ASTM ISO/ASTM51650-21

Standard Practice for Use of a Cellulose Triacetate Dosimetry System

SIGNIFICANCE AND USE
4.1 The CTA dosimetry system provides a means for measuring absorbed dose based on a change in optical absorbance in the CTA dosimeter following exposure to ionizing radiation (2-10).  
4.2 CTA dosimetry systems are commonly used in industrial radiation processing, for example in the modification of polymers and sterilization of health care products.  
4.3 CTA dosimeter film can be particularly useful in absorbed dose mapping because it is available in a reel of 100 m whereby the user can cut any length of strip for use. When the CTA film is measured using a strip measurement device with a narrow distance interval (for example, 2 mm), it can provide high resolution results in a linear direction.  
4.4 CTA is used to measure relative dose such as depth dose profiles in electron beam and reference phantom tests to assess irradiator changes in gamma.  
4.5 When CTA is used as a routine monitoring dosimeter the user must take into consideration the effects of the multiple influence quantities that can affect the result and use appropriate techniques, as discussed herein, for characterizing and mitigating such influences and understanding their contribution to measurement uncertainty. Without such effort the dosimetry system may not meet the user’s requirements for dosimetric release of some types of products (for example, health care products).
SCOPE
1.1 This is a practice for using a cellulose triacetate (CTA) dosimetry system to measure absorbed dose in materials irradiated by photons or electrons in terms of absorbed dose to water. CTA is used as a routine dosimetry system or used for relative dose measurements (that is, non-traceable dose measurements).  
1.2 The CTA dosimeter is classified as a type II dosimeter on the basis of the complex effect of influence quantities on its response (see ISO/ASTM Practice 52628).  
1.3 This document is one of a set of standards that provides recommendations for properly implementing dosimetry in radiation processing, and describes a means of achieving compliance with the requirements of ISO/ASTM 52628 “Practice for Dosimetry in Radiation Processing” for a CTA dosimetry system. It is intended to be read in conjunction with ISO/ASTM 52628.  
1.4 This practice covers the use of CTA dosimetry systems under the following conditions:  
1.4.1 The absorbed dose range is 10 kGy to 300 kGy.
Note 1: The dosimeter film irradiated to doses exceeding 200 kGy becomes brittle to some degree and must be handled with care. This may limit the practical dose range depending on the type of testing and handling required.  
1.4.2 The absorbed-dose rate range is 3 Gy/s to 4 ×1010 Gy·s (1).2  
1.4.3 The photon energy range is 0.1 to 50 MeV.  
1.4.4 The electron energy range is 0.2 to 50 MeV.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Sep-2021
• ICS: 17.240 - Radiation measurements
• Technical Committee: E61 - Radiation Processing
• Drafting Committee: E61.02 - Dosimetry Systems

Relations

• Replaces: ASTM ISO/ASTM51650-13 - Standard Practice for Use of a Cellulose Triacetate Dosimetry System
• Effective Date: 01-Oct-2021

Overview

ASTM ISO/ASTM 51650-21: Standard Practice for Use of a Cellulose Triacetate Dosimetry System establishes procedures for employing cellulose triacetate (CTA) dosimetry systems to measure absorbed dose in materials irradiated by photons or electrons. This standard is primarily used in industrial radiation processing applications, including polymer modification and the sterilization of healthcare products. It provides guidance for both routine dosimetry (for traceable, process-control measurements) and relative dose measurements where compliance with established reference dosimetry systems is required.

The CTA dosimetry system operates by utilizing the change in optical absorbance of CTA film after exposure to ionizing radiation. These changes are measured using calibrated spectrophotometers, yielding accurate absorbed dose determinations within the prescribed dose, dose-rate, and energy ranges.

Key Topics

• Absorbed Dose Measurement: The method is based on precise changes in optical absorbance of CTA film caused by exposure to ionizing radiation, quantifying absorbed dose to water.
• Application Range:
  • Absorbed dose: 10 kGy to 300 kGy
  • Absorbed-dose rate: 3 Gy/s to 4 × 10¹⁰ Gy/s
  • Photon energy: 0.1 to 50 MeV
  • Electron energy: 0.2 to 50 MeV
• Dosimetry System Components:
  • CTA dosimeter film (commonly supplied in long reels for flexible use and high-resolution absorbed dose mapping)
  • Calibrated spectrophotometer and associated reference filters
  • Dosimeter holders and optional thickness gauges
• Influence Quantities: Recognizes that several factors can affect CTA dosimeter response, including pre-irradiation conditions (film age, humidity, temperature, UV exposure), irradiation parameters (temperature, dose rate, fractionation), post-irradiation storage (time, temperature, humidity), and measurement environment.
• Calibration: Emphasizes user-specific calibration reflecting actual use conditions, accounting for all influence factors to ensure measurement accuracy and compliance with ISO/ASTM 52628.
• Uncertainty Estimation: Requires the estimation and documentation of measurement uncertainty, including contributions from each step-calibration, dosimeter response, equipment variability, and environmental effects.

Applications

• Industrial Radiation Processing: CTA dosimetry is extensively applied in the modification of polymers and sterilization of healthcare products, providing reliable absorbed dose measurements that support quality assurance and regulatory compliance.
• Absorbed Dose Mapping: The film format allows users to cut custom lengths, making CTA particularly suited for high-resolution dose mapping within large or complex items, or for depth-dose profiling in electron beam and gamma irradiator validation.
• Routine and Reference Measurements: CTA films are employed for routine process monitoring in high-throughput environments as well as for benchmarking against reference dosimetry systems.
• Process Qualification and Validation: Used across sectors where the sterility and quality of irradiated products is regulated, ensuring traceability and consistency of radiation dose delivery.

Related Standards

For comprehensive implementation, users should be familiar with related ASTM and ISO standards, including:

• ISO/ASTM 52628: Practice for Dosimetry in Radiation Processing (overarching recommendations for dosimetry system use)
• ISO/ASTM 51261: Practice for Calibration of Routine Dosimetry Systems for Radiation Processing
• ISO/ASTM 51707: Guide for Estimating Uncertainties in Dosimetry for Radiation Processing
• ASTM E170: Terminology Relating to Radiation Measurements and Dosimetry
• ISO 12749-4: Nuclear energy-Vocabulary-Dosimetry for radiation processing

Keywords: absorbed dose, cellulose triacetate dosimetry, CTA dosimeter, industrial radiation processing, electron beam, gamma radiation, dose mapping, radiation sterilization, ISO/ASTM 51650-21.

By adhering to the requirements of ISO/ASTM 51650-21, organizations can ensure that CTA dosimetry systems deliver reliable, accurate, and reproducible results integral to radiation processing quality control.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: 51650 − 21
Standard Practice for
Use of a Cellulose Triacetate Dosimetry System
This standard is issued under the fixed designation 51650; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.6 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This is a practice for using a cellulose triacetate (CTA)
responsibility of the user of this standard to establish appro-
dosimetry system to measure absorbed dose in materials
priate safety, health, and environmental practices and deter-
irradiated by photons or electrons in terms of absorbed dose to
mine the applicability of regulatory limitations prior to use.
water. CTA is used as a routine dosimetry system or used for
1.7 This international standard was developed in accor-
relative dose measurements (that is, non-traceable dose mea-
dance with internationally recognized principles on standard-
surements).
ization established in the Decision on Principles for the
1.2 The CTA dosimeter is classified as a type II dosimeter
Development of International Standards, Guides and Recom-
on the basis of the complex effect of influence quantities on its
mendations issued by the World Trade Organization Technical
response (see ISO/ASTM Practice 52628).
Barriers to Trade (TBT) Committee.
1.3 This document is one of a set of standards that provides
2. Referenced documents
recommendations for properly implementing dosimetry in
radiation processing, and describes a means of achieving 2.1 ASTM Standards:
compliance with the requirements of ISO/ASTM 52628 “Prac-
E275 Practice for Describing and Measuring Performance of
tice for Dosimetry in Radiation Processing” for a CTA dosim- Ultraviolet and Visible Spectrophotometers
etry system. It is intended to be read in conjunction with E3083 Terminology Relating to Radiation Processing: Do-
ISO/ASTM 52628. simetry and Applications
2.2 ISO/ASTM Standards:
1.4 This practice covers the use of CTA dosimetry systems
51261 Practice for Calibration of Routine Dosimetry Sys-
under the following conditions:
tems for Radiation Processing
1.4.1 The absorbed dose range is 10 kGy to 300 kGy.
51707 Guide for Estimating Uncertainties in Dosimetry for
NOTE 1—The dosimeter film irradiated to doses exceeding 200 kGy
Radiation Processing
becomes brittle to some degree and must be handled with care. This may
51818 Standard Specification for Synthetic Fiber Reinforced
limit the practical dose range depending on the type of testing and
Concrete Culvert, Storm Drain, and Sewer Pipe
handling required.
52628 Practice for Dosimetry in Radiation Processing
1.4.2 The absorbed-dose rate range is 3 Gy/s to 4 ×10
52701 Guide for Performance Characterization of Dosim-
Gy·s (1).
eters and Dosimetry Systems for Use in Radiation Pro-
1.4.3 The photon energy range is 0.1 to 50 MeV.
cessing
1.4.4 The electron energy range is 0.2 to 50 MeV.
2.3 International Commission on Radiation Units and Mea-
1.5 The values stated in SI units are to be regarded as
surements (ICRU) Reports:
standard. No other units of measurement are included in this
ICRU Report 85a Fundamental Quantities and Units for
standard.
Ionizing Radiation
ICRU Report 80 Dosimetry Systems for Use in Radiation
Processing
This practice is under the jurisdiction of ASTM Committee E61 on Radiation
Processing and is the direct responsibility of Subcommittee E61.02 on Dosimetry
Systems. Originally developed as a joint ASTM/ISO standard in conjunction with
ISO/TC 85/WG 3. For referenced ASTM and ISO/ASTM standards, visit the ASTM website,
Current edition approved Oct. 1, 2021. Published May 2024. Originally approved www.astm.org, or contact ASTM Customer Service at [e-mail]. For
in 1994. Last previous edition approved in 2013 as ISO/ASTM 51650:2013(E). Annual Book of ASTM Standards volume information, refer to the standard’s
DOI: 10.1520/51650-21. Document Summary page on the ASTM website.
2 4
The boldface numbers in parentheses refer to the bibliography at the end of this Available from the International Commission on Radiation Units and
standard. Measurements, 7910 Woodmont Ave., suite 800, Bethesda, MD 20814, USA.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
51650 − 21
2.4 ISO Standard: 4.2 CTA dosimetry systems are commonly used in industrial
12749-4 Nuclear energy—Vocabulary—Part 4: Dosimetry radiation processing, for example in the modification of poly-
for radiation processing mers and sterilization of health care products.
2.5 Joint Committee for Guides in Metrology (JCGM)
4.3 CTA dosimeter film can be particularly useful in ab-
Reports:
sorbed dose mapping because it is available in a reel of 100 m
JCGM 100:2008, GUM 1995, with minor corrections,
whereby the user can cut any length of strip for use. When the
Evaluation of measurement data – Guide to the Expres-
CTA film is measured using a strip measurement device with a
sion of Uncertainty in Measurement
narrow distance interval (for example, 2 mm), it can provide
JCGM 200:2008, VIM, International vocabulary of metrol-
high resolution results in a linear direction.
ogy – Basis and general concepts and associated terms
4.4 CTA is used to measure relative dose such as depth dose
profiles in electron beam and reference phantom tests to assess
3. Terminology
irradiator changes in gamma.
3.1 Definitions:
4.5 When CTA is used as a routine monitoring dosimeter the
3.1.1 cellulose triacetate dosimeter—piece of CTA film that,
user must take into consideration the effects of the multiple
during exposure to ionizing radiation, exhibits a quantifiable
influence quantities that can affect the result and use appropri-
change in specific net absorbance as a function of absorbed
ate techniques, as discussed herein, for characterizing and
dose.
mitigating such influences and understanding their contribution
3.1.2 dosimeter batch—quantity of dosimeters made from a
to measurement uncertainty. Without such effort the dosimetry
specific mass of material with uniform composition, fabricated
system may not meet the user’s requirements for dosimetric
in a single production run under controlled, consistent
release of some types of products (for example, health care
conditions, and having a unique identification code.
products).
3.1.3 dosimeter response—reproducible, quantifiable
5. Overview
change produced in the dosimeter by ionizing radiation.
5.1 CTA dosimeters are manufactured by casting cellulose
3.1.3.1 Discussion—For CTA dosimeters, the response
triacetate with a plasticizer, triphenylphosphate, and solvents,
value (indication) is obtained by measurement of the specific
for example, a methylene chloride–methanol mixture (2, 7).
net absorbance.
5.2 The commercially available dosimeter film is in the
3.1.4 dosimeter stock—part of a dosimeter batch held by the
user. format of 8 mm width and 100 m length rolled on a spool,
which is described in the informative annex.
3.1.5 specific net absorbance (Δk)—net absorbance, ΔA , at
λ
a selected wavelength, λ, divided by the optical pathlength, d,
5.3 Ionizing radiation induces chemical reactions in CTA
through the dosimeter as follows: and the plasticizer, which create or enhance optical absorption
bands in the ultraviolet regions of the electromagnetic spec-
Δk 5 ΔA /d (1)
λ
trum. Optical absorbance at appropriate wavelengths within
3.2 Definitions of other terms used in this practice that
these radiation-induced absorption bands is quantitatively re-
pertain to radiation measurement and dosimetry may be found
lated to the absorbed dose. ICRU Report 80 provides informa-
in ISO/ASTM Practice 52628. Other terms that pertain to
tion on the scientific basis and historical development of the
radiation measurement and dosimetry may be found in ASTM
CTA dosimetry systems in current use.
Terminology E3083 and ISO Terminology 12749-4. Where
5.4 The difference between the specific net absorbance of
appropriate, definitions used in these standards have been
un-irradiated and irradiated CTA dosimeter depends on the
derived from, and are consistent with definitions in ICRU
analysis wavelength used to make the absorbance measure-
Report 85a, and general metrological definitions given in the
ment. Typically, the manufacturer recommends the analysis
VIM.
wavelength that optimizes sensitivity and post-irradiation sta-
bility. The analysis wavelengths recommended for some com-
4. Significance and Use
monly used systems are given in Table A1.1.
4.1 The CTA dosimetry system provides a means for mea-
5.4.1 The user’s choice of calibration method, analysis
suring absorbed dose based on a change in optical absorbance
wavelength, spectral bandwidth, dose range of utilization, and
in the CTA dosimeter following exposure to ionizing radiation
usage procedures, including allowed ranges of influence quan-
(2-10).
tity conditions, shall be documented.
6. Influence quantities
Available from International Organization for Standardization (ISO), ISO
6.1 Factors other than absorbed dose which influence the
Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
dosimeter response are referred to as influence quantities.
Switzerland, https://www.iso.org.
These influence quantities include those related to the dosim-
Document produced by Working Group 1 of the Joint Committee for Guides in
Metrology (JCGM/WG 1). Available free of charge at the BIPM website (http://
eter before, during, and after irradiation and those related to the
www.bipm.org).
dosimeter response measurements (see ISO/ASTM Guide
Document produced by Working Group 2 of the Joint Committee for Guides in
52701). Influence quantities affecting dosimeter response are
Metrology (JCGM/WG 2). Available free of charge at the BIPM website (http://
www.bipm.org). discussed below.
51650 − 21
6.2 Pre-Irradiation Conditions: 6.3.2 Absorbed-Dose Rate—The dosimeter response is af-
fected by the absorbed-dose rate. There is a large variation in
6.2.1 Dosimeter Conditioning and Packaging—The dosim-
response between low and high dose rates of irradiation over
eter may require conditioning and packaging, particularly for
the entire absorbed dose range (4, 7, 8, 9, 13, 14). The user
low dose rate irradiation. See 6.3.4.
must select a calibration method that accounts for this fact (see
NOTE 2—Conditioning CTA film and packaging pieces of it in envi-
Section 9) and should include a component of uncertainty for
ronmentally impermeable pouches under controlled relative humidity
dose rate if the rate varies between calibration and routine use.
conditions will provide for the most consistent dosimeter response.
6.3.3 Dose Fractionation—The dosimeter response is af-
6.2.2 Time Since Manufacture—The pre-irradiation absor-
fected by dose given in fractions (multiple, separate irradia-
bance increases slowly with time presumably due to oxidation
tions) and the effect is greater in high dose rate processes (14).
on the surface of the film (7, 11). The pre-irradiation absor-
The user shall characterize the impact of fractionation on the
bance of the outer layer(s) of a roll of CTA film may, therefore,
accuracy of dose measurements or calibrate and use the
increase more than the inner layers; hence, it may be advisable
dosimeter under specified fractionation conditions.
to discard the outer layer(s) of the film. Measure the pre-
6.3.4 Relative Humidity—The dosimeter response is af-
irradiation absorbance before using the dosimeter.
fected by relative humidity during irradiation, particularly at
Alternatively, compare the pre-irradiation absorbance to the
low dose rates and relative humidity extremes (4, 7, 9, 11, 12).
average value noted at the time of calibration to determine if
The user may choose to control relative humidity during
there is any change that shall be taken into account.
calibration and use by sealing the CTA film in impermeable
NOTE 3—The pre-irradiation absorbance to be used in the calculation of packaging to mitigate this effect. The user shall characterize the
specific net absorbance will either be the value as measured before
effect and account for it as a component of measurement
irradiation by the user, or a user-determined average value.
uncertainty.
6.2.3 Temperature—Avoid exposure to temperatures outside 6.3.5 Exposure to Light—The dosimeter is not affected by
the manufacturer’s recommended range. The effects of low or
exposure to normal room lighting. Refer to 6.2.5 for additional
high temperatures on the product for short or long durations information (7, 11).
have not been dutifully examined but the product is a chemical
6.3.6 Radiation Energy—There is no known effect on do-
dosimeter and may have some inherent risks, as such.
simeter response. However, the irradiation of 125 micron thick
Therefore, store the product under stable temperature condi-
CTA film using electron energies below 300 keV can result in
tions such as that of an office or laboratory upon receipt and for
a dose gradient within the film. Refer to ISO/ASTM 51818 for
the duration of the CTA film’s shelf life. Any impact of
more details on dosimetry considerations when using <300
temperatures during shipping and storage on the product must
keV electrons.
be taken into account during incoming stock receiving inspec-
6.4 Post-Irradiation Conditions:
tion (see Section 8) or the dosimeter calibration (see Section 9),
6.4.1 Time—The dosimeter response varies with the time
or both.
interval between radiation exposure and dosimeter measure-
6.2.4 Relative Humidity—It is good practice to store the film
ment (4, 7, 10, 11, 12, 14). After high dose rate irradiation such
in a controlled environment prior to use. Research on this topic
as electron beam the absorbance might decrease 10 % or more
generally used unspecified controlled storage conditions.
during the first 20 min after irradiation and then increase
Otherwise, the user must characterize the effect of variable
slowly 3-5 % over the next 3 h. See Fig. A2.1 and Fig. A2.2 in
relative humidity storage conditions on the subsequent perfor-
Annex A2. The absorbance increases approximately 6 % or
mance of the dosimeter.
more over 10 days of elapsed time after irradiation with less
6.2.5 Exposure to Light—The dosimeter is insensitive to UV
than 1 % contribution in the last 5 days. See Fig. A2.3 in Annex
and visible light from normal room lighting; however, expo-
A2. After low dose rate irradiation using sources such as
sure to direct sunlight results in an increase in absorbance (7,
gamma or X-ray, the absorbance changes more slowly, increas-
11).
ing approximately 2 % after 2 h elapsed time. See Fig. A2.5 in
6.3 Conditions During Irradiation: Annex A2 (7, 11).
6.4.1.1 A procedure shall be established to control the
6.3.1 Irradiation Temperature—The dosimeter response is
directly correlated to temperature. The variation in dosimeter allowable time interval between irradiation and measurement;
for example, a desired measurement time after irradiation (for
response from 20 °C to 40 °C is approximately +5 % while the
example, 2 h) with some prescribed allowance for variation
variation from 0 °C to 65 °C is greater than +20 % (7, 9-12).
(for example, 615 min). The uncertainty of the measurement
Calibration of the film under the conditions of use is recom-
of absorbed dose due to the user’s allowance for variation in
mended to avoid creating a bias in the calibration function due
time after irradiation shall be determined and included in the
to the irradiation temperature differences between calibration
user’s measurement uncertainty budget (see ISO/ASTM 51707
and routine use. However, temperature variation over longer
for details on uncertainty of measurement).
time intervals (months) will lead to a seasonal effect. The
amount of this effect is not fully understood and may vary with 6.4.2 Temperature—The storage temperature after irradia-
other influence quantities. Users shall account for this by tion does have an effect at various points over the time interval
including a component of uncertainty for temperature variation after electron beam irradiation. See Fig. A2.2 and Fig. A2.4 in
during irradiation in their uncertainty budget or by re- Annex A2 (7, 9, 11). After irradiation, store the film in a stable
calibration. environment.
51650 − 21
6.4.3 Conditioning Treatment—No advantageous post- 7.3.1.2 Verify the wavelength accuracy at or near the
irradiation treatment is available or recommended (4). analysis wavelength using calibrated references.
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: ISO/ASTM 51650 − 2013(E) 51650 − 21
Standard Practice for
Use of a Cellulose Triacetate Dosimetry System
This standard is issued under the fixed designation ISO/ASTM 51650; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This is a practice for using a cellulose triacetate (CTA) dosimetry system to measure absorbed dose in materials irradiated by
photons or electrons in terms of absorbed dose to water. The CTA dosimetry system is classifiedis used as a routine dosimetry
system.system or used for relative dose measurements (that is, non-traceable dose measurements).
1.2 The CTA dosimeter is classified as a type II dosimeter on the basis of the complex effect of influence quantities on its response
(see ASTMISO/ASTM Practice E262852628).
1.3 This document is one of a set of standards that provides recommendations for properly implementing dosimetry in radiation
processing, and describes a means of achieving compliance with the requirements of ASTMISO/ASTM E262852628 “Practice for
Dosimetry in Radiation Processing” for a CTA dosimetry system. It is intended to be read in conjunction with ASTMISO/ASTM
E262852628.
1.4 This practice covers the use of CTA dosimetry systems under the following conditions:
1.4.1 The absorbed dose range is 10 kGy to 300 kGy.
NOTE 1—The dosimeter film irradiated to doses exceeding 200 kGy becomes brittle to some degree and must be handled with care. This may limit the
practical dose range depending on the type of testing and handling required.
10 2
1.4.2 The absorbed-dose rate range is 3 Gy/s to 4×104 ×10 Gy/sGy·s (1).
1.4.3 The photon energy range is 0.1 to 50 MeV.
1.4.4 The electron energy range is 0.2 to 50 MeV.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
This practice is under the jurisdiction of ASTM Committee E61 on Radiation Processing and is the direct responsibility of Subcommittee E61.02 on Dosimetry Systems,
and is also under the jurisdiction of . Originally developed as a joint ASTM/ISO standard in conjunction with ISO/TC 85/WG 3.
Current edition approved April 9, 2013Oct. 1, 2021. Published June 2013May 2024. Originally published as ASTM E 1650–94 with title: Practice for Use of Cellulose
Acetate Dosimetry Systems. ASTM E 1650–94 was adopted by ISO in 1998 with the intermediate designation ISO 15570:1998(E). The present Third Edition of International
Standard ISO/ASTM 51650:2013(E) is a major revision of the Second Edition of ISO/ASTM 51650:2005(E).approved in 1994. Last previous edition approved in 2013 as
ISO/ASTM 51650:2013(E). DOI: 10.1520/51650-21.
The boldface numbers in parentheses refer to the bibliography at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
51650 − 21
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced documents
2.1 ASTM Standards:
E170 Terminology Relating to Radiation Measurements and Dosimetry
E275 Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
E2628E3083 Practice for Dosimetry in Radiation ProcessingTerminology Relating to Radiation Processing: Dosimetry and
Applications
E2701 Guide for Performance Characterization of Dosimeters and Dosimetry Systems for Use in Radiation Processing
2.2 ISO/ASTM Standards:
51261 Practice for Calibration of Routine Dosimetry Systems for Radiation Processing
51707 Guide for Estimating Uncertainties in Dosimetry for Radiation Processing
51818 Standard Specification for Synthetic Fiber Reinforced Concrete Culvert, Storm Drain, and Sewer Pipe
52628 Practice for Dosimetry in Radiation Processing
52701 Guide for Performance Characterization of Dosimeters and Dosimetry Systems for Use in Radiation Processing
2.3 International Commission on Radiation Units and Measurements (ICRU) Reports:
ICRU Report 85a Fundamental Quantities and Units for Ionizing Radiation
ICRU Report 80 Dosimetry Systems for Use in Radiation Processing
2.4 ISO Standard:
12749-4 Nuclear energy—Vocabulary—Part 4: Dosimetry for radiation processing
2.5 Joint Committee for Guides in Metrology (JCGM) Reports:
JCGM 100:2008, GUM 1995, with minor corrections, Evaluation of measurement data – Guide to the Expression of Uncertainty
in Measurement
JCGM 200:2008, VIM, International vocabulary of metrology – Basis and general concepts and associated terms
3. Terminology
3.1 Definitions:
3.1.1 absorbed-dose mapping—measurement of absorbed dose within an irradiated product to produce a one-, two- or
three-dimensional distribution of absorbed dose, thus rendering a map of absorbed-dose values.
3.1.1.1 Discussion—
The CTA dosimeter strip with appropriate length provides the opportunity for high resolution measurement of dose distribution,
such as depth dose distribution.
3.1.2 absorbed-dose rate (D˙)—absorbed dose in a material per incremental time interval, i.e., the quotient of dD by dt. Also see
-1
E170. The SI unit is Gy s . (ICRU-60, 4.2.6)
˙
D 5 dD/dt (1)
3.1.2.1 Discussion—
(1) The absorbed-dose rate is often specified in terms of its average value over longer time intervals, for example, in units of
-1 -1
Gy·min or Gy·h . (2) In gamma industrial irradiators, dose rate may be significantly different at different locations. (3) In
electron-beam irradiators with pulsed or scanned beam, there are two types of dose rate: average value over several pulses (scans)
and instantaneous value within a pulse (scan). These two values can be significantly different.
3.1.3 calibration curve—expression of the relation between indication and corresponding measured quantity value. (VIM:2008)
3.1.3.1 Discussion—
In radiation processing standards, the term “dosimeter response” is generally used for “indication”.
For referenced ASTM and ISO/ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book
of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from the International Commission on Radiation Units and Measurements, 7910 Woodmont Ave., suite 800, Bethesda, MD 20814, USA.
Available from International Organization for Standardization (ISO), ISO Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva, Switzerland,
https://www.iso.org.
Document produced by Working Group 1 of the Joint Committee for Guides in Metrology (JCGM/WG 1). Available free of charge at the BIPM website
(http://www.bipm.org).
Document produced by Working Group 2 of the Joint Committee for Guides in Metrology (JCGM/WG 2). Available free of charge at the BIPM website
(http://www.bipm.org).
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3.1.1 cellulose triacetate dosimeter—piece of CTA film that, during exposure to ionizing radiation, exhibits a quantifiable change
in specific net absorbance as a function of absorbed dose.
3.1.5 dosimeter—device that, when irradiated, exhibits a quantifiable change that can be related to absorbed dose in a given
material using appropriate measurement instruments and procedures.
3.1.2 dosimeter batch—quantity of dosimeters made from a specific mass of material with uniform composition, fabricated in a
single production run under controlled, consistent conditions, and having a unique identification code.
3.1.3 dosimeter response—reproducible, quantifiable effectchange produced in the dosimeter by ionizing radiation.
3.1.3.1 Discussion—
For CTA dosimeters, the specific net absorbance is the dosimeter response.response value (indication) is obtained by measurement
of the specific net absorbance.
3.1.4 dosimeter stock—part of a dosimeter batch held by the user.
3.1.9 measurement management system—set of interrelated or interacting elements necessary to achieve metrological confirmation
and continual control of measurement processes.
3.1.10 reference standard dosimetry system—dosimetry system, generally having the highest metrological quality available at a
given location or in a given organization, from which measurements made there are derived.
3.1.11 response—see dosimeter response.
3.1.12 routine dosimetry system—dosimetry system calibrated against a reference standard dosimetry system and used for routine
absorbed dose measurements, including dose mapping and process monitoring.
3.1.5 specific net absorbance (Δk)—net absorbance, ΔA , at a selected wavelength, λ, divided by the optical pathlength, d, through
λ
the dosimeter as follows:
Δk 5 ΔA /d (1)
λ
3.1.14 Definitions of other terms used in this practice that pertain to radiation measurement and dosimetry may be found in ASTM
Terminology E170. Definitions in E170 are compatible with ICRU Report 85a; that document, therefore, may be used as an
alternative reference.
3.2 Definitions of other terms used in this practice that pertain to radiation measurement and dosimetry may be found in
ISO/ASTM Practice 52628. Other terms that pertain to radiation measurement and dosimetry may be found in ASTM Terminology
E3083 and ISO Terminology 12749-4. Where appropriate, definitions used in these standards have been derived from, and are
consistent with definitions in ICRU Report 85a, and general metrological definitions given in the VIM.
4. Significance and useUse
4.1 The CTA dosimetry system provides a means for measuring absorbed dose based on a change in optical absorbance in the CTA
dosimeter following exposure to ionizing radiation (2, 3-2-10).
4.2 CTA dosimetry systems are commonly used in industrial radiation processing, for example in the modification of polymers
and sterilization of health care products.
4.3 CTA dosimeter film is can be particularly useful in absorbed dose mapping because it is available in a strip format and if reel
of 100 m whereby the user can cut any length of strip for use. When the CTA film is measured using a strip measurement device,
device with a narrow distance interval (for example, 2 mm), it can provide a dose map with higher resolution than using discrete
points.high resolution results in a linear direction.
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4.4 CTA is used to measure relative dose such as depth dose profiles in electron beam and reference phantom tests to assess
irradiator changes in gamma.
4.5 When CTA is used as a routine monitoring dosimeter the user must take into consideration the effects of the multiple influence
quantities that can affect the result and use appropriate techniques, as discussed herein, for characterizing and mitigating such
influences and understanding their contribution to measurement uncertainty. Without such effort the dosimetry system may not
meet the user’s requirements for dosimetric release of some types of products (for example, health care products).
5. Overview
5.1 CTA dosimeters are manufactured by casting cellulose triacetate with a plasticizer, triphenylphosphate, and solvents, for
example, a methylene chloride–methanol mixture (2, 7).
5.2 The commercially available dosimeter film is in the format of 8 mm width and 100 m length rolled on a spool, which is
described in the informative annex.
5.3 Ionizing radiation induces chemical reactions in CTA and the plasticizer, which create or enhance optical absorption bands in
the ultraviolet regions of the electromagnetic spectrum. Optical absorbance at appropriate wavelengths within these radiation-
induced absorption bands is quantitatively related to the absorbed dose. ICRU Report 80 provides information on the scientific
basis and historical development of the CTA dosimetry systems in current use.
5.4 The difference between the specific net absorbance of un-irradiated and irradiated CTA dosimeter depends significantly on the
analysis wavelength used to make the absorbance measurement. Typically, the manufacturer recommends the analysis wavelength
that optimizes sensitivity and post-irradiation stability. The analysis wavelengths recommended for some commonly used systems
are given in Table A1.1.
5.4.1 The user’s choice of calibration method, analysis wavelength, spectral bandwidth, dose range of utilization, and usage
procedures, including allowed ranges of influence quantity conditions, shall be documented.
6. Influence quantities
6.1 Factors other than absorbed dose which influence the dosimeter response are referred to as influence quantities. These
influence quantities include those related to the dosimeter before, during, and after irradiation and those related to the dosimeter
response measurements (see ASTMISO/ASTM Guide E270152701). Influence quantities affecting dosimeter response are
discussed below.
6.2 Pre-Irradiation Conditions:
6.2.1 Dosimeter Conditioning and Packaging—The dosimeter may require conditioning and packaging, particularly for low dose
rate (gamma) irradiation. See 6.3.4.
NOTE 2—Conditioning CTA film and packaging pieces of it in environmentally impermeable pouches under controlled relative humidity conditions will
provide for the most consistent dosimeter response, however the film is often used with no packaging.response.
6.2.2 Time Since Manufacture—The pre-irradiation absorbance increases very slowly with time and depends on the access to air
(oxygen).presumably due to oxidation on the surface of the film (7, 11). The pre-irradiation absorbance of the outer layer(s) of a
roll of CTA film may, therefore, increase more than the inner layers; hence, it may be advisable to discard the outer layer(s) of the
film. Measure the pre-irradiation absorbance before using the dosimeter. Alternatively, compare the pre-irradiation absorbance to
the average value noted at the time of calibration to determine if there is any significant change that shouldshall be taken into
account.
NOTE 3—The pre-irradiation absorbance to be used in the calculation of specific net absorbance will either be the value as measured before irradiation
by the user, or a user-determined average pre-irradiation absorbance.value.
6.2.3 Temperature—Avoid exposure to temperatures outside the manufacturer’s recommended range to reduce the potential for
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adverse effects on dosimeter response.range. The effects of low or high temperatures on the product for short or long durations have
not been dutifully examined but the product is a chemical dosimeter and may have some inherent risks, as such. Therefore, store
the product under stable temperature conditions such as that of an office or laboratory upon receipt and for the duration of the CTA
film’s shelf life. Any impact of temperatures during shipping and storage on the product must be taken into account during
incoming stock receiving inspection (see Section 8) or the dosimeter calibration (see Section 9), or both.
6.2.4 Relative Humidity—There is no known effect on dosimeter response.It is good practice to store the film in a controlled
environment prior to use. Research on this topic generally used unspecified controlled storage conditions. Otherwise, the user must
characterize the effect of variable relative humidity storage conditions on the subsequent performance of the dosimeter.
6.2.5 Exposure to Light—The dosimeter is insensitive to visible light; UV and visible light from normal room lighting; however,
exposure to UV light may have an effect and should be characterized. Exposure to UV prior to irradiation may increase the
pre-irradiation absorbance of the film, and depends on the intensity of the UV direct sunlight results in an increase in absorbance
(7, 11).
6.3 Conditions During Irradiation:
6.3.1 Irradiation Temperature—The dosimeter response is affected by temperature, particularly at low dose rates, and this effect
shall be characterized directly correlated to temperature. The variation in dosimeter response from 20 °C to 40 °C is approximately
+5 % while the variation from 0 °C to 65 °C is greater than +20 % (127, 119-12, 9, 10). Calibration of the film under the conditions
of use is recommended to avoid creating a bias in the calibration function due to the irradiation temperature differences between
calibration and routine use. However, temperature variation over longer time intervals (months) will lead to a seasonal effect. The
amount of this effect is not fully understood and may vary with other influence quantities. Users shall account for this by including
a component of uncertainty for temperature variation during irradiation in their uncertainty budget or by re-calibration.
6.3.2 Absorbed-Dose Rate—The dosimeter response is affected by the absorbed-dose rate and this effect shall be characterized
rate. There is a large variation in response between low and high dose rates of irradiation over the entire absorbed dose range (4,
7, 8, 9, 13, 14-414, 7-9). The user must select a calibration method that accounts for this fact (see Section 9) and should include
a component of uncertainty for dose rate if the rate varies between calibration and routine use.
6.3.3 Dose Fractionation—The dosimeter response is affected by dose fractionation and shall be characterized given in fractions
(multiple, separate irradiations) and the effect is greater in high dose rate processes (14). The user shall characterize the impact
of fractionation on the accuracy of dose measurements or calibrate and use the dosimeter under specified fractionation conditions.
6.3.4 Relative Humidity—The dosimeter response is affected by relative humidity, humidity during irradiation, particularly at low
dose rates and relative humidity extremes. This effect shall be characterized extremes (124, 117, 49, 711, 912). The user may
choose to control relative humidity during calibration and use by sealing the CTA film in impermeable packaging to mitigate this
effect. The user shall characterize the effect and account for it as a component of measurement uncertainty.
6.3.5 Exposure to Light—The dosimeter is insensitive to visible light, however, exposure to UV light may have an effect and
should be characterized. Exposure to UVnot affected by exposure to normal room lighting. Refer to 6.2.5 during irradiation may
increase the optical absorbance of the film, and likely depends on the intensity of the UV for additional information (7, 11).
6.3.6 Radiation Energy—There is no known effect on dosimeter response, however,response. However, the irradiation of 125
micron thick CTA film using electron energies below 300 keV can result in a dose gradient throughwithin the film. Refer to
ISO/ASTM 51818 for more details on dosimetry considerations when using <300 keV electrons.
6.4 Post-Irradiation Conditions:
6.4.1 Time—The dosimeter response varies with the time interval between radiation exposure and dosimeter measurement (4, 7,
10, 11, 12, 14, 11, 4, 10). This effect shall be characterized and the measurement After high dose rate irradiation such as electron
beam the absorbance might decrease 10 % or more during the first 20 min after irradiation and then increase slowly 3-5 % over
the next 3 h. See Fig. A2.1 and Fig. A2.2 in Annex A2time standardized. The absorbance increases approximately 6 % or more
over 10 days of elapsed time after irradiation with less than 1 % contribution in the last 5 days. See Fig. A2.3 in Annex A2. After
low dose rate irradiation using sources such as gamma or X-ray, the absorbance changes more slowly, increasing approximately
2 % after 2 h elapsed time. See Fig. A2.5 in Annex A2 (7, 11).
6.4.1.1 A procedure shall be established to control the allowable time interval between irradiation and measurement; for example,
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a desired measurement time after irradiation (for example, 2 h) with some prescribed allowance for variation (for example, 615
min). The uncertainty of the measurement of absorbed dose due to the user’s allowance for variation in time after irradiation shall
be determined and included in the user’s measurement uncertainty budget (see ISO/ASTM 51707 for details on uncertainty of
measurement).
NOTE 3—The absorbance first decreases and then slowly increases with storage time longer than fifteen minutes after high dose-rate electron beam
irradiation. The dosimeter response will become more stable about two hours after irradiation. Therefore, it is recommended that the absorbance of the
dosimeter be measured at a constant time period, for example, two hours after irradiation (11, 4, 7).
6.4.2 Temperature—The temperature of CTA film storage storage temperature after irradiation does have an effect and shall be
characterized. The user may need to control the post-irradiation storageat various points over the time interval after electron beam
irradiation. See Fig. A2.2 temperature withinand Fig. A2.4 ain Annex A2defined range (7, 9, 11). After irradiation, store the film
in a stable environment.
6.4.3 Conditioning Treatment—No advantageous post-irradiation treatment has been found is available or recommended (4).
6.4.4 Relative Humidity—Humidity (RH)—The rate of change of the post-irradiation absorbance may be is affected by relative
humidity and shall be characterized. The user may need to control the post-irradiation storage relative humidity within a defined
range but the effect is generally less than 1 % in the first 4 h (127, 119, 711, 912). After irradiation, store the film in a stable
environment.
6.4.5 Exposure to Light—The dosimeter is insensitive to visible light, however, If the film is exposed to UV light after the
irradiation (such
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