ML21068A410

From kanterella
Jump to navigation Jump to search
Advisory Committee on the Medical Uses of Isotopes (ACMUI) March 16, 2021 Meeting Ebinder and Handout
ML21068A410
Person / Time
Issue date: 03/16/2021
From:
Advisory Committee on the Medical Uses of Isotopes
To:
Jamerson K
References
Download: ML21068A410 (70)
v • d • e


Text

Advisory Committee on the Medical Uses of Isotopes March 16, 2021

MEETING AGENDA ADVISORY COMMITTEE ON THE MEDICAL USES OF ISOTOPES March 16, 2021 Virtual Meeting NOTE: Sessions of the meeting may be closed pursuant to 5 U.S.C. 552(b) to discuss organizational and personnel matters that relate solely to internal personnel rules and practices of the ACMUI; information the release of which would constitute a clearly unwarranted invasion of personal privacy; information the premature disclosure of which would be likely to significantly frustrate implementation of a proposed agency action; and disclosure of information which would risk circumvention of an agency regulation or statute.

TUESDAY, MARCH 16, 2021 OPEN SESSION

1. Opening Remarks Mr. Einberg will formally open the meeting and Mr. Williams will provide opening remarks.

C. Einberg, NRC K. Williams, NRC

2. Old Business Ms. Jamerson will review past ACMUI recommendations and provide NRC responses.

K. Jamerson, NRC 10:00 - 12:30

3. Extravasations in Nuclear Medicine Dr. Jochem van der Pol will provide an overview of his study on the consequences of radiopharmaceutical extravasation and therapeutic interventions.

J. van der Pol, MD, Maastricht University Medical Centre

4. Open Forum The ACMUI will identify medical topics of interest for further discussion.

ACMUI

5. Patient Release Evaluation of Emerging Brachytherapy Sources Dr. Tapp will provide an overview of the current status of the NRCs evaluation of patient release following administration of new emerging brachytherapy sources.

K. Tapp, PhD, NRC 12:30 - 1:00 BREAK

6. ACMUI Reporting Structure Ms. Jamerson will provide an overview of the current reporting structure.

Members will discuss the reporting structure of the Committee and provide feedback to the NRC.

K. Jamerson, NRC 1:00 - 3:00

7. Calibration Procedures for Brachytherapy Sources Dr. Larry DeWerd will provide a presentation on the calibration procedures for existing brachytherapy sources and considerations for emerging manual brachytherapy sources.

L. DeWerd, PhD, University of Wisconsin

8. Open Forum The ACMUI will continue discussion on medical topics of interest.

ACMUI

9. Administrative Closing Ms. Jamerson will provide a meeting summary and propose dates for the fall 2021 meeting.

K. Jamerson, NRC 3:00 ADJOURN

2019 ACMUI RECOMMENDATIONS AND ACTION ITEMS ITEM DATE Target Completion Date for NRC Action 17 The ACMUI endorsed the Appropriateness of Medical Event Reporting Subcommittee report and the recommendations provided therein.

9/10/2019 Partially Accepted Open Summer/Fall 2021 18 The ACMUI endorsed the Evaluation of Extravasations Subcommittee Report, as amended, to note that under future revisions to Part 35 rulemakings, extravasations be captured as a type of passive patient intervention in the definition of patient intervention.

9/10/2019 Accepted Open Summer/Fall 2021 STATUS 1

2020 ACMUI RECOMMENDATIONS AND ACTION ITEMS ITEM DATE Target Completion Date for NRC Action 4

The ACMUI endorsed the Patient Intervention subcommittee report, as presented, and the recommendations provided therein.

03/30/2020 Accepted Open Summer/Fall 2021 10 The ACMUI endorsed the Medical Event Subcommittee Report as presented.

09/21/2020 Accepted Propose closure 11 As part of the Non-Medical Events report, the ACMUI recommended to the NRC staff and/or NMP to evaluate the issue of detection of short-lived medical isotopes in municipal waste (waste from nuclear medicine patients that might be triggering the landfill alarms) and provide some level of guidance, best practices, or additional instructions.

09/21/2020 Accepted Open Fall 2021 12 The ACMUI tentatively scheduled its spring 2021 meeting for March 15-16, 2021. The alternate date is March 22-23, 2021.

Virtual or in-person meeting is TBD, as well as timing of next ACMUI Commission meeting.

09/22/2020 Accepted Propose closure STATUS 1

March16,2021 JochemvanderPol Nuclear Medicine Physician MaastrichtUniversityMedical Center RadionuclideExtravasation Introduction Amsterdam Maastricht JochemvanderPol Nuclear Medicine Physician (2017)

MaastrichtUniversityMedical Center Clinical areasofinterest:neurological,oncological and cardiovascular imaging Scientific areasofinterest:cardiovascular nuclear imaging 1

2

ExtravasationLiteratureStudy

  • Discussionfollowingacaseof99mTctracerextravasation
  • Protocol:how to actincaseofextravasation
  • Noguidelines DutchAssociationofNuclear Medicine (NVNG),

EANM,SNMMI,DGN(Germany)

  • find literature ExtravasationLiteratureStudy Localprotocol:howtoactincaseofextravasation?

Noguidelines DutchAssociationofNuclear Medicine (NVNG),EANM, SNMMI,DGN(Germany) extensive literature searchand analysis,why not publish 3

4

ExtravasationLiteratureStudy Localprotocol:howtoactincaseofextravasation?

- Can extravasation cause deterministic effects,such asskinburn?

- Shouldyouapplyanykindoftherapy?

- Cooling orwarming?

- Should you perform dosimetry and how?

Methods Extensive literature searchinPubmed and Embase Searchstrings:

5 6

Methods Merging ofresults Embase and Pubmed Screeningofabstractsby two persons If abstractmentioned humaneradioactive tracerextravasation, publication wasmarked for further analysis.

Marked publications were retrieved from onlinesources,university libraries orby trackingauthors and subsequent emailcorrespondence Bibliographies were screened to complementdatabasesearch Methods Datawasextracted from publications:

- Number ofcases

- tracerinvolved

- Injection place

- Estimated extravasated volumeand activity

- Estimated tissuedose

- Followupduration and method

- Applied medical interventions

- Advised/discouraged 7

8

Results 4523abstracts(1123inboth searchengines)

Rejected abstracts 1012animal studies 2622extravasation/infiltration ofsubstance other than radiopharmaceutical 196Extravasation asapathological finding not associated with injection ofradiopharmaceutical (ie99mTcMAG3excretion 603Radionuclideuse for other purposes (s.a. radio immunoassays)

Results

  • Fulltext retrieval81publications
  • After screeningreferences,afurther 27publications were retrieved (108)
  • 44publications about radiopharmaceutical extravasation:
  • 37diagnostic
  • 8therapeutic
  • 10expertopinionbased publications 9

10

Results:DiagnosticTracerExtravasations Results:DiagnosticTracerextravasations Wagner,T.,etal.(2011)."Afalsepositivefindingintherapeuticevaluation:

hypermetabolic axillarylymphnodeinalymphomapatientfollowingFDG extravasation."Nucl MedRevCentEastEur 14(2):109111.

11 12

Results:DiagnosticTracerextravasations Wagner,T.,etal.(2011)."Afalsepositivefindingintherapeuticevaluation:

hypermetabolic axillarylymphnodeinalymphomapatientfollowingFDG extravasation."Nucl MedRevCentEastEur 14(2):109111.

Results:DiagnosticTracerextravasations Alibazoglu,H.,etal.(1998)."InjectionartifactonFDGPETimaging."ClinicalNuclear Medicine 23(4):264265.

13 14

Results:DiagnosticTracerExtravasations Evaluation190FDGPETscans 39(21%)with visible focusinjection site 36less than 1%injected dose 3with 3,0%,7,7%17,5%

PercentchangeinSUVmaxrangedfrom021%

HallN.,Z.J.(2006)."ImpactofFDGextravasationonSUVmeasurements."JNucl Med 47(suppl 1):115P.(SNMMI2006Posterpresentation)

Results:DiagnosticTracerextravasations Evaluation400FDGPETscans 42(10,5%)with noticable extravasation 5caseswith repeat studieswithouttherapy Mediastinal SUVchange9,3%

Hepatic SUVchange:11,7%

Osman,M.M.,etal.(2011)."FDGDoseExtravasationsinPET/CT:Frequency andImpactonSUVMeasurements."FrontOncol 1:41.

15 16

Results:DiagnosticTracerExtravasations Results:DiagnosticTracerextravasations Boxen,I.(1985)."Inadvertentlymphoscintigraphy?"Clin Nucl Med10(1):2526 17 18

Results:DiagnosticTracerExtravasations Results:DiagnosticTracerextravasations Breen,S.L.andA.A.Driedger (1991)."Radiationinjuryfrominterstitialinjectionof iodine131iodocholesterol."JNucl Med 32(5):892.

34MbqIodocholesterol After 13days erythematous pruritic patch Completetracerretention after 7days 19 20

Results:DiagnosticTracerExtravasations Anon.(1988)."Europeansystemforreportingofadversereactionsanddrugdefects:

Thirdreport19841985."EuropeanNuclearMedicineSocietyNewsLetter(9):487490.

Results:TherapeuticTracerExtravasations Anon.(1988)."Europeansystemforreportingofadversereactionsanddrugdefects:

Thirdreport19841985."EuropeanNuclearMedicineSocietyNewsLetter(9):487490.

21 22

Results:TherapeuticTracerExtravasations Results:TherapeuticTracerExtravasations 23 24

Results:TherapeuticTracerextravasations Anon.(1988)."Europeansystemforreportingofadversereactions anddrugdefects:Thirdreport19841985."EuropeanNuclear MedicineSocietyNewsLetter(9):487490.

Results:TherapeuticTracerExtravasations Anon.(1988)."Europeansystemforreportingofadversereactions anddrugdefects:Thirdreport19841985."EuropeanNuclear MedicineSocietyNewsLetter(9):487490.

25 26

==

Conclusions:==

LiteratureStudy

  • Extravasation oftracersiscommon
  • Noadverseeffects of18F,99mTc,123Iand Ga68reported >

noreason to assume extravastion ofthesetracershasclinical significance.

  • Sporadic reports ofother diagnostic tracershavedescribed softtissuelesion
  • Multipelereports ofsevereadverseeventsfollowing therapeutic tracerextravasation.

WhatisthefrequencyofextravasationsinNuclearMedicineand whatcriteriashouldbeusedforidentifyinganextravasation (visualization,%injecteddose,etc.)?

Frequency:unknown MUMC20072018 Reportedradionuclideextravasations3(FDG)(est.

6.000/year)

Reportedcontrastextravasation:91(est.50.000/year)

Literature Nonationalregistration 27 28

WhatisthefrequencyofextravasationsinNuclearMedicineandwhat criteriashouldbeusedforidentifyinganextravasation(visualization,%

injecteddose,etc.)?

Whatcriteria:

Clinical:painfulinjection,swellingandrednessorpalor

%Injecteddose Diagnostic:doesntseemtoberelevant.

Qualityisaparameteranynuclearmedicinephysicianshould monitor.

Ifqualityisbelowstandards,considerrepeatstudy,alwaysperform internalregistrationforqualityimprovement(irrespectiveofthe cause)

Therapeutic:anyextravasationnotedatanytimepoint shouldbe adequatelytreatedandregistered,irrespectiveofdose Whatistheappropriatenessofreportingextravasationsthatresultin acertaintissuedosethreshold(0.5Sv)asaMedicalEvent(Adverse Event)?

  • Howwillthedosebecalculated?
  • Erythemathreshold 2.5Sv 29 30

HowdoestheEuropeancommunityaddressreportingof extravasations?

  • NoEuropeanlegislation TheEUdoesnotdefinehealthpolicies,northeorganisation andprovisionofhealthservicesandmedicalcare.Instead,its actionservestocomplementnationalpoliciesandtosupport cooperationbetweenmembercountriesinthefieldofpublic health.

HowdoestheEuropeancommunityaddressreportingof extravasations?

Dutchlegislation:

Nodefinitionsormentioningof(radiopharmaceutical) extravasation Differentdefinitionsofadverseevents:

Complications Incidents Calamity 31 32

HowdoestheEuropeancommunityaddressreportingof extravasations?

Complication:anunintentionalandundesiredoutcomeduringorfollowingtheactions ofamedicalcareprovider,whichdemandsadaptationofthemedicalprocedureof causesirreparabledamage Workedaccordingtomedicalstandards Unintendedoucome Incident:Anunintentionalorunexpectedevent,thatisrelatedtoqualityof healthcareandthatcouldhaveledtothedeathofaclient[patient]orseriousharmful consequencesforaclient[patient]

Calamity:Anunintentionalorunexpectedevent,thatisrelatedtoqualityofhealthcare andthathasledtothedeathofaclient[patient]orseriousharmfulconsequencesfora client[patient]

HowdoestheEuropeancommunityaddressreportingof extravasations?

Whendowereporttohealthcareauthorities:

Calamities Incidentsandcomplicationsarereportedandregisteredlocally,as advisedbyhealthcareprofessionalsocieties.

unlesswhenthenatureisnotclearandcalamityisnotruled outAuthoritiesadviseonevent.

33 34

Whataretheissues/challengesindeterminingthetissue dosefromanextravasation?

Geometry Pointsourcenot realistic,distance >10times diameter Discshaped source,complexmathematics Activityconcentration isagreat factorindose calculations Whataretheissues/challengesindeterminingthetissue dosefromanextravasation?

Geometry Pointsourcenot realistic,distance >10times diameter Discshaped source,complexmathematics Activityconcentration isagreat factorindose calculations 35 36

Whataretheissues/challengesindeterminingthetissue dosefromanextravasation?

Geometry Pointsourcenot realistic,distance >10times diameter Discshaped source,complexmathematics Activityconcentration isagreat factorindose calculations What about cystic distribution?

Homogenity ofdistribution?

Realworld:very complexgeometry with evolving boundaries Whataretheissues/challengesindeterminingthetissue dosefromanextravasation?

Biological halflife Probably less relevantfor shorthalflifePETtracers Morerelevantfor tracerswith longer halflife Dynamic behaviour:multipleacquisitions 37 38

Whatpersonneltraining,qualifications,andqualityassuranceshould beinplacetomonitor/preventforextravasationsinmedicine?

Technician ProperlytrainedforobtainingIVaccess (Specialexceptiontoperformmedicalprocedure)

Nuclearmedicinephysician/Radiologist Alwayscheckimagequality.Ifnotadequate:repeatstudy!

Signsof(significant)traceraccumulationnearinjectionsite?

Whatpersonneltraining,qualifications,andqualityassuranceshould beinplacetomonitor/preventforextravasationsinmedicine?

  • Radiationsafetyofficer/qualityofficer
  • Keeplocalregistrationofextravasationcases
  • Goal:qualityimprovement

- Traintechnicians/NMphysicianswithbadtrackrecords 39 40

Acknowledgements Prof.F.Mottaghy Dr.S.V lProf.J.Bucerius Prof.M.deHaanlDr.R.Wierts 41

OPEN FORUM No Handout

1 PatientReleaseConsiderations AssociatedwithTemporary BrachytherapyDevices KatieTapp,PhD MedicalRadiationSafetyTeam March16,2021 Overview

  • Thispresentationwillprovideanoverviewof

- Temporaryimplantdevices,

- Thescopeofstaffsevaluationofpatientrelease forthosewithtemporaryimplants,

- Themanyregulatoryquestionsthestaffintendsto answerthroughitsevaluation,

- Nextsteps.

1 2

2 PatientReleaseRegulations (10CFR35.75)

  • Alicenseemayauthorizethereleasefromits controlofanyindividualwhohasbeen administeredimplantscontainingbyproduct materialifthedosetoanyotherindividualfrom exposuretothereleasedindividualisnotlikelyto exceed5mSv(0.5rem).
  • Alicenseeshallprovidethereleasedindividual withinstructionsonactionsrecommendedto maintaindosestootherindividualsaslowasis reasonablyachievableifthedosetoanyother individualislikelytoexceed1mSv(0.1rem).

PatientReleaseRegulations (10CFR35.75)

  • Before2002,patientreleaseregulationsonly allowedreleaseofpermanentimplants
  • In2002,theregulationswereamendedto allowpatientstobereleasedwithalltypesof implantsifthedoselimitsweremet.
  • RegulatoryGuide8.39doesnotprovide guidancefortemporaryimplants.

3 4

3 TemporaryImplants

  • Temporaryimplantsareexpectedtobe removedfromthepatientataspecifictimeto delivertheprescribeddose.
  • Examplesoftemporaryimplantsinclude:

- EyePlaques

- BrachytherapySeeds

- Emergingbrachytherapydevices,including:

  • AlphaDaRT
  • CivaDerm EyePlaqueBrachytherapy
  • Plaquesaretemporarilyattachedtothewallof theeye
  • Licensedunder10CFR35.400andpatients releasedunder10CFR35.75.

5 6

4 BrachytherapySeeds

  • Ir192seedshavebeenusedinribbonsfor temporaryimplantbrachytherapy.
  • Manyofthesepatientsstayinthehospital duringtreatment.
  • I125seedsarealsousedforradioactiveseed localization.Thesepatientsarereleased followingimplantationandreturntohavethe seedsexcised.

AlphaDart

  • Alpha DaRT is thefirst manual brachytherapydevice which uses diffusingalpha emittingradiation for therapeutictreatment.
  • AlphaDartseedscontain 224Ra.
  • Insidethetumor,thesource diffusesasthe224Raatoms decaydownitsdecaychain.

7 8

5 AlphaDart(cont.)

  • Currently,thistherapyutilizestemporary implantsbuttheymaybeusedforpermanent therapyinthefuture.
  • Staffexpectstoprovideadraft10CFR 35.1000licensingguidancefortheACMUI reviewinearlysummer.

CivaDerm

  • Temporarybrachytherapyusing Pd103sourcesaffixedtotheskin surface.
  • Patientswillneedtoreturntothe licenseetohavethesources removed.
  • Sourcesareselfshieldedwitha coldandhotside.
  • Staffisstillevaluatingthelicensing pathwayforuse.

9 10

6 CivaDerm (cont.)

  • Sourcesareaffixedby:

- placingonclean,dryskin

- Attachedwithasurgicalbandage

- Securedwithadditionalradiationshieldcover

- Coveredwithawaterproofshield RegulatoryConsiderations Evaluation Public Exposure Medical Event Removed Incidental Lost Source Other 11 12

7 RegulatoryConsiderations Evaluation Public Exposure Medical Event Removed Incidental Lost Source Other PatientRelease

  • 10CFR35.75stateslicenseesmayauthorizethe releasefromitscontrolofanyindividual whohas beenadministeredimplantscontainingbyproduct materialifthedosetoanyotherindividualfrom exposuretothereleasedindividualisnotlikelyto exceed5mSv(0.5rem).
  • Licenseeswillneedconfidencethatthesource willnotbecomedislodged,asitispossiblea loosesourcecouldexceedthislimit.

13 14

8 PublicDoseLimits

  • PublicdoselimitsinPart20excludeexposure toindividuals administeredradioactive materialandreleasedunder10CFR35.75.
  • Publicdoselimitsdonotappeartoexclude dosefromsourceswhicharedislodgedfrom patients.
  • Furtherevaluationisongoingtodetermineif publicdoselimitslistedinPart20applyto sourcesdislodgedfrompatients.

PublicExposurePotential

  • Licensingevaluationspriortoauthorizing releaseofpatientswithtemporaryimplants mustconsider:

- Easeofwhichasourcecouldbecomedislodged, and

- Publicexposurepotential DoserateformaximumactivitysheetforCivaDerm Doserateat5cm (mrem/hr)

Doserateat100 cm(mrem/hr)

Cold 968 2.52 Hot 23,883 31.23 15 16

9 RegulatoryConsiderations Evaluation Public Exposure Medical Event Removed Incidental Lose Source Other LicenseeEvaluation

  • 10CFR35.41requireslicenseestohave procedurestoensurehighconfidencethat eachadministrationisinaccordancewiththe writtendirective.
  • Theseproceduresmustaddressthefollowing items:

- Verifyingtheadministrationisinaccordancewith thewrittendirective,and

- Determiningifamedicaleventhasoccurred.

17 18

10 MedicalEvent

  • Ifasourceisdislodgedorifapatientdoesnot returnataspecifiedtime,itcouldleadtoa medicaleventunder10CFR35.3045:

- (a.1.i)adosethatdiffersfromtheprescribeddose bymorethan0.5Sv (50rem)toanorganortissue andthetotaldosedelivereddiffersfromthe prescribeddoseby20percentormore,or MedicalEvent(cont.)

- (a.1.iii)Adosetotheskinoranorganortissue otherthanthetreatmentsitethatexceedsby

  • (A)0.5Sv (50rem)ormoretheexpecteddosetothat sitefromtheprocedureiftheadministrationhadbeen giveninaccordancewiththewrittendirectiveprepared orrevisedbeforeadministration;and
  • (B)50percentormoretheexpecteddosetothatsite fromtheprocedureiftheadministrationhadbeen giveninaccordancewiththewrittendirectiveprepared orrevisedbeforeadministration.

19 20

11 PatientIntervention

  • Patientinterventionmeansactionsbythe patientorhumanresearchsubject,whether intentionalorunintentional,suchas dislodgingorremovingtreatmentdevicesor prematurelyterminatingtheadministration.
  • Ifthesourcecomesoffduetoanaction by thepatient,itcouldbeconsideredpatient interventionandnotamedicalevent.
  • Moreguidanceisneeded.

RegulatoryConsiderations Evaluation Public Exposure Medical Event Removed Incidental Lost Source Other 21 22

12 LostSource

  • Ifthelicenseeisunabletoretrievea temporarysource,thesourcecouldbe consideredlost.
  • 10CFR20.2201requireslicenseestoreport lossoflicensedmaterialabovespecified limits.

- Telephonicreportsneedtobemadewithin24 hoursor30daysdependingontheactivity.

LostSource(cont.)

  • Writtenreportsarerequired30daysafter initialtelephonereportandneedtoinclude:

- Descriptionofcircumstances

- Statementofprobabledisposition

- Exposureofindividuals

- Actionstakentotrytorecoverthematerial

- Procedurestopreventanotherlostsource 23 24

13 BrachytherapySourceAccountability

  • Ifasourceislost,thelicenseewouldnotbe abletoaccountforthesourceorbeableto completetherecordrequiredper10CFR 35.2406fortemporaryimplants.

RegulatoryConsiderations UnreturnedSource Lost Source Medical Event Removed Incidental Public Exposure Other 25 26

14 OtherConsiderations

  • Astheimplantsaretemporary,thewritten directivewillneedtoincludedoseunlike permanentbrachytherapyimplantswhich usessourcestrength.

NextSteps

  • Staffwillcontinuetoevaluatetheseregulatory questionsregardingreleaseofpatientswith temporaryimplants.
  • StaffwillprovideACMUIwiththeresultsof thisevaluationandanyassociatedlicensing guidancedocuments.
  • StaffwillbeprovidingAMCUIwithdraft10 CFR35.1000licensingguidanceforAlphaDart.

27 28

15 Acronyms

  • ACMUI-AdvisoryCommitteeontheMedical UsesofIsotopes
  • CFR-CodeofFederalRegulations
  • I125-iodine125
  • Ir192-iridium192 29

1 ACMUI Reporting Structure Kellee Jamerson, ACMUI Coordinator Medical Radiation Safety Team March 16, 2021 Outline

  • Current Reporting Structure
  • Annual Review
  • Meetings
  • Discussion 2

1 2

2 Current Reporting Structure 3

The Commission EDO Margaret Doane Director, NMSS John Lubinski Director, MSST Kevin Williams ACMUI Chief, MSEB Christian Einberg Annual Review In September 2012, the ACMUI recommended to have an annual review of reporting structure.

4 3

4

3 Meetings Two meetings at Headquarters each year

- March/April

- September/October Approximately 2-3 teleconferences (as needed) 5 ACMUI Discussion 6

5 6

4 Points of Contact

- Kevin.Williams@nrc.gov

- Christian.Einberg@nrc.gov

- Kellee.Jamerson@nrc.gov 7

Acronyms

  • DFO - Designated Federal Officer
  • EDO - Executive Director for Operations
  • MSST - Division of Materials Safety, Security, States, and Tribal Programs
  • MSEB - Medical Safety and Events Assessment Branch
  • NMSS - Office of Nuclear Material Safety and Safeguards 8

7 8

1 Professor Larry DeWerd, PhD, FAAPM Medical Radiation Research Center Dept of Medical Physics (SMPH)

University of Wisconsin Madison, WI The desirable quantity is absorbed dose to water. This quantity is determined from AAPM TG 43 The calibration quantity is air kerma strength which is converted with a dose rate constant Note that the quantity activity is NOT used for brachytherapy sources.

Air kerma strength is quantity of radiation emitted from source after cladding 1

2

2 Photon Source: Air kerma strength - symbol Sk. Given as unit U where U[=]Gy-m2/h.

Values of Sk can be up to 260 U.

Beta sources:

Absorbed dose rate in water at a depth done with an extrapolation chamber (usually 2 mm)

I will cover photon sources because of time constraints and then some future calibrations Low energy photon sources (both high and low dose rate)

High energy photon sources (used for High Dose rate brachytherapy - both high and low dose rate)

Beta brachytherapy sources (used for Intravascular Brachytherapy for prevention of restenosis, eye plaques for tumors and Ophthalmic Applicators used to treat eye)

Majority use in Brachytherapy is Low energy -

low dose rate and High energy - high dose rate 3

4

3 Energy DoseRate Type Primary calibration standardat NIST Low Low

LDRseeds, 125I,103Pd, 131Cs WAFAC High High HDR afterloaders (192Ir)

IonChamber 7Distance Technique

1. Use of a free air chamber (WAFAC) for Low energy Low Dose sources
2. Use of a thimble chamber in air (UW) for High energy High dose sources
3. Use of an extrapolation chamber for beta sources.

5 6

4 To provide effective treatment to neoplastic disease must quantify dose to tissue of interest Standard should be specified by a clinically relevant metric Presently this quantity is air-kerma strength for photon sources. In Europe, the quantity is Reference Air Kerma Rate (RAKR)

The quantity is Energy deposited per unit mass (i.e.

J/kg) at a distance in vacuo Air Kerma Strength (Gym2/hr)

 Actual characterization of source output in terms of the dose delivered to air. Related to exposure primarily by W/e, which is the average energy required to produce an ion pair in dry air.

Endorsed by the AAPM for use in treatment planning protocols and adopted in TG 43.

7 8

5 (r,)

SK is air kerma strength G is geometry factor is dose rate constant g is radial dose function F is anisotropy function Air Kerma Strength - Determined in clinic by a well chamber traceable to NIST Dose rate constant,, measured by TLD and Monte Carlo calculated.

Radial dose function, g(r), and anisotropy function, F (r,) are all measured by TLD and calculated by Monte Carlo. G is the geometry factor All are consensus values.

9 10

6 For x-ray sources: standard is at 50 cm in air

- equation modified somewhat

Lamperti FAC used 11 12

7 Medical physicist needs to calibrate source or if multiple sources at least 10%

of the sources For LDR sources, there have been examples of dead seeds, some seeds with twice the output of the others in the batch.

Dont just trust what manufacturer has sent. Measure it!!!!

Calibration differs among sources because of cladding - 5% differences 13 14

8

  • NIST has transferred calibrations to ADCLs for LDR sources. all ADCL Secondary Laboratories fall within + 0.6%
  • ADCLs have traceability to NIST.

Beta sources: All ADCL secondary Laboratories fall within + 2%

Uncertainties for Proficiency tests Gamma sources: + 2% (k=2)

Beta sources: + 3% (k=2)

Palladium 103 introduced in 1987 with NO NIST standard - used a Cd source Manufacturer changed calibration using a different Cd source, self-shielding of the source encapsulation was different This resulted in a sudden 9% shift in calibration. Manufacturer communicated this by letter to users in 1997 15 16

9 Palladium 103 dose has changed many times.

Manufacturer caused 9% shift in calibration and dose to patient.

Shows importance of a standard and that physicists calibrate the sources.

17 18

10 Clinical calibration using a well chamber.

The insert is part of the calibration.

The chambers and methodology for brachytherapy calibrations is different from Nuclear Medicine and PET, which use a dose calibrator.

A dose calibrator reads in activity not dose or Air kerma Also energy dependence of a dose calibrator is more severe than vented well chamber The quantity used for Nuclear Medicine and PET is activity and the unit is Bq (Curies).

This quantity is not Dose!

An activity may be administered by syringe but to know the dose received by a given tissue is different.

Expansion on this point when look at future 19 20

11 ADCL Calibrated Well chamber: Provides the most convenient, accurate and precise measure of source strength.

Know the characteristics of chamber, whether it can measure LDR or HDR or both. What is between the source and the collector of the well?

Pressurized chambers (sealed) can leak 1% per year Use an electrometer that can measure a low enough signal without leakage for LDR sources If a single seed is used Rdg1 is obtained If multiple seeds of the same strength are measured, the reading is RdgM=n Rdg1 If average strength per seed is needed, the total train air kerma strength is divided by the number of seeds, n.

If strands of different strength an average is obtained.

21 22

12 Because of variation of thicknesses of needles (caused by manufacturer tolerances) sources have a 15% variation by needle.

Sources cannot be measured in Needles Energy response of vented chambers is not severe compared to pressurized chambers The following curve indicates why each energy and each chamber requires calibration 23 24

13 0.899 0.885 0.889 1

0 0.2 0.4 0.6 0.8 1

1.2 23 27 397 660 Normalized Response Energy cal coeff HDR 1000 25 26

14 Higher energy sources require other techniques FAC are too big to use.

A chamber with a known volume can be used or a chamber with a flat and calibrated energy response NIST does not offer a primary HDR 192Ir source calibration 7-Distance in-air technique first proposed at the University of Wisconsin by Goetsch et al. in 1991 - this is after the chamber calibration Allows ADCLs to provide NIST traceable calibrations for HDR 192Ir NIST traceability is provided by an interpolated chamber correction factor 27 28

15 Establishing NIST traceability requires two steps calibration of ion chamber using that chamber to calibrate source.

Known volume chamber used by NPL.

If the chamber used has a flat energy response, 2 points interpolated to the weighted average energy is all that is needed.

29 30

16 The ionization chamber is calibrated at two energy points to interpolate to the weighted average energy of the HDR 192Ir source, which is approximately 397 keV.

The two points are M250 (x-ray) and Cs-137 with interpolation.

The same buildup cap with thickness sufficient to provide CPE for highest energy must be used for both NIST calibrations Mainegra-Hing and Rogers argued that the interpolation should be based upon an interpolation proportional to ion chamber response. Thus, The energy for 192Ir is 397 keV The second aspect is to calibrate the source at distances 31 32

17 All primary labs do a variation on the 7-distance technique.

NPL has a known measured volume chamber Others determine their factor by interpolation Many do all 4 coordinate directions 33 34

18 There are 5 HDR sources on the market Monte Carlo modeling shows that there may be a difference between them.

We investigated all sources using the 7-D technique Published in Med Phys 38: 6721-6729 (2011)

UWADCL measurement was originally based on the Classic Nucletron HDR source The classic Nucletron source has been measured over more than a 21 year period.

Each individual source has been compared to the other via 3 well chambers The value for the well chamber after measurement by the 7 distance technique is always within + 0.5%

35 36

19 HDR Source Model

% difference from Working Standard Classic Nucletron 0.47 Nucletron V2 0.10 VariSource VS2000 1.13 GammaMed Plus 0.20 Flexisource 0.89 Average for all sources 0.01 When all source models are averaged the value is 0.01% compared to the 21 year old value.

All source models will use the same calibration factor since all agree within 1% when the uncertainty of measurement is +2%.

Comparisons with other labs (Henri - Becquerel, NPL, PTB, NRCC) within 0.5%

Summary of measurements with all sources -

statistically different but all within 1% of the mean 37 38

20 Half Life of 192Ir is short - replace source every 3 to 4 months.

Use 60Co have 5 years. But maintenance becomes essential Calibration still done as for HDR, known volume chamber at 7 distances. Calibration at cobalt energy Need to develop consensus values - dose rate constant, etc.

Targeted Radionuclide Therapy Or Targeted Radiopharmaceutical Therapy (TRT)

Alphas and betas: 224Ra, Ac, Po Present calibration in activity Prefer absorbed dose to water Difficult since alpha and betas - how much goes to the specific area desired?

39 40

21 Betas calibrated with an extrapolation chamber. Windowless extrapolation chamber for beta eye plaques.

I have a graduate student trying to do calibration for alphas and betas with a windowless extrapolation chamber - PhD thesis Hopefully will get Absorbed Dose to Water that would be delivered from amount of activity deposited in tissue of interest.

Thanks to Customers of MRRC whose calibrations support graduate research.

All graduate students and staff that I have provoked with my thoughts.

Any Questions.

41 42

OPEN FORUM No Handout

Sunday Monday Tuesday Wednesday Thursday Friday Saturday 29 30 31 1

2 3

4 5

6 7

8 9

10 11 Labor Day Rosh Hashanah 12 13 14 15 16 17 18 Yom Kippur 19 20 21 22 23 24 25 Sukkot 26 27 28 29 30 1

2 3

4 September 2021 Notes

Sunday Monday Tuesday Wednesday Thursday Friday Saturday 26 27 28 29 30 1

2 3

4 5

6 7

8 9

10 11 12 13 14 15 16 Columbus Day 17 18 19 20 21 22 23 24 25 26 27 28 29 30 ASTRO Annual Meeting ASTRO Annual Meeting ASTRO Annual Meeting ASTRO Annual Meeting 31 1

October 2021 Notes

Retrieved from "https://kanterella.com/w/index.php?title=ML21068A410&oldid=3820945"