofisodosesfromtheproposed method,thevaluesbetweenthedosesonthetopandonthebottom ofaquadraticarrangementoforganicsolutionsareeasilyobtained. 4. Conclusions

MEH-PPV/Alq3isasuitablesmartmaterialforapplicationina

novel,disposable,andpersonalreal-timeradiationsensortoavoid hazardoussituations.Theoverlapbetweentheemissionspectrum ofAlq3andtheabsorptionspectrumofpristineanddamaged

MEH-PPVistheoperatingprincipleofthissensorwhichworksasanovel “trafficlightdevice”.Aseriesofexperimentswasperformed, demon-stratinglinearityintheshiftofPLandabsorptionasafunctionof thedose.Itisalsoshownthereforethatanarrayofvialscontaining solutionscanbeusedtomapthe2Dradiationdosedeliveredina water-basedphantom.Whatmakesthisanoutstandingdeviceis theeasyindicationofthedeliveredradiationdosetoatarget mate-rial,thusensuring properfunctioningofLINACs. Althougheach patientisdifferentandthereforeeachradiotherapytreatmentis unique,itisimportanttoremarkthatthemonitoringofthisdevice mayalsobeachieved byfirstestablishing calibrationcondition valuesobtainedbypassingaspecificdeliveredradiationdoseto theMEH-PPV/Alq3systemwithdifferentcomposition(wt/wt).This

innovativetoolmustbecarefullydesignedtoobtainthemaximum advantages:apersonal,verylowcost(<US$1),andeasy-to-read doseindicatordevice.Theseadvantagesarekeyrequirementsfor thesuccessfuldevelopmentof innovationsin radiationtherapy. OneofthebeneﬁtsoftenpointedoutinconnectionwithRef.[8] isthattheX-raydosedetectorbasedoncolor-changingof MEH-PPV/Alq3hasthecapabilityofeasilyprovidingtheradiationdose

shortlybeforetheradiationtreatmentofcancerpatients,avoiding afataloverdose.Infact,conventionaldosimetersofferan electri-calread-outthatissigniﬁcantlyeasiertomonitorthanadosimeter whereaspectroscopicmeasurementisrequiredtodeterminethe delivereddose.However,theideathateachpatientwillbeableto monitortheresponseoftheradiationdetectorusinga standard-izedcolorchartshortlybeforebeingirradiatedwithmiscalibrated radiotherapymachinesensuresthateverytreatmentwillbeassafe aspossible,avoidinganyhazard.Acheckagainsttheorganic solu-tionandthecolorcharteasilyindicatesthedosedeliveredfrom theLINAC.Amorepractical implementationofsuchtechnology wouldclearlyneedtobebasedonasolidthinﬁlmforanumberof safetyreasonsandtobeeasilyusedinclinicalapplications,andthus becominganimportantsubjectofstudyforfuturepublications. Acknowledgments

TheauthorswishtothankClaireLochnerforproof-readingthe manuscript.TheresearchwassupportedbytheCNPqunderthe grantnumbers305646/2010-9andPDE200682/2011-3,byRede Nanobiomed/Capes, by Fapitec-SE/CNPq, by Fapemig underthe grantnumbersPPM-00596-11,PPM-00306-09andAPQ-04124-10, andbyINEO/CNPqAgenciesfromBrazil.AndreaG.C.Bianchiwas alsosupportedbyCapes(BEX0761/11-7),CNPq(472565/2011-7), andFapemig(APQ-00802-11).

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Biographies

ThiagoSchimitbergerisaPhDcandidateofFederalUniversityofMinasGeraisin ScienceandNuclearTechniques.HiscurrentresearchisthefabricationofX-ray dosimeteranditsapplicationinmedicalﬁelds.

GiovanaRibeiroFerreiraisaPhDcandidateofFederalUniversityofOuroPreto inMaterialsScienceandEngineering.Hercurrentresearchistheinvestigationof photodegradationprocessofpoly(p-phenylenevinylenes)derivative.

MarceloFrotaSaraivareceivedhisMedicalPhysicsSpecializationdegreefrom HospitaloftheMedicalSchoolofUniversityofSãoPaulo.Presently,heisthe coor-dinatorofRadiotherapyCenterofCristianoVarellaFoundation(HospitaldoCâncer deMuriaé),MuriaéBrazil.Hismainresearchinterestsincluderadiationtherapyand medicaldevices.

AndreaGomesCamposBianchireceivedherPhDdegreefromUniversityofSão Pauloin2003,andcurrentlysheisanafﬁliateresearchatVisualizationGroupat LawrenceBerkeleyNationalLaboratory.SheisaProfessorinDepartmentofPhysics, FederalUniversityofOuroPreto,MGBrazil.

RodrigoFernandoBianchiisaprofessorinDepartmentofPhysics,Federal Uni-versityofOuroPreto,MGBrazil.HereceivedhisPhDinMaterialsScienceand EngineeringfromUniversityofSãoPauloin2002.Heservedasapostdoctoral researchassociateattheInstituteofPhysicsofSãoCarlosatUniversityofSãoPaulo (2002–2006).Presently,heisavisingscholaratDepartmentofElectrical Engineer-ingandComputerScienceatUniversityofCalifornia-Berkeley,USA.Hiscurrent researchinterestsincludeorganicelectronicandmedicaldevices.