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RAD 100RAD 100 -- IntroductionIntroduction
to Clinical Radiographyto Clinical Radiography
Chapter 9: Basic RadiationChapter 9: Basic Radiation
ProtectionProtection
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Basic Radiation ProtectionBasic Radiation Protection
Ionizing Radiation is used to produce aIonizing Radiation is used to produce a
diagnostic image for the radiologistdiagnostic image for the radiologist
Benefits must outweigh the riskBenefits must outweigh the risk
Sources of radiation include:Sources of radiation include:
Natural or background:Natural or background: energy from sun & otherenergy from sun & other
planets and naturally occurring radioactive substancesplanets and naturally occurring radioactive substances
present on the earth such as uranium and radonpresent on the earth such as uranium and radon ManMan--made:made: nuclear energy, radionuclides, and medicalnuclear energy, radionuclides, and medical
& dental x& dental x--raysrays
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XX--rays travel at speed of lightrays travel at speed of light
3 things must be present for x3 things must be present for x--rayray
productionproduction
A source of electronsA source of electrons
A force to rapidly move themA force to rapidly move them
Something to stop the movement rapidly!Something to stop the movement rapidly!
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These 3 items are met by theThese 3 items are met by the
xx--ray tube & the electricityray tube & the electricity
supplied to the tube.supplied to the tube. The tube is composed of:The tube is composed of:
AnodeAnode positive terminalpositive terminal
CathodeCathode negative terminalnegative terminal
FilamentFilament made of thoriated tungsten (Thismade of thoriated tungsten (This
provides the source of electrons)provides the source of electrons)
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XX--ray production occurs when:ray production occurs when:
Kilovoltage is applied to filamentKilovoltage is applied to filament
The stream of electrons is rapidly acceleratedThe stream of electrons is rapidly accelerated
to the anodeto the anode Upon striking the anode, they undergo energyUpon striking the anode, they undergo energy
conversionconversion This produces both heat and energyThis produces both heat and energy
The beam that results is heterogenous andThe beam that results is heterogenous andmeasure in kiloelectron volts (keV)measure in kiloelectron volts (keV)
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XX--rays are produced!rays are produced!
These xThese x--rays are known as the primary beamrays are known as the primary beam
and exit the tube through a glass window in theand exit the tube through a glass window in the
tube.tube.
Once they strike the patient 3 possibilities exist:Once they strike the patient 3 possibilities exist:
They can be absorbedThey can be absorbed
They can transfer some energy & then scatterThey can transfer some energy & then scatter
They can pass through the patient unaffectedThey can pass through the patient unaffected
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XX--rays interact withrays interact with
matter in five ways:matter in five ways: 3 of these occur within the diagnostic3 of these occur within the diagnostic
range of xrange of x--ray energiesray energies
Classic coherent scatteringClassic coherent scattering Photoelectric interactionsPhotoelectric interactions
This type of interaction results in the greatestThis type of interaction results in the greatesthazard to patientshazard to patients
Compton scatteringCompton scattering This type of interaction results in the greatestThis type of interaction results in the greatest
amount of exposure to us as radiographers!amount of exposure to us as radiographers!
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XX--rays interact withrays interact with
matter in five ways:matter in five ways: 2 more interactions occur in energies that2 more interactions occur in energies that
are higher than levels which occurr inare higher than levels which occurr in
diagnostic xdiagnostic x--rayray
Pair productionPair production
PhotodisintregationPhotodisintregation
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Ionizing radiation can be quantifiedIonizing radiation can be quantified
Units of measurement:Units of measurement: Units most commonly used since 1920s in Table 9Units most commonly used since 1920s in Table 9--11
SI (International System of Units) was adopted in 1985SI (International System of Units) was adopted in 1985 (Roentgen/R) or Coulomb/kilogram(Roentgen/R) or Coulomb/kilogram measure of exposuremeasure of exposure
in airin air
(Rad) or Gray/G(Rad) or Gray/G measures absorbed dose in any mediummeasures absorbed dose in any medium
(Rem) or Sievert/Sv(Rem) or Sievert/Sv radiation equivalent to manradiation equivalent to man
(The unit of absorbed dose in man regardless of type of(The unit of absorbed dose in man regardless of type ofradiation that is used.)radiation that is used.)
(Curie) or Becquerel(Curie) or Becquerel measures activity (how fast ameasures activity (how fast a
radionuclide decays)radionuclide decays)
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Standards for RegulationStandards for Regulation
of Exposureof Exposure Limits must be set to ensure safety forLimits must be set to ensure safety for
both patient and the radiation workersboth patient and the radiation workers
National Council on Radiation ProtectionNational Council on Radiation Protection(NCRP)(NCRP)
Advisory group that helps to establish radiationAdvisory group that helps to establish radiation
protection standardsprotection standards
Current practice is to apply ALARA concept:Current practice is to apply ALARA concept:
As Low As Reasonably AchievableAs Low As Reasonably Achievable
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Effective dose limit recommendations:Effective dose limit recommendations:
Annual whole body dose for theAnnual whole body dose for the
occupational worker is:occupational worker is:
50 mSv (5 rem)50 mSv (5 rem)
Annual whole body dose for the generalAnnual whole body dose for the general
population is 1/10 the exposure forpopulation is 1/10 the exposure forworkers, or:workers, or:
5 mSv (.5 rem)5 mSv (.5 rem)
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Review of cellular structure and howReview of cellular structure and how
radiation interacts with cells:radiation interacts with cells:
A cell is the simplest unit of protoplasmA cell is the simplest unit of protoplasmthat is capable of living independently.that is capable of living independently.
Cells are divided into:Cells are divided into: the nucleus which is made up of genesthe nucleus which is made up of genes
the cytoplasm which is primarily made of waterthe cytoplasm which is primarily made of water
There are 2 cell types.There are 2 cell types.
Somatic cells which perform the bodysSomatic cells which perform the bodysfunctionsfunctions
Germ cells which are reproductive cellsGerm cells which are reproductive cells
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How do cells respond to radiation?How do cells respond to radiation?
The total body response: the radiationThe total body response: the radiation
effects to all systems of the bodyeffects to all systems of the body
3 general stages:3 general stages:
Prodomal stage: NVD stageProdomal stage: NVD stage
Latent period: the patient feels well, but the bodyLatent period: the patient feels well, but the body
is undergoing biologic changes that will lead tois undergoing biologic changes that will lead to
Manifest stage: Leads to either recovery or deathManifest stage: Leads to either recovery or death
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As a result of overexposure, there are 3As a result of overexposure, there are 3
radiation syndromes that occurradiation syndromes that occur
Bone marrow syndromeBone marrow syndrome
Results in infection, hemorrhage and anemiaResults in infection, hemorrhage and anemia
Gastrointestinal syndromeGastrointestinal syndrome
Results in excessive diarrhea, nausea &Results in excessive diarrhea, nausea &
vomitingvomiting
Central nervous system syndromeCentral nervous system syndrome Results in convulsions, coma and eventuallyResults in convulsions, coma and eventually
death due to increased intracranial pressuredeath due to increased intracranial pressure
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Other effects of radiation areOther effects of radiation are
also important!also important! Late effects can develop over a longLate effects can develop over a long
period after the exposureperiod after the exposure
These late effects are divided into 2 groupsThese late effects are divided into 2 groups Somatic effects: develops in those peopleSomatic effects: develops in those people
exposedexposed 2 most common somatic effects are cataracts and2 most common somatic effects are cataracts and
cancer developmentcancer development
Genetic effects: occur in future generations as aGenetic effects: occur in future generations as aresult of damage to germ cells when mutatedresult of damage to germ cells when mutatedcells are fertilized by another mutated cellcells are fertilized by another mutated cell
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How do we protect the patient?How do we protect the patient?
Use the ALARA conceptUse the ALARA concept
Use the 3 cardinal principles of protectionUse the 3 cardinal principles of protection
TimeTime Use proper techniques to reduce repeatsUse proper techniques to reduce repeats
DistanceDistance
Not the most reasonable method for the patient, but worksNot the most reasonable method for the patient, but works
well for you!well for you!
ShieldingShielding
When the primary beam is within 4When the primary beam is within 4--5 cm. of reproductive5 cm. of reproductive
organs (See Fig. 9organs (See Fig. 9--9, pg, 120)9, pg, 120)
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Other methods of patientOther methods of patient
protection:protection:
Beam restrictionBeam restriction
Proper film/screen combinationsProper film/screen combinations
Correct technical factor selectionCorrect technical factor selection
Using proper filtration exiting from xUsing proper filtration exiting from x--rayray
beambeam
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How do we protect ourselves?How do we protect ourselves?
TimeTime Limit your time in exposure, especially during fluoroscopyLimit your time in exposure, especially during fluoroscopy
DistanceDistance the best protection of all!the best protection of all! Inverse square law: doubling your distance reduces your exposure toInverse square law: doubling your distance reduces your exposure to
of original of original Use immobilization devices or restraints when possible to reduce yourUse immobilization devices or restraints when possible to reduce your
exposureexposure
ShieldingShielding -- use lead aprons & glovesuse lead aprons & gloves These devices should contain between .25 & I.0 mm of leadThese devices should contain between .25 & I.0 mm of lead
Fixed barriersFixed barriers Primary barriers: those struck by primary beamPrimary barriers: those struck by primary beam
Secondary barriers: those struck by scatter beam (lead or concrete)Secondary barriers: those struck by scatter beam (lead or concrete)
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Student pregnancy is covered by theStudent pregnancy is covered by the
Nuclear Regulatory Commision (NRC)Nuclear Regulatory Commision (NRC)
Once pregnancy is known, a limit of .05Once pregnancy is known, a limit of .05rem (.5 mSv) per month should applyrem (.5 mSv) per month should apply
Though average exposure to the radiologicThough average exposure to the radiologictechnologist is unlikely to exceed thesetechnologist is unlikely to exceed theselimits, there is little reason not to declare alimits, there is little reason not to declare apregnancy or alter a clinical assignment.pregnancy or alter a clinical assignment.
Declaration is voluntary & must be made inDeclaration is voluntary & must be made inwritingwriting
A second monitor is used at the level of the fetusA second monitor is used at the level of the fetusand must not exceed .005 rem (.05 mSv)/monthand must not exceed .005 rem (.05 mSv)/month
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Radiation monitoringRadiation monitoring
determines your exposure.determines your exposure. Most 5 most common personnel devices are:Most 5 most common personnel devices are:
OSL (optically stimulated luminescence)OSL (optically stimulated luminescence)
dosimeter: most common methoddosimeter: most common method Worn between the collar & waist outside of a leadWorn between the collar & waist outside of a lead
apronapron
Advantageous because it is unaffected by heat,Advantageous because it is unaffected by heat,
moisture and pressuremoisture and pressure Its disadvantage is that you cannot get anIts disadvantage is that you cannot get an
immediate reading of exposureimmediate reading of exposure
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Radiation monitoring:Radiation monitoring:
Film Badges: these were the mostFilm Badges: these were the most
popular and least expensive ways topopular and least expensive ways to
monitor exposuremonitor exposure Its main disadvantage is its inability to get anIts main disadvantage is its inability to get an
immediate reading of exposureimmediate reading of exposure
Thermoluminescent dosimeters: usesThermoluminescent dosimeters: useslithium fluoride crystalslithium fluoride crystals
Advantageous because they can be reusedAdvantageous because they can be reused
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Radiation monitoring:Radiation monitoring:
Pocket dosimeters: used when anPocket dosimeters: used when an
immediate reading is desiredimmediate reading is desired
Disadvantage: subject to false readings andDisadvantage: subject to false readings and
does not provide a permanent recorddoes not provide a permanent record
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Radiation monitoring:Radiation monitoring:
Field survey instruments can also detectField survey instruments can also detect
the presence of radiation in the airthe presence of radiation in the air
A common type is GeigerA common type is Geiger--Muller counterMuller counter
These units are used in nuclear medicine toThese units are used in nuclear medicine todetect the possibility of spilled radionuclidesdetect the possibility of spilled radionuclides