EN ISO 4037-2:2021

SLOVENSKI STANDARD
01-april-2021
Radiološka zaščita - Referenčno sevanje z rentgenskimi in gama žarki za
kalibracijo dozimetrov in merilnikov doze sevanja ter za ugotavljanje njihovega
odzivanja kot funkcije fotonske energije - 2. del: Dozimetrija za zaščito pred
sevanjem v energijskem območju od 8 keV do 1,3 MeV in od 4 MeV do 9 MeV (ISO
4037-2:2019)
Radiological protection - X and gamma reference radiation for calibrating dosemeters
and doserate meters and for determining their response as a function of photon energy -
Part 2: Dosimetry for radiation protection over the energy ranges from 8 keV to 1,3 MeV
and 4 MeV to 9 MeV (ISO 4037-2:2019)
Strahlenschutz - Röntgen- und Gamma-Referenzstrahlungsfelder zur Kalibrierung von
Dosimetern und Dosisleistungsmessgeräten und zur Bestimmung ihres
Ansprechvermögens als Funktion der Photonenenergie - Teil 2: Strahlenschutz-
Dosimetrie in den Energiebereichen 8 keV bis 1,3 MeV und 4 MeV bis 9 MeV (ISO 4037-
2:2019)
Radioprotection - Rayonnements X et gamma de référence pour l'étalonnage des
dosimètres et des débitmètres, et pour la détermination de leur réponse en fonction de
l'énergie des photons - Partie 2: Dosimétrie pour la radioprotection dans les gammes
d'énergie de 8 keV à 1,3 MeV et de 4 MeV à 9 MeV (ISO 4037-2:2019)
Ta slovenski standard je istoveten z: EN ISO 4037-2:2021
ICS:
13.280 Varstvo pred sevanjem Radiation protection
17.240 Merjenje sevanja Radiation measurements
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 4037-2
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2021
EUROPÄISCHE NORM
ICS 17.240
English Version
Radiological protection - X and gamma reference radiation
for calibrating dosemeters and doserate meters and for
determining their response as a function of photon energy
- Part 2: Dosimetry for radiation protection over the
energy ranges from 8 keV to 1,3 MeV and 4 MeV to 9 MeV
(ISO 4037-2:2019)
Radioprotection - Rayonnements X et gamma de Strahlenschutz - Röntgen- und Gamma-
référence pour l'étalonnage des dosimètres et des Referenzstrahlungsfelder zur Kalibrierung von
débitmètres, et pour la détermination de leur réponse Dosimetern und Dosisleistungsmessgeräten und zur
en fonction de l'énergie des photons - Partie 2: Bestimmung ihres Ansprechvermögens als Funktion
Dosimétrie pour la radioprotection dans les gammes der Photonenenergie - Teil 2: Strahlenschutz-
d'énergie de 8 keV à 1,3 MeV et de 4 MeV à 9 MeV (ISO Dosimetrie in den Energiebereichen 8 keV bis 1,3 MeV
4037-2:2019) und 4 MeV bis 9 MeV (ISO 4037-2:2019)
This European Standard was approved by CEN on 18 January 2021.

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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 4037-2:2021 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
The text of ISO 4037-2:2019 has been prepared by Technical Committee ISO/TC 85 "Nuclear energy,
nuclear technologies, and radiological protection” of the International Organization for Standardization
(ISO) and has been taken over as EN ISO 4037-2:2021 by Technical Committee CEN/TC 430 “Nuclear
energy, nuclear technologies, and radiological protection” the secretariat of which is held by AFNOR.
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 August 2021, and conflicting national standards shall
be withdrawn at the latest by August 2021.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 4037-2:2019 has been approved by CEN as EN ISO 4037-2:2021 without any
modification.
INTERNATIONAL ISO
STANDARD 4037-2
Second edition
2019-01
Corrected version
2019-03
Radiological protection — X and
gamma reference radiation for
calibrating dosemeters and doserate
meters and for determining their
response as a function of photon
energy —
Part 2:
Dosimetry for radiation protection
over the energy ranges from 8 keV to
1,3 MeV and 4 MeV to 9 MeV
Radioprotection — Rayonnements X et gamma de référence
pour l'étalonnage des dosimètres et des débitmètres, et pour la
détermination de leur réponse en fonction de l'énergie des photons —
Partie 2: Dosimétrie pour la radioprotection dans les gammes
d'énergie de 8 keV à 1,3 MeV et de 4 MeV à 9 MeV
Reference number
ISO 4037-2:2019(E)
©
ISO 2019
ISO 4037-2:2019(E)
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

ISO 4037-2:2019(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Standard instrument . 3
4.1 General . 3
4.2 Calibration of the standard instrument . 3
4.3 Energy dependence of the response of the standard instrument . 3
5 Conversion from the measured quantity air kerma, K , to the required phantom
a
related measuring quantity . 4
5.1 General . 4
5.2 Determination of conversion coefficients . 6
5.2.1 General. 6
5.2.2 Calculation of conversion coefficients from spectral fluence . 6
5.3 Validation of reference fields and of listed conversion coefficients using dosimetry. 7
6 Direct calibration of the reference field in terms of the required phantom related
measuring quantity . 8
7 Measurement procedures applicable to ionization chambers . 8
7.1 Geometrical conditions . 8
7.2 Chamber support and stem scatter . 8
7.3 Location and orientation of the standard chamber . 8
7.4 Measurement corrections . 8
7.4.1 General. 8
7.4.2 Corrections for air temperature, pressure and humidity variation from
reference calibration conditions . 9
7.4.3 Corrections for radiation-induced leakage, including ambient radiation . 9
7.4.4 Incomplete ion collection .10
7.4.5 Beam non-uniformity .10
8 Additional procedures and precautions specific to gamma radiation dosimetry
using radionuclide sources .10
8.1 Use of certified source output .10
8.2 Use of electron equilibrium caps .10
8.3 Radioactive source decay .10
8.4 Radionuclide impurities .10
8.5 Interpolation between calibration positions .10
9 Additional procedures and precautions specific to X-radiation dosimetry .11
9.1 Variation of X-radiation output .11
9.2 Monitor .11
9.3 Adjustment of air kerma rate .11
10 Dosimetry of reference radiation at photon energies between 4 MeV and 9 MeV .12
10.1 Dosimetric quantities .12
10.2 Measurement of the dosimetric quantities .12
10.2.1 General.12
10.2.2 Air kerma (rate) .13
10.2.3 Phantom related operational quantities H*(10), H (10), H'(3) and H (3) .13
p p
10.3 Measurement geometry .13
10.4 Monitor .13
10.5 Determination of air kerma (rate) free-in-air .14
10.5.1 General.14
ISO 4037-2:2019(E)
10.5.2 Measurement conditions .14
10.5.3 Direct measurement with an ionization chamber .14
10.5.4 Determination of air kerma (rate) from photon fluence (rate) .17
11 Uncertainty of measurement .18
11.1 General .18
11.2 Components of uncertainty .18
11.2.1 General.18
11.2.2 Uncertainties in the calibration of a secondary standard .18
11.2.3 Uncertainties in the measurements of the reference radiation due to the
standard instrument and its use .19
11.3 Statement of uncertainty .19
Annex A (normative) Technical details of the instruments and their operation .20
Annex B (informative) Measurement of photon spectra .23
Bibliography .26
iv © ISO 2019 – All rights reserved

ISO 4037-2:2019(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 85, Nuclear energy, nuclear technologies
and radiological protection, Subcommittee SC 2, Radiological protection.
This second edition cancels and replaces the first edition (ISO 4037-2:1997), which has been technically
revised.
A list of all the parts in the ISO 4037 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
This corrected version of ISO 4037-2:2019 incorporates the following corrections:
— In 10.5.2.2, the subscripts to the values have been reapplied;
— In Table 5, the headers in columns 4 and 5 have been reinserted.
ISO 4037-2:2019(E)
Introduction
The maintenance release of this document incorporates the improvements to high voltage generators
from 1996 to 2017 (e.g., the use of high frequency switching supplies providing nearly constant
potential), and the spectral measurements at irradiation facilities equipped with such generators
[1]
(e.g., the catalogue of X-ray spectra by Ankerhold ). It also incorporates all published information
with the aim to adjust the requirements for the technical parameters of the reference fields to the
targeted overall uncertainty of about 6 % to 10 % for the phantom related operational quantities of
[2]
the International Commission on Radiation Units and Measurements (ICRU) . It does not change the
general concept of the existing ISO 4037.
ISO 4037, focusing on photon reference radiation fields, is divided into four parts. ISO 4037-1 gives the
methods of production and characterization of reference radiation fields in terms of the quantities
spectral photon fluence and air kerma free-in-air. This document describes the dosimetry of the
reference radiation qualities in terms of air kerma and in terms of the phantom related operational
[2]
quantities of the International Commission on Radiation Units and Measurements (ICRU) . ISO 4037-3
describes the methods for calibrating and determining the response of dosemeters and doserate
[2]
meters in terms of the phantom related operational quantities of the ICRU . ISO 4037-4 gives special
considerations and additional requirements for calibration of area and personal dosemeters in low
energy X reference radiation fields, which are reference fields with generating potential lower or equal
to 30 kV.
In this document, two methods are given to determine the phantom related operational quantities.
Both methods need a reference field according to ISO 4037-1. The first method requires the dosimetry
with respect to air kerma free-in-air and after that the selected operational quantity is derived by the
application of a conversion coefficient that relates the air kerma free-in-air to the selected operational
quantity. For matched reference fields, this conversion coefficient is taken from ISO 4037-3, for
characterized reference fields the conversion coefficient is determined using spectrometry. The second
method, applicable for characterized reference fields, requires the direct dosimetry with respect to the
selected operational quantity. For all calibrations secondary standard instruments are required, which
have a nearly constant energy dependence of the response to the selected quantity.
The general procedures described in ISO 29661 are used as far as possible in this document. Also, the
used symbols are in line with ISO 29661.
vi © ISO 2019 – All rights reserved

INTERNATIONAL STANDARD ISO 4037-2:2019(E)
Radiological protection — X and gamma reference
radiation for calibrating dosemeters and doserate meters
and for determining their response as a function of photon
energy —
Part 2:
Dosimetry for radiation protection over the energy ranges
from 8 keV to 1,3 MeV and 4 MeV to 9 MeV
1 Scope
This document specifies the procedures for the dosimetry of X and gamma reference radiation for the
calibration of radiation protection instruments over the energy range from approximately 8 keV to
1,3 MeV and from 4 MeV to 9 MeV and for air kerma rates above 1 µGy/h. The considered measuring
quantities are the air kerma free-in-air, K , and the phantom related operational quantities of the
a
[2]
International Commission on Radiation Units and Measurements (ICRU) , H*(10), H (10), H'(3), H (3),
p p
H'(0,07) and H (0,07), together with the respective dose rates. The methods of production are given in
p
ISO 4037-1.
This document can also be used for the radiation qualities specified in ISO 4037-1:2019, Annexes A, B
and C, but this does not mean that a calibration certificate for radiation qualities described in these
annexes is in conformity with the requirements of ISO 4037.
The requirements and methods given in this document are targeted at an overall uncertainty (k = 2)
of the dose(rate) of about 6 % to 10 % for the phantom related operational quantities in the reference
fields. To achieve this, two production methods of the reference fields are proposed in ISO 4037-1.
The first is to produce “matched reference fields”, which follow the requirements so closely that
recommended conversion coefficients can be used. The existence of only a small difference in the
spectral distribution of the “matched reference field” compared to the nominal reference field is
validated by procedures, which are given and described in detail in this document. For matched
reference radiation fields, recommended conversion coefficients are given in ISO 4037-3 only for
specified distances between source and dosemeter, e.g., 1,0 m and 2,5 m. For other distances, the user
has to decide if these conversion coefficients can be used.
The second method is to produce “characterized reference fields”. Either this is done by determining the
conversion coefficients using spectrometry, or the required value is measured directly using secondary
standard dosimeters. This method applies to any radiation quality, for any measuring quantity and,
if applicable, for any phantom and angle of radiation incidence. The conversion coefficients can be
determined for any distance, provided the air kerma rate is not below 1 µGy/h.
Both methods require charged particle equilibrium for the reference field. However this is not always
established in the workplace field for which the dosemeter shall be calibrated. This is especially true
at photon energies without inherent charged particle equilibrium at the reference depth d, which
depends on the actual combination of energy and reference depth d. Electrons of energies above 65 keV,
0,75 MeV and 2,1 MeV can just penetrate 0,07 mm, 3 mm and 10 mm of ICRU tissue, respectively, and
the radiation qualities with photon energies above these values are considered as radiation qualities
without inherent charged particle equilibrium for the quantities defined at these depths.
This document is not applicable for the dosimetry of pulsed reference fields.
ISO 4037-2:2019(E)
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 4037-1, Radiological protection — X and gamma reference radiation for calibrating dosemeters and
doserate meters and for determining their response as a function of photon energy — Part 1: Radiation
characteristics and production methods
ISO 4037-3, Radiological protection — X and gamma reference radiation for calibrating dosemeters and
doserate meters and for determining their response as a function of photon energy — Part 3: Calibration of
area and personal dosemeters and the measurement of their response as a function of energy and angle of
incidence
ISO 4037-4, Radiological protection — X and gamma reference radiation for calibrating dosemeters and
doserate meters and for determining their response as a function of photon energy — Part 4: Calibration of
area and personal dosemeters in low energy X reference radiation fields
ISO 29661, Reference radiation fields for radiation protection — Definitions and fundamental concepts
ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated
terms (VIM)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4037-1, ISO 29661,
ISO 80000-10, ISO/IEC Guide 99, and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
ionization chamber
ionization detector consisting of a chamber filled with a suitable gas, in which an electric field,
insufficient to induce gas multiplication, is provided for the collection at the electrodes of charges
associated with the ions and the electrons produced in the sensitive volume of the detector by the
[3]
ionizing radiation
Note 1 to entry: The ionization chamber includes the sensitive volume, the collecting and polarizing electrodes,
the guard electrode, if any, the chamber wall, the parts of the insulator adjacent to the sensitive volume and any
necessary caps to ensure electron equilibrium.
3.2
ionization chamber assembly
ionization chamber (3.1) and all other parts to which the chamber is permanently attached, except the
measuring assembly
Note 1 to entry: For a cable-connected chamber, it includes the stem, the electrical fitting and any permanently
attached cable or pre-amplifier. For a thin-window chamber, it includes any block of material in which the
ionization chamber is permanently embedded.
2 © ISO 2019 – All rights reserved

ISO 4037-2:2019(E)
3.3
leakage current
total detector current flowing at the operating bias in the absence of radiation
[SOURCE: International Electrotechnical Vocabulary]
3.4
measuring assembly
device for measuring the current or charge from the ionization chamber (3.1) and converting it into a
form suitable for display, control or storage
3.5
pulse height spectrum
distribution of number of pulses N with respect to charge Q generated in the detector, dN/dQ
3.6
unfolding
determination of the spectral fluence Φ from the (measured) pulse height spectrum (3.5), dN/dQ
Ε
3.7
zero shift
sudden change in the scale reading of either polarity of a measuring assembly (3.4) when the setting
control is changed from the "zero" mode to the "measure" mode, with the input connected to an
ionization chamber (3.1) in the absence of ionizing radiation other than ambient radiation
4 Standard instrument
4.1 General
The instrument to be used for the measurement of the reference radiation shall be a primary or
secondary standard or other appropriate instrument, whose calibration is traceable to a primary
standard. Generally, this comprises an ionization chamber assembly and a measuring assembly. The
instrument shall be operated as described in Annex A and be specific for the dosimetric quantity to be
measured. Therefore, several different types of instruments for the measuring quantities, K , H*(10),
a
H (10), H'(3), H (3), H'(0,07) and H (0,07) and the appropriate phantoms are required for characterized
p p p
reference fields. This means, for the example of a H (10) chamber, that it is put into the reference field
p
without any further phantom and the indication is the H (10) value at the reference point of the H (10)
p p
chamber. If conversion coefficients from the measured quantity to the required quantity according to
Clause 5 are used, then only one type of instrument for the measuring quantity air kerma free-in-air,
K , is routinely required. For matched reference fields a second instrument, preferably for the definition
a
depth 10 mm, is required for the verification.
4.2 Calibration of the standard instrument
The standard instrument shall be either a primary standard or a secondary standard traceably
calibrated for the ranges of energies, air kerma rates and quantity values for which it is intended to be
used. The expanded overall uncertainty (k = 2) of the calibration factor(s) of this instrument shall not
exceed 4 % in the energy range from above 30 keV to 1,5 MeV and shall not exceed 6 % in the energy
range above and below this energy range.
4.3 Energy dependence of the response of the standard instrument
The standard instrument shall fulfil two requirements. First, the ratio of the maximum value to the
minimum value of the response of the instrument, R /R , shall not exceed the limit values, (R /
max min max
R ) , given in Table 1 over the energy range for which the standard instrument is to be used. This is
min lim
valid for the mean energy values, E Φ , see ISO 4037-1:2019, 3.8. The requirements depend on the
()
measuring quantity, as given in Table 1. Second, if determined for two different radiation qualities of a
ISO 4037-2:2019(E)
given series, which are adjacent to each other with respect to mean energy, this response ratio shall not
exceed 1 + 0,4 × [(R /R ) − 1]. If both requirements cannot be met for the whole range, at least
max min lim
the second requirement shall be met.
Table 1 — Requirements on energy dependence of the response of standard instrument
Range of mean
Upper limit of the response ratio, [R /R ] , within the range of mean
max min lim
energy for the measuring quantity
energy, E Φ
()
keV K H'(0,07), H (0,07) H'(3), H (3) H*(10), H (10)
a p p p
8 to ≤30 1,2 1,2 1,3 1,4
>30 1,1 1,1 1,15 1,2
The calibration factor and the correction factors for the standard instrument refer to specific spectra.
If the energy dependence of the response of the standard instrument cannot be neglected and if the
spectral distribution of the radiation for which the dosimetry shall be performed differs significantly
from that used for the calibration, a correction factor may have to be applied. This may be the case if
the radiation series for the calibration of the standard instrument and the radiation series for which
the dosimetry shall be performed are different. The aim shall be that the expanded overall uncertainty
(k = 2) of the calibration factor used shall not exceed 5 %.
Whenever practicable, the reference radiations used to calibrate the secondary standard instrument
should be the same as those used for the calibration of radiation protection instruments.
5 Conversion from the measured quantity air kerma, K , to the required
a
phantom related measuring quantity
5.1 General
If only a standard instrument for the air kerma, K , free-in-air is used for dosimetric measurements,
a
then for all the other phantom related operational quantities H*(10), H (10), H'(3), H (3), H'(0,07) and
p p
H (0,07) appropriate conversion coefficients shall be applied to the measured air kerma values. These
p
conversion coefficients shall, in principle, be determined by spectrometry for any reference field, any
measuring quantity and, if applicable, for any phantom and angle of radiation incidence.
The air kerma is given by the sum of the air collision kerma, K , and the air radiative kerma,
a,coll
K : K = K +K The air collision kerma, K , is related to the air kerma by the equation
a,rad a a,coll a,rad a,coll
K = K · (1 − g ), where g is the fraction of the energy of the electrons liberated by photons that
a,coll a a a
is lost by radiative processes (bremsstrahlung, fluorescence radiation or annihilation radiation
of positrons). Values of (1 − g ) for mono-energetic radiation are those from Seltzer (calculated as
a
described in Reference [5]) and are given in the upper part of Table 2. In the lower part of that Table 2,
values for the reference radiations S-Cs, S-Co, R-C and R-F are given. Values are interpolated for S-Cs,
[8] [9]
taken from Roos and Grosswendt for S-Co and from PTB-Dos-32 for R-C and R-F. For water or air
and for energies lower than 1,3 MeV, g is less than 0,003 and below 1,5 MeV the values of (1 − g ) can be
a a
[35]
considered to be unity, see ICRU Report 47 , A.2.1.
The air collision kerma is the part that leads to the production of electrons that dissipate their energy
as ionization in or near the electron tracks in the medium – and is consequently obtained in Monte
Carlo calculations as the energy deposited. The interpretation that was made in ISO 29661 was that the
original conversion coefficients which were derived from ICRU Report 57 actually refer to air collision
kerma. This approach is adopted in ISO 4037 in the following way: For energies up to and including that
of the S-Co reference field the original values are used, as the application of the factor (1 − g ) does not
a
change numerical values truncated to three significant digits. Conversion coefficients for the R-C and
R-F given in ISO 4037-3 differ from those given in ICRU and the previous edition of ISO 4037-3:1999 by
the factor (1 − g ) = 0,987 and (1 − g ) = 0,978, respectively.
a a
4 © ISO 2019 – All rights reserved

ISO 4037-2:2019(E)
Table 2 — Typical values for the bremsstrahlung correction
Photon energy Recommended value of
MeV
1− g
a
0,2 1,000
0,3 0,999
0,4 0,999
0,6 0,999
0,8 0,998
1,0 0,997
1,25 0,997
1,5 0,996
2,0 0,994
3,0 0,991
4,0 0,987
5,0 0,983
6,0 0,979
8,0 0,971
10,0 0,963
a
S-Cs 0,998
b
S-Co 0,997
c
R-C 0,987
c
R-F 0,978
a
Value obtained by interpolation to 0,662 MeV.
b [8]
Value taken from Roos and Grosswendt .
c [9]
Values taken from PTB-Dos-32 .
For the highest level of dissemination of the phantom related quantities, e.g., by National Metrology
Institutes, spectrometry is required for X-ray qualities with generating potential of and below 60 kV
and for high energy photon fields with energies above that of the S-Co reference field. The air kerma,
K , shall be determined by a primary or at least directly traceable standard and spectrometry of the
a
reference field shall be performed, e.g. according to Annex B, both at the point of test.
For secondary standard laboratories for the realization of the phantom related quantities and for
matched reference radiation fields, recommended values of conversion coefficients can be used, which
are given in ISO 4037-3. These coefficients are determined at an X-ray unit with a constant potential
high voltage generator deemed to be representative of the reference radiations specified in ISO 4037-1.
The phantom related operational quantities, here indicated by the symbol H, are then calculated as
given by Formula (1).
Hh=⋅K (1)
K a
ISO 4037-2:2019(E)
where
H is one of the phantom related operational quantities H*(10), H (10), H'(3), H (3), H'(0,07) or
p p
H (0,07);
p
h is the conversion coefficient for the quantity under consideration; and
K
K is the air kerma determined according to this document.
a
5.2 Determination of conversion coefficients
5.2.1 General
The determination of the appropriate conversion coefficients is based on spectrometry. A suitable
spectrometer is used to measure the spectrum of the radiation quality under consideration. From this
spectrum, the exact conversion coefficient can be calculated and applied to the measured value of the
air kerma, K , free-in-air. This calculation uses conversion coefficients pertaining to mono-energetic
a
[4]
radiation given by both ICRP and ICRU from air kerma free-in-air to the phantom related quantity
under consideration. Such spectrometry and the calculation of the exact conversion coefficient shall,
in principle, be performed for the X-ray unit used to produce the reference radiation fields and for
any required measuring quantity. A possible method to avoid the complex spectrometry is the use of
recommended conversion coefficients listed in ISO 4037-3 for matched reference radiation fields. This
is described in Clause 6.
5.2.2 Calculation of conversion coefficients from spectral fluence
The spectral fluence of the reference field is determined for every radiation quality, U, with a
spectrometer. Details of the spectrometer and its use can be found in Annex B. The spectral fluence
is then converted to a spectral air kerma by multiplying the spectral fluence with the conversion
coefficients pertaining to mono-energetic radiation. For the conversion coefficients pertaining to mono-
[4]
energetic radiation see, e.g., ICRU Report 57 or use Φ·E·(µ /ρ) as value of the conversion coefficient.
tr
[10]
Values for (µ /ρ) can be calculated from the µ values for air from ICRU Report 90 and the (1 – g)
tr en
values from Seltzer by using µ = µ /(1 – g). For (1 – g) values see Table 2. The integral over this
tr en
distribution of the spectral air kerma gives the air kerma, K , of the reference field with the radiation
a
quality, U. The distribution itself is then multiplied with the conversion coefficients pertaining to mono-
energetic radiation from air kerma to the respective measurand, H*(10), H (10), H'(3), H (3), H'(0,07)
p p
[4]
and H (0,07), (see ICRP and ICRU and ISO 4037-3), to get the conversion coefficient for the spectrum
p
considered. For H (10), H'(3), H (3), H'(0,07) and H (0,07), the conversion coefficients pertaining to
p p p
mono-energetic radiation depend also on the angle α between the reference direction of the dosemeter
and the direction of radiation incidence of the unidirectional reference field and for H (10), H (3) and
p p
H (0,07) on the type of the phantom. These spectral distributions for the respective phantom related
p
quantities are then integrated to get the value of the respective measurand. The value of this measurand
divided by the value of the air kerma, K , and multiplied, where necessary, by the factor (1 – g ) gives
a a
the conversion coefficients, h* (10, U), h (10, U, α) , h' (3; U, α), h (3, U, α) , h' (0,07; U, α) and
K pK ph K pK ph K
h (0,07; U, α) from the air kerma free-in-air to the respective phantom related qualities.
pK ph
The notation used for the presentation of conversion coefficients is explained in the following: The
example of h' (0,07; U, α) refers to the conversion coefficient from air kerma K to directional dose
K a
equivalent in a depth of 0,07 mm for the reference field of the radiation quality, U, and angle of
radiation incidence, α. The prime is replaced by an asterisk for ambient dose equivalent or by the letter
p as a subscript for personal dose equivalent. For personal dose equivalent, the type of the phantom
is indicated by a subscript at the end. The subscripts rod, pill, cyl and slab stand for rod phantom,
pillar phantom, cylinder phantom and slab phantom, respectively. Recommended values of all these
conversion coefficients valid for matched reference fields are given in ISO 4037-3:2019, Clauses 6 and 8.
6 © ISO 2019 – All rights reserved
...