IDEAL DOSIMETRY SYSTEM DOSIMETRY SYSTEMS IN CURRENT … · 51276 FWT – 60 film VIS -...

IDEAL DOSIMETRY SYSTEMIDEAL DOSIMETRY SYSTEM

DOSIMETRY SYSTEMS IN CURRENT DOSIMETRY SYSTEMS IN CURRENT USEUSE

A. KOVA. KOVÁÁCSCS

InstituteInstitute

ofof

IsotopesIsotopesHungarianHungarian

AcademyAcademy

ofof

SciencesSciences

HH--1525. Budapest, P.O.B. 77. Hungary1525. Budapest, P.O.B. 77. Hungary

BACKGROUNDBACKGROUND

In radiation processing validation and process control In radiation processing validation and process control (sterilization, food irradiation, etc.) depend on the (sterilization, food irradiation, etc.) depend on the measurement of absorbed dose.measurement of absorbed dose.

Measurements of absorbed dose shall be performed Measurements of absorbed dose shall be performed using a dosimetric system or systems having a known using a dosimetric system or systems having a known level of accuracy and precision (European standard level of accuracy and precision (European standard EN552:1994).EN552:1994).

The calibration of each dosimetric system shall be The calibration of each dosimetric system shall be traceable to an appropriate national standardtraceable to an appropriate national standard..

DosimetryDosimetry –– principlesprinciples

andand requirementsrequirements

DeterminationDetermination ofof absorbedabsorbed dosedose inin productproduct specificspecificdosimetrydosimetry systemssystems –– similaritysimilarity inin radiationradiation absorptionabsorptioncharacteristicscharacteristics..

DosimetryDosimetry –– asas part part ofof thethe totaltotal qualityquality systemsystem -- providesprovidesqualityquality assuranceassurance andand documentationdocumentation thatthat thethe irradiationirradiationprocedureprocedure has has beenbeen carriedcarried out out accordingaccording toto specificationsspecifications..

AccurateAccurate, , traceabletraceable dosedose measurementsmeasurements provideprovideindependentindependent, , inexpensiveinexpensive meansmeans forfor qualityquality controlcontrol ininradiationradiation proessingproessing..

DosimetryDosimetry

––

applicationapplication

andand

systemssystems

FieldsFields ofof applicationapplication::--

installationinstallation

qualificationqualification;;

--

operationaloperational

qualificationqualification;;--

performanceperformance

qualificationqualification;;

--

processprocess

controlcontrol;;

DosimetryDosimetry providesprovides documentationdocumentation inin thethe processesprocesses, , ifif

--

thethe

measurementmeasurement

is is traceabletraceable

toto

a a nationalnational

standard,standard,--

thethe

uncertaintyuncertainty

ofof

thethe

systemsystem

is is knownknown..

AppliedApplied systemssystems::--

primaryprimary--, , secondarysecondary--, , transfertransfer

standardsstandards;;

--

routineroutine

systemssystems;;

DosimetryDosimetry systemssystems

inin radiationradiation processingprocessing

PrimaryPrimary

standard standard systemssystems::

--

DosimeterDosimeter

ofof

thethe

highesthighest

metrologicalmetrological

qualityquality, , establishedestablished

andand

maintainedmaintained

asas

anan

absorbedabsorbed

dosedose

standard standard byby

a a nationalnational

oror

internationalinternational

standardsstandards organizationorganization

forfor

calibrationcalibration

ofof

radiationradiation

environmentsenvironments

((fieldsfields););

--

ApplicationApplication

is is basedbased

onon

measurementmeasurement

ofof

basicbasic physicalphysical

quantitiesquantities;;

--

Most Most commoncommon

systemssystems: : ionizationionization

chamberschambers, , calorimeterscalorimeters;;



ReferenceReference


--

DosimeterDosimeter

ofof

highhigh


qualityquality

usedused

asas

a standard a standard toto provideprovide

measurementsmeasurements

traceabletraceable

toto

measurementsmeasurements

mademade

byby

primaryprimary

standardstandard

systemssystems;;--

TheseThese

systemssystems

requirerequire


andand

areare

usedused

toto

calibratecalibrate

radiationradiation

environmentsenvironments

andand

routineroutine

dosimetersdosimeters;;--

SolidSolid

phasephase

dosimetrydosimetry

systemssystems

::

alaninealanine

((pelletpellet, , rodrod, film);, film);--

LiquidLiquid

phasephase

dosimetrydosimetry

systemssystems

: :

FrickeFricke

solutionsolution;;potassiumpotassium

dichromatedichromate

solutionsolution;;

ethanolethanol--monochlorobenzenemonochlorobenzene

solutionsolution;;cericceric--cerouscerous

solutionsolution;;

--

CalorimetersCalorimeters;;

AlanineAlanine

dosimetrydosimetry

(ISO/ASTM 51607)(ISO/ASTM 51607)

--

ESR ESR analysisanalysis; ; MeasuresMeasures

freefree

radicalradical

concentrationconcentration;;

-- DoseDose

rangerange: 10 : 10 GyGy

––

100 100 kGykGy;;

-- ReproducibilityReproducibility

<< 0.5 %;0.5 %;

DichromateDichromate

dosimetrydosimetry


-- ColourColour

changechange

byby

spectrophotometryspectrophotometry;;

-- DoseDose

rangerange: 10 : 10 ––

50 50 kGykGy;;

-- ReproducibilityReproducibility

<< 0.5 %;0.5 %;



TransferTransfer


--

IntermediaryIntermediary

systemsystem

withwith

highhigh


qualitiesqualities, , suitablesuitable

forfor transferringtransferring

dosedose

informationinformation

fromfrom

anan

accreditedaccredited/standard /standard

laboratorylaboratory

toto

anan

irradiationirradiation

facilityfacility

toto

establishestablish

traceabilitytraceability;;

--

TheseThese

systemssystems

requirerequire


andand

postpost


stabilitystability;;

--

DosimetryDosimetry

systemssystems::

--

alaninealanine; ;

--

ECB, ECB, cericceric--cerouscerous, , potassiumpotassium


solutionssolutions;;



RoutineRoutine

systemssystems::

--

DosimetryDosimetry

systemssystems

usedused

inin

radiationradiation

processingprocessing

facilitiesfacilities

forfor absorbedabsorbed

dosedose

mappingmapping

andand

processprocess

monitoring;monitoring;

--

SystemsSystems,,capablecapable

ofof

givinggiving

reproduciblereproducible

signalssignals

--

TheseThese

systemssystems

requirerequire

calibrationcalibration;;--

DosimeterDosimeter

systemssystems::

--

PerspexPerspex

((redred--, , amberamber--, , GammachromeGammachrome););--

radiochromicradiochromic

filmsfilms

(FWT(FWT--60, B3, 60, B3, GafchromicGafchromic););

--

ECB, ECB, cericceric--cerouscerous

solutionssolutions;;--

ProcessProcess

calorimeterscalorimeters

((waterwater, , graphitegraphite, , polystyrenepolystyrene););

PerspexPerspex

dosimetrydosimetry


ColourColour

changechange

--

spectrophotometryspectrophotometry;;DoseDose

rangerange: 0.5 : 0.5 ––

50 50 kGykGy;;

ReproducibilityReproducibility

<<

3 %;3 %;PostPost


changechange

ofof

signalsignal;;

RadiochromicRadiochromic

dyedye

filmsfilms

(ISO/ASTM 51275) (ISO/ASTM 51275)

ColourColour

changechange

--

spectrophotometryspectrophotometry;;FWTFWT--

6060: : 33

––

1150 50 kGykGy;;

B3: 2 B3: 2 ––

100 100 kGykGy;;GafChromicGafChromic: 1 : 1 GyGy

––

40 40 kGykGy;;


inin presentpresent practicepractice

DosimeterDosimeter

systemsystem MethodMethod

ofof

analysisanalysisUsefulUseful

dosedose

rangerange, , GyGy

NominalNominal

precisionprecision

limitslimits

ReferencesReferences

FrickeFricke

solutionsolutionUV UV ––

spectrospectro--

photometryphotometry2x10 2x10 ––

4x104x1022 1 %1 %ASTM E ASTM E

1026 1026 --

0404

CericCeric

––

cerouscerous

sulphatesulphate

UV UV ––

spectrophotomspectrophotom././

PotentiometryPotentiometry101033

––

101066 3 %3 %ISO/ASTMISO/ASTM

5120551205

PotassiumPotassium


UVUV--VISVIS

spectrophotomspectrophotom..5x105x1033

––

4x104x1044 1 %1 %ISO/ASTMISO/ASTM

5140151401

EthanolEthanol--monomono

chlorobenzenechlorobenzene

TitrationTitration,,oror

HF HF oscillometryoscillometry4x104x1022

––3x103x1055 3 %3 %ISO/ASTMISO/ASTM

5153851538

L L --

alaninealanine EPREPR 1 1 ––

101055 0.5 %0.5 %ISO/ASTMISO/ASTM

5160751607

PerspexPerspex

systemssystemsVIS VIS --

spectrospectro--

photometryphotometry101033

––

5x105x1044 4 %4 %ISO/ASTMISO/ASTM

5127651276

FWT FWT ––

6060

filmfilm

VIS VIS --

spectrospectro--


--


5127551275

B 3B 3

filmfilm

VIS VIS --

spectrospectro--


--


5127551275

CelluloseCellulose

triacetatetriacetate

UV UV ––

spectrospectro--


--


5165051650

CalorimetryCalorimetryResistanceResistance//

temperaturetemperature

1.5x101.5x1033

––

5x105x10442 %2 %

ISO/ASTMISO/ASTM

5163151631

EnvironmentalEnvironmental

effectseffects

onon

dosimetrydosimetry

systemssystems

DosimeterDosimeter MeasurementMeasurement

timetime

afterafter

irrirr..

HumidityHumidity DoseDose

raterate

((GyGy

ss--11))

IrradiationIrradiation

temptemp. .

coeffcoeff., (., (ooCC))--11

AlanineAlanine immediatelyimmediately yesyes << 101088 + 0.25 %+ 0.25 %

DichromateDichromate 24 24 hourshours nono 0.7 0.7 ––

5x105x1022 --

0.2 %0.2 %

CericCeric--cerouscerous immediatelyimmediately nono << 101066 concconc. . depdep..

ECBECB immediatelyimmediately nono << 101088 + 0.05 %+ 0.05 %

CalorimetersCalorimeters immediatelyimmediately nono << 101088 --

PerspexPerspex 24 24 hourshours yesyes << 101055 + 1 %+ 1 %

FWTFWT--6060 5 min/60 5 min/60 ooCC yesyes << 10101313 + 0.2 %+ 0.2 %

B3B3 5 min/60 5 min/60 ooCC yesyes << 10101313 + 0.3 %+ 0.3 %

SunnaSunna 20 min/70 20 min/70 ooCC nono << 10101313 + 0.2 %+ 0.2 %

NEW APPROACHESNEW APPROACHES

New New requirementsrequirements::standardizationstandardization ofof existingexisting dosimetrydosimetrymethodsmethods;;increasedincreased reliabilityreliability toto encourageencourage industryindustry forforwiderwider useuse ofof ionizingionizing radiationradiation;;newnew technologiestechnologies ((maymay) ) requirerequire newnewdosimetrydosimetry methodsmethods;;introductionintroduction ofof improvedimproved calibrationcalibrationproceduresprocedures;;

New New approachesapproaches –– novelnovel

dosimetrydosimetry systemssystems

RequirementsRequirements::

New New technologiestechnologies ((environmentalenvironmental processesprocesses, , foodfoodirradiationirradiation atat lowlow temperaturestemperatures, , anthraxanthrax, , pharmaceuticalspharmaceuticals, , XX--rayray technologiestechnologies, , highhigh dosedose controlcontrol););

AchievedAchieved byby::

ImprovementImprovement ofof existingexisting dosimetrydosimetry systemssystems;;IntroductionIntroduction ofof newnew systemssystems;;

SystemsSystems basedbased

onon conductivityconductivity

evaluationevaluation

EthanolEthanol--monochlorobenzenemonochlorobenzenesolutionsolution (1 (1 –– 300 300 kGykGy))((nonnon--destructivedestructive

methodmethod))

AqueousAqueous –– alaninealanine solutionsolution(1 (1 –– 100 100 kGykGy))

PolyanilinePolyaniline basedbased polymerpolymercompositescomposites (5 (5 –– 150 150 kGykGy))


onon fluorimetryfluorimetry

PrinciplesPrinciples::AbsorbedAbsorbed energyenergy is is emittedemitted asas fluorescentfluorescent lightlight duedue toto opticalopticalexcitationexcitation (OSL (OSL –– opticallyoptically stimulatedstimulated luminescenceluminescence););FluorescenceFluorescence appearsappears micromicro-- oror nanosecondsnanoseconds afterafter excitationexcitation;;

AdvantagesAdvantages::Wide Wide dynamicdynamic rangerange;;HighHigh sensitivitysensitivity;;PassivePassive andand realreal timetime dosimetrydosimetry;;VariableVariable geometriesgeometries;;InexpensiveInexpensive detectorsdetectors;;MultipurposeMultipurpose applicationsapplications ((medicalmedical diagnosticdiagnostic, , radiationradiationprocessingprocessing, , radiationradiation protectionprotection, , spacespace studiesstudies, , etcetc); );


onon fluorimetryfluorimetry

ApplicationApplication possibilitiespossibilities::

RadiationRadiation inducedinduced decaydecay ofoforiginallyoriginally fluorescentfluorescentmoleculesmolecules ((anthraceneanthracene, , fluoresceinfluorescein derivativesderivatives, , etcetc););

AppearanceAppearance ofof radiationradiationinducedinduced fluorescencefluorescence duedue totoformationformation ofof newnewfluorescentfluorescent radiolysisradiolysisproductsproducts ((SunnaSunna film);film);

The The SunnaSunna dosimeterdosimeter

PrinciplesPrinciples::

LiFLiF disperseddispersed uniformlyuniformly ininPE (1 cm x 3 cm x 0.4 cm);PE (1 cm x 3 cm x 0.4 cm);

ColourColour centerscenters (F(F--, M, M--, N, N--, , R R centerscenters) ) formform duedue totoionizingionizing radiationradiation;;

RedRed, , greengreen oror IR OSL IR OSL ororUV UV absorptionabsorption usedused forfordosimetrydosimetry;;

Net Fluorescence for Sunna 0399-20 Dosimeter

01020304050607080

400 500 600 700 800 900 1000 1100Wavelength (nm)

Perc

ent T

rans

mis

sion

or In

tens

ity

Excitation Spectrum GREEN FluorescenceRED Fluorescence

insert infraredspectra

The The SunnaSunna dosimeterdosimeter

ApplicationApplication possibilitiespossibilities::

EvaluationEvaluation ofof greengreen OSL OSL (50 (50 GyGy –– 250 250 kGykGy););

EvaluationEvaluation ofof UV UV absorbanceabsorbance (5 (5 –– 100 100 kGykGy););

EvaluationEvaluation ofof IR OSL IR OSL (10 (10 GyGy –– 10 10 kGykGy););

0

100

200

300

400

500

600

700

800

900

1000

0 50 100 150 200 250 300 350

Absorbed Dose (kGy)

Net S

igna

l (fs

u)

4.5 MeV E-beam, 25 kGy per pass Co-60, continuous


onon opticaloptical

absorptionabsorption ((tetrazoliumtetrazolium

saltssalts))TetrazoliumTetrazolium saltssalts studiedstudied::

CompoundCompound

ProductProduct

λλ

maxmax..

DoseDose

rangerange::

tetrazoliumtetrazolium

violetviolet

(TV)(TV)

525 525 nmnm

0.01 0.01 ––

30 30 kGykGytetrazoliumtetrazolium

redred

(TTC)(TTC)

490 490 nmnm

0.01 0.01 ––

100 100 kGykGy


blueblue

(TB)(TB)

520 520 nmnm

0.01 0.01 ––

10 10 kGykGynitronitro

blueblue


(NBT) (NBT) 522 522 andand

612 612 nmnm

0.01 0.01 ––

25 25 kGykGy

--

heterocyclicheterocyclic

organicorganic

compoundscompounds, , whichwhich

uponupon


yieldyield

highlyhighly colouredcoloured

waterwater

insolubleinsoluble

formazansformazans

duedue

toto

radiolyticradiolytic

reductionreduction..

MeasurementMeasurement

ofof

absorbedabsorbed

dosedose

byby

measuringmeasuring opticaloptical

absorptionabsorption

ofof

oror

reflectedreflected

lightlight

fromfrom

NBT NBT --

PVA filmPVA film

InstrumentInstrument toto measuremeasure

reflectedreflected lightlight

ReflectometerReflectometer::

CalorimetricCalorimetric systemssystems

4 4 –– 10 10 MeVMeV: : --

graphitegraphite, , waterwater, PS , PS calorimeterscalorimeters;;

--

calibrationcalibration, , nominalnominal

dosedose measurementsmeasurements;;

1.5 1.5 –– 4 4 MeVMeV::--

PS PS calorimetercalorimeter;;

--

calibrationcalibration, , nominalnominal

dosedose determinationdetermination;;

80 80 –– 120 120 keVkeV::--

graphitegraphite

calorimetercalorimeter;;

--

toto

developdevelop

a a primaryprimary

standard standard systemsystem;;--

calibrationcalibration;;

NovelNovel approachesapproaches

-- methodologymethodologyDosimetryDosimetry automationautomation –– toto reducereduce humanhuman errorserrors

--

AutomatedAutomated

evaluationevaluation

systemssystems

((AerialAerial, , BrukerBruker, , etcetc.);.);--

AutomatedAutomated

scanningscanning

ofof

imagesimages

((dosedose

distributiondistribution) ) ––

RisRisøøScanScan;;

RealReal timetime dosimeterdosimeter applicationapplication

--

ToTo

determinedetermine

combinedcombined


temperaturetemperature

––

dosedose

raterate

effectseffects;;

MathematicalMathematical methodsmethods (RPSMUG (RPSMUG –– forfor modelingmodeling andand simulationsimulation))ToTo assistassist productproduct design;design;ToTo determinedetermine dwelldwell timetime settingsetting;;Rapid Rapid estimationestimation ofof dosedose distributiondistribution;;Parallel Parallel irradiationirradiation ofof complexcomplex productsproducts;;

SelectionSelection criteriacriteria

QualityQuality controlcontrol has has toto be be basedbased onon thethe assuranceassurance thatthat thethe processprocesswaswas carriedcarried out out withinwithin prescribedprescribed dosedose limitslimits

ThisThis

requiresrequires

properproper

useuse

andand

selectionselection

ofof

dosimetrydosimetry

systemssystems

SelectionSelection

criteriacriteria::--

accordingaccording

toto

thethe

processprocess

toto

be be controlledcontrolled

((sterilizationsterilization, ,

polymerpolymer

modificationmodification, , foodfood

processingprocessing, , etcetc.); .); dosedose

rangerange: 50 : 50 GyGy ––

300 300 kGykGy;;

--

accordingaccording

toto

dosimeterdosimeter

characteristicscharacteristics;;

SelectionSelection criteriacriteria

ReliableReliable calibrationcalibration andand standardizationstandardization;;BroadBroad absorbedabsorbed dosedose rangerange;;Limited Limited oror no no dependencedependence ofof responseresponse withwith dosedose, , dosedose raterate, , energyenergy;;RadiationRadiation absorptionabsorption characteristicscharacteristics similarsimilar toto productproduct;;StabilityStability, , reproducibilityreproducibility, , simplicitysimplicity, , lowlow costcost, , availabilityavailability;;SmallSmall sizesize –– goodgood resolutionresolution capabilitiescapabilities;;KnownKnown environmentalenvironmental ((influenceinfluence) ) factorsfactors;;SimpleSimple handlinghandling andand readread--outout procedureprocedure;;Limited Limited variationvariation withinwithin andand amongamong batchesbatches;;LongLong shelfshelf lifelife;;RuggednessRuggedness;;PortabilityPortability;;

""IdealIdeal

dosimetrydosimetry

systemsystem""

W.L. W.L. McLaughlinMcLaughlin: : „„ IfIf youyou havehave oneone dosimeterdosimeter youyou thinkthink youyou knowknow thethe dosedose. . IfIf youyou havehave twotwo dosimetersdosimeters youyou start start toto wonderwonder…”…”

Optimum Optimum conditionsconditions: : -- widewide dosedose rangerange –– gamma/EB/gamma/EB/XX--rayray-- no no environmentalenvironmental effectseffects-- immediateimmediate evaluationevaluation afterafter irradiationirradiation-- lowlow priceprice-- multiplemultiple useuse-- automatedautomated, , nonnon--destructivedestructive evaluationevaluation

PresentlyPresently availableavailable systemssystems::-- processprocess calorimeterscalorimeters-- ESR ESR alaninealanine-- oscillometricoscillometric ECBECB-- ((SunnaSunna film)film)

FACTORS AFFECTING DOSIMETER FACTORS AFFECTING DOSIMETER ACCURACYACCURACY

1.1.

IrradiationIrradiation

conditionsconditions

areare

differentdifferent

fromfrom


conditionsconditions::

--

temperaturetemperature, , dosedose

raterate, , relativerelative

humidityhumidity, , energyenergy

spectrumspectrum, , irradiationirradiation

geometrygeometry, , etcetc..

2.2.

StorageStorage

conditionsconditions::

--

beforebefore

andand

afterafter


3.3.

InstrumentalInstrumental

errorserrors::

--

absorbanceabsorbance

andand

wavelengthwavelength

scalescale, , scatteredscattered

lightlight, , transfertransfer

ofof calibrationcalibration

curvecurve

fromfrom

oneone

instrumentinstrument

toto

anotheranother

oneone, , etcetc..

Accuracy and PrecisionAccuracy and Precision

AIM OF CALIBRATIONAIM OF CALIBRATION

Determine relationship Determine relationship between response of a between response of a dosimeter and absorbed dosimeter and absorbed dose.dose.

Influence factors:Influence factors:--

dose ratedose rate

--

temperaturetemperature--

timetime

--

humidity, etc. humidity, etc.

Minimize effects of Minimize effects of influence factors by influence factors by optimum calibration optimum calibration conditions.conditions.

DosimetryDosimetry calibrationcalibration

–– newnew trendstrends

InIn--plantplant calibrationcalibration::

CalibrationCalibration phantomsphantoms(Gamma, (Gamma, electronelectron););

Internet Internet calibrationcalibration(NIST):(NIST):

protectedprotected software;software;alaninealanine dosimetrydosimetry;;

CALIBRATION OF DOSIMETRY CALIBRATION OF DOSIMETRY SYSTEMSYSTEM

Calibration of dosimeterCalibration of dosimeterCalibration of equipmentCalibration of equipment

CALIBRATION OF EQUIPMENT (1)CALIBRATION OF EQUIPMENT (1)

All All measurement equipmentmeasurement equipment must be calibratedmust be calibrated and be traceable to and be traceable to national standards.national standards.

Certain measurement equipment cannot be calibrated (e.g. signal Certain measurement equipment cannot be calibrated (e.g. signal amplitude amplitude from an EPR spectrometer) from an EPR spectrometer)

thereforetherefore⇓⇓

the the stability of the equipment has to be demonstratedstability of the equipment has to be demonstrated by the use of by the use of measurement standards (e.g. stable EPR spin standards).measurement standards (e.g. stable EPR spin standards).

CALIBRATION OF EQUIPMENT (2)CALIBRATION OF EQUIPMENT (2)

--

Spectrophotometer:Spectrophotometer:absorbance and wavelength scale with calibrated optical filters;absorbance and wavelength scale with calibrated optical filters;

--

Thickness gauge:Thickness gauge:calibrated gauge blocks;calibrated gauge blocks;

--Thermometers:Thermometers:calibrated thermometers;calibrated thermometers;

--

Resistance measurement (OhmResistance measurement (Ohm--meter for calorimeters):meter for calorimeters):calibrated reference resistor;calibrated reference resistor;

--

Humidity meters:Humidity meters:saturated salt solutions;saturated salt solutions;

CALIBRATION OF DOSIMETERS (1)CALIBRATION OF DOSIMETERS (1)

Irradiation of dosimetersIrradiation of dosimeters

Measurement Measurement ((analysisanalysis) ) of dosimeters (with calibrated instrument)of dosimeters (with calibrated instrument)

Generation of calibration curve or response functionGeneration of calibration curve or response function

Initial Initial ccalibrationalibration verification, and periodically confirmation of validityverification, and periodically confirmation of validity

TraceabilityTraceability chainchain

CALIBRATION OF DOSIMETERS (2)CALIBRATION OF DOSIMETERS (2)--

Dose range:Dose range:Larger dose range than intended use;Larger dose range than intended use;

--

Number of dose points: Number of dose points: (4 dosimeters at each point)(4 dosimeters at each point)Dose range less than one decadeDose range less than one decade: : 5 points (at least)5 points (at least)--

arithmetically (10 arithmetically (10 --

20 20 --

30 30 --

40 40 --

50 50 kGykGy););

Dose range greater than one decadeDose range greater than one decade: : 5 points (at least) per decade5 points (at least) per decade--

geometricalgeometricallyly

(1 (1 --

1.5 1.5 --

2.3 2.3 --

3.4 3.4 --

5.1 5.1 --

7.6 7.6 --

11.4 11.4 --

17 17 --

26 26 --

38 38 --

58 58 --

87 kGy);87 kGy);

--

Batch calibration:Batch calibration:Each new batch must be calibrated (annual checks);Each new batch must be calibrated (annual checks);DonDon’’t use manufacturers`s calibration curve t use manufacturers`s calibration curve --

unless verified;unless verified;

--

Post irradiation stability:Post irradiation stability:

to control! to control!

IRRADIATION OF DOSIMETERSIRRADIATION OF DOSIMETERS1. 1. Irradiation at a Irradiation at a calibration calibration facilitfacilityy

Irradiation of dosimeters in the reference radiation field of a Irradiation of dosimeters in the reference radiation field of a calibration laboratory calibration laboratory ((oror

ofof

anan

inin--househouse


facilityfacility) ) followed followed

by by ““calibration verificationcalibration verification””

in the irradiation plant.in the irradiation plant.

a./ advantagesa./ advantages--

easy to obtain full dose range;easy to obtain full dose range;

--

irradiation to accurately known doses under controlled and irradiation to accurately known doses under controlled and documented conditions;documented conditions;

b./ disadvantages:b./ disadvantages:--

different conditions from real use (uncertainties);different conditions from real use (uncertainties);

--

transport of dosimeters (pretransport of dosimeters (pre--

and postand post--irradiation storage irradiation storage effects effects --

uncertainties);uncertainties);

CCalialibrationbration

facilityfacility

Calibration

holder ↓

IRRADIATION OF DOSIMETERSIRRADIATION OF DOSIMETERS22..

Irradiation Irradiation in plantin plant

Routine dosimeters are irradiated together with reference or traRoutine dosimeters are irradiated together with reference or transfer standard nsfer standard dosimeters in dosimeters in ““calibration phantomscalibration phantoms””

in the irradiation plant.in the irradiation plant.

a./ advantages:a./ advantages:--

calibration and production conditions are similarcalibration and production conditions are similar(environmental conditions); (environmental conditions);

b./ disadvantages:b./ disadvantages:--

difficult to obtain full dose range in certain plants;difficult to obtain full dose range in certain plants;

c./ care must be taken:c./ care must be taken:--

to ensure that all dosimeters irradiated together receive the to ensure that all dosimeters irradiated together receive the same same

absorbed doseabsorbed dose

GAMMA IRRADIATION PHANTOMGAMMA IRRADIATION PHANTOM

--

To be placed in a regionTo be placed in a regionof low dose gradient;of low dose gradient;

--

The effect of irradiationThe effect of irradiationtemperature on the referencetemperature on the referencedosimeters must be considered:dosimeters must be considered:

TTeffeff

= = TTminmin

+ 2/3 (+ 2/3 (TTmaxmax

--

TTminmin

););

--

Use of temperature labels;Use of temperature labels;

ELECTRON BEAM PHANTOMELECTRON BEAM PHANTOM--

It is irradiated separately,It is irradiated separately,not in e.g. dummy product;not in e.g. dummy product;

--

Specific location on the depthSpecific location on the depthdose curve should be chosen;dose curve should be chosen;

-

The effective irradiation temperature can be considered:

Teff

= (Tmin

+ Tmax

) / 2;

IMPORTANCE OF TRACEABILITYIMPORTANCE OF TRACEABILITY

The The abilityability

toto

show show thatthat

a a measurementmeasurement

is is consistentconsistent

withwith

thethe

appropriateappropriate

nationalnational

oror

internationalinternational

standardsstandards

throughthrough

anan

unbrokenunbroken

chainchain

ofof

comparisoncomparison

((primaryprimary

standard standard lablab. . →→ secondarysecondary

standard standard lablab. . →→ routineroutine

lablab.).)

((verificationverification

is is neededneeded))

CALIBRATION VERIFICATIONCALIBRATION VERIFICATION

--

Calibration curves prepared for routine dosimeters in a Calibration curves prepared for routine dosimeters in a calibration facility (or incalibration facility (or in--house calibration facility) must be house calibration facility) must be verified for the actual conditions of use in the production verified for the actual conditions of use in the production irradiation facility;irradiation facility;

--

Routine dosimeters have to be irradiated together with Routine dosimeters have to be irradiated together with reference or transfer standard dosimeters to at least three reference or transfer standard dosimeters to at least three different absorbed doses.different absorbed doses.

--

Absorbed dose results originating from the two types of Absorbed dose results originating from the two types of dosimeters must be analyzed with respect to any systematic dosimeters must be analyzed with respect to any systematic trends for potential corrections if neededtrends for potential corrections if needed..

ANALYSISANALYSIS

1. Analysis of dosimeters1. Analysis of dosimeters--

use of calibrated instrumentation;use of calibrated instrumentation;

--

time of analysis after irradiation (potential changes oftime of analysis after irradiation (potential changes of

dosimeter dosimeter responseresponse

after irradiation);after irradiation);

2. Analysis of calibration data2. Analysis of calibration data--

mean response and sample standard deviation;mean response and sample standard deviation;

--

calculation of coefficient of variation;calculation of coefficient of variation;

3. Preparation of calibration curve3. Preparation of calibration curve

--

signal = f(dose)signal = f(dose)--

evaluation of mathematical expression (e.g. calculation of "perevaluation of mathematical expression (e.g. calculation of "percentage centage

residuals")residuals")

toto

selectselect

bestbest

fitfit;;

EXAMINATION OF RESIDUALSEXAMINATION OF RESIDUALSSelectSelect thethe mathematicalmathematical expressionexpression forfor thethe dosedose=f(=f(signalsignal) ) relationshiprelationship((e.ge.g. . lowestlowest

orderorder

polynomialpolynomial););

DetermineDetermine thethe coefficientscoefficients ofof thethe polynomialpolynomial ((useuse individualindividualdosimeterdosimeter pointspoints););

CalculateCalculate thethe dosedose forfor eacheach calibratedcalibrated dosimeterdosimeter;;

CalculateCalculate ""percentagepercentage residualsresiduals""::

((DDcalculatedcalculated

––

DDdelivereddelivered

) / ) / DDdelivereddelivered

x100x100

PlotPlot ""percentagepercentage residualsresiduals"" againstagainst dosedose andand examineexamine datadata forforanyany systematicsystematic trendstrends;;

EXAMINATION OF RESIDUALSEXAMINATION OF RESIDUALS ((exampleexample))

Calibration

curve

and

function

→ Percentage

residual

↓ ↓

Harwell AH 4thy = -1,6466E-07x4 + 5,3813E-05x3 - 8,2926E-03x2 + 8,5069E-01x -

7,1433E-03R2 = 9,9999E-01

0,0

5,0

10,0

15,0

20,0

25,0

30,0

35,0

40,0

45,0

0 20 40 60 80 100 120

Dose kGy

Resp

onse

AH 4th order

-1

-0,8

-0,6

-0,4

-0,2

0

0,2

0,4

0,6

0,8

1

1 10 100

Dose kGy

Res

idua

l %

THANK YOU FOR YOUR ATTENTION!THANK YOU FOR YOUR ATTENTION!

Accuracy

Precision

IDEAL DOSIMETRY SYSTEM DOSIMETRY SYSTEMS IN CURRENT … · 51276 FWT – 60 film VIS -...

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