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
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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
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The Geiger-Muller CounterThe Geiger-Muller Counter
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The Scintillation CounterThe Scintillation Counter