PERSONNEL PERSONNEL MONITORING MONITORING

DEVICESDEVICES

DR. PRAMOD TIKEDR. PRAMOD TIKE

Department of Radiation Oncology,TATA MEMORIAL HOSPITAL, MUMBAI

Background RadiationBackground Radiation

Radiation is a part of natural environmentRadiation is a part of natural environmentTerrestrial radiationTerrestrial radiationCosmic radiationCosmic radiationRadiation from radioactive elements in our Radiation from radioactive elements in our

bodies = bodies = 4040K , half life = 1.3x10K , half life = 1.3x1099 yr. yr.Medical procedures etcMedical procedures etc

Background radiationBackground radiationNaturally occurring Naturally occurring

radiationradiation

terrestrial radiationterrestrial radiation cosmic radiationcosmic radiation radioactive elements in radioactive elements in

our bodies (our bodies (4040K , K , 1414C)C)TotalTotal

mSv/yr.mSv/yr.

0.400.40

0.440.44

0.180.18

1.021.02

Background radiationBackground radiation Contd.…...Contd.…...

Man made radiationMan made radiation Global fall outGlobal fall out nuclear powernuclear power X rays (excluding X rays (excluding

Fluoro)Fluoro) nuclear medicinenuclear medicine occupationaloccupational MiscellaneousMiscellaneous

TotalTotal

Total Average whole Total Average whole body dose/yearbody dose/year

(including fluoroscopy, (including fluoroscopy, rounded off to)rounded off to)

mSv/yr.mSv/yr.0.040.04

0.00030.0003

0.720.72

0.010.01

0.0080.008

0.020.02

0.7980.798

= = 1.02+0.798 = 1.02+0.798 = 1.821.82 2.00 mSv/year2.00 mSv/year

RADIATION PROTECTION

MONITORING

DEPARTMENTAL PERSONNEL

IONIZATION CHAMBERS GEIGER-MULLER COUNTER

FILM

FILM BADGES TLD BADGES

POCKET DOSIMETERS NEUTRON BADGES

OPTICALLY STIMULATED

PROTECTION

SCINTILLATION COUNTERSCINTILLATION COUNTER

Radiation ProtectionRadiation Protection

ICRPICRP (International Commission on Radiological Protection)(International Commission on Radiological Protection)

NCRPNCRP (National Council on Radiation Protection and (National Council on Radiation Protection and Measurements)Measurements)

NRCNRC (Nuclear regulatory Commission) (Nuclear regulatory Commission) 6060Co and Co and 192192IrIr

AERBAERB (Atomic Energy Regulatory Board) (Atomic Energy Regulatory Board)

RECOMMENDATIONSRECOMMENDATIONS OCCUPATIONAL EXPOSURES(ANNUAL)OCCUPATIONAL EXPOSURES(ANNUAL) in mSv in mSv

Effective Dose EquivalentEffective Dose Equivalent 5050DE for tissues & organsDE for tissues & organs

Lens of EyeLens of Eye 150 150 Skin, hands & feet Skin, hands & feet 500500

Cumulative doseCumulative dose 10 mSv X age10 mSv X ageCumulative dose(ICRP) Cumulative dose(ICRP) 20mSv/yr averaged over 5 yr20mSv/yr averaged over 5 yr

From NCRP recommendations on limits for exposure to ionizing radiation. Report no.91. Bethesda

RECOMMENDATIONS Contd…RECOMMENDATIONS Contd…

Public Exposures ( Annual)Public Exposures ( Annual) in mSv in mSvEDE limit, Continuous/FrequentEDE limit, Continuous/Frequent 11EDE limit, Infrequent exposureEDE limit, Infrequent exposure 55DE limits for lens, skin & ExtremitiesDE limits for lens, skin & Extremities 5050

EDUCATION & TRAINING (ANNUAL)EDUCATION & TRAINING (ANNUAL) Effective dose equivalent/StochasticEffective dose equivalent/Stochastic 11DE DE for Lens,skin&Extrimities/ Non Stochasticfor Lens,skin&Extrimities/ Non Stochastic 5050

From NCRP recommendations on limits for exposure to ionizing radiation. Report no.91. Bethesda

EMBRYO-FETUS EXPOSURESEMBRYO-FETUS EXPOSURESTotal dose equivalent limitTotal dose equivalent limit 5 mSv5 mSvDose equivalent limit in a monthDose equivalent limit in a month 0.5 mSv0.5 mSvEffective dose limit (ICRP)Effective dose limit (ICRP) 2 mSv2 mSv

RECOMMENDATIONS Contd…RECOMMENDATIONS Contd…

From NCRP recommendations on limits for exposure to ionizing radiation. Report no.91. Bethesda

RECOMMENDATIONSRECOMMENDATIONS

GOVERNMENT OF INDIAATOMIC ENERGY REGULATORY BOARD

NIYAMAK BHAVAN, ANUSHAKTINAGAR, MUMBAI – 400 094

MAXIMUM PERMISSABLE EFFECTIVE DOSE EQUIVALENT

ANNUAL = 20 mSv

FOR 5 YEARS = 100 mSv

Eg. If in a year 30 mSv exposure than 100-30=70 mSv permissible in 4 yrs.

NEED OF MONITORINGNEED OF MONITORING

Provision of apparently adequate barriers & Provision of apparently adequate barriers & protective devices does not guarantee the protective devices does not guarantee the safety of workers concernedsafety of workers concernedbarrier not adequatebarrier not adequatecracks or errors in constructioncracks or errors in constructionworkers may ignore or fail to take full workers may ignore or fail to take full advantage advantage

of protection providedof protection providedAny installation must be thoroughly surveyed. Any installation must be thoroughly surveyed. Each worker should be monitored so that Each worker should be monitored so that

he/she is not over irradiated.he/she is not over irradiated.

PERSONNEL MONITORINGPERSONNEL MONITORING

Measurement of the total dose received by Measurement of the total dose received by individual radiation workers over a individual radiation workers over a specified period of time.specified period of time.

Sensor used for measurement of this dose Sensor used for measurement of this dose is known as personnel monitoring device.is known as personnel monitoring device.

AIM:-AIM:-

To monitor and control individual doses To monitor and control individual doses regularly.regularly.

To report and investigate To report and investigate overexposures overexposures

Maintain life time cumulative dose Maintain life time cumulative dose records of the users of the service.records of the users of the service.

Commonly used PMDs areCommonly used PMDs are

Thermo Luminescent Dosimeters( TLD )Thermo Luminescent Dosimeters( TLD )

Commonly used PMDs areCommonly used PMDs are

FILM BADGES

OTHER

Direct reading pocket dosemeters

Optically stimulated devices (OSD).

Specialized personal monitoring devices-neutron radiation.

Thermoluminescent Dosimeters (TLDs)Thermoluminescent Dosimeters (TLDs) Most versatile techniqueMost versatile techniqueMeasurement of x-gamma, beta & gammaMeasurement of x-gamma, beta & gammaPopular because of Popular because of

Their small sizeTheir small sizeEase of handlingEase of handlingHigh sensitivity in desired dose rangeHigh sensitivity in desired dose rangePossibility of obtaining them in desired shape and Possibility of obtaining them in desired shape and

sizesize ruggedness and inertness to climate variations. ruggedness and inertness to climate variations.

The TLD badge The TLD badge

Consists of a TLD card loaded in a cassette Consists of a TLD card loaded in a cassette having suitable metallic filtershaving suitable metallic filters

A TLD card essentially consists of three A TLD card essentially consists of three CaSO4:Dy-Teflon TLD Discs CaSO4:Dy-Teflon TLD Discs (13.2 mm dia x 0.8 mm (13.2 mm dia x 0.8 mm thick ) thick )

Mechanically clipped over three symmetrical Mechanically clipped over three symmetrical circular holes each of diameter 12 mm on a circular holes each of diameter 12 mm on a nickel plated aluminum platenickel plated aluminum plate

The TLD Badge contd.The TLD Badge contd.

An asymmetric V cut provided at one end of An asymmetric V cut provided at one end of the card ensures a fixed orientation of card in the card ensures a fixed orientation of card in the TLD cassettethe TLD cassette

A thin paper wrapper provides personal data A thin paper wrapper provides personal data

and the period of useand the period of use

To protect the TLD discs from dust and To protect the TLD discs from dust and

mishandling, the card along with its wrapper mishandling, the card along with its wrapper is sealed in a thin plastic (polythene) pouch is sealed in a thin plastic (polythene) pouch

When TLD card is inserted in the proper When TLD card is inserted in the proper position in the cassette, the first disc (D1) position in the cassette, the first disc (D1) sandwiched between a pair of filter sandwiched between a pair of filter combination of 1 mm Al and 0.9 mm Cu. The combination of 1 mm Al and 0.9 mm Cu. The Copper filter is nearer to the TLD disc.Copper filter is nearer to the TLD disc.

The second disc (D2) is sandwiched between The second disc (D2) is sandwiched between a pair of 1.5 mm thick plastic filters. a pair of 1.5 mm thick plastic filters.

The third disc (D3) is positioned under a The third disc (D3) is positioned under a circular open window. circular open window.

The TLD Badge contd.The TLD Badge contd.

(D1) sandwiched between a pair of filter (D1) sandwiched between a pair of filter combination of 1 mm Al and 0.9 mm Cucombination of 1 mm Al and 0.9 mm Cu

(D2) is sandwiched between a pair of 1.5 (D2) is sandwiched between a pair of 1.5 mm thick plastic filtersmm thick plastic filters

(D3) is positioned under a circular (D3) is positioned under a circular open windowopen window

Asymmetric V cutAsymmetric V cut

Nickel plated aluminum plateNickel plated aluminum plate

paper wrapper provides personal data and the period of usepaper wrapper provides personal data and the period of use

TLD

cassettecassette

0390 CDr. Pramod Tike

Radiation oncologyJUL-SEP 2006

A TLD BADGE

For X & gamma

For beta

For all as control

Types of TL Badges: Types of TL Badges:

1.1. Chest Badge: used for estimation of Chest Badge: used for estimation of the whole body dose, worn at the the whole body dose, worn at the chest level.chest level.

2.2. Wrist Badge: has a strap to be worn Wrist Badge: has a strap to be worn around wrist. It is used to estimate the around wrist. It is used to estimate the dose to hands and forearms when dose to hands and forearms when they are likely to be selectively they are likely to be selectively exposed.exposed.

TL process & properties:TL process & properties:

TL is a property exhibited by a large no. of TL is a property exhibited by a large no. of crystalline materials in which light is crystalline materials in which light is emitted from an irradiated phosphor on emitted from an irradiated phosphor on heating heating

The intensity of the emitted light is The intensity of the emitted light is proportional to the radiation dose proportional to the radiation dose absorbed by the material absorbed by the material

TL process & properties: Contd..TL process & properties: Contd..

TL phosphors can be produced in many shapes TL phosphors can be produced in many shapes have a small size and can be reused by the have a small size and can be reused by the process of annealing, makes them an attractive process of annealing, makes them an attractive radiation dosimeter radiation dosimeter

several TL phosphors available such as lithium several TL phosphors available such as lithium fluoride (LiF), lithium borate (Lifluoride (LiF), lithium borate (Li22 B B440077) Calcium ) Calcium

sulphate (CaSosulphate (CaSo44) and calcium fluoride (Ca F) and calcium fluoride (Ca F22))

LiF is most extensively used LiF is most extensively used

TL Photon

Schematic diagram explaining the process of thermoluminescence.

CONDUCTION BAND

VALENCE BAND

Irradiation Heating

Ionizing radiation

Electron trapEnergy

Characteristics of LiF & CaSo4 TLD

CharacteristicLiF

Density (gm/cm3) 2.64 (Powder ~ 1.3)

Effective atomic number 8.2

TL emission spectra (A) Range 3500-6000

Temperature of main glow peak 195°C

Useful range in Gy 10-5 to 103

Fading < 5 % in 12 weeks

Light Sensitivity Essentially none

Physical form Powder, rods, discs, chips

CaSO4

2.61

15.3

4780-5710

220-250°C

μ Gy to 103

6 % in 6 months

Essentially none

Powder, discs, chips

Source: LiF from F. Khan & CaSo4 from A.F.McKinly

Glow Curve and Dose ResponseGlow Curve and Dose Response: :

A plot of TL against temperature is called glowA plot of TL against temperature is called glow curve.curve. As the temperature of the TL material exposed to As the temperature of the TL material exposed to

radiation is increased, the probability of releasing radiation is increased, the probability of releasing trapped electrons increases.trapped electrons increases.

In any glow curve, the TL output first increases slowly, In any glow curve, the TL output first increases slowly, reaches a maximum value and falls again to zeroreaches a maximum value and falls again to zero

GLOW CURVE Contd..GLOW CURVE Contd..

May contain many glow curvesMay contain many glow curvesMost prominent one is importantMost prominent one is importantCharacteristic property Characteristic property Can be altered by change in dopant conc. and Can be altered by change in dopant conc. and

trace impuritiestrace impurities Intensity mainly dependent on the amount of Intensity mainly dependent on the amount of

radiation dose radiation dose Ideally a single and a stable glow peak around Ideally a single and a stable glow peak around

200200C are preferredC are preferred

FadingFadingDef:Def: After exposure of a TL phosphor to IR, the After exposure of a TL phosphor to IR, the

latent measure of the absorbed dose is the no. latent measure of the absorbed dose is the no. of eof e-- which remains trapped in the various which remains trapped in the various trapping levels. Unintentional release of these trapping levels. Unintentional release of these ee-- before readout is called fading before readout is called fading

Due to thermally or optically stimulated release Due to thermally or optically stimulated release of the eof the e-- or the combination of both. or the combination of both.

Other TL usedOther TL used

Lithium borate (LiLithium borate (Li22 B B440077) Calcium sulphate ) Calcium sulphate (CaSo(CaSo44) and calcium fluoride (Ca F) and calcium fluoride (Ca F22) with ) with various added impurities.various added impurities.

Have higher atomic number.Have higher atomic number.

The impurity ↑ the sensitivity by 10-100 times The impurity ↑ the sensitivity by 10-100 times that of LiF but because of their higher Z value that of LiF but because of their higher Z value they show rapid variation in response between they show rapid variation in response between 30 KeV and 30 KeV and 6060Co. Co.

Thelmedor-6000* TLD reader is used to read Thelmedor-6000* TLD reader is used to read the irradiated TLD powder.the irradiated TLD powder.

The irradiated material is placed in a The irradiated material is placed in a planchette (heater cup) where it is heated for a planchette (heater cup) where it is heated for a reproducible heating cycle.reproducible heating cycle.

The emitted light is measured by a PMT The emitted light is measured by a PMT (photomultiplier) tube which converts light into (photomultiplier) tube which converts light into electrical current or charge. This is then electrical current or charge. This is then amplified and measured by a recorder or amplified and measured by a recorder or counter counter

Heater Power Supply

Recorder

P M T

Amplifier

TLDSamples

HighVoltage

Schematic diagram showing apparatus for measuring thermoluminescence

REXON UL-320TLD Reader

THELMEDOR MODEL 6000TLD READER

COLLECTED

PACKED IN BOX AND SEALED

SENT TO BARC VIA POST

DOSE ESTIMATION

ANNELING DONE AT 400OC IN OVEN

DISTRIBUTION

SENT FROM BARC VIA POST

PACKED IN BOX AND SEALED

TLD CAN NOW BE USED AGAIN

FILM BADGEFILM BADGEFEATURES :FEATURES :1.1. Used to measure external individual Used to measure external individual

doses from x,β,γ and thermal neutron doses from x,β,γ and thermal neutron radradnn

2.2. Consists of a film pack loaded in a film Consists of a film pack loaded in a film holder having suitable metallic filtersholder having suitable metallic filters

TYPES OF FILM BADGESTYPES OF FILM BADGES

1. CHEST BADGE: whole body dose1. CHEST BADGE: whole body dose

2. WRIST BADGE: dose to extremities2. WRIST BADGE: dose to extremities

3.HEAD BADGE : dose to skull3.HEAD BADGE : dose to skull

MECHANISMMECHANISM

Charged particles pass through photographic Charged particles pass through photographic emulsion to produce latent image emulsion to produce latent image

Upon developing produces blackening where Upon developing produces blackening where ionization event recorded.ionization event recorded.

Relatively permanent.Relatively permanent.

DURING EXPOSUREDURING EXPOSURE

Xray quantum/ charged particle

Incident Silver bromide (AgBr) grain

High energy electrons

Moves through conduction band

Captured by sensitive specks to

become -vely charged

Ag+ + e- = Ag0

Interstitial Ag+ +ve charge attracted

Neutral Ag/ metallic Silver is latent image

Exposed part

Ag0

Unexposed part

Ag+

Developer ( quinol)

Fixer ( sodium Thiosulphate )

Metallic silver remains Ag+ gets dissolved

Produce blackeningO.D. reading on Optical densitometer

FILM PROCESSINGFILM PROCESSING

The Calibration curveThe Calibration curve

Film

den

sity

abo

ve f

og le

vel

Exposure in mR

500 1000 1500

0.5

1.0

1.5

2.0

Example:DENSITY ABOVE’FOG’ EXPOSURE

= 0.75= 640 mR

A typical Film BadgeA typical Film Badge

OpenPb

1mm

Cu1mm

Cu0.15mm

Cd1mm

OpenPb1mm

Cu1mm

Cu0.15mm

Cd1mm

Plastic1mm

Plastic1mm

•Plastic holder lined with stainless steel

•Dental Xray film( 40mmx30mm )

•Various filters to make independent of radiation energies (10Kev-2Mev)

•Paper wrapped film( eg. Eastman Kodak type-II double coated emulsion)

•Range 0.1 mSv to 10 mSv

A typical Film BadgeA typical Film Badge

OpenPb

1mm

Cu1mm

Cu0.15mm

Cd1mm

OpenPb1mm

Cu1mm

Cu0.15mm

Cd1mm

Plastic1mm

Plastic1mm

All can pass

ββNeutrons

Low Energy XHigh Energy X

γ

DOSE EVALUATIONDOSE EVALUATION β dose calculation:β dose calculation: O.D. of film under Open O.D. of film under Open

& plastic filters.& plastic filters.

γ Dose calculation:γ Dose calculation: open and Pb optical open and Pb optical density of film, evaluated with a known density of film, evaluated with a known calibration graph. calibration graph.

X ray dose calculation:X ray dose calculation: O.D. of film under O.D. of film under CuCu1 1 && CuCu22 & open. & open.

AdvantagesAdvantages

Estimation of doses due to x,β,γ, thermal Estimation of doses due to x,β,γ, thermal neutron.neutron.

Whether the dose is genuine or not.Whether the dose is genuine or not. Using a combination of filters- wide range of Using a combination of filters- wide range of

exposureexposurePermanent record of dose.Permanent record of dose.

DisadvantagesDisadvantages

FadingFadingProcessing takes more timeProcessing takes more timePacking should be light proofPacking should be light proofShelf life is lessShelf life is lessSensitivity to humidity & temperature.Sensitivity to humidity & temperature.Not reusableNot reusable

Dose reportsDose reports

Computer generate dose reports using Computer generate dose reports using preloaded calibration graph/ algorithmspreloaded calibration graph/ algorithms

These reports are sent to institution on These reports are sent to institution on monthly,bimonthly,trimonthly or quarterly.monthly,bimonthly,trimonthly or quarterly.

Cumulative dose record for the current Cumulative dose record for the current year is updatedyear is updated

Annual dose reports are sent after the end Annual dose reports are sent after the end of the year and cumulative lifetime doses of the year and cumulative lifetime doses are calculatedare calculated

Over exposureOver exposure

Dose equivalent recorded by chest badge Dose equivalent recorded by chest badge exceeding 10 mSv.exceeding 10 mSv.

Same is reported to the institution and Same is reported to the institution and individual also, to find out the cause.individual also, to find out the cause.

Preventive measures for future.Preventive measures for future.

DOs and DON’TsDOs and DON’Ts

Take good care at all times. Take good care at all times. Wear all times during work.Wear all times during work.May be worn either at the wrist,head/neck May be worn either at the wrist,head/neck

area or chest height as a whole body area or chest height as a whole body monitor.monitor.

Must be placed under the protective Must be placed under the protective clothing. clothing.

Not transferableNot transferable

Not dropped/accidentally placed to be exposed to a Not dropped/accidentally placed to be exposed to a level of radiation higher than the ambient level.level of radiation higher than the ambient level.

Not accidentally splashed or otherwise Not accidentally splashed or otherwise contaminated by a radioactive liquid. contaminated by a radioactive liquid.

Outside working hours, the monitor is stored in Outside working hours, the monitor is stored in a safe place.(eg. any radiation source/source of a safe place.(eg. any radiation source/source of intense heat such as a radiator.intense heat such as a radiator.

Report any problems with the monitor to the Report any problems with the monitor to the Monitoring Supervisor or to the RSOMonitoring Supervisor or to the RSO

Neutron MonitorsNeutron Monitors

Radiation workers who may be exposed Radiation workers who may be exposed externally to neutrons are required to wear externally to neutrons are required to wear a special "neutron" badge in addition to a special "neutron" badge in addition to the ordinary TLD badgethe ordinary TLD badge

DIRECT READING POCKET DIRECT READING POCKET DOSIMETERSDOSIMETERS

Condenser chamberCondenser chamberDirect readingDirect readingTo know reading immediately To know reading immediately

after exposureafter exposureAir

Metal shield

insulator Conducting layer

+ + + + + + + + +

+ + + + + + + + +

- - - - - - - - - - - -

- - - - - - - - - - - -

+ + + + + + + + ++ + + + + + + + +- - - - - - - - - - - - - - - - - -

Air equivalent wall

Optically stimulated luminescenceOptically stimulated luminescence

Measure radiation exposure due to X-ray, Measure radiation exposure due to X-ray, gamma and beta radiation through a thin layer gamma and beta radiation through a thin layer of aluminium oxide.of aluminium oxide.

After use, the aluminium oxide is stimulated After use, the aluminium oxide is stimulated with laser light causing it to fluoresce in with laser light causing it to fluoresce in proportion to the amount of radiation exposure.proportion to the amount of radiation exposure.

These devices are extremely sensitive and These devices are extremely sensitive and more accurate than TLD or film dosimeters.more accurate than TLD or film dosimeters.

Luxel optically stimulated luminescence dosimeter

OSLOSL

BACK

THANK YOU

Dose Equivalent (H)Dose Equivalent (H)

H = D x Q where,H = D x Q where,D = absorbed doseD = absorbed doseQ = quality factor of the radiationQ = quality factor of the radiationUnit of H = sievert (Sv)Unit of H = sievert (Sv)1 Sv = 1 J/Kg1 Sv = 1 J/Kg If dose(d) is expressed in rads, then If dose(d) is expressed in rads, then unit of H = rem = 1/100 J/Kgunit of H = rem = 1/100 J/Kg

Effective Dose Equivalent(HEffective Dose Equivalent(HEE))

The sum of the weighted dose equivalents The sum of the weighted dose equivalents for irradiated tissues or organs is called for irradiated tissues or organs is called Effective Dose Equivalent.Effective Dose Equivalent.

HHE E = Σ W= Σ WTT . H . HT T Where,Where,WWT T = = weighting factor of tissue Tweighting factor of tissue T

HHTT = = mean dose equivalent received bymean dose equivalent received by tissue Ttissue T

The weighting factor represents risk of tissue The weighting factor represents risk of tissue when body is irradiated uniformly.when body is irradiated uniformly.

Recommended values of Weighting Recommended values of Weighting factorsfactors

Tissue (T)Tissue (T) GonadsGonads BreastBreast Red bone marrowRed bone marrow LungLung ThyroidThyroid Bone surfaceBone surface RemainderRemainder

TotalTotal

from NCRPfrom NCRP

WWTT

0.250.25

0.150.15

0.120.12

0.120.12

0.030.03

0.030.03

0.300.30

1.001.00

THE ION CHAMBERTHE ION CHAMBER

BACK

The Geiger-Muller CounterThe Geiger-Muller Counter

BACK

The Scintillation CounterThe Scintillation Counter