An Overview about Radiation Protection_2024

An overview about radiation protection

2. What is the sources of ionizing radiation?

3. Radiologyisconcernedwiththeapplicationofradiationto
thehumanbodyfordiagnosticallyandtherapeuticallypurposes.
Thisrequiresanunderstandingof:
•the basic nature of radiation
•interaction between radiation and matter
•radiation detection
•biological effects of radiation
toevaluatetheadvantagesanddisadvantagesofthevarious
medicalapplicationsofradiationanditslimitations.

4. Therearevariouskindofradiationwhichcanbeclassifiedin
electromagneticradiation(EM)andparticleradiation(p).TheX-raysand
-raysarepartoftheelectromagneticspectrum;bothhaveawavelength
rangebetween10
-4
and10
1
nm,theydifferonlyintheirorigin.
Nature and Origin of Radiation

5. WheninteractingwithmatterEM-radiationshowsparticlelikebehavior.
The'particles'arecalledphotons.Theenergyofthephoton
andthefrequency(orwavelength)oftheEM-radiationare
determinedbythePlanckconstanth:
h=6.62
-34
Js = 4.12 10
-21
MeVs
The photon energy for X-rays and -rays is in the eV to MeV range.

6. X-raysoriginateeitherfromcharacteristicdeexcitation
processesintheatoms(K
,K
transitions)(CharacteristicX-rays).
Thephotonenergycorrespondstothedifferenceinbindingenergyof
theelectronsintheexcitedlevelstotheK-level.

7. X-raysalsooriginatefromenergylossofhighenergy
chargedparticles(e.g.electrons)duetointeractionwiththe
atomicnucleus(bremsstrahlung)

8. TheX-rayshaveasmoothenergyspectrum,
duetothecontinuesenergylosseffectsinthe
Coulombfieldofthenucleus.

9. -rayshavetypicallyhigherenergiesthanX-rays.They
originatemainlyfromdeexcitationprocesseswithinthenucleus.
ThenucleusofmassMischaracterizedbyZprotonsofmass
mpandNneutronsofmassm
n.ThemassnumberA=Z+N.
example:
18
8O
10.
A
ZElement
Z
ThebindingenergyBEofthenucleusisthe
differencebetweenthemassofthenucleusandthe
massoftheZprotonsandNneutrons.
Themassisoftenexpressedintermsof
amu(atomicmassunits)whichisdefinedby
As higher the binding energy as more stable is the
nucleus. The binding energy is often calculated in terms of
the mass excess:

10. As higher the binding energy as more stable is the
nucleus. The binding energy is often calculated in terms of
the mass excess:
EXAMPLE binding energy for
18
O

11. Nuclei with equal Z but different A, N are called isotopes
the three stable oxygen isotopes are:
16
8O
8,
17
8O
9, and
18
8O
10
Nuclei with equal N but different A, Z are called isotones
three N=10 isotones are:
17
7N
10,
18
8O
10, and
19
9F
10
Nuclei with equal A but different Z, N are called isobars
three A=18 isobars are:
18
7N
11,
18
8O
10, and
18
9F
9
Allthesenucleihavedifferentbindingenergies
becausetheydifferinthenumberofprotonsandneutrons
fromeachother.

12. Thenucleuscanbeinhigherexcitationifitrotates
(rotationalenergy),ifitvibrates(vibrationalenergy),ifthesingle
particlesareinhigherquantummechanicallyallowedstates
(singleparticleexcitation).
-emissionoccursbydeexcitationofahighexcitation
levelofthenucleustothegroundstate.Theenergydifference
betweenthetwoexcitedstatescorrespondstotheenergyof
the-radiation.

13. Particleradiationistypicallyinducedbydecayprocessesofthe
nucleus.Inthesedecayprocessesaninternalreorganizationofthe
nucleonstakesplacebywhichamoreenergeticallyfavorablestatecan
bereached(minimumofmass,maximuminbindingenergy).
In-decayprocessesaneutronisconverted
intoaprotonbyelectronemission(
-
-decay),oraprotonisconvertedin
aneutronbypositronemission(
+
-decay):

14. -radiationareelectronswhichareemittedinthedecay
processwithacertainkineticenergywhichoriginatesfromthe
energydifferencebetweenthedecayingnucleus(mother)andthe
decayproduct(daughter).Aspartoftheenergyisdistributedtoa
thirdparticle(neutrino)the-spectrumofaparticulardecay
processisasmoothdistribution.

15. Thereleasedenergyis
translatedintothekineticenergyof
theemitteda-particleandtheheavy
recoilnucleus.
In-decayprocessesthenucleusreduceshismassbyemittinga
4
2He
2(helium)nucleus(-particle)toreachalessmassivestate.
-decayoccursinparticularforheavymassivenuclei.Thekinetic
energyoftheemittedaparticlesisdeterminedbythemassofthemotherand
daughtersystem.

16. Neutrondecayoccurseitherasconsequenceofapreceding
-decay,(-delayedneutrondecay)orasaresultofareactionoffission
process.
Inmostcasesconcernedwithmedicalapplicationsneutronsare
originatedinfission,thesplittingofaheavynucleusintwoapproximately
equallymassedsmallernuclei.

17. or
Natural Decay Law
TherateofthedecayprocessisdeterminedbytheactivityA
(numberofdecayprocessespersecond)oftheradioactivesample.
The activity is proportional to the number of radioactive nuclei (radionuclide)
is the decay constant!
DifferentialequationforN(t)canbesolved

18. N(t
0),A(t
0)aretheinitialnumberofradionuclidesand
initialactivity,respectively.
Thehalflifet
1/2ofaradionuclideisthetimebywhichthe
numberofradionuclideshasreducedto50%.
Thisshowsadirectcorrelation
betweenhalflifeanddecayconstantfor
eachradionuclide.
The lifetime r of a nucleus is defined by:
Quiteoftentheexpression
“lifetime”canbefoundforradionuclides.
Thismeansthatafteraperiodcorrespondingtothe“lifetime”
ofaradioactivenucleustheinitialabundancehasdecreasedto36.8%of
itsinitialvalue,ofanucleuscanbefound!

21. UnitforexposureEistheRoentgen[R]
whichisdefinedbytheionizationbetweenEM-radiationandair.1
RoentgenistheamountofEM-radiationwhichproducesin1gramofair
2.5810
-7
Catnormaltemperature(22°C)andpressure(760Torr)
conditions.
Dosimetry Units
Duetotheinteractionbetweenradiationandmaterial
ionizationoccursintheradiatedmaterial!(Energytransferfromthe
highenergeticradiationphotonsorparticlestoatomicelectrons.)The
ionizationcanbeusedasmeasurefortheamountofexposurewhich
thematerialhadtoradiation.
1 R = 2.58 10
-4
C/kg

22. TheexposurerateER(=ionization/time)canberelated
totheactivityAofasource(inunitsmCi)via:
Fistheexposureconstantinunits[(Rcm
2
)/(hmCi)],
anddisthedistancebetweensourceandmaterialinunits[cm].The
exposureconstantischaracteristicalfortheradiationsource:

23. TheabsorbeddoseDofradiationinanykindof
materialdependsonthetypicalionizationenergyoftheparticular
material.Theabsorbeddoseisdefinedintermsoftheabsorbed
radiationenergypermassW
1P.
Itthereforeclearlydependsontheenergylossbehavior
ofthevariouskindsofradiation.
Theunitfortheabsorbeddoseis:
1 Gray = 1Gy = 1 J/kg = 10
4
erg/kg = 100 rad
TheaverageionizationenergyforairisW
1P34eV/ion.With
1eV=1.602210
-19
Jandthechargeperionis1.610
-19
,thisyieldsfor
theabsorbeddoseinairDfor1RexposureofEMradiation:
D = 1R • 34 J/C = 2.58 10
-4
C/kg34 J/C = 8.8 10
-3
J/kg =
8.8 10
-3
Gy = 0.88 rad

24. Theaverageionizationenergydependscriticallyonthematerial.

25. Thereisanempiricalrelationbetweentheamountof
ionizationinairandtheabsorbeddoseforagivenphoton
energyandabsorber(bodytissue).
Theabsorbeddoseinradsperroentgenofexposureis
knownastheroentgen-to-radconversionfactorC
Cisapproximatelyequaltooneforsoftbodytissueinthe
energyrangeofdiagnosticradiology.
Theincreaseforbonematerialisduetohigher
photoelectricabsorptioncrosssectionforlowenergyphotons.

26. Dose (rad) = Exposure (R) x R to Rad Conversion factor

30. Exposure,exposurerateandabsorbeddoseareindependentof
thenatureofradiation.Biologicaldamagedependsmainlyontheenergy
lossoftheradiationtothebodymaterial.Theseenergylossesdiffer
considerablyforthevariouskindsofradiation.Toassessthebiological
effectsofthedifferentkindofradiationsbetter,asnewempiricalunitthe
doseequivalentHisintroduced:
DOSE EQUIVALENT
withthequalityfactorQwhichdependsstronglyontheionizationpowerofthe
variouskindsofradiationperpathlength.InfirstapproximationQZofradiation
particles,Q(,X,)1.
As higher Q as higher the damage the radiation does!

32. EFFECTIVE DOSE
Thevariousbodyorganshave
differentresponsetoradiation.To
determinethespecificsensitivityto
radiationexposureatissuespecific
organweightingfactorw
Thasbeen
establishedtoassignaparticularorgan
ortissueTacertainexposurerisk.
Thegivenweightingfactorsinthetableimplyforexamplethatan
equivalentdoseof1mSvtothelungentailsthesameprobabilityofdamaging
effectsasanequivalentdosetotheliverof(0.12/0.05)1mSv=2.4mSv
ThesumoftheproductsoftheequivalentdosetotheorganH
Tandthe
weightingfactorw
TforeachorganirradiatediscalledtheeffectivedoseH
:HH
TT
T
=

Like H
T, H
is expressed in units Sv or rem!.

35. Thereisnodirectevidence
ofradiation-inducedgeneticeffectsin
humans,evenathighdoses.Various
analysesindicatethattherateof
geneticdisordersproducedin
humansisexpectedtobeextremely
low,ontheorderofafewdisorders
permillionlivebornperremof
parentalexposure.

36. Thepotentialbiologicaleffectsanddamagescausedby
radiationdependontheconditionsoftheradiationexposure.
The different kinds of radiation have different energy loss effects LET.
It is determined by:
quality of radiation
quantity of radiation
received dose of radiation
exposure conditions (spatial distribution)

37. Energy loss effects depends on nature and probability of interaction
between radiation particle and body material.
Particles with high energy loss effects cause typically greater damage.
Tonormalizetheseeffectsasanempiricalparameterthe
RelativeBiologicalEffectivenessRBEofradiationforproducinga
givenbiologicaleffectisintroduced:
The RBEfor different kinds of radiation can be expressed in terms of
energy loss effects LET.

38. ForlowLETradiation,RBELET,forhigherLETtheRBE
increasestoamaximum,thesubsequentdropiscausedbytheoverkill
effect.
These high energies are sufficient to kill more cells than actually available!

39. Radiation damage to body organs, tissue, and cells is a
purely statistical effect
Ashighertheradiationdoseasmorelikelysomeeffectswill
occur.AshighertheLETand/ortheRBEasmorelikelydamagemay
occur.Theeffectsaretypicallydescribedbyempiricaldose-response
curves.
Schematicrepresentationofdose-responsefunctionE(D)atlowdosesD
forhigh-LET(curveH)andlow-LET(curveL
1,)radiations.L
2isthe
extensionofthelinearbeginningofL
1.

40. Radiationcancauseimmediateeffects(radiation
sickness),butalsolongtermeffectswhichmayoccurmany
years(cancer)orseveralgenerationslater(geneticeffects).
Biologicaleffectsofradiationresultfrombothdirectand
indirectactionofradiation.
Directactionisbasedondirectinteractionbetween
radiationparticlesandcomplexbodycellmolecules,(for
exampledirectbreak-upofDNAmolecules)

41. Indirectactionismorecomplexanddependsheavilyonthe
energylosseffectsofradiationinthebodytissueandthesubsequent
chemistry.
1.Radiation deposits energy into the body tissue by energy
loss effects
compton scattering, photo-excitation for -and X-rays
scattering and ionization processes for -, p, n-particles (LET)
2.Energylosscausesionizationandbreak-upofsimplebody
molecules:
H
2O →H
+
+ OH
−
3.OH
−
radical attacks DNA-molecule.
4.Resulting biological damage depends on the kind of alteration and
can cause cancer or long-term genetic alterations.

42. RADIATION
DIRECT IONIZATION
OF DNA
IONIZATION OF
OTHER MOLECULES, e.g.,H
2O
radiation + H
2O →H
2O
+
+ e
−
H
2O
+
→H
+
+ OH
0
e
−
+ H
2O →H
0
+ OH
−
OXIDATION OF DNA
BY OH RADICALS
NO EFFECTENZYMATIC REPAIR
CHEMICAL
RESTORATION
DNA
RESTORED
PERMANENT DAMAGE IN DNA
BIOLOGICAL EFFECTS
1. GENETIC EFFECTS
2. SOMATIC EFFECTS
CANCER
STERILITY

43. The time scales for the short and long term effects of radiation are
symbolized in the figure and listed in the table

45. There are many biological effects a high dose of radiation can cause:
Theresultsarebasedonseveraldatasourcesonradiation
exposuretohumans
Pleasereadtextbook
survivors of the atomic bomb detonations at Hiroshima and Nagasaki
medicalexposuretopatients(inparticularintheearlyfortiesandfifties)
evaluations of populations with high occupational exposure
evaluationsofpopulationswithhighradiationbackground(highaltitude)

47. Skin Effects
Thefirstevidence
ofbiologicaleffectsof
radiationexposureappears
ontheexposedskin.
Thedifferentstages
dependonthedoseandon
thelocationoftheexposure.

48. Acute Radiation Syndrome
Thebodyconsistsofcellsofdifferentradiationsensitivity,a
largedoseofradiationdeliveredacutelydoeslargerdamagethan
thesamedoesdeliveredoveralongperiodoftime.
Thebodyresponsetoalargeacutedosemanifestsitselfin
theacuteradiationsyndrome.

49. The first (prodomal) symptoms show up after 6 hours
Thesesymptomssubsideduringthe
latentperiod,whichlastsbetweenone
(highdoses)andfourweeks(lowdoses)
andisconsideredanincubationperiod
duringwhichtheorgandamageis
progressing
Thelatentperiodendswiththeonsetof
theclinicalexpressionofthebiological
damage,themanifestillnessstage,which
laststwotothreeweeks
Survival of the manifest illness stage practically guaranties full recovery
of the patient

50. The severity and the timescale for the acute radiation syndrome
depends on the maximum delivered dose.
The first symptoms show up after 6 hours
If the whole body exposure exceeds a critical threshold rate of
50 -100 rad the symptoms show up more rapidly and
drastically.

52. Longtermradiationrisksaremoredifficulttoassess.
Thepredictionsarebasedontheuseofriskmodels.
Themainproblemaretheinsufficientstatisticallongtermdata
aboutradiationvictimswhichmakereliablemodelpredictionsdifficult.

53. In particular for low LET exposure linear and quadratic dose-
response models differ considerably in their risk assessment

56. Theriskassessmentdependsontheageoftheexposed
person,differentorganshaveadifferentresponsetoradiation,
thereforetheriskofcancerdiffersconsiderably.

59. Thetotallifetimedetrimentincurredeachyearfromradiation
byaworkerexposedtothelimitsoverhis/herlifetimeshouldbeno
greaterthantheannualriskofaccidentaldeathina"safe"industry
environment.
Annual rate of fatal accidents ranges from 0.210
−4
(service industries)
to 510
−4
(min in industries).
Foranaveragedmeasuredeffectivedoseof2.1mSvfor
radiationworkers,thetotaldetrimenttoreceiveradiationdamageis:
21 10
−3
Sv/y 4.0 10
−2
Sv
−1
= 8.4 10
−4
y
−1
0.001 y
−1
Thislevelisintherangeoftheaverageannualriskfor
accidentaldeathforallindustries.

60. Tocontrolthedistributionofexposureoveraworkingcareer
theannualeffectivedoseislimitedto50mSv(notincludingmedical
andnaturalbackgroundexposure)
To account for the cumulative effects of radiation, an age-dependent
limit of 10 mSv • age (y) is introduced.
Workersatageof64attheendoftheircareerwithan
accumulatedeffectivedoseof640mSvwouldhavealifetimedetrimentof:
0.64Sv • 4.0•10
-2
Sv
-1
= 2.6•10
-2
incomparisontheirlifetimeriskofafatalaccidentovertheir50yworking
careerisofcomparableorder:
50y • 5.0•10
-4
y
-1
= 2.5•10
-2
Forspecificorgansspeciallimitsfortheannualequivalent
dosearerecommended.

63. There are two kinds of radiation monitors used for medical purposes:
survey monitors
personal monitors

64. Primary Use Of Radiation Instruments

65. Survey Meter
Geiger Muller instruments
Scitilationinstruments
Ionization chamber
Instruments

66. Survey Meters
Survey meters are used to determine the extend of possible
contaminations.
Mostfrequentlyusedisthe
Geiger-Miller(GM)meter,whichare
basedontheionizationeffectsof
radiationingas.Theradiationis
completelyabsorbedinthecounter
gas,createsachargedparticles
whicharecollectedinthefieldofthe
appliedvoltageandconvertedtoan
electricalpulse.
Thenumberofpulsescorrespondstothenumberofabsorbed
particles,butisindependentfromtheappliedcollectionvoltage.
ThereforetheGMdetectorisusedformeasuringtherateofthe
radiationnottheabsorbeddose(energy).

67. Surveymeters,fieldsurveymeters,ratemeters,radiacmeters,radiation
detectionmeters,low-rangemeters,high-rangemeters,airbornemeters,falloutmeters,
remotemonitors,Geigercounters,andeven'doseratemeters'arealldescribing
instrumentsthatmeasureexposurerateortheintensityofradiationatalocationatsome
pointintime.It'slikethespeedometerofacar;bothpresentmeasurementsrelativeto
time.Alloftheseabove'meters',theGeigercounter,too(whichutilizesaGeigertube
ratherthananionchamber),willshowtheirradiationintensityreadingsrelativetotime,
suchasR/hrormR/hrlikethescaleattheright,sameasacarspeedometerwillshow
miles/hr.Ifyouenteredaradioactiveareaandyourmetersays60R/hrthenthatmeansif
youweretostaythereforawholehouryouwouldbeexposedto60R.Sameasdrivinga
carforanhourat60mph,you'dbe60milesdowntheroadafterthathour,atthatrate

68. CD V-715 Civil Defense High-Range Survey Meter
0-500 R/hr range
3.25pounds,diecastaluminumanddrawnsteelcase,watertight,
willfloat.PoweredwithoneD-sizedbattery,continuouslyfor150
hours,longerifonintermittentbasis.
Instrumentaccuracyonanyofitsfourrangesiswithin+-20%of
truedoserate.Accuracymaintainedthroughouttemperature
rangesof-20Fto+125F,relativehumiditiesto100%andaltitudes
upto25,000'.

69. The low-range Civil Defense survey meter is the CD V-700

70. In the proportional range the number of collected ions
(pulse height) is proportional to the applied potential.
Proportional Counter

71. GM-counters are sensitive for low levels of radiation
GM counters are sensitive for -, -, and -radiation provided the
particle energy is sufficient for penetrating the detector entrance
window.
(WarningthemR/hrreadingoftheGM-counterwillbeusually
lowerthantherealexposurerateduetothelowenergyabsorption
inthemonitorwindow.)
GM counters are best used for radiation detection not for measurement
of dose
GM counters can be calibrated for absorbed dose reading by using
calibrated -sources.

72. Personnel Monitor Devices
The most common monitor devices to determine the personal exposure
history are:
Radiation Film Badges
Pocket Dosimeter
TLD Badges

73. Radiationfilmbadgesarecomposedoftwopiecesoffilm,
coveredbylighttightpaperinacompactplasticcontainer.Various
filtersinthebadgeholderallowareastoberestrictedtoX-ray,-ray,-
raysonly.
Radiationcausesablackening(silver)ofthefilmmaterial
(mostlyasilverbromideemulsion)Thesensitivityofthefilmmaterialis
limited
For -radiation the sensitivity is in the range of 10 -1800 mrem.
For -radiation the sensitivity is in the range of 50 -1000 mrem.
Specialfilmmaterialisusedforneutronmonitoring.
Thebadgeisusuallynotsensitiveforradiationbecausethe
-particlesareabsorbedinthelight-tightpaper.

74. Pocket dosimeter
Thepocketdosimeterorpendosimeterisacommonsmallsized
ionchamberwhichmeasurestheoriginatedchargebydirectcollectionona
quartzfiberelectroscope.
TheU-shapedfiberisclosetoaU-shapedwire.Ifthefiberis
chargeditwillbedeflectedawayfromthewire.Thepositionof
deflectionisameasureoftheaccumulatedradiationdose.

75. Thedosimeterrecordstotalexposurefromtheinitial
chargingtothetimeofreading.
Itisanactivedeviceastheradiationexposurecanbe
readimmediatelyasopposedtothepassivefilmbadgewhichis
onlyreadafterapproximatelysixmonths.

76. Dosimeters,whicharealsoavailableinhighorlowranges,canbeinthe
formofabadge,pen/tubetype,orevenadigitalreadoutandallmeasureexposureor
thetotalaccumulatedamountofradiationtowhichyouwereexposed.(TheCivil
Defensepen/tubetubewouldshowareadinglikebelowwhenlookingthroughit.)It's
alsosimilartotheodometerofacar;wherebothmeasureanaccumulationofunits.
ThedosimeterwillindicateacertaintotalnumberofRormRexposurereceived,just
asthecarodometerwillregisteracertainnumberofmilestraveled.

77. Whole-Body Counting
NaI Systems

78. Whole-Body Counting
HPGe-Based Systems
High-Purity Germanium detector systems offer many advantages
over their NaI counter parts which include:
More robust analysis algorithms
Greater stability over long periods of use
Superior identification capabilities for
individual nuclide peaks
Advanced peak deconvolution, peak
background subtraction,
and peak interference corrections

79. Total dose ranges (for Dose-Depth
Monitors)
5 krad to 1 Mrad
Proton cross-section (for Proton SEU
Monitor)
5 10
-7
cm
2
Input voltage 12 -40 V
Power SEU / Dose Depth Monitors 300 / 900 mW
Data interface RS232 / RS 422
Temperature range -40 to + 55°C
Mass SEU / Dose Depth Monitors 350 / 500 g
Dimensions SEU
135 x 100 x 250
mm
3
Dose-Depth
135 x 155 x 250
mm
3
Optional data recorder
Small,lowpoweredreal-timeRadiationMonitorsformanned
andunmannedspacecraftapplications.TotalDoseandDose-Depth
Monitorsforexternaland/orinternalradiationenvironmentmonitoringfor
electronics,materialsandhumanradiationprotectiontasks.Singleevent
upset(SEU)monitorsforapplicationssuchasprotoninducedupset
monitoringforsatellitesinLEO.Allmonitorsarebasedonuniquesilicon
radiationsensorsandaresmallenoughforon-boardhousekeeping
tasks.