ISO/ASTM 51707:2005

Guide for estimating uncertainties in dosimetry for radiation processing

ISO/ASTM 51707:2005 defines possible sources of uncertainty in dosimetry performed in gamma, X-ray (bremsstrahlung), and electron irradiation facilities and offers procedures for estimating the resulting magnitude of the uncertainties in the measurement of absorbed dose using a dosimetry system.

Guide pour l'estimation des incertitudes en dosimétrie pour le traitement par irradiation

General Information

• Status: Withdrawn
• Publication Date: 19-Jul-2005
• Withdrawal Date: 19-Jul-2005
• ICS: 17.240 - Radiation measurements
• Technical Committee: ISO/TC 85 - Nuclear energy, nuclear technologies, and radiological protection
• Drafting Committee: ISO/TC 85 - Nuclear energy, nuclear technologies, and radiological protection
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 17-Mar-2015

Relations

• Revised: ISO/ASTM 51707:2015 - Guide for estimation of measurement uncertainty in dosimetry for radiation processing
• Effective Date: 07-Jun-2014
• Revises: ISO/ASTM 51707:2002 - Guide for estimating uncertainties in dosimetry for radiation processing
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO/ASTM
STANDARD 51707
Second edition
2005-05-15
Guide for estimating uncertainties in
dosimetry for radiation processing
Guide pour l’estimation des incertitudes en dosimétrie pour le
traitement par irradiation
Reference number
ISO/ASTM 51707:2005(E)
© ISO/ASTM International 2005

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ISO/ASTM 51707:2005(E)
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ii © ISO/ASTM International 2005 – All rights reserved

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ISO/ASTM FDIS 51707:2005(E)
Contents Page
1 Scope . 1
2 Referenced documents . 1
3 Terminology . 1
4 Significance and use . 4
5 Basic concepts—components of uncertainty . 4
6 Evaluation of standard uncertainty . 6
7 Sources of uncertainty . 9
8 Combining uncertainties—statement of uncertainty . 11
9 Information provided by uncertainty . 12
10 Keywords . 12
Annexes . 12
Bibliography . 24
Figure 1 Graphical illustration of value, error, and uncertainty . 7
Figure 2 Graphical illustration of evaluating type B standard uncertainty . 8
Figure A2.1 Irradiation temperature dependence . 14
Figure A4.1 Response curve (3rd order polynomial) for Red 4034 dosimetry data in Table A4.2 . 19
Figure A4.2 Calculated dose residuals for Red 4034 perspex dosimetry . 19
Figure A5.1 Plot of the data, fitted calibration curve Eq A5.1 (solid line), and the 95 % confidence
intervals (dashed lines) for the predicted values for single observations . 22
Figure A5.2 Plot of the dose residuals and of the 95-percentile dose uncertainties (dashed lines)
as a function of dose for the inverse calibration curve Eq A5.2 . 23
Table 1 Examples of uncertainty in absorbed dose administered by a gamma ray calibration
facility . 9
Table 2 Examples of uncertainty in dosimeter readings . 10
Table 3 Examples of uncertainty in calibration curve . 10
Table 4 Examples of uncertainty due to routine use . 11
Table A4.1 Components of uncertainty (k = 1) for dose delivered to dosimeters . 16
Table A4.2 Example of intrinsic variation in dosimeter response . 17
Table A4.3 Example of variation in spectrophotometric readout (Type B) . 18
Table A4.4 Estimate of uncertainty based on sample data . 20
Table A5.1 Comparison of dosimetry systems . 20
Table A5.2 Calibration curve analysis . 21
Table A5.3 Comparison of calculated and measured specific absorbance and calculated and
measured absorbed dose . 21
Table A5.4 Components of uncertainty . 21
© ISO/ASTM International 2005 – All rights reserved iii

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ISO/ASTM 51707:2005(E)
Foreword
ISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies
(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.
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.
ASTM International is one of the world’s largest voluntary standards development organizations with global
participation from affected stakeholders. ASTM technical committees follow rigorous due process balloting
procedures.
A project between ISO and ASTM International has been formed to develop and maintain a group of
ISO/ASTM radiation processing dosimetry standards. Under this project, ASTM Subcommittee E10.01,
Dosimetry for Radiation Processing, is responsible for the development and maintenance of these dosimetry
standards with unrestricted participation and input from appropriate ISO member bodies.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. Neither ISO nor ASTM International shall be held responsible for identifying any or all such patent
rights.
International Standard ISO/ASTM 51707 was developed by ASTM Committee E10, Nuclear Technology and
Applications, through Subcommittee E10.01, and by Technical Committee ISO/TC 85, Nuclear energy.
Thissecondeditioncancelsandreplacesthefirstedition(ISO/ASTM51707:2002),whichhasbeentechnically
revised.
iv © ISO/ASTM International 2005 – All rights reserved

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ISO/ASTM 51707:2005(E)
Standard Guide for
Estimating Uncertainties in Dosimetry for Radiation
1
Processing
This standard is issued under the fixed designation ISO/ASTM 51707; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision.
1. Scope E177 PracticeforUseoftheTermsPrecisionandAccuracy
as Applied to Measurement of a Property of a Material
1.1 This guide defines possible sources of uncertainty in
E178 Practice for Dealing With Outlying Observations
dosimetry performed in gamma, X-ray (bremsstrahlung), and
E456 Terminology Relating to Quality and Statistics
electron irradiation facilities and offers procedures for estimat-
E876 Practice for Use of Statistics In the Evaluation of
ing the resulting magnitude of the uncertainties in the mea-
Spectrometric Data
surement of absorbed dose using a dosimetry system. Basic
E1249 PracticeforMinimizingDosimetryErrorsinRadia-
concepts of measurement, estimate of the measured value of a
tion Hardness Testing of Silicon Electronic Devices Using
quantity, “true value”, error, and uncertainty are defined and
Co-60 Sources
discussed. Components of uncertainty are discussed and meth-
3
2.2 ISO/ASTM Standards:
ods are given for evaluating and estimating their values. How
51204 Practice for Dosimetry in Gamma Irradiation Facili-
these contribute to the standard uncertainty in the reported
ties for Food Processing
values of absorbed dose are considered and methods are given
51205 PracticeforUseofaCeric-CerousSulfateDosimetry
for calculating the combined standard uncertainty and an
System
estimate of expanded (overall) uncertainty. The methodology
51261 Guide for Selection and Calibration of Dosimetry
for evaluating components of uncertainty follows ISO proce-
Systems for Radiation Processing
dures (see 2.3). The traditional concepts of precision and bias
51275 Practice for Use of a Radiochromic Film Dosimetry
are not used in this document. Examples are given in five
System
annexes.
51400 Practice for Characterization and Performance of a
1.2 This guide assumes a working knowledge of statistics.
2 High-Dose Radiation Dosimetry Calibration Laboratory
Several statistical texts are included in the references (1-4).
51431 Practice for Dosimetry in Electron Beam and X-ray
1.3 This standard does not purport to address all of the
(Bremsstrahlung) Irradiation Facilities for Food Process-
safety concerns, if any, associated with its use. It is the
ing
responsibility of the user of this standard to establish appro-
2.3 ISO Documents:
priate safety and health practices and determine the applica-
ISO,1995,ISBN92-67-10188-9 GuidetotheExpressionof
bility of regulatory limitations prior to use.
4
Uncertainty in Measurement
2. Referenced documents
ISO 11137 Sterilization of Health Care Products-
3
Requirements for Validation and Routine Control-
2.1 ASTM Standards:
5
Radiation Sterilization
E170 Terminology Relating to Radiation Measurements
6
2.4 ICRU Reports:
and Dosimetry
ICRU Report 14 Radiation Dosimetry: X Rays and Gamma
RayswithMaximumPhotonEnergiesBetween0.6and50
1
This guide is under the jurisdiction of ASTM Committee E10 on Nuclear
MeV
Technology and Applications and is the direct responsibility of Subcommittee
ICRUReport17 RadiationDosimetry:XRaysGeneratedat
E10.01 on Dosimetry for Radiation Processing, and is also under the jurisdiction of
Potentials of 5 to 150 kV
ISO/TC 85/WG 3.
Current edition approved by ASTM June 1, 2004. Published May 15, 2005. ICRU Report 34 The Dosimetry of Pulsed Radiation
Originally published as ASTM E 1707–95. Last previous ASTM edition
ICRUReport35 RadiationDosimetry:ElectronBeamswith
e1 e1
E1707–95 . ASTM E1707–95 was adopted by ISO in 1998 with the interme-
Energies Between 1 and 50 MeV
diate designation ISO 15572:1998(E). The present International Standard ISO/
ASTM 51707:2005(E) is a major revision of the last previous edition ISO/ASTM
51707:2002(E), which replaced ISO 15572.
2 4
Theboldfacenumbersinparenthesesrefertothebibliographyattheendofthis Available from ISO Central Secretariat, Postal 56, 1211 Geneva 20 Switzer-
guide. land.
3 5
For referenced ASTM and ISO/ASTM standards, visit the ASTM website, Available from Association for the Advancement of Medical Instrumentation,
www.astm.org, or contact ASTM Customer Service at [e-mail]. For 1110 North Glebe Road, Suite 220, Arlington, VA 22201-4795, U.S.A.
6
Annual Book of ASTM Standards volume information, refer to the standard’s Available from International Commission on Radiation Units and Measure-
Document Summary page on the ASTM website. ments, 7910 Woodmont Ave., Suite 800 Bethesda, MD 20814, U.S.A.
© ISO/ASTM International 2005 – All rights reserved
1

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ISO/ASTM 51707:2005(E)
ICRU Report 37 Stopping Powers for Electrons and 3.1.11.1 Discussion—A coverage factor, k, is typically in
Positrons the range of 2 to 3 (see 8.3).
ICRU Report 60 Fundamental Quantities and Units for 3.1.12 dosimeter batch—quantity of dosimeters made from
Ionizing Radiation a specific mass of material with uniform composition, fabri-
cated in a single production run under controlled, consistent
3. Terminology conditions and having a unique identification code.
3.1.13 dosimetry system—system used for determining ab-
3.1 Definitions:
sorbed dose, consisting of dosimeters, measurement instru-
3.1.1 absorbed dose, D—quantity of ionizing radiation
ments and their associated reference standards, and procedures
energy imparted per unit mass of a specified material. The SI
for the system’s use.
unit of absorbed dose is the gray (Gy) where 1 gray is
3.1.14 error (of measurement)—result of a measurement
equivalent to the absorption of 1 joule per kilogram of the
specified material (1 Gy = 1 J/kg). The mathematical relation- minus a true value of the measurand.
– –
3.1.14.1 Discussion—Thequantityissometimescalled“ab-
ship is the quotient of de by dm, where de is the mean energy
solute error of measurement” when it is necessary to distin-
impartedbyionizingradiationtomatterofmassdm(seeICRU
guish it from relative error. If the result of a measurement
60).
depends on the values of quantities other than the measurand,
–
D 5de/dm (1)
the errors of the measured values of these quantities contribute
to the error of the result of the measurement.
3.1.2 accuracy of measurement—closeness of the agree-
mentbetweentheresultofameasurementandthetruevalueof
3.1.15 expanded uncertainty—quantitydefiningtheinterval
the measurand. about the result of a measurement that may be expected to
3.1.3 calibration curve—graphical representation of the encompass a large fraction of the distribution of values that
dosimetry system’s response function.
could reasonably be attributed to the measurand.
3.1.4 coeffıcient of variation—sample standard deviation
3.1.15.1 Discussion—Expanded uncertainty is also referred
expressed as a percentage of sample mean value (see 3.1.38
toas“overalluncertainty”(see2.3,GuidetotheExpressionof
and 3.1.39).
Uncertainty in Measurement). To associate a specific level of
confidence with the interval defined by the expanded uncer-
–
CV 5S /x 3100% (2)
n21
tainty requires explicit or implicit assumptions regarding the
3.1.5 combined standard uncertainty—standard uncertainty
probability distribution characterized by the measurement
of the result of a measurement when that result is obtained
result and its combined standard uncertainty. The level of
from the values of a number of other quantities, equal to the
confidencethatmaybeattributedtothisintervalcanbeknown
positive square root of a sum of terms, the terms being the
only to the extent to which such assumptions may be justified.
variances or covariances of these other quantities weighted
3.1.16 expectedvalue—sumofpossiblevaluesofavariable
according to how the measurement result varies with changes
weighted by the probability of the value occurring. For a
in these quantities.
discrete random variable it is found from the expression:
3.1.6 confidence interval—interval estimate that contains
E 5 ( PV (3)
i i i
the mean value of a parameter with a given probability.
3.1.7 confidence level—probability that a confidence inter- where:
th
val estimate contains the value of a parameter. V = i value of discrete random variable, and
i
th
P = probability of i value.
3.1.8 corrected result—result of a measurement after cor-
i
rection for systematic error. For a continuous random variable x it is found from the
expression:
3.1.9 correction—value that, added algebraically to the
uncorrected result of a measurement, compensates for system-
E 5 *xf~x!dx (4)
atic error.
where:
3.1.9.1 Discussion—The correction is equal to the negative
f(x) = probability density function and the integral is ex-
of the systematic error. Some systematic errors may be
tended over the intervals of variation of x.
estimated and compensated for by applying appropriate cor-
3.1.17 influence quantity—quantity that is not included in
rections. However, since the systematic error cannot be known
the specification of the measurand but that nonetheless affects
perfectly, the compensation cannot be complete.
the result of the measurement.
3.1.10 correction factor—numerical factor by which the
uncorrected result of a measurement is multiplied to compen- 3.1.17.1 Discussion—Thisquantityisunderstoodtoinclude
sate for a systematic error. values associated with reference materials, and reference data
uponwhichtheresultofthemeasurementmaydepend,aswell
3.1.10.1 Discussion—Since the systematic error cannot be
as phenomena such as short-term instrument fluctuations and
known perfectly, the compensation cannot be complete.
parameters such as temperature, time, and humidity.
3.1.11 coverage factor—numerical factor used as a multi-
plierofthecombinedstandarduncertaintyinordertoobtainan 3.1.18 measurand—specific quantity subject to measure-
expanded uncertainty. ment.
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ISO/ASTM 51707:2005(E)
3.1.18.1 Discussion—A specification of a measurand may 3.1.30.1 Discussion—This is sometimes called “assigned
include statements about other quantities such as time, humid- value,” or “assigned reference value.”
ity, or temperature. For example, equilibrium absorbed dose in
3.1.31 relative error (of measurement)—error of measure-
water at 25°C.
ment divided by a true value of the measurand.
3.1.19 measurement—set of operations having the object of
3.1.31.1 Discussion—Since a true value cannot be deter-
determining a value of a quantity.
mined, in practice a reference value is used.
3.1.20 measurement procedure—set of operations, in spe-
3.1.32 repeatability (of results of measurements)—
cific terms, used in the performance of particular measure-
closeness of the agreement between the results of successive
ments according to a given method.
measurements of the same measurand carried out subject to all
3.1.21 measurementsystem—systemusedforevaluatingthe
of the following conditions: the same measurement procedure,
measurand.
the same observer, the same measuring instrument, used under
3.1.22 measurement traceability—ability to demonstrate by
the same conditions, the same location, and repetition over a
means of an unbroken chain of comparisons that a measure-
short period of time.
ment is in agreement within acceptable limits of uncertainty
3.1.32.1 Discussion—These conditions are called “repeat-
with comparable nationally or internationally recognized stan-
ability conditions.” Repeatability may be expressed quantita-
dards.
tively in terms of the dispersion characteristics of the results.
3.1.23 method of measurement—logical sequence of opera-
3.1.33 reproducibility (of results of measurements)—
tions used in the performance of measurements according to a
closenessofagreementbetweentheresultsofmeasurementsof
given principle.
the same measurand, where the measurements are carried out
3.1.23.1 Discussion—Methods of measurement may be
under changed conditions such as differing: principle or
qualified in various ways such as: substitution method, differ-
method of measurement, observer, measuring instrument, lo-
ential method, and null method.
cation, conditions of use, and time.
3.1.24 outlier—measurement result that deviates markedly
3.1.33.1 Discussion—A valid statement of reproducibility
from others within a set of measurement results.
requires specification of the conditions that were changed for
3.1.25 primary standard dosimeter—dosimeter of the high-
the measurements. Reproducibility may be expressed quanti-
est metrological quality, established and maintained as an
tatively in terms of the dispersion characteristics of the results.
absorbeddosestandardbyanationalorinternationalstandards
In this context, results of measurement are understood to be
organization.
corrected results.
3.1.26 principle of measurement—scientific basis of a
3.1.34 response function—mathematical representation of
method of measurement.
therelationshipbetweendosimeterresponseandabsorbeddose
3.1.27 quadrature—method of estimating combined uncer-
for a given dosimetry system.
tainty from independent sources by taking the square root of
3.1.35 result of a measurement—value attributed to a mea-
thesumofthesquaresofindividualcomponentsofuncertainty
surand, obtained by measurement.
(for example, coefficient of variation).
3.1.35.1 Discussion—When the term “result of a measure-
3.1.28 random error—result of a measurement minus the
ment” is used, it should be made clear whether it refers to: the
mean result of a large number of measurements of the same
indication, the uncorrected result, the corrected result, and
measurandthataremadeunderconditionsofrepeatability(see
whether several values are averaged. A complete statement of
3.1.32).
the result of the measurement includes information about the
3.1.28.1 Discussion—Inthisdefinition(andthatforsystem-
uncertainty of the measurement.
atic error), the term mean result of a large number of
3.1.36 routine dosimeter—dosimeter calibrated against a
measurements of the same measurand is understood as the
primary-, reference-, or transfer-standard dosimeter and used
expected value or mean of all possible measured values of the
for routine absorbed-dose measurement.
measurand obtained under conditions of repeatability. The
definition of random error cannot be misinterpreted to imply
3.1.37 sample mean—measure of the average value of a
that for a series of observations, the random error of an
data set which is representative of the mean of the population.
individual observation is known and can be eliminated by
It is determined by summing all the values in the data set and
applying a correction.
dividing by the number of items (n) in the data set. It is found
3.1.29 reference standard dosimeter—dosimeter of high from the expression:
metrological quality, used as a standard to provide measure-
1
¯
x 5 x,i 51,2,3.n (5)
mentstraceabletomeasurementsmadeusingprimarystandard (
i
n
i
dosimeters.
where:
3.1.30 reference value (of a quantity)—value attributed to a
x = individual values of parameters with i=1,2,3. n.
specific quantity and accepted, sometimes by convention, as i
having an uncertainty appropriate for a given purpose; for 3.1.38 sample standard deviation, S —measure of disper-
n−1
example, the value assigned to the quantity realized by a sion of values expressed as the positive square root of the
reference standard. sample variance.
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ISO/ASTM 51707:2005(E)
3.1.39 sample variance—sum of the squared deviations of 3.1.49 value (of a quantity)—magnitude of a specific quan-
individual values from the sample mean divided by (n–1), titygenerallyexpressedasaunitofmeasurementmultipliedby
given by the expression: a number, for example, 25 kGy.
¯
2
( ~x 2x!
i
2
4. Significance and use
S 5 (6)
n21
n 21!
~
4.1 Gamma, electron, and X-ray (bremsstrahlung) facilities
where:
routinely irradiate a variety of products such as food, medical
x = individual value of parameter with i=1, 2 . n, and
i devices, aseptic packaging and commodities (see ISO/ASTM
x¯ = mean of n values of parameter (see 3.1.37).
Practices 51204 and 51431). Process parameters must be
3.1.40 standard uncertainty—uncertainty of the result of a
carefullycontrolledtoensurethattheseproductsareprocessed
measurement expressed as a standard deviation.
within specifications (see ISO 11137, Section 2.3). Accurate
dosimetryisessentialinprocesscontrol(seeISO/ASTMGuide
3.1.41 systematic error—mean result of a large number of
repeated measurements of the same measurand minus a true 51261).Forabsorbeddosemeasurementstobemeaningful,the
combined uncertainty associated with these measurements
value of the measurand.
must be estimated and its magnitude quantified.
3.1.41.1 Discussion—The repeated measurements are car-
ried out under conditions of “repeatability.” Like true value,
NOTE 1—For a comprehensive discussion of various dosimetry meth-
systematic error and its causes cannot be completely known.
ods applicable to the radiation types and energies discussed in this guide,
The error of the result of a measurement may often be
see ICRU Reports 14, 17, 34, 35 and Refs (5, 6).
consideredasarisingfromanumberofrandomandsystematic
4.2 This guide uses the methodology adopted by the Inter-
effects that contribute individual components of error to the
nationalOrganizationforStandardizationforestimatinguncer-
error of the result (seeASTMTerminologies E170 and E456,
tainties in dosimetry for radiation processing (see 2.3).ASTM
and Practice E177).
traditionally uses the terms of precision and bias where
3.1.42 traceability—see measurement traceability.
precision is a measure of the extent to which replicate
3.1.43 transfer standard dosimeter—dosimeter, often a ref-
measurements made under specified conditions are in agree-
erence standard dosimeter, suitable for transport between
ment and bias is a systematic error (seeASTM Terminologies
different locations, used to compare absorbed-dose measure-
E170 and E456, and Practice E177). As seen from this
ments.
standard, components of uncertainty are evaluated as either
3.1.44 true value—value of measurand that would be ob-
Type A or Type B rather than in terms of precision and bias.
tained by a perfect measurement.
Error is different from Type A and Type B components of
3.1.44.1 Discussion—True value is by its nature indetermi- uncertainty.
nateandonlyanidealizedconcept.Inthisguidetheterms“true
4.3 Although this guide provides a framework for assessing
valueofameasurand”and“valueofameasurand”areviewed
uncertainty, it cannot substitute for critical thinking, intellec-
as equivalent (see 5.1.1). tual honesty, and professional skill. The evaluation of uncer-
tainty is neither a routine task nor a purely mathematical one;
3.1.45 Type A evaluation (of standard uncertainty)—
it depends on detailed knowledge of the nature of the measur-
methodofevaluationofastandarduncertaintybythestatistical
and and of the measurement method and procedure used. The
analysis of a series of observations.
quality and utility of the uncertainty quoted for the result of a
3.1.46 Type B evaluation (of standard uncertainty)—
measurement therefore ultimately depends on the understand-
method of evaluation of a standard uncertainty by means other
ing, critical analysis, and integrity of those who contribute to
than the statistical analysis of a series of observations.
the assignment of its value.
3.1.47 uncertainty (of measurement)—parameter, associ-
4.4 Processrequirementsmaynecessitateestablishmentofa
ated with a measurand or derived quantity, that characterizes
target uncertainty, which provides a point of reference for
the distribution of the values that could reasonably be attrib-
evaluating whether the calculated value of uncertainty is
uted to the measurand or derived quantity.
acceptable for the process under consideration.
3.1.47.1 Discussion—For example, uncertainty may be a
4.5 Resultsofanuncertaintyassessmentmaybeusedtoaid
standard deviation (or a given multiple of it), or the width of a
in the evaluation of the statistical control in the given applica-
confidence interval. Uncertainty of measurement comprises, in
tion.Controllablecomponentsofuncertaintymayberankedby
general,manycomponents.Someofthesecomponentsmaybe
comparison to total uncertainty. This ranking may be used to
evaluatedfromthestatisticaldistributionoftheresultsofseries
identify areas for corrective action to reduce the total uncer-
of measurements and can be characterized by experimental
tainty.
standard deviations. The other components, which can also be
characterized by standard deviations, are evaluated from as-
5. Basic concepts—components of uncertainty
sumed probability distributions based on experience or other
information.Itisunderstoodthatallcomponentsofuncertainty
5.1 Measurement:
contribute to the distribution.
5.1.1 The objective of a measurement is to determine the
3.1.48 uncorrected result—result of a measurement before value of the measurand, that is, the value of the specific
correction for the assumed
...