EN ISO 11137-3:2006

SLOVENSKI STANDARD
01-julij-2006
1DGRPHãþD
OSIST prEN ISO 11137-3:2004
SIST EN 552:2000
SIST EN 552:2000/A1:2000
SIST EN 552:2000/A2:2001
Sterilizacija izdelkov za zdravstveno nego - Sevanje - 3. del: Smernica glede
vidikov doziranja (ISO 11137-3:2006)
Sterilization of health care products - Radiation - Part 3: Guidance on dosimetric aspects
(ISO 11137-3:2006)
Sterilisation von Produkten für die Gesundheitsfürsorge - Strahlen - Teil 3: Anleitung zu
dosimetrischen Aspekten (ISO/FDIS 11137-3:2006)
Stérilisation des produits de santé - Irradiation - Partie 3: Directives relatives aux aspects
dosimétriques (ISO 11137-3:2006)
Ta slovenski standard je istoveten z: EN ISO 11137-3:2006
ICS:
11.080.01
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 11137-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2006
ICS 11.080.01 Supersedes EN 552:1994
English Version
Sterilization of health care products - Radiation - Part 3:
Guidance on dosimetric aspects (ISO 11137-3:2006)
Stérilisation des produits de santé - Irradiation - Partie 3: Sterilisation von Produkten für die Gesundheitsfürsorge -
Directives relatives aux aspects dosimétriques (ISO 11137- Strahlen - Teil 3: Anleitung zu dosimetrischen Aspekten
3:2006) (ISO/FDIS 11137-3:2006)
This European Standard was approved by CEN on 13 April 2006.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,
Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 11137-3:2006: E
worldwide for CEN national Members.

Foreword
This document (EN ISO 11137-3:2006) has been prepared by Technical Committee ISO/TC 198
"Sterilization of health care products" in collaboration with Technical Committee CEN/TC 204
"Sterilization of medical devices", the secretariat of which is held by BSI.

This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by October 2006, and conflicting national standards
shall be withdrawn at the latest by April 2009.

This document supersedes EN 552:1994.

This document has been prepared under a mandate given to CEN by the European Commission
and the European Free Trade Association, and supports essential requirements of EU Directive(s).

For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this
document.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Cyprus,
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,
Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Endorsement notice
The text of ISO 11137-3:2006 has been approved by CEN as EN ISO 11137-3:2006 without any
modifications.
ANNEX ZA
(informative)
Relationship between this European Standard and the Essential
Requirements of EU Directives 90/385/EEC concerning active
implantable medical devices, 93/42/EEC concerning medical devices
and 98/79/EEC concerning in vitro diagnostic medical devices

This European Standard has been prepared under a mandate given to CEN by the European
Commission and the European Free Trade Association to provide one means of conforming to
Essential Requirements of the New Approach Directive, EU Directives 90/385/EEC concerning
active implantable medical devices, 93/42/EEC concerning medical devices and 98/79/EEC
concerning in vitro diagnostic medical devices.

Once this standard is cited in the Official Journal of the European Communities under that Directive
and has been implemented as a national standard in at least one Member State, compliance with
the normative clauses of this standard given in Table ZA.1 confers, within the limits of the scope of
this standard, a presumption of conformity with the corresponding Essential Requirements of that
Directive and associated EFTA regulations.

Table ZA.1 — Correspondence between this European Standard and EU Directives
90/385/EEC concerning active implantable medical devices, 93/42/EEC concerning medical
devices and 98/79/EEC concerning in vitro diagnostic medical devices

Clause(s)/Sub-clause(s) Essential Essential Essential Qualifying
of this European Requirements Requirements Requirements remarks/Notes
Standard (ERs) of Directive (ERs) of (ERs) of Directive
90/385/EEC Directive 98/79/EEC
93/42/EEC
In part
4, 5, 6, 7, 8, 9, 10, 11, 12 7 8.3 B.2.3
In part
4, 5, 6, 7, 8, 9, 10, 11, 12 8.4 B.2.4

WARNING: Other requirements and other EU Directives may be applicable to the product(s) falling
within the scope of this standard.

INTERNATIONAL ISO
STANDARD 11137-3
First edition
2006-04-15
Sterilization of health care products —
Radiation —
Part 3:
Guidance on dosimetric aspects
Stérilisation des produits de santé — Irradiation —
Partie 3: Directives relatives aux aspects dosimétriques

Reference number
ISO 11137-3:2006(E)
©
ISO 2006
ISO 11137-3:2006(E)
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ii © ISO 2006 – All rights reserved

ISO 11137-3:2006(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Measurement of dose. 1
5 Selection and calibration of dosimetry systems . 2
5.1 General. 2
5.2 Selection of dosimetry systems. 2
5.3 Calibration of dosimetry system . 2
6 Establishing the maximum acceptable dose . 2
7 Establishing the sterilization dose. 3
8 Installation qualification. 4
9 Operational qualification. 4
9.1 General. 4
9.2 Gamma irradiators. 5
9.3 Electron beam irradiators . 6
9.4 X-ray irradiators . 7
10 Performance qualification. 8
10.1 General. 8
10.2 Gamma and X-ray . 9
10.3 Electron beam . 10
11 Routine monitoring and control . 11
11.1 General. 11
11.2 Frequency of dose measurements . 11
Annex A (informative) Mathematical modelling . 12
Bibliography . 15

ISO 11137-3:2006(E)
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 11137-3 was prepared by Technical Committee ISO/TC 198, Sterilization of health care product.
This first edition, together with ISO 11137-1 and ISO 11137-2, cancels and replaces ISO 11137:1995.
ISO 11137 consists of the following parts, under the general title Sterilization of health care products —
Radiation:
⎯ Part 1: Requirements for development, validation and routine control of a sterilization process for medical
devices
⎯ Part 2: Establishing the sterilization dose
⎯ Part 3: Guidance on dosimetric aspects
iv © ISO 2006 – All rights reserved

ISO 11137-3:2006(E)
Introduction
An integral part of radiation sterilization is the ability to measure dose. Dose is measured during all stages of
development, validation and routine monitoring of the sterilization process. It has to be demonstrated that
dose measurement is traceable to a national or International Standard, that the uncertainty of measurement is
known, and that the influence of temperature, humidity and other environmental considerations on dosimeter
response is known and taken into account. Process parameters are established and applied based on dose
measurements. This part of ISO 11137 provides guidance on the application of dose measurements
(dosimetry) during all stages of the sterilization process.
ISO 11137-1 describes requirements that, if met, will provide a radiation sterilization process, intended to
sterilize medical devices, which has appropriate microbicidal activity. Furthermore, compliance with the
requirements helps ensure that this activity is both reliable and reproducible so that predictions can be made,
with reasonable confidence, that there is a low level of probability of there being a viable microorganism
present on product after sterilization.
Generic requirements of the quality management system for design and development, production, installation
and servicing are given in ISO 9001 and particular requirements for quality management systems for medical
device production are given in ISO 13485. The standards for quality management systems recognize that, for
certain processes used in manufacturing or reprocessing, the effectiveness of the process cannot be fully
verified by subsequent inspection and testing of the product. Sterilization is an example of such a process. For
this reason, sterilization processes are validated for use, the performance of the sterilization process
monitored routinely and the equipment maintained.
Requirements in regard to dosimetry are given in ISO 11137-1 and ISO 11137-2. This part of ISO 11137 gives
guidance to these requirements. The guidance given is not normative and is not provided as a checklist for
auditors. The guidance provides explanations and methods that are regarded as being suitable means for
complying with the requirements. Methods other than those given in the guidance may be used, if they are
effective in achieving compliance with the requirements of ISO 11137-1.
INTERNATIONAL STANDARD ISO 11137-3:2006(E)

Sterilization of health care products — Radiation —
Part 3:
Guidance on dosimetric aspects
1 Scope
This part of ISO 11137 gives guidance on the requirements in ISO 11137 parts 1 and 2 relating to dosimetry.
Dosimetry procedures related to the development, validation and routine control of a radiation sterilization
process are described.
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 referenced
document (including any amendments) applies.
ISO 11137-1, Sterilization of health care products — Radiation — Part 1: Requirements for development,
validation and routine control of a sterilization process for medical devices
ISO 11137-2:2006, Sterilization of health care products — Radiation — Part 2: Establishing the sterilization
dose
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11137-1, ISO 11137-2 and the
following apply.
3.1
dosimetry system
interrelated elements used for determining absorbed dose, including dosimeters, instruments, associated
reference standards and procedures for their use
[ISO/TS 11139:2005]
4 Measurement of dose
Measurement of absorbed dose in connection with the radiation sterilization of medical devices is expressed
in terms of absorbed dose to water. Dosimetry systems should be calibrated in terms of absorbed dose to
water. In this part of ISO 11137, absorbed dose is referred to as dose.
ISO 11137-3:2006(E)
5 Selection and calibration of dosimetry systems
5.1 General
The dosimetry system(s) used to monitor the irradiation of product has to be capable of providing accurate
and precise results over the entire dose range of interest.
5.2 Selection of dosimetry systems
5.2.1 Dosimetric measurements are required in sterilization dose establishment, validation and routine
control of radiation sterilization; different dosimetry systems might be needed for these different tasks. In dose
establishment, for example, the range of doses required for a verification or incremental dose experiment
might be outside the recommended (and calibrated) operating range of the dosimetry system used for the
measurement of sterilization dose and, in such circumstances, an alternative system would have to be
employed.
5.2.2 Guidance on the selection of appropriate dosimetry systems used in radiation sterilization can be
found in ISO/ASTM 51261. The properties of individual dosimetry systems and procedures for their use are
given in the ISO/ASTM Practices listed in the Bibliography.
5.3 Calibration of dosimetry system
5.3.1 It is a requirement in ISO 11137-1 that dose measurements be traceable to an appropriate national or
International Standard and that their level of uncertainty be known. Consequently, all significant sources of
measurement uncertainty should be identified and their magnitudes assessed.
5.3.2 Calibration of dosimetry systems for use in radiation sterilization is a significant activity. The response
of most systems is influenced by the conditions of irradiation and measurement (e.g. temperature, humidity,
dose rate and interval of time between termination of irradiation and measurement). In addition, the effects of
these conditions are often interrelated and they can vary from batch to batch of dosimeters. Therefore,
calibration should be carried out under conditions that match as closely as possible the actual conditions of
use. This means that calibration is needed for each radiation facility and it is not acceptable to use the
outcome of a calibration supplied by the dosimeter manufacturer without additional experimental verification of
its validity.
5.3.3 A recognized national metrology institute or other calibration laboratory accredited to ISO/IEC 17025,
or its equivalent, should be used in order to ensure traceability to a national or International Standard. A
calibration certificate provided by a laboratory not having formal recognition or accreditation will not
necessarily be proof of traceability to a national or International Standard and additional documentary
evidence will be required.
5.3.4 The ability to make accurate dose measurements depends on the calibration and consistency of
performance of the entire dosimetry system. This means that all equipment associated with the measurement
procedure, not just the dosimeters, is controlled and its performance verified.
5.3.5 Detailed calibration procedures are given in ISO/ASTM 51261. Information on estimating and
reporting uncertainty of measurement can be found in ISO/ASTM 51707. Additional guidance is given in
[19]
Sharpe and Miller .
6 Establishing the maximum acceptable dose
6.1 Testing to establish the maximum acceptable dose must be carried out using product or samples of
materials that have been irradiated to doses greater than those anticipated during actual processing. The
value of the maximum dose received during sterilization will be influenced by the characteristics of the
irradiator and the loading pattern of the product. Thus, transfer of the process to another irradiator, or a
change to the loading pattern, might result in a change to the maximum dose to product.
2 © ISO 2006 – All rights reserved

ISO 11137-3:2006(E)
6.2 Irradiation geometries for testing of product or samples of materials should be chosen to ensure that the
dose is determined accurately and is as uniform as practicable. Irradiation in containers used for routine
sterilization processing will usually produce too wide a range of doses to the product to be meaningful for
testing purposes. If routine irradiator containers are used, the location of test product should be such that the
range of doses that product receives is minimized.
6.3 The doses required in product or materials testing might be outside calibration range of available
dosimeter systems. In such cases it may suffice to deliver the dose in increments, with monitoring of each
increment of dose. The total dose is equal to the sum of the incremental doses.
7 Establishing the sterilization dose
7.1 The methods of establishing the sterilization dose (see ISO 11137-2) require product, or portions
thereof (Sample Item Portion [SIP]), to be irradiated at doses within specified tolerance levels. The dosimetry
system used to monitor such doses shall be capable of providing accurate and precise measurements over
the entire dose range of interest. In order to avoid compromising the outcome of the dose setting or dose
substantiation methods, the dosimetry system used needs to be sufficiently accurate to ensure measurement
within the tolerances specified in the method.
7.2 The dose tolerances specified in the dose setting and substantiation methods refer to the maximum,
and in some cases minimum, doses that can be delivered to any point on/in a given product item or SIP.
Implicit in this requirement is the fact that the distribution of dose applied to product is known; this can require
detailed dose mapping of individual product items, particularly in the case of electron beam irradiation. Such
dose mapping is similar to that required for Performance Qualification (PQ, see Clause 10).
7.3 Configuration of product during irradiation should be chosen to achieve minimum variation in dose, both
within individual items and between items. This can necessitate the irradiation of product items individually; in
exceptional cases, it might be necessary to dismantle and repackage the product in order to achieve an
acceptable range of doses applied to the item. In this context, see also 5.4.1 of ISO 11137-2:2006.
7.4 To determine the range of doses applied to product, or portions thereof, dose mapping exercises are
performed. These dose mapping exercises do not have to be carried out at the same dose as used for dose
setting irradiations. The use of higher doses can enable the dosimetry system to be used in a more accurate
part of its operating range, thereby improving the overall accuracy of the dose mapping.
7.5 Consideration should be given to the performance of replicate dose mapping exercises. Performance of
replicates will reduce measurement uncertainties.
7.6 Irradiation for dose-setting or substantiation purposes using gamma rays is normally carried out using
either a special facility that is designed for irradiation with doses lower than the sterilization dose or a defined
location outside the normal product path in a sterilization facility, such as on a turntable or research carrier.
7.7 Irradiation for dose setting or substantiation purposes using electrons or X-rays can normally be carried
out at the facility used for sterilization, as low doses can be achieved by reducing irradiator output power
and/or increasing conveyor speed.
7.8 Irradiation using electrons can be carried out with the product surrounded by material to scatter the
electrons and produce a more uniform dose distribution.
7.9 In the performance of a verification dose experiment, it is required that the highest dose does not
exceed the verification dose by more than 10 %. The highest dose is either measured directly during the
irradiation or calculated from dose mapping data. If dose mapping data are used, account should be taken of
the statistical variability of the data. One approach to achieving this is given in Panel on Gamma & Electron
[20]
Irradiation .
7.10 A repeat of the verification dose experiment is allowed if the arithmetic mean of the highest and lowest
doses is less than 90 % of the intended verification dose. The highest and the lowest doses can either be
measured directly during irradiation or calculated from dose mapping data.
ISO 11137-3:2006(E)
7.11 Methods 2A and 2B (see ISO 11137-2:2006) each require performance of an incremental dose
experiment in which product is irradiated at a series of nominal doses, with the additional requirement that the
dose for each increment is measured independently. The highest dose within each dose increment is required
to be within a specified dose range and is either measured directly during the irradiation or calculated from
dose mapping data. If dose mapping data are used, account should be taken of the statistical variability of the
[20]
data. One approach to achieving this is given in Panel on Gamma & Electron Irradiation .
7.12 Methods 2A and 2B allow a repeat of an incremental dose irradiation using a further set of product, or
SIPs, if the arithmetic mean of the highest and lowest doses at that increment is less than the lower limit of the
specified range. The highest and the lowest doses are either measured directly during the irradiation or
calculated from dose mapping data.
8 Installation qualification
8.1 The purpose of Installation Qualification (IQ) is to demonstrate that the irradiator has been supplied and
installed in accordance with its specifications.
8.2 There is a requirement in ISO 11137-1 to determine the characteristics of the beam for an electron or
an X-ray irradiator. These characteristics include electron or X-ray energy, average beam current and, if
applicable, scan width and scan uniformity. The details of characterization depend on the design and
construction of the irradiator. Some examples are given in 8.4 and 8.5, but these should not be considered
exhaustive.
8.3 Most methods of determining the electron beam characteristics involve dosimetry, although in many
cases only relative measurements (for example, measurement of scan width) are required. In instances where
relative measurements are made, measurement traceability might not be required.
8.4 For X-ray irradiators, it is required to measure either the electron beam energy or X-ray energy during
IQ. Where the design of the X-ray irradiator permits, it is usual to measure the electron beam energy.
8.5 For electron accelerators, consideration should be given to the relationship between the scan frequency,
the scan width, pulse repetition rate (for pulse accelerators) and the conveyor speed relative to the cross-
sectional distribution of the electron beam at the product surface in order to ensure that there is sufficient
overlap to provide the required degree of dose uniformity.
8.6 Characterization of scan uniformity involves, in many cases, measurement of the uniformity both in the
direction of the scan and in the direction of the product travel.
8.7 Details of the methods for electron beam characterization can be found in ISO/ASTM 51649, and those
for X-ray characterization in ISO/ASTM 51608.
8.8 There are no specific dosimetric requirements for IQ of gamma irradiators. However, depending on
irradiator specification, it might be necessary to carry out dose measurements and/or dose mapping in IQ to
verify operation within the specification. Dose measurements similar to those used in Operational Qualification
(OQ) could be utilized.
9 Operational qualification
9.1 General
The purpose of OQ is to demonstrate that the irradiator, as installed, is capable of operating and delivering
appropriate doses within defined acceptance criteria. This is achieved by determining dose distributions
through dose mapping exercises and relating these distributions to process parameters.
4 © ISO 2006 – All rights reserved

ISO 11137-3:2006(E)
9.2 Gamma irradiators
9.2.1 Dose mapping for OQ is carried out to characterize the irradiator with respect to the distribution and
reproducibility of dose and to establish the effect of process interruption on dose. Dose mapping should be
performed by placing dosimeters in an irradiation container filled to its design limits with material of
homogeneous density. This density should be within the density range for which the irradiator is to be used. At
least two dose mapping exercises should be carried out, one with material close to the lower limit of the
density range for which the irradiator is intended to be used and another with material close to the upper limit
of this range.
9.2.2 A sufficient number of irradiation containers (at least three) should be dose mapped at each chosen
density to allow determination of variability of dose and dose distribution between containers. The detail and
number of replicate dose mapping exercises required will be influenced by the amount of knowledge gained
from previous OQ dose mapping exercises on the same or similar irradiators. This means that a greater
number of replicate exercises might be required for a new installation than for qualification dose mapping
exercises after replenishment of sources.
9.2.3 During dose mapping for OQ, the irradiator should have in place a sufficient number of containers to
mimic effectively an irradiator filled with containers holding material of the same density as that being dose
mapped. The number of containers required to achieve this depends on the irradiator design.
9.2.4 Individual dosimeters, dosimeter strips or dosimeter sheets should be placed in a three-dimensional
array sufficient to determine and resolve the dose distribution throughout the entire volume of the irradiation
container. The number of dosimeters will depend upon the size of the irradiation container and the design of
the irradiation facility. With a 1,0 m × 1,0 m × 0,5 m container, for example, dosimeters might be placed in a
three-dimensional 20 cm grid (i.e. at 20 cm intervals) throughout the container. For requalification dose
mapping, data from previous exercises can be used to optimise the positioning of the dosimeters.
Mathematical modelling techniques, such as Monte Carlo or Point Kernel calculations, can also be useful in
optimizing the positioning of dosimeters. See Annex A.
9.2.5 Data from dose mapping exercises can be used to establish the relationships between timer setting
and the magnitude of dose at a defined location within the irradiation container for material of different
densities. Approximate values for these relationships could be supplied by the irradiator manufacturer or
obtained from calculations using mathematical models. Dose mapping data can then be used to refine these
approximate relationships for the particular irradiator. See Annex A.
9.2.6 A separate dose mapping exercise should be carried out or a calculation of transit dose performed in
order to assess the effect of process interruption. The appropriateness of calculations of transit dose should
be verified by dosimetry. This exercise can be done through irradiating a container having dosimeters or
dosimeter strips located as described above, and interrupting the process when the container is close to the
source where dose is expected to be most influenced by source transit. The effect of process interruption is
evaluated by comparing the results with those of dose mapping exercises carried out under normal process
conditions. It might be necessary to interrupt the process multiple times in order to evaluate accurately the
effect.
9.2.7 The response of some dosimeters is known to be influenced by the period of time that lapses between
irradiation and measurement; the magnitude of this effect can depend on temperature during this period.
These factors should be taken into account when interpreting measurements from dosimeters that have been
subjected to process interruption.
9.2.8 Dose mapping should be carried out to determine the effects on dose and dose distribution that may
occur in irradiation containers as a result of changing to product of different density. The acceptable range of
densities that can be processed together can be determined based on these measurements. The effect of
density changes on dose and dose distribution can be determined by sequentially processing two materials
with different densities and dose mapping the last container of the first material density and the first container
of the second material density. The data for these containers should be compared to the homogeneous dose
mapping data for these materials to determine the additional dose variation when the two material densities
are irradiated sequentially.
ISO 11137-3:2006(E)
9.2.9 A separate dose mapping exercise should be performed for special conveyor systems (research
loops) or fixed locations in the irradiation cell (turntables) designated for manual placement of products.
Consideration should be given to the effect on dosimetry of the conditions associated with the use of such
conveyors and locations, e.g. dose rate and temperature.
9.2.10 Additional dose mapping studies can be performed that will provide data to reduce or eliminate dose
mapping studies in PQ. Examples of such studies include a) the effects of partially-filled irradiation containers
that can occur at the end of an irradiation batch, and b) the loading of test materials in the centre of the
irradiation container, which might be used to reduce the product width within the irradiation container in order
to achieve the desired maximum to minimum dose ratio.
Partially-filled irradiation containers can receive higher doses than full containers; therefore, dosimeters
should be placed at potential maximum dose zones in the partially filled containers as well as adjacent full
containers during the dose mapping exercise.
Loading of product in the centre of the irradiation container can result in a change in the magnitude and
distribution of dose as compared to full containers. In such circumstances, dosimeters should be placed at
potential minimum and maximum dose zones.
9.2.11 Data from OQ dose mapping exercises will often provide useful indication of the probable locations of
maximum and minimum doses in actual product loads.
9.3 Electron beam irradiators
9.3.1 Dose mapping for OQ is carried out to characterize the irradiator with respect to the distribution and
reproducibility of dose and to establish the effect of a process interruption on the dose. Dose mapping should
be carried out over a range of selected operating parameters which covers the operational limits to be used in
the irradiation of products. Dose mapping should be performed by placing dosimeters in the irradiation
container filled to its design limits with material of homogeneous density. This density should be within the
density range for which the irradiator is to be used. Generally, it is necessary to use one density only for OQ
dose mapping but more detailed information can be obtained by using more than one density, e.g. materials of
density close to the limits of density range for which the irradiator is intended to be used.
9.3.2 A sufficient number of irradiation containers (at least three) should be dose mapped at each chosen
set of operating parameters in order to allow determination of variability of dose and dose distribution between
containers. The detail and number of replicate dose mapping exercises required will be influenced by the
amount of knowledge gained from previous OQ dose mapping exercises. This means that a greater number of
replicate exercises can be required for a new installation than for requalification at defined intervals.
9.3.3 The dose distribution in the irradiation container being mapped can be affected by material in the
preceding or following containers. This effect should be assessed and its magnitude determined. Depending
on the irradiator design, it might be necessary to precede or follow the containers being dose mapped with
containers filled with a material of similar density.
9.3.4 Dosimeters should be placed in a three dimensional array, including the surface, of the test material to
be irradiated. The dosimeters should be sufficient in number to measure the dose distribution throughout the
entire volume of the irradiation container. The number of dosimeters will depend upon the size of the
irradiation container, the design of the irradiator and the energy of the electron accelerator.
The dosimeters may be sheets, continuous dosimeter strips, discrete dosimeters or discrete dosimeters
placed adjacent to each other to form strips.
Data from previous exercises can be used to optimize the location of the dosimeters. Mathematical modelling
techniques, such as Monte Carlo calculations, can be used in optimizing the positioning of dosimeters.
See Annex A.
9.3.5 Data from the dose mapping exercises can be used to determine the relationships between
characteristics of the beam, the conveyor speed and the magnitude of dose at a defined location within, or on,
an irradiation container filled with a homogeneous material of known density. An alternative approach is to
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ISO 11137-3:2006(E)
define a location with a fixed geometry for a dosimeter that is travelling with, but separate from, the irradiation
container and determine the relationships between characteristics of the beam, the conveyor speed and the
magnitude of dose at that location. This position can be used as a defined monitoring position during routine
processing.
9.3.6 Specific dose measurements should be carried out in order to assess the effect of process
interruption on dose. This effect can be determined by placing dosimeters or dosimeter strips at the position
where the effect of a process interruption is expected to be greatest. This location is often on the surface of
the irradiation container facing the electron beam. The irradiation container is irradiated under normal process
conditions and the process is interrupted when the irradiation container is in the beam. The process is
restarted and the effect of the process interruption is determined by comparison of dose measured with
process interruption with dose measured without process interruption.
9.3.7 The response of some dosimeters is known to be influenced by the period of time between irradiation
and measurement; the magnitude of this effect can depend on temperature during this period. This should be
taken into account when interpreting measurements from dosimeters that have been subjected to process
interruption.
9.3.8 Depending on the irradiator design, dose mapping should be carried out to determine the effects on
dose and dose distribution that can occur in irradiation containers as a result of changing to product of
different density. The acceptable range of densities that may be processed together can be determined based
on these measurements. The effect of density changes on dose and dose distribution can be determined by
sequentially processing two materials with different densities and dose mapping the last container of the first
material density and the first container of the second material density. The data for these containers should be
compared to the homogeneous dose mapping data for these test materials in order to determine the additional
dose variation when the two material densities are irradiated sequentially.
9.3.9 Data from OQ dose mapping can provide an indication of the locations of maximum and minimum
doses in product loads.
9.4 X-ray irradiators
9.4.1 Dose mapping for OQ is carried out to characterize the irradiator with respect to the distribution and
reproducibility of dose, and to establish the effect of a process interruption on the dose. Dose mapping should
be performed by placing dosimeters in an irradiation container filled to its design limits with a material of
homogeneous density. This density should be within the density range for which the irradiator is to be used.
Dose mapping should be carried out over a range of selected operating parameters and material densities
that cover the operational limits encountered in the irradiation of products. At least two material densities
should be used – one close to the lower limit of the density range for which the irradiator is intended to be
used and another close to the upper limit of this range.
9.4.2 A sufficient number of irradiation containers (at least three) should be dose mapped at each chosen
set of operating parameters in order to allow determination of variability of dose and dose distribution between
containers. The detail and number of replicate dose mapping exercises required will be influenced by the
amount of knowledge gained from previous OQ dose mapping exercises. This means that a greater number of
replicate exercises can be required for a new installation than for requalification at defined intervals.
9.4.3 During dose mapping for OQ, the irradiator should have in place a sufficient number of containers to
mimic effectively an irradiator filled with containers holding material of the same density as that being dose
mapped. The number of containers required to achieve this depends on the irradiator design.
9.4.4 Individual dosimeters, dosimeter strips or dosimeter sheets should be placed in a three-dimensional
array sufficient to measure the dose distribution throughout the entire volume of the irradiation container. The
number of dosimeters will depend upon the size of the irradiation container, the design of the irradiation facility,
and on the energy of the X-ray beam. With a 1,0 m × 1,0 m × 0,5 m container, for example, dosimeters might
be placed in a three-dimensional 20 cm grid (i.e. at 20 cm intervals) throughout the container. For
requalification dose mapping, data from previous exercises can be used to optimize the positioni
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