Gamma Ray Emitting Brachytherapy Sources

1 Page 1 NBSMeasurement Services: NEWNIST Apr i1 PUBLICATION 20,1989 JamesT.Weaver ThomasP.Loftus RobertLoevinger U.S.DepartmentofCommerce NationalBureauofStandards Open at page → 2 Page 2 CenterforRadiationResearch TheCenterforRadiationResearchisamajorcomponentoftheNationalMeasurementLaboratoryintheNational BureauofStandards. TheCenterprovidestheNationwithstandardsandmeasurementservicesforionizing radiati... Open at page → 3 Page 3 NBSMEASUREMENTSERVICES: CALIBRATIONOFGAMMA-RAY- EMITTINGBRACHYTHERAPYSOURCES JamesT.Weaver ThomasP.Loftus RobertLoevinger CenterforRadiationResearch NationalMeasurementLaboratory NationalBureauofStandards Gaithersburg,MD... Open at page → 4 Page 4 LibraryofCongressCatalogCardNumber:88-600609 NationalBureauofStandardsSpecialPublication250-19 Natl.Bur.Stand.(U.S.),Spec.Publ.250-19,60pages(Dec.1988) CODEN:XNBSAV Commercialproducts—materialsandinstruments—areidentifie... Open at page → 5 Page 5 PREFACE ThecalibrationandrelatedmeasurementservicesoftheNationalBureau ofStandardsareintendedtoassistthemakersandusersofprecision measuringinstruments inachievingthehighestpossiblelevelsof accuracy,quality,andproductivit... Open at page → 6 Page 6 Abstract .Thecalibration ofsmallradioactivesourcesusedforinterstitial radiationtherapy(brachytherapy )isperformed intermsofthephysical quantitiesexposureorairkerma. Thecalibrations arelistedinNBSSpecial Publication 250as... Open at page → 7 Page 7 TableofContents Page Abstract iv ListofTables vi ListofFigures viii Foreword ix 1.Introduction 1 1.1.Description oftheservice 1 2.Designphilosophyandtheory 5 3.Thelong-half-life radionuclides --^^^Csand^^Co ^ 3.1.Therepl... Open at page → 8 Page 8 ListofTables Page 1-1.Characteristics oftheradionuclides acceptedforbrachytherapy calibration 3 1-2.Rateconstantsforthebrachytherapy radionuclides calibrated at NBS 4 3-1.EngravingonNBSstandard ^^"^Csand^^Cosources 9 3-2... Open at page → 9 Page 9 ListofTables(Continued) Page 4-1.Constancycheckofaluminumreentrantionizationchamberforthe years1977through1987 22 4-2.Dimensionsandmaterialsfortwotypesof^"^^Irseeds 23 4-3.Reentrantchambercalibration factorsatSTPfor^'^^r... Open at page → 10 Page 10 ListofFigures Page Figure1.Calibration rangeforbrachytherapy sources 6 Figure2.Cross-section viewofthepolystyrenebasethatsupportsthe 2.8-litersphericalaluminumionizationchamber 10 Figure3.Aluminumreentrantionizationchamb... Open at page → 11 Page 11 FOREWORD NBSSpecialPublications 250-16and250-19 canbeconsideredmonuments totheskillanddedication ofThomasP.Loftus. TomcametotheRadiological EquipmentSectionofNBSin1951,workingunderDr.ScottSmith,Section Chief,andDr.H.0.Wy... Open at page → 13 Page 13 1.Introduction Thisreportdescribesthestatusofthecalibrationservicefor brachytherapy gamma-raysources,asofDecember1987. Section 1definesthe physicalquantitiesexposureandairkerma,intermsofwhichthecalibrations areperformed;... Open at page → 14 Page 14 Then X=dQ/dm . (1) TheSIunitofexposureisthecoulombperkilogram(C/kg);thespecialunit ofexposure,theroentgen(R),isequalto2.58x10"'+C/kg(exactly). The ionizationarisingfromtheabsorptionofbremsstrahlungemittedbythe secondarye... Open at page → 15 Page 15 multiplicative constantisneededtoconverttheformerquantitytothe latter. Whilethetextissimplified byusingtheword"exposure"toimply bothphysicalquantities, airkermaisnamedexplicitlywhennumericalmagni- tudesareinvolved,orwhen... Open at page → 16 Page 16 Brachytherapy sourcesaregamma-ray-emitting radionuclides encapsulated inasuitablemetal,ordinarilychosentobeinnocuoustotissue. Theycome inavarietyofforms,oftenreferredtoas"seeds,""tubes,"or"needles," butsometimescomingint... Open at page → 17 Page 17 2. Oesignphilosophyandtheory Rrachytherapy sourcesareprovidedwithcalibrations internsofexposure rateatonemeterperpendicular totheaxisofthesource,correctedto vacuum. Thecalibration isbasedonmeasurements ofotherbrachythera... Open at page → 18 Page 18 6 Open at page → 19 Page 19 Figure1.Calibration rangeforbrachytherapy sources. y A.Sphericalionizationchamberfor^^Coand^^'^Cssources. B.Sourceholderfor^^Coand^^^Cssources. C.Slideforsourceholder. Distancefromsourcecentertochambercenteris variablefr... Open at page → 20 Page 20 3. Thelong-half-life radionuclides --^^^Csand^QCo 3.1.Thereplacementmethod Small-source calibration bythereplacementmethodconsistsof measurement oftheradiationfromastandardsourceS,andthen,after replacingthestandardwithth... Open at page → 21 Page 21 Table3-1.EngravingonNBSstandard ^^'^Csand^^Cosources. Engraving on Sourceidentity Cylinderwall Endwall SOCo"500" ICN 2-9-76 995 500MC CO-60 60Co"100" CO-60 100MC 996 2-9-76 ICN I37cs "500" Csl37 N.C.C. D49 I37cs "50" Csl... Open at page → 22 Page 22 Ttft83798 CONNECTORWITH frreinsolation Figure ?..Cross-section viewofthepolystyrenebasethatsupportsthe 2.8-litersphericalaluminumionizationchamber. Italsoprovides high-voltage insulation, andsupportstheguardringandthe co... Open at page → 23 Page 23 Table3-3. Typicalrecombination dataforthe2.8-litersphericalaluminum ionizationchamber(HB806:27). Thepolarityofthechamberwall isnegative. Thetablegivesthereciprocal ofthenormalized current. Collection Normalizedvaluesfort... Open at page → 24 Page 24 Therestriction onthelengthofasourcetobecalibrated isonlythatitfit intothetrough. Intheworstcase,ifalltheactivityofasourcecapsule 50mminlengthwereconcentrated atoneend(25mmoffcenter),the geometrical error,neglectingobliqu... Open at page → 25 Page 25 Table3-5.Relativeexposureratesfor^^'^Csworkingstandards,basedon1967 measurements. Source Relativeexposurerates "son" ion "50" 10.80 "5" 0.932 3.2.2. Presentstandards TheNBSexposurestandardsfor^^Coand i^tq^ gammarayswerer... Open at page → 26 Page 26 Inadditiontotheoriginalmeasurement in1967,the"500"sourcehas beencheckedtwiceinopen-airgeometry, in1978andin1983. Table3-7gives theoriginalmeasurements andtheexposureratescorrectedtothe1974and 1986exposurestandards. Table... Open at page → 27 Page 27 Table3-9. Bestvaluesfor^^'^Csworkingstandardsbasedonmeanofthree measurements ofthe"500"sourceintheperiod1967-1983. The dataareconsistentwiththe1986exposurestandard,andare correctedto1986Jan01usingahalf-lifeof30.0years. S... Open at page → 28 Page 28 3.3.2. Presentstandards Comparedto^^"^Cs,therearenowfewrequestsfor^°Cosmall-source calibrations. Onereasonperhapsistherelativelyshorthalf-lifefor^°Co ^'^^y)' Theshorthalf-lifefor^^Coalsoposestheproblemof maintainingstand... Open at page → 29 Page 29 Table3-12. MeanexposurerateforthetwoICN^°Cosources,adjustedtothe 1986standard. Source ICN Meanexposurerate 19%Janni (mRm2/h) 100 500 26.39±0.1% 141.3 Asshownintable3-11,theICN100sourcewasmeasuredonthree occasions,withati... Open at page → 30 Page 30 3.4.Uncertaintyassessmentfor^^^Csand""^Cosources Themethodofuncertaintyassessmentusedherefollowstherecommendation oftheComiteInternational desPoidsetMesures(CIPM). Theuncertainty estimatesareoftwokinds. Conventional stat... Open at page → 31 Page 31 Table3-14.Uncertaintyanalysisfor^^'^Csand^^Cosourcecalibration by substitution. A B {%) (%) (a)Measurement ofsecondaryworkingstandard usingprimarygraphitestandardchambers. Volume n.l 0.05 Charge 0.04 0.1 Timing 0.03 0.03... Open at page → 32 Page 32 NotestoTable3-14 Theuncertaintyestimatesareattheone-sigmalevel,andareinpercent. The columnsheadedAandBrefertotheestimatesdescribed inthetextasTypeA andTypeB. Chargeincludesuncertainties forbothvoltageandcapacitance. Aird... Open at page → 33 Page 33 4. Theshort-ha1f-1iferadionuclides --^^^rand ^^Sj 4.1.Thereentrantchamber Areentrant-type (well-type) ionizationchamber,illustrated infigure3, isemployedinthecalibration ofsmallsourcesoftheseradionuclides. The chamberisa... Open at page → 34 Page 34 Incontrasttothecalibration ofsmallsourcesof^°Coand^'^^Cs,where thereferenceforcalibration residesinsourcestandards,thereferencefor exposurestandardization of^^^Irand ^^Sj sourcesresidesinthecalibration factorsforthereent... Open at page → 35 Page 35 Sincethealuminumsphereisathighpotential, itisnecessarytouse aninsulatingholderwhenputting ^'^'^Irsourcesintothebrassreentranttube. Theholderisaglassvial65mminlengthwithanouterdiameterof9.2mm andawallthicknessof1.4mm(0.29... Open at page → 36 Page 36 Theionizationcurrentsproducedby^'^^Irsourcesinthereentrant chambermustbecorrectedforrecombination. Testsshowthatatacollection potential of1100volts,andionizationcurrentsuptoabout80pA,the recombination correction isconsta... Open at page → 37 Page 37 Themeanofthedecay-corrected currentsis31.21pA(usingthehalf-life 73.83days). Thereentrantionizationchambercalibrationfactorforthe stainless-steel-clad ^'^^Irsourcesis3.209kRm^/As,andsincethe ionizationcurrentislessthan80p... Open at page → 38 Page 38 Table4-5. ^^^lseedtypesandtheirassociatedreentrant ionization-chamber calibration factors. 3-MCo. Model No. Type Details* Calibrationfactors Before1986 1986Jan01 (kRm2/As) (kRm2/As) 6701 Gold- 1251adsorbedontworesin 3.85... Open at page → 39 Page 39 Duetoexperimental difficulties, longperiodsoftimeelapsedbetween theinitialfree-air-chamber andreentrant-chamber measurements forsomeof the1251seeds. However,forthemostpart,theFAC-reentrant chamber measurement intervalwas... Open at page → 40 Page 40 Forthepurposeofcalculatingtheuncertainties intheattenuation corrections, thevalue(1.5±0.7) x10~3cm~iisadopted. Becauseofthe assumptionofexponential attenuation, thefractionaluncertainty intheair attenuationcorrectionfact... Open at page → 41 Page 41 2.Withthehigh-voltaye supplyturnedoff,thehiyh-voltage connection tothereentrantchambershouldbechecked. Itisgoodpracticetoturnthe screwthatactsastheconnectortothechamberwallandtorotatetheclip connectingthehigh-voltagewire... Open at page → 42 Page 42 9.Withtheelectrometer feedbackshorted,turnoffthehighvoltage switchandreturnthesourcetoitsdrawerinthesafe. Thesourceis unloadedfromthethistletubebylettingitslideoutintothewhiteplastic tray. 10.Checkthatthehighvoltageisoff... Open at page → 43 Page 43 Importantinformationalwaystoberecorded isasfollows: 1.Personperformingcalibration. 2.Date. 3.Equipment(Indicateifsame,ordifferentfrom,equipmentused previously) . 4.Capacitance (Identify,referencecalibration). 5.HVandpola... Open at page → 44 Page 44 14.Applytheappropriaterecombination correctiontothecomputed ionizationcurrent. 15.Multiplythemeancorrectedionizationcurrentbytheappropriate reentrantchambercalibrationfactortodeterminetheexposure(or airkerma)rateatonemet... Open at page → 45 Page 45 Table4-7.Uncertaintyanalysisfor^^^Irsourcecalibrationwiththe reentrantchamber. A B (%) {%) Measurementofarrayofseedsusing graphitestandardchambers Volume 0.01 Charge 0.03 0.05 Timing 0.01 Airdensity 0.03 0.05 Recombinati... Open at page → 46 Page 46 Table4-7.Continued (%) {%) Measurement ofsingleunknownsource1n reentrantchamber Charge 0.05 0.1 Timing 0.01 Airdensity 0.05 0.1 Recombination loss 0.1 Leakageandradiationbackground 0.02 Reproducibility inreentrantchamber... Open at page → 47 Page 47 Table4-8.Uncertaintyanalysisfor I25j sourcecalibrationwiththe reentrantchamber. A1 1 AU-•mark Ag-•wire INO-mark A n D D A A D D A D ts (/o) (/o) [lo) (A) Sourcearray Exposurerate U.1)/ 0.07 0.33 0.0/ 0.33 Leakage 0.4 0.2... Open at page → 48 Page 48 NotestoTable4-8. Theuncertaintyestimatesareattheone-signalevel,andareinpercent. The columnsheadedAandBrefertotheestimatesdescribedinthetextasTypeA andTypeB. ThecolumnsheadedAu-mark,Ag-wire,andNo-markrefertothegold-narker... Open at page → 49 Page 49 Basedontheassessment ofuncertainties describedhere,thefollowing areadoptedastheoveralluncertainties forsourcescalibratedwiththe reentrantionizationchamber: Theoveralluncertainty isconsideredtohavetheapproximatesignifican... Open at page → 50 Page 50 Radiationbadgesmustbewornatalltimeswhileworkingwithbrachy- therapysources. Inparticular, fingerbadgesmustbewornwhenthesources arebeingmanipulated inanymanner. Therateconstantslistedintable1-2 canbeusedtoestimateexposures... Open at page → 51 Page 51 References [1]NBS,NBSCalibrationServicesUsersGuide1986-88 .NBSSpecial Publication250,G.A.Uriano,etal.,Editors,U.S.Departmentof Commerce,NationalBureauofStandards, U.S.GovernmentPrintingOffice, Washington, D.C.July1986. [... Open at page → 52 Page 52 [14]Loftus,T.P.,Exposurestandardization ofiodine-125seedsusedfor brachytherapy. J.Res.Nat.Rur.Stand.(U.S.)89,295-303(1984). [15]Kubo,H.,Exposurecontribution fromTiKxraysproducedinthetitanium capsuleoftheclinical1-125seed... Open at page → 53 Page 53 APPENDIXA AttachmentconcerningadjustmentofNBSexposurerates. ExposurerateswereadjustedatNBSon1986Jan01totakeintoaccount recentrefinements insomeofthephysicalparameters .Exposureratesin allreportsissuedafter1986Jan01arelow... Open at page → 55 Page 55 APPENDIXB DG7890/86 TFN234668 DB851:156-163 1986May9 U.S.DEPARTMENTOFCOMMERCE NATIONALBUREAUOFSTANDARDS GAITHERSBURG ,MARYLAND20899 ReportofExposure-rateMeasurement of OneCesium-137SourceEngraved3M151267 Submittedby Colo... Open at page → 56 Page 56 DG7890/86 1986May9 Page2of3 Thecylindricalsourceengraved3M151267isapproximately 20mminlength and3mmindiameter. Nodetermination ofradionuclidic puritywas performed . Thestrengthofthissourceisgivenintermsoftheexposureratea... Open at page → 57 Page 57 AttachmentconcerningadjustmentofNBSexposurerates. ExposurerateswereadjustedatNBSon1986Jan01totakeintoaccount recentrefinements insomeofthephysicalparameters. Exposureratesin allreportsissuedafter1986Jan01arelowerthanthee... Open at page → 59 Page 59 APPENDIXC DG8798/87 TFN240725 DB875:151-161 1987Dec17 U.S.DEPARTMENTOFCOMMERCE NATIONALBUREAUOFSTANDARDS GAITHERSBURG. MD20899 Page 1of3 REPORTOFAIR-KERMA-RATEMEASUREMENT Iridium-192Seed Manufacturedby For BestIndustries... Open at page → 60 Page 60 DG8798/87 1987Dec17 1 Page2of3 TheAmericanAssociationofPhysicistsinMedicinehasrecommendedthat air-kermastrengthbegivenintheunitsmicrograysmeterssquaredperhour ("Specification ofBrachytherapy SourceStrength",AAPMReportNo.... Open at page → 61 Page 61 AttachmentconcerningadjustmentofNBSexposurerates. ExposurerateswereadjustedatNBSon1986Jan01totakeintoaccount recentrefinements insomeofthephysicalparameters. Exposureratesin allreportsissuedafter1986Jan01arelowerthanthee... Open at page → 63 Page 63 APPENDIXD DG8844/88 U.S.DEPARTMENTOFCOMMERCE Page 1of2 TFN241000 NATIONALBUREAUOFSTANDARDS DB875:162-200 GAITHERSBURG ,MD20899 DB882:4-12 1988Mar08 REPORTOFAIR-KERMA-RATEMEASUREMENT Model6711Iodine-125Seed LotNo.ISW-804... Open at page → 64 Page 64 DG8844/88 1988Mar08 Page2of2 TheAmericanAssociationofPhysicistsinMedicinehasrecoiiunendedthatair kermastrengthbegivenintheunitsmicrograysmeterssquaredperhour ("Specification ofBrachytherapy SourceStrength",AAPMReportNo.2... Open at page → 65 Page 65 AttachmentconcerningadjustmentofNBSexposurerates. ExposurerateswereadjustedatNBSon1986Jan01totakeintoaccount recentrefinements insomeofthephysicalparameters. Exposureratesin allreportsissuedafter1985Jan01arelowerthanthee... Open at page → 67 Page 67 NBS-n4A(REV.2-8C) U.S.DEPT.OFCOMM. 1,PUBLICATIONOR 2.PerformingOrgan.ReportNo,3.PublicationDate BIBLIOGRAPHICDATA RPPnRTMO Decenber1988 SHEET(Seeinstructions) NBS/SP-250/19 4.TITLEANDSUBTITLE NBSMeasurementServices: Cali... Open at page → 71 Page 71 THESP250SERIESONNBSMEASUREMENTSERVICES* SP250-1 SpectralRadianceCalibrations SN003-O03-02792-8 $3.50 SP250-2 FarUltravioletDetectorStandards PB87227609 SP250-3 RadiometricStandardsintheVacuum Ultraviolet SN003-003-02806-... Open at page → 72 Page 72 U.S.DepartmentofCommerce NationalBureauofStandards Gaithersburg,MD20899 OfficialBusiness PenaltyforPrivateUse$300 Open at page →