ISO 21439:2009
(Main)Clinical dosimetry — Beta radiation sources for brachytherapy
Clinical dosimetry — Beta radiation sources for brachytherapy
ISO 21439:2009 specifies methods for the determination of absorbed-dose distributions in water or tissue that are required prior to initiating procedures for the application of beta radiation in ophthalmic tumour and intravascular brachytherapy]. Recommendations are given for beta-radiation source calibration, dosemetry measurements, dose calculation, dosemetric quality assurance, as well as for beta-radiation brachytherapy treatment planning. Guidance is also given for estimating the uncertainty of the absorbed dose to water. ISO 21439:2009 is applicable to “sealed” radioactive sources, such as plane and concave surface sources, source trains of single seeds, line sources, shell and volume sources, for which only the beta radiation emitted is of therapeutic relevance. The standardization of procedures in clinical dosemetry described in ISO 21439:2009 serves as a basis for the reliable application of beta-radiation brachytherapy. The specific dosemetric methods described in ISO 21439:2009 apply to sources for the curative treatment of ophthalmic disease, for intravascular brachytherapy treatment, for overcoming the problem of restenosis and for other clinical applications using beta radiation. ISO 21439:2009 is geared towards organizations wishing to establish reference methods in dosemetry aiming at clinical demands for an appropriately small uncertainty of the delivered dose. ISO 21439:2009 does not exclude the possibility that there can be other methods leading to the same or smaller measurement uncertainties.
Dosimétrie clinique — Sources de radiation bêta pour curiethérapie
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 21439
First edition
2009-02-15
Clinical dosimetry — Beta radiation
sources for brachytherapy
Dosimétrie clinique — Sources de radiation bêta pour curiethérapie
Reference number
©
ISO 2009
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ii © ISO 2009 – All rights reserved
Contents Page
Foreword .v
Introduction.vi
1 Scope.1
2 Normative references.1
3 Terms and definitions .2
4 Beta radiation sources and source data.8
4.1 Ophthalmic and dural brachytherapy sources.8
4.2 Intravascular brachytherapy sources .9
4.3 Characteristics of radionuclides.9
4.4 Source specification .9
5 Dose calculation parameters and formalisms.11
5.1 General .11
5.2 Radiation-field parameterization.12
5.3 Radial dose profile .13
5.4 Normalization of relative-dose data for seed sources.14
5.5 Adaptation of the TG-43/60 formalism for a long beta radiation line source.16
5.6 Reference data sets.17
5.7 Parameters for source uniformity characterization.17
6 Calibration and traceability .19
6.1 Measurand.19
6.2 Traceability.19
6.3 Reference point .19
6.4 Primary standards .19
6.5 Secondary standards.19
6.6 Transfer standards .19
6.7 Calibration of therapeutic beta radiation sources .20
7 Dose measurements in-phantom and measurement corrections.20
7.1 Measurements in water or a water-equivalent phantom .20
7.2 Detectors for beta radiation.21
7.3 Conversion of absorbed dose in solid phantoms to absorbed dose to water.22
7.4 Effective point of measurement in the detector.24
8 Theoretical modelling .25
8.1 Point-dose kernels .25
8.2 Monte Carlo simulation.26
9 Uncertainties in source calibrations .28
9.1 General .28
9.2 Uncertainty of primary standards.28
9.3 Uncertainty of secondary standards .28
9.4 Uncertainty of transfer standards.28
9.5 Relationship of dosimetry uncertainty to positional error.29
9.6 Uncertainty in theoretical modeling .29
10 Treatment planning and reporting.30
10.1 General .30
10.2 General aspects of treatment planning.30
10.3 Documentation in ophthalmic brachytherapy.30
10.4 Uncertainty of the dose delivered in ophthalmic brachytherapy .30
10.5 Documentation in intravascular brachytherapy.31
10.6 Reporting uncertainties in intravascular brachytherapy.33
11 Clinical quality control .33
11.1 Acceptance tests .33
11.2 Constancy checks .37
Annex A (normative) Reference data .38
Annex B (informative) Reference data sheet examples .43
Annex C (informative) Primary standards for beta radiation dosimetry.52
Annex D (informative) Detectors and phantom materials for clinical dosimetry of beta radiation
brachytherapy sources .58
Annex E (informative) Monte Carlo calculations.68
Annex F (informative) Treatment planning .77
Bibliography .82
iv © ISO 2009 – All rights reserved
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 21439 was prepared by Technical Committee ISO/TC 85, Nuclear energy, Subcommittee SC 2, Radiation
protection.
Introduction
Clinical dosimetry covers the methods by which values of the relevant physical quantity, absorbed dose to
water, can be measured at a given point by the use of calibrated instruments in a clinical setting. The
application of beta radiation sources for brachytherapy requires new and skilled methods for adequate clinical
dosimetry necessitated by the short range of the beta radiation. This causes large dose-rate gradients around
beta radiation sources, and hence it is necessary that the detector volumes for absorbed-dose measurements
be extremely small. This leads to the requirement for highly specialized detectors and calibration techniques,
and it is necessary to scrutinize closely every calibration obtained in one beta radiation field and determine if it
is applicable in another field.
It is necessary that an appropriate quality system be implemented and maintained in the hospital for clinical
beta radiation source dosimetry. It is the responsibility of the medical physicist to carry out testing and
calibration activities for any source in such a way as to meet the requirements for adequate dosimetry. This
International Standard gives guidance on how to satisfy these needs.
vi © ISO 2009 – All rights reserved
INTERNATIONAL STANDARD ISO 21439:2009(E)
Clinical dosimetry — Beta radiation sources for brachytherapy
1 Scope
This International Standard specifies methods for the determination of absorbed-dose distributions in water or
tissue that are required prior to initiating procedures for the application of beta radiation in ophthalmic tumour
[1], [2], [3]
and intravascular brachytherapy . Recommendations are given for beta radiation source calibration,
dosimetry measurements, dose calculation, dosimetric quality assurance, as well as for beta radiation
brachytherapy treatment planning. Guidance is also given for estimating the uncertainty of the absorbed dose
to water. This International Standard is applicable to “sealed” radioactive sources, such as plane and concave
surface sources, source trains of single seeds, line sources, and shell and volume sources, for which only the
beta radiation emitted is of therapeutic relevance.
The standardization of procedures in clinical dosimetry described in this International Standard serves as a
basis for the reliable application of beta radiation brachytherapy. The specific dosimetric methods described in
this International Standard apply to sources for the curative treatment of ophthalmic disease, for intravascular
brachytherapy treatment, for overcoming the problem of restenosis and for other clinical applications using
beta radiation.
This International Standard is geared towards organizations wishing to establish reference methods in
dosimetry aiming at clinical demands for an appropriately small uncertainty of the delivered dose. This
International Standard does not exclude the possibility that there can be other methods leading to the same or
smaller measurement uncertainties.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the cited document
(including any amendments) applies.
ISO/IEC Guide 98-3, Uncertainty in measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated terms
(VIM)
ISO 6980-2, Nuclear energy — Reference beta particle radiation — Part 2: Calibration fundamentals related to
basic quantities characterizing the radiation field
ICRU Report 51, Quantities and Units in Radiation Protection Dosimetry
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ICRU Report 51, ISO Guide 99 and
ISO 6980-2, and the following apply.
3.1
absorbed dose
D
quotient of dε by dm, where dε is the mean energy imparted by ionizing radiation to matter of mass dm, as
given by Equation (1):
dε
D = (1)
dm
NOTE The absorbed dose is designated in units of joules per kilogram, with the special name of gray (Gy).
3.2
absorbed dose to water
D
w
quotient of dε by dm, where dε is the mean energy imparted to water by ionizing radiation to a medium of
mass dm, as given by Equation (2):
dε
D = (2)
w
dm
NOTE The absorbed dose to water is designated in units of joules per kilogram, with the special name of gray (Gy).
3.3
acceptance test
contractual test carried out by the user on receipt of a new instrument or source(s) in order to verify
compliance with contractual specifications
NOTE 1 An acceptance test of an instrument is carried out after new equipment has been installed, or major
modifications have been made to existing equipment.
NOTE 2 An acceptance test of a source is carried out on each source before being put into service for the first time. If a
consignment contains more than one source, it is carried out on all sources of a particular type.
3.4
active source length
ASL
length of the source over which the absorbed dose rate at a defined distance from the source axis is within a
specified ratio of the maximum absorbed dose rate at this distance
3.5
afterloading
automatically or manually controlled transfer of one or more sealed radioactive sources between a storage
container and pre-positioned source applicators for brachytherapy
2 © ISO 2009 – All rights reserved
3.6
average beta energy
E
ave
quotient of beta energy averaged over the distribution, Φ , of the beta particle fluence with respect to energy
E
as given by Equation (3):
E
max
EΦ ()EEd
E
∫
E = (3)
ave
E
max
Φ d E
E
∫
where Φ = dΦ/dE
E
3.7
brachytherapy
intracavitary, interstitial, superficial (including ophthalmic), or intraluminal (e.g. intravascular) radiotherapy in
the immediate vicinity of one or more sealed or unsealed radioactive sources
3.8
calibration
set of operations that establish, under specific conditions, the relationship between values of a quantity and
the corresponding values traceable to primary standards
NOTE 1 For an instrument, a calibration establishes, under specific conditions, the relationship between values of a
quantity indicated by a measuring instrument or measuring system and the corresponding values realized from the
standards.
NOTE 2 For a source, a calibration establishes, under specific conditions, the value of a quantity produced by the
source.
3.9
clinical target volume
CTV
gross tumour or target volume (GTV) with the addition of a margin that accounts for cells that are clinically
suspected but have unproven involvement
NOTE In malignant disease, e.g. ophthalmic tumours, these oncological safety margins account for subclinical
disease. In restenosis treatment, the CTV includes the full interventional length (IL) of the vessel with all vessel wall layers
and with the addition of proximal and distal safety margins to include all tissue possibly injured during the interventional
process.
3.10
detector test source
radiation source used for the determination of the long-term stability of a radiation detector
3.11
dosimeter
〈beta radiation therapy〉 equipment that uses detectors for the measurement of absorbed dose, or absorbed
dose rate, in beta radiation fields as used in radiation therapy
NOTE A radiotherapy dosimeter contains the following components: one or more detector assemblies, a measuring
assembly (including possibly a separate display device), one or more detector test sources (optional) and one or more
phantoms (optional).
3.12
dwell time
time a radioactive source or source train remains at a selected treatment position
3.13
effective point of measurement
P
eff
point at which the absorbed dose rate in an undisturbed medium is determined from the detector signal
3.14
extrapolation chamber
ionization chamber capable of having a collection volume that is continuously variable to a vanishingly small
value by changing the separation of the electrodes, which allows the user to extrapolate the measured
ionization density to zero collecting volume
NOTE The extrapolation chamber serves as a primary standard, under proper conditions of use (see Annex C).
3.15
fluence
Φ
quotient of dN by dA , where dN is the number of particles incident on a sphere of cross-sectional area dA , as
s s
given by Equation (4):
Φ = dN/dA (4)
s
3.16
gross tumour or target volume
GTV
macroscopic extent and location of target tissue that can be observed or visualized using applicable imaging
modalities
NOTE In malignant disease, e.g. ophthalmic tumours, target tissue means the demonstrable tumour growth. In
restenosis treatment, the GTV includes the full vessel extent injured during the interventional process.
3.17
influence quantity
quantity that can have a bearing on the result of a measurement without being the subject of the
measurement
3.18
interventional length
IL
length of the vessel injured during the interventional process
3.19
lesion length
LL
stenotic or occluded length of the vessel segment as determined by the interventionalist
3.20
maximum beta energy
E
max
highest value of the energy of beta radiation emitted by a particular radionuclide that can emit one or several
continuous spectra of beta radiation each with a characteristic maximum energy
3.21
measurement standard
instrument that defines, represents physically, maintains or reproduces the unit of measurement of a quantity
(or multiple or sub-multiple of that unit) in order to transfer it to other instruments by comparison
4 © ISO 2009 – All rights reserved
3.22
planning target volume
PTV
clinical target volume (CTV) plus safety margins to account for physiological movements and changes, as well
as for various set-up uncertainties
3.23
point of test
point at which the conventional true value is determined and at which the reference point of the dosimeter is
placed for calibration and test purposes
3.24
primary standard
measurement standard (of the highest metrological quality) that defines, represents physically, maintains or
reproduces the unit of measurement of a quantity (or a multiple or sub-multiple of that unit) in order to transfer
it to other instruments by comparison
NOTE 1 The primary standard is operated by a national laboratory under reference conditions and its accuracy has
been verified by comparison with the comparable standards of institutions participating in the International Measurement
System.
NOTE 2 A primary standard realizes the quantity being measured without reference to any other standard of the same
type.
3.25
ionizing radiation
emission and propagation of energy through space or through a material medium in the form of
electromagnetic waves or particles that have the potential to ionize an atom or molecule through atomic
interactions
3.26
radiation detector
equipment, generally a sub-assembly, or substance that, in the presence of radiation, provides by either direct
or indirect means a signal or other indication suitable for use in measuring one or more quantities of the
incident radiation
3.27
reference absorbed dose to water
D
o
absorbed dose to water at the reference point
3.28
reference conditions
set of influence quantities for which the calibration is valid without any correction
NOTE The reference conditions for the quantity being measured may be chosen consistent with the properties of the
instrument being calibrated. The quantity being measured is not an influence quantity.
3.29
reference isodose length
RIL
vessel length at the reference distance enclosed by a certain defined percentage isodose of the reference
dose at P
Ref
NOTE 1 The reference distance is measured from the source axis to a line parallel to the source axis on which P is
Ref
located.
NOTE 2 For example, ESTRO recommends the 90 % isodose.
3.30
reference lumen diameter
RLD
diameter of the vessel lumen after angioplasty as determined by angiography in a representative plane within
the planning target volume
3.31
reference orientation of a detector
orientation of the dosimetry detector with respect to the direction of the incident radiation stated by the
manufacturer
3.32
radionuclide purity
proportion of the total activity present in the form of the stated radionuclide
NOTE The radionuclide purity is generally expressed as a percentage.
3.33
reference point
P
ref
〈for source calibration〉 point in a source radiation field at which the reference absorbed dose rate is specified,
and which is also used for normalization of relative measurements
3.34
reference point of a detector
point of a detector that is placed at the point of test for calibrating or testing purposes
NOTE The distance of measurement refers to the distance between the reference points of the radiation source and
of the detector.
3.35
routine calibration
calibration appropriate to a routine application of a source or an instrument
NOTE A routine calibration may be of a confirmatory nature when it is performed either to check the calibration
carried out by the manufacturer together with an instrument, or to check whether the calibration is sufficiently stable during
the continued, long-term use of a source or an instrument. When considering the most practical way to perform a routine
calibration, results obtained in a type test can turn out to be helpful, for example in selecting the phantom.
3.36
secondary standard
standard whose value is assigned by comparison with a primary standard of the same quantity
3.37
source applicator
〈brachytherapy〉 device to position one or more radiation sources at the intended treatment positions
NOTE The radiation source may be a fixed part of the applicator, and the applicator may, furthermore, include
protective shielding and/or a source guide.
3.38
source train
sequence of sealed radioactive sources, possibly separated by non-radioactive spacers, that is specified by a
single value and calibrated as a whole
3.39
special calibration
calibration of a source or an instrument for a special case similar to that performed in connection with a type
test
NOTE A special calibration is performed, for example, if the source or instrument is used under special
circumstances or if the routine or type testing provides insufficient information.
6 © ISO 2009 – All rights reserved
3.40
standard test conditions
conditions under which all influence quantities and instrument parameters have their standard test values
NOTE Ideally, calibrations should be carried out under reference conditions. As this is not always achievable (e.g. for
ambient air pressure) or convenient (e.g. for ambient temperature), a (small) interval around the reference values may be
used. In principle, corrections should be made for the deviations of the calibration factor (if dimensionless) or calibration
coefficient (if the instrument indication has different units from the calibration quantity) from its value under reference
conditions caused by these deviations. In practice, the uncertainty aimed at serves as a criterion to determine whether it is
necessary to take an influence quantity into account by an explicit correction or whether its effect may be incorporated into
the uncertainty. During type tests, all values of influence quantities that are not the subject of the test are fixed within the
interval of the standard test conditions.
3.41
test
〈of an instrument〉 measurement intended to confirm that an instrument is functioning correctly and/or the
quantitative determination of the variations of the indication of the instrument over a range of radiation, electric
and environmental conditions
NOTE Four distinct categories of instrument testing, of which calibration is a part, are generally recognized: type test,
acceptance test, special calibration, routine calibration.
3.42
test
〈of a source〉 measurement intended to confirm that a source is functioning correctly and/or that the
encapsulation is intact, and/or the quantitative determination of the variations of the field of the source over a
range of radiation, electric and environmental conditions
NOTE Four distinct categories of source testing, of which calibration is part, are generally recognized: type test,
acceptance test, special calibration, routine calibration.
3.43
traceability
property of the result of a measurement or the value of a standard whereby it can be related to stated
references, usually national standards or International Standards, through an unbroken chain of comparisons
each having a stated uncertainty
3.44
transfer standard
standard used as an intermediary to compare standards and establish traceability
3.45
treatment parameter
factor that describes one aspect of the irradiation of a patient during radiotherapy, such as radiation energy,
absorbed dose, treatment time
3.46
treatment time
time between initiation and termination of irradiation, excluding any time in the ready state after interruption
3.47
type test
〈of an instrument〉 test intended to determine the characteristics of a particular type or model of a production
instrument
NOTE 1 This type test involves extensive testing over a wide range of quantities that can have a bearing on the result
of a measurement without being the objective of the measurement: the “influence quantities”. For ionizing radiation
detectors, such influence quantities are, for instance, energy, angle of incidence, dose or dose rate and radiation type,
usually under a variety of environmental conditions.
NOTE 2 A type test is normally performed on a prototype or on an instrument taken at random from a production batch
and intended to be typical of the type. A type test will normally be carried out by National or Secondary Standard
Laboratories, which may make the information available to the instrument user.
3.48
type test
〈of a source〉 test intended to determine the characteristics of a particular type or model of a production source
NOTE 1 This type test involves extensive testing for a number of conditions that can have a bearing on the result of an
irradiation.
NOTE 2 A type test is normally performed on a prototype or on a source taken at random from a production batch and
intended to be typical of the type. A type test will normally be carried out by National or Secondary Standard Laboratories,
which may make the information available to the source user.
3.49
water equivalence
property of a material that approximates the radiation attenuation and scattering properties of water for a
specified range of radiation energies
3.50
water-equivalent material
material that absorbs and scatters a specified radiation quality to the same degree as water for a specified
range of radiation energies
3.51
water phantom
water-equivalent phantom
object made from water or a water-equivalent material having essentially the same radiation interaction
properties as liquid water with respect to the dosimetric procedure under consideration
4 Beta radiation sources and source data
4.1 Ophthalmic and dural brachytherapy sources
Brachytherapy has been used since the beginning of the 20th century when applications using radium and
radon seeds in skin applicators were performed. Besides beta radiation, these natural radioactive sources
emit alpha and gamma radiation. A typical indication is the control of the formation of keloids. The
development of artificial, less radiotoxic radioactive sources allowed an increase in the activity concentration
and thus a reduction in treatment time, and an improvement in radiation protection as well. With the
experience of ophthalmic brachytherapy using cobalt-60 ( Co) applicators, beta radiation from
90 90
strontium-90/yttrium-90 ( Sr + Y) planar and later curved applicators also started being used in the 1950s
for the treatment of lesions of the eye, such as pterygia. Often referred to as “plaques”, in this International
Standard, they are referred to as “applicators” or “radioactive ophthalmic brachytherapy sources”.
In the 1980s, radiotherapy for eye malignancies (e.g. uveal melanoma, retinoblastoma,
[4], [5], [6], [7], [8], [9]
hemangioma) was found to offer a therapeutic alternative to enucleation, being at least
equally effective in controlling tumour growth and at the same time eye- and vision-sparing. For such
ophthalmic treatments, a number of different beta emitters, and also photon sources, were used in the past,
90 90 106 106 60
e.g., strontium-90/yttrium-90 ( Sr+ Y), ruthenium-106/rhodium-106 ( Ru+ Rh), cobalt-60 ( Co), iridium-
192 198 226 106 106
192 ( Ir), gold-198 ( Au) and radium-226 ( Ra). Presently Ru + Rh ophthalmic brachytherapy
90 90
sources are widely used, especially in Europe, and remain commercially available. Also Sr + Y ophthalmic
[10]
brachytherapy sources are applied for a few cases , although they are currently not being manufactured.
For completeness, we mention that in the US, custom-made ophthalmic brachytherapy sources employing
125 103
iodine-125 ( I) or palladium-103 ( Pd) are mainly used. Also, eye applicators which combine iodine-125
and ruthenium-106/rhodium-106 have recently been introduced into the clinical routine at Essen University
[11]
Hospital . Clinical dosimetry of this applicator and photon sources are both beyond the scope of this
International Standard.
8 © ISO 2009 – All rights reserved
Very recently, thin yttrium-90 ( Y) foil applicators have been used to treat spinal dura after tumour removal to
[12]
control microscopic residual disease .
4.2 Intravascular brachytherapy sources
In intravascular brachytherapy (IVB), the vessel section injured by the interventional process of widening is
[13], [14], [15]
treated with either beta or photon radiation . In the coronary artery tree, the injured section lengths
are usually on the order of 2 cm to 4 cm in arteries with diameters of 2 mm to 4 mm. It is also necessary to
treat longer or more complex target volumes (long lesions up to 9 cm, multifocal lesions or bifurcations) in
coronaries and in large peripheral vessels (tens of centimetres). This requires line sources with a very narrow
diameter, less than 1 mm, able to fit through a brachytherapy catheter. Typical arrangements include
encapsulated line sources mounted on the end of wires that can be used to insert and remove the sources to
and from the treatment volume. Line sources may also be realized from linear arrays of “seeds,” which can be
delivered to the target site either manually or automatically. Radionuclides that have been used for these
32 90 90 90
sources include P, Sr + Y, and Y. The physical length of these sources varies (3 cm to 6 cm) to
adequately cover the target volume. Stepping short wire sources (0,5 cm to 2 cm) are used to treat longer
target volumes.
Other sources have been applied to the restenosis problem, however they were for the most part unsealed
and their dosimetry is beyond the scope of this International Standard. For completeness, they include Re
186 133 32 [14]
and Re radioactive liquid, Xe gas-filled balloons, P-coated balloons and radioactive stents ; no
further details on these sources are given in this International Standard.
4.3 Characteristics of radionuclides
Table 1 shows a compilation of half-lives (with uncertainties), and maximum and average energies for the
[16]
different beta radiation sources most commonly used for clinical applications .
Table 1 — Properties of radionuclides in the most commonly used
clinical beta radiation sources
Half life E E
max avg Major photon radiation with
Beta emitter
percentage per decay
d MeV MeV
Sr 10 523 ± 22 0,546 0,195 8 none
Y 2,667 ± 0,008 2,280 1 0,933 6 none
P 14,263 ± 0,003 1,710 5 0,694 9 none
Ru 373,59 ± 0,15 0,039 4 0,010 none
Rh (3,449 ± 0,009) E-4 3,541 0 1,410 0,512 MeV (20 %)
0,622 MeV (10 %)
1,0 MeV (1,6 %)
1,13 MeV (0,4 %)
1,55 MeV (0,2 %)
4.4 Source specification
4.4.1 General
The manufacturer of brachytherapy sources shall provide the following information:
⎯ reference data set (RDS) of the given source type, and
⎯ calibration data (CD) of the specific source.
NOTE Appropriate documents containing the required data include the source certificate (SC) (as given in
[175] [17]
ISO 2919 and IAEA No. TS-R-1 ) and the “Instructions for use”.
The manufacturer is liable for his products according to legal requirements. Thus, the reference data set and
the calibration data shall contain all data on which treatment planning at the required level is based. The
measurement information required in the calibration data is important also for the clinical user who is required
to make an independent verification of the source properties.
See Annex B for examples of data sheets.
4.4.2 Reference data set
4.4.2.1 General
The RDS shall contain at least
⎯ the manufacturer's name, and address;
⎯ the radionuclide, half life and maximum beta energy of the nuclide, and major photon radiation
components and energies;
⎯ a statement of radionuclide purity;
⎯ source type identification, nominal dose rate and nominal contained activity;
⎯ design of the source, including dimensions and composition (both radioactive core and encapsulation).
4.4.2.2 Reference data set for area sources
An RDS specifically for area (ophthalmic concave or planar) sources shall contain at least
⎯ the active and physical diameters, window thickness and material, radius of curvature, dimensions of
cutouts (e.g. see Annex B: product data sheet);
⎯ typical values of the relative axial dose rate (depth dose distribution) with a resolution of at least 1 mm
starting closer than 1 mm from the applicator surface to the bremsstrahlung background;
⎯ typical two-dimensional distribution of the relative dose rate with a resolution of at least 10 % (in at least
one plane including the source axis and, in the case of asymmetric sources, in a second orthogonal plane
through the cutout), as well as in at least one plane perpendicular to the source axis preferably through
the reference point.
4.4.2.3 Reference data set for line sources
An RDS specifically for line (intravascular seed arrays, wire or balloon) sources shall contain at least
⎯ the seed number (if applicable), nominal inactive and active source length and diameter, number and
position of markers on active and dummy sources, design and dimensions of the catheter and relevant
tolerances;
⎯ typical values of the relative radial dose rate as a function of the distance from the source axis with a
resolution of at least 0,1 mm from 0,5 mm to the bremsstrahlung background, including values at about
50 %, 75 %, and 125 % of the range of the beta radiation;
⎯ typical values of the relative longitudinal dose rate, along a line parallel to the source axis through P ;
ref
⎯ support for three-dimensional dosimetry for intravascular sources (optional) (see 5.4).
10 © ISO 2009 – All rights reserved
4.4.3 Calibration data
4.4.3.1 General
Calibration data (CD) shall contain at least the reference dose rate at the calibration date/time with uncertainty
(expanded with k = 2), with the method of determination and with a statement on the traceability to a primary
standard.
4.4.3.2 Calibration data for area sources
Calibration data specifically for area (ophthalmic concave or planar) sources shall contain at least
⎯ tabulated values of the absorbed dose rate to water (relative or absolute) as a function of distance from
the applicator surface along the source axis, with a resolution of at least 1 mm, starting closer than 1 mm
from the applicator surface and extending to the bremsstrahlung background, with uncertainty (expanded
with k = 2) and method of determination;
⎯ relative dose rate distribution at 1,0 mm distance from the surface normalized to the value at the axis with
uncertainty (expanded with k = 2) and method of determination, and values of derived source non-
uniformity (see 5.7.3) and source asymmetry (see 5.7.4);
⎯ relative dose rate distribution in planes perpendicular to the source axis (to allow comparison with
measurements in the clinic; see 11.1.6) (optional);
⎯ source data to support three-dimensional dose distribution calculation (optional).
4.4.3.3 Calibration data for line sources
Calibration data specifically for line (intravascular seed arrays, wire or balloon) sources shall contain at least
⎯ relative radial dose rate distribution (measured on a line vertical to the source axis through P with
ref
resolutions of at least 0,5 mm);
⎯ relative longitudinal dose rate distribution (measured at a line parallel to the source axis through P );
ref
⎯ statement on active source length;
⎯ value of source non-uniformity (see 5.7.3);
⎯ statement on equatorial anisotropy (see 5.7.5).
5 Dose calculation parameters and formalisms
5.1 General
In 5.2 to 5.7 are introduced the relevant radiation-field parameters and formalisms for expressing dose
distributions about beta radiation sources. In this International Standard, discussion is limited to four source
geometries: point, line, planar and concave.
5.2 Parameters of the radiation field
5.2.1 General
It is often convenient to parameterize the radiation field rather than to express the absorbed dose rate as a
function of position around the source. An obvious first step in this parameterization is to use the absorbed
dose rate at the reference point, and then use a relative value of the absorbed dose rate at other points.
These relative values do not change with time (as does the absorbed dose rate for radionuclide sources) and
presumably are the same from source to source for the same radionuclide and source construction.
5.2.2 Reference absorbed dose to water
The choice of the reference distance for the reference absorbed dose (rate) to water is based on the geometry
of the sources used, the characteristic of the near-field dose distribution of the applied beta nuclides and the
distance of clinical interest. Therefore, the reference point for planar beta radiation sources is located 1 mm from
the source surface and for concave sources, 2 mm from the source surface, both on a line passing through the
centre of the source area. The choice of 2 mm for the reference point distance for concave applicators, rather than
[18]
the 1 mm recommended by the ICRU Report 72 , is justified by the difficult source geometry, which makes
measurements at the closer distance a problem. For beta radiation point and line sources, the reference point is
located at a distance of 2 mm measured from the source centre, and for line sources it is perpendicular to the
[18], [19], [20], [21],[22], [23]
source axis .
The absorbed dose rate at the reference point, P , defined as the reference absorbed dose rate to water, is
ref
r r
&
denoted by D()r , where r is the location of the reference point. The absorbed dose rate at any arbitrary
00 0
r
location, r , about the source is then given by Equation (5):
rrr
&&
D()rD= (r )R(r) (5)
r
where R()r is the relative absorbed dose rate function.
5.2.3 Dose distribution coordinate systems
r
The choice of coordinate system in which to express r is usually guided by the source geometry. For point-
r
like sources, it is convenient to use spherical coordinates, rr( ,θ,φ); however for planar, concave and line
r
sources, a cylindrical coordinate system, rz(ρφ, , ) , is better adapted, especially if the source exhibits
symmetry around the source axis. In this case, the absorbed dose rate varies only in the radial
...
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