rt06 brachy1 sources web
TRANSCRIPT
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Radiation Protection inRadiation Protection inRadiotherapyRadiotherapy
Part 6Part 6
Properties and safety of radiotherapyProperties and safety of radiotherapy
sources and equipment used forsources and equipment used for
brachytherapybrachytherapy
IAEA Training Material on Radiation Protection in Radiotherapy
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 2
BrachytherapyBrachytherapy
Breast implant using
radioactive 192-Ir wire
The use of radioactive sources in closeThe use of radioactive sources in close
proximity to the target area for radiotherapyproximity to the target area for radiotherapy
X Ray of a gynaecological
implant using an applicatorloaded with 137-Cs sources
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 3
Brachytherapy overviewBrachytherapy overview Brachytherapy uses encapsulatedBrachytherapy uses encapsulated
radioactive sources to deliver a highradioactive sources to deliver a high
dose to tissues near the sourcedose to tissues near the source brachys (Greek) = short (distance)brachys (Greek) = short (distance)
Inverse square law determines most ofInverse square law determines most of
the dose distributionthe dose distribution
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 4
BrachytherapyBrachytherapy Characterized by strongCharacterized by strong
dose gradientsdose gradients
Many different techniquesMany different techniquesand sources availableand sources available
Implants are highlyImplants are highly
customized for individualcustomized for individualpatientspatients
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 5
BrachytherapyBrachytherapy Use of radioactive materials in direct contactUse of radioactive materials in direct contact
with patientswith patients -- more radiation safety issuesmore radiation safety issues
than in external beam radiotherapythan in external beam radiotherapy
Less than 10% of radiotherapy patients areLess than 10% of radiotherapy patients are
treated with brachytherapytreated with brachytherapy
Per patient treated the number of accidents inPer patient treated the number of accidents in
brachytherapy is considerably higher than inbrachytherapy is considerably higher than inEBTEBT
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 6
Objectives of part 6Objectives of part 6
To be familiar with typical radioactive sources used inTo be familiar with typical radioactive sources used in
cancer treatmentcancer treatment
To be aware of different implant types andTo be aware of different implant types and
techniquestechniques To appreciate the implications of life implantsTo appreciate the implications of life implants vs.vs.
manual and remote afterloadingmanual and remote afterloading
To understand the differences between low and highTo understand the differences between low and high
dose rate brachytherapy equipmentdose rate brachytherapy equipment To be familiar with some special current implantTo be familiar with some special current implant
techniques (prostate seed implants, endovasculartechniques (prostate seed implants, endovascular
brachytherapy)brachytherapy)
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 7
ContentsContents Lecture 1: Brachytherapy Sources andLecture 1: Brachytherapy Sources and
equipmentequipment
Lecture 2: Brachytherapy techniquesLecture 2: Brachytherapy techniques
(including special techniques such as(including special techniques such as
prostate seed implants andprostate seed implants and
endovascular brachytherapy)endovascular brachytherapy)
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 8
Flow of brachytherapyFlow of brachytherapy
information in the courseinformation in the coursePart 2: Physics
Part 6: Brachytherapy (Description of techniques and
equipment)
Part 11: Good practice in brachytherapy (Information
placed in context of BSS with emphasis on radiation
protection)
Parts 14 (Transport), 15 (Security of sources) and 16
(Discharge of patients): Additional and supporting
information - most of it directly relevant for
brachytherapy practice
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Radiation Protection inRadiation Protection inRadiotherapyRadiotherapy
Part 6Part 6
BrachytherapyBrachytherapyLecture 1: Brachytherapy Sources and EquipmentLecture 1: Brachytherapy Sources and Equipment
IAEA Training Material on Radiation Protection in Radiotherapy
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 10
ObjectivesObjectives To understand the concept of sealed sourceTo understand the concept of sealed source
To know the most common isotopes used forTo know the most common isotopes used for
brachytherapybrachytherapy
To be familiar with general rules for source handlingTo be familiar with general rules for source handling
and testingand testing
To be aware of differences between permanentTo be aware of differences between permanent
implants, low (LDR) and high dose rate (HDR)implants, low (LDR) and high dose rate (HDR)
applicationsapplications To understand the basic fundamentals ofTo understand the basic fundamentals of
brachytherapy equipment designbrachytherapy equipment design
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 11
ContentsContents1 Sealed sources1 Sealed sources
2 The ideal source for radiotherapy2 The ideal source for radiotherapy
3 Brachytherapy sources in use3 Brachytherapy sources in use
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 12
HenriHenri
BecquerelBecquerel
(1852(1852--1908)1908)
Discovered radioactivity in 1896
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 13
1. Sealed sources1. Sealed sources
IAEA BSS glossary: RadioactiveIAEA BSS glossary: Radioactive
material that is a) permanently sealed inmaterial that is a) permanently sealed in
a capsule or b) closely bound and in aa capsule or b) closely bound and in asolid form.solid form.
In other words: the activity is fixed to itsIn other words: the activity is fixed to its
carrier and contamination of thecarrier and contamination of theenvironment is not possible as long asenvironment is not possible as long as
the source is intactthe source is intact
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 14
Sealed sourcesSealed sources
Have an activity which can be derivedHave an activity which can be derived
from a calibration certificate and the halffrom a calibration certificate and the half
life of the isotope (nothing is lost)life of the isotope (nothing is lost)
MUST be checked for integrity regularlyMUST be checked for integrity regularly
-- a good means of doing this is by wipea good means of doing this is by wipe
teststests
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 15
Sealed and unsealed sources inSealed and unsealed sources in
radiotherapyradiotherapy Both are used to treat cancerBoth are used to treat cancer
Sealed sources are used forSealed sources are used for
brachytherapybrachytherapy -- they are discussed herethey are discussed here
Unsealed sources may be used forUnsealed sources may be used for
systemic treatmentssystemic treatments -- they arethey are
discussed in more detail in the coursediscussed in more detail in the courseon Nuclear Medicineon Nuclear Medicine
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 16
Some examples for unsealedSome examples for unsealed
source radiotherapysource radiotherapy 131131--I for thyroid treatmentI for thyroid treatment
8989--Sr and 153Sr and 153--Sm for treatment of boneSm for treatment of bone
metastasismetastasis
3232--P for hematological cancersP for hematological cancers
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 17
NoteNote
All brachytherapy sources are of anAll brachytherapy sources are of an
activity which makes them of regulatoryactivity which makes them of regulatory
concernconcern
Therefore, persons ordering, receiving,Therefore, persons ordering, receiving,
handling, storing and disposing themhandling, storing and disposing them
must have appropriate training and holdmust have appropriate training and holdthe appropriate licensethe appropriate license
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2. The ideal source in2. The ideal source in
brachytherapybrachytherapy
What do you think one would expect fromWhat do you think one would expect from
and ideal brachytherapy source?and ideal brachytherapy source?
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 19
Clinical usefulness determined byClinical usefulness determined by
Half lifeHalf life = the time after which half of the= the time after which half of the
original activity is still present in the sourceoriginal activity is still present in the source
Specific activitySpecific activity = activity per gram of= activity per gram of
material. The higher the specific activity, thematerial. The higher the specific activity, thesmaller a source of a particular activity can besmaller a source of a particular activity can be
mademade
Radiation energyRadiation energy determines the range ofdetermines the range of
radiation in tissue (AND the requirements forradiation in tissue (AND the requirements for
shielding)shielding)
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 20
The Ideal Brachytherapy sourceThe Ideal Brachytherapy source
Pure gamma emitterPure gamma emitter -- betas or alphas are toobetas or alphas are too
short in range and result in very high doses toshort in range and result in very high doses to
small volumes around the sourcesmall volumes around the source
Medium gamma energyMedium gamma energy high enough to treat the target with homogenoushigh enough to treat the target with homogenous
dosedose
low enough to avoid normal tissues and reducelow enough to avoid normal tissues and reduce
shielding requirementsshielding requirements
High specific activityHigh specific activity
suitable also for high dose rate applicationssuitable also for high dose rate applications
smallsmall
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 21
The Ideal Brachytherapy sourceThe Ideal Brachytherapy source
Stable daughter productStable daughter product
For temporary implants: long half lifeFor temporary implants: long half life
allows economical reallows economical re--use of sourcesuse of sources For permanent implants: medium halfFor permanent implants: medium half
lifelife
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 22
3. Real brachytherapy Sources3. Real brachytherapy Sources
A variety of source types and isotopes areA variety of source types and isotopes are
currently in usecurrently in use
They differ for different applications becauseThey differ for different applications because
ofof half life,half life,
size (specific activity) andsize (specific activity) and
radiation energyradiation energy
When deciding on a source one must alsoWhen deciding on a source one must also
keep the shielding requirements in mindkeep the shielding requirements in mind
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 23
Brachytherapy SourcesBrachytherapy SourcesRadionuclide Half-life Photon Energy (MeV) Half-value Layer (mm lead)
226Ra 1600 years 0.047 - 2.45 (0.83 ave) 8.0
222Rn 3.83 days 0.047 - 2.45 (0.83 ave) 8.0
60Co 5.26 years 1.17, 1.33 11.0137
Cs 30.0 years 0.662 5.5
192Ir 74.2 days 0.136 - 1.06 (0.38 ave) 2.5
198Au 2.7 days 0.412 2.5
125
I 60.2 days 0.028 ave 0.025103
Pd 17.0 days 0.021 ave 0.008
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 24
BrachytherapyBrachytherapy
source typessource types(ICRU report(ICRU report
58)58)
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 25
Brachytherapy sourcesBrachytherapy sources
The first isotope used clinically was radiumThe first isotope used clinically was radium
around 1903around 1903
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 26
Brachytherapy sourcesBrachytherapy sources
However, radium and radon have onlyHowever, radium and radon have only
historical importancehistorical importance -- they should not be usedthey should not be used
in a modern radiotherapy departmentin a modern radiotherapy department
Because:Because: wide energy spectrum leading to high dose close towide energy spectrum leading to high dose close to
the source and still high dose around the patientthe source and still high dose around the patient --
shielding difficultshielding difficult
Radon, the daughter product of radium, is a nobleRadon, the daughter product of radium, is a noblegas which is very difficult to containgas which is very difficult to contain -- contaminationcontamination
riskrisk
The long half life means disposal is very difficultThe long half life means disposal is very difficult
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 27
Popular sources: 137Popular sources: 137--CsCs
Cesium 137Cesium 137
Main substitute for radiumMain substitute for radium
Mostly used in gynecologicalMostly used in gynecological
applicationsapplications
Long half life of 30 yearsLong half life of 30 years ------> decay> decay
correction necessary every 6 monthscorrection necessary every 6 months Sources are expensive and must beSources are expensive and must be
replaced every 10 to 15 yearsreplaced every 10 to 15 years
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 28
Popular sources: 192Popular sources: 192--IrIr
Iridium 192Iridium 192
Many different forms availableMany different forms available
Most important source for HDR applicationsMost important source for HDR applications Medium half life (75 days)Medium half life (75 days) -- decay correctiondecay correction
necessary for each treatmentnecessary for each treatment
Needs to be replaced every 3 to 4 months toNeeds to be replaced every 3 to 4 months to
maintain effective activity and therefore anmaintain effective activity and therefore anacceptable treatment timeacceptable treatment time
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 29
Popular sources: 192Popular sources: 192--IrIr
Iridium 192Iridium 192
High specific activityHigh specific activity -- therefore even hightherefore even high
activity sources can be miniaturized essentialactivity sources can be miniaturized essential
for HDR applicationsfor HDR applications
A bit easier to shield than 137A bit easier to shield than 137--CsCs -- becausebecause
the gamma energies of 192the gamma energies of 192--Ir range from 136Ir range from 136
to 1062keV (effective energy around 350keV)to 1062keV (effective energy around 350keV)
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 30
HDR 192HDR 192--Ir sourceIr source
10 Ci (370GBq)10 Ci (370GBq)
diameter of the order of 1mmdiameter of the order of 1mm
length of the order of 10mmlength of the order of 10mm dual encapsulationdual encapsulation
attached to steel cableattached to steel cable
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 31
HDR source: anisotropy ofHDR source: anisotropy of
dosedose
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 32
Popular sources: 125Popular sources: 125--II
Very low energyVery low energy -- therefore shielding istherefore shielding is
easy and radiation from an implant iseasy and radiation from an implant is
easily absorbed in the patient:easily absorbed in the patient:permanent implants are possiblepermanent implants are possible
Mostly used in theMostly used in the
form of seedsform of seeds
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 33
125125--I seedsI seeds
Many different designsMany different designs
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 34
125125--I seedsI seeds
Design aims andDesign aims and
features:features:
sealed sourcesealed source nonnon--toxic tissuetoxic tissue
compatible encapsulationcompatible encapsulation
isotropic dose distributionisotropic dose distribution
radioradio--opaque foropaque forlocalizationlocalization
Mentor
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 35
X Ray visibility of 125X Ray visibility of 125--I seedsI seeds
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 36
125125--I seedsI seeds
A different design:A different design:
radioradio--opaque for X Rayopaque for X Ray
visualizationvisualization MRI compatibilityMRI compatibility
desirabledesirable
No contaminationNo contamination
A source example
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 37
Symmetry of dose distributionSymmetry of dose distribution
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 38
Other isotopes used for seedsOther isotopes used for seeds
Gold 198Gold 198
Half Life = 2.7 daysHalf Life = 2.7 days --
short enough to letshort enough to letactivity decay in theactivity decay in the
patientpatient
Energy = 412 keVEnergy = 412 keV
TVL lead = aroundTVL lead = around
8mm8mm
Palladium 103Palladium 103
Half Life = 17 daysHalf Life = 17 days --
dose rate about 2.5dose rate about 2.5times larger than fortimes larger than for
125125--II
Energy = 22 keVEnergy = 22 keV
TVL lead = 0.05mmTVL lead = 0.05mm
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 39
Brachytherapy SourcesBrachytherapy SourcesA variety of source shapes and forms:A variety of source shapes and forms:
pellets = balls of approximately 3 mm diameter
seeds = small cylinders about 1 mm diameter and 4 mm
length
needles = between 15 and 45 mm active length tubes = about 14 mm length, used for gynaecological
implants
hairpins = shaped as hairpins, approximately 60 mm active
length
wire = any length, usually customised in the hospital -inactive ends may be added
HDR sources = high activity miniature cylinder sources
approximately 1mm diameter, 10mm length
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 40
Source form examplesSource form examples
Seeds (discussed before):Seeds (discussed before): small containers for activitysmall containers for activity
usually 125usually 125--I, 103I, 103--Pd or 198Pd or 198--Au for permanentAu for permanent
implant such as prostate cancerimplant such as prostate cancer
Needles and hairpins:Needles and hairpins: for life implants in the operating theatrefor life implants in the operating theatre -- activityactivity
is directly introduced in the target region of theis directly introduced in the target region of the
patientpatient
usually 192usually 192--Ir for temporary implantsIr for temporary implants e.g.e.g. of theof the
tonguetongue
Scale in mm
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 41
Source form: 192Source form: 192--Ir wireIr wire
Used for LDR interstitial implantsUsed for LDR interstitial implants
Cut to appropriate length prior to implant toCut to appropriate length prior to implant to
suit individual patientsuit individual patient Cutting using manual technique or cutter...Cutting using manual technique or cutter...
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 42
Source form 192Source form 192--Ir wiresIr wires
192192--Ir wire:Ir wire: activity between 0.5 andactivity between 0.5 and
10mCi per cm10mCi per cm
used for interstitialused for interstitial
implantsimplants
low to medium dose ratelow to medium dose rate
can be cut from 50 cmcan be cut from 50 cm
long coils to the desiredlong coils to the desiredlength for a particularlength for a particular
patientpatient
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 43
Source form exampleSource form example
192192--Ir wire:Ir wire: activity between 0.5 andactivity between 0.5 and
10mCi per cm10mCi per cm
used for interstitialused for interstitial
implantsimplants
low to medium dose ratelow to medium dose rate
can be cut from 50 cmcan be cut from 50 cm
long coils to the desiredlong coils to the desiredlength for a particularlength for a particular
patientpatient
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 44
The requirements of BSS:The requirements of BSS:
Appendix IV.8. Registrants and licensees, in specific coAppendix IV.8. Registrants and licensees, in specific co--operationoperation
with suppliers, shall ensure that the following responsibilities bewith suppliers, shall ensure that the following responsibilities be
discharged, if applicable:discharged, if applicable:
(a)(a) toto provide a well designed and constructed sourceprovide a well designed and constructed source that:that:
(i)(i) provides for protection and safety in compliance with theprovides for protection and safety in compliance with theStandards;Standards;
(ii)(ii)meets engineering, performance and functional specifications; andmeets engineering, performance and functional specifications; and
(iii)(iii) meets quality norms commensurate with the protection and safetymeets quality norms commensurate with the protection and safety
significance of components and systems;significance of components and systems;
(b)(b) toto ensure that sources be testedensure that sources be tested to demonstrateto demonstrate
compliance with the appropriate specifications; andcompliance with the appropriate specifications; and
(c)(c) toto make available informationmake available information in a major world languagein a major world language
acceptable to the user concerning the proper installation andacceptable to the user concerning the proper installation and
use of the source and its associated risks.use of the source and its associated risks.
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 45
SummarySummary
A wide variety of radioactive sources haveA wide variety of radioactive sources have
been used for brachytherapy in manybeen used for brachytherapy in many
different physical formsdifferent physical forms
The most common sources are 137The most common sources are 137--Cs, 192Cs, 192--Ir and 125Ir and 125--II
Regular check of source integrity is essentialRegular check of source integrity is essential
to ensure the source can be classified asto ensure the source can be classified assealedsealed
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 46
ReferencesReferences
Johns H E and Cunningham J R 1983 The Physics of
Radiology, 4th edition (Springfield: C Thomas)
Khan F M 1994 The Physics of Radiation Therapy,
2nd edition (Williams & Wilkins, Baltimore)
Williams J R and Thwaites D I 1993 Radiotherapy
Physics in Practice (Oxford: Oxford University Press)
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Any questions?Any questions?
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Question
Question
Why would people use 198Why would people use 198--Au forAu for
brachytherapy?brachytherapy?
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Radiation Protection in Radiotherapy Part 6, lecture 1: Brachytherapy sources 49
Some clues for an answerSome clues for an answer
Key features of 198Key features of 198--Au are:Au are:
small sources (seed)small sources (seed)
short half life (2.7 days)short half life (2.7 days)
inert materialinert material
photon energy 412keVphoton energy 412keV
Therefore, ideal for permanent implant