SIST ISO 9236-3:2011
Photography - Sensitometry of screen/film systems for medical radiography - Part 3: Determination of sensitometric curve shape, speed and average gradient for mammography
Photography - Sensitometry of screen/film systems for medical radiography - Part 3: Determination of sensitometric curve shape, speed and average gradient for mammography
Specifies methods for determination of the sensitometric curve shape, average gradient and speed of a single sample of a screen/film/filmholder/processing system in mammograhpy.
Photographie - Sensitométrie des ensembles film/écran pour la radiographie médicale - Partie 3: Détermination de la forme de la courbe sensitométrique, de la sensibilité et du contraste moyen pour la mammographie
Fotografija - Senzitometrija zaslonsko-filmskih sistemov za medicinsko radiografijo - 3. del: Določanje oblike senzitometrične krivulje, splošne občutljivosti in povprečnega gradienta za mamografijo
Določa metode za določanje oblike senzitometrične krivulje, povprečnega gradienta in občutljivosti enojnega vzorca sistema zaslona/filma/držala za film/procesiranja pri mamografiji.
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INTERNATIONAL ISO
STANDARD 9236-3
First edition
1999-02-01
Photography — Sensitometry of screen/film
systems for medical radiography —
Part 3:
Determination of sensitometric curve shape,
speed and average gradient for mammography
Photographie — Sensitométrie des ensembles film/écran pour la
radiographie médicale —
Partie 3: Détermination de la forme de la courbe sensitométrique, de la
sensibilité et du contraste moyen pour la mammographie
A
Reference number
ISO 9236-3:1999(E)
---------------------- Page: 1 ----------------------
ISO 9236-3:1999(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.
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.
International Standard ISO 9236-3 was prepared by Technical Committee
ISO/TC 42, Photography.
ISO 9236 consists of the following parts, under the general title
Photography — Sensitometry of screen/film systems for medical radio-
graphy:
— Part 1: Determination of sensitometric curve shape, speed and
average gradient
— Part 2: Determination of the modulation transfer function (MTF)
— Part 3: Determination of sensitometric curve shape, speed and
average gradient for mammography
Annexes A and B of this part of ISO 9236 are for information only.
© ISO 1999
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
ii
---------------------- Page: 2 ----------------------
©
ISO ISO 9236-3:1999(E)
Introduction
This part of ISO 9236 provides methods for determining the sensitometric
curve shape, the average gradient and the speed of radiographic screen/
film/filmholder/processing systems used in mammography.
The sensitometric curve, which is also needed for the determination of
other properties (as, for example, the modulation transfer function) is
measured under low-scatter conditions via intensity scale X-ray sensito-
metry, using a sensitometer which is mainly based on the photometric
inverse square law. For the determination of the sensitometric curve
shape, the irradiation of the screen/film/filmholder combination need be
measured only in relative units.
While the average gradient is determined from the sensitometric curve
shape, speed has to be measured in a separate way, since the exposure
conditions should simulate as closely as possible those which are used in
practice. Therefore, scattered radiation is included, accompanied by a
slight change of beam quality compared to the beam quality used for
intensity scale sensitometry. The clinical exposure is simulated by using
both an appropriate phantom and tube voltage. The screen/film/filmholder
combination is exposed behind the phantom. The exposure shall be
measured in absolute units (gray, Gy) in order to determine the speed.
Speed is generally dependent on X-ray energy, the amount of scattered
radiation and the exposure time. Therefore, some variation in speed values
may be expected under practical conditions. However, as the range of tube
voltages applied in screen/film mammography is small, this part of
ISO 9236 describes only one beam quality for speed measurement. The
measurement conditions described in this part of ISO 9236 provide values
for speed and average gradient which are representative of those found
under practical conditions.
iii
---------------------- Page: 3 ----------------------
©
INTERNATIONAL STANDARD ISO ISO 9236-3:1999(E)
Photography — Sensitometry of screen/film systems for medical
radiography —
Part 3:
Determination of sensitometric curve shape, speed and average
gradient for mammography
1 Scope
This part of ISO 9236 specifies methods for determination of the sensitometric curve shape, average gradient and
speed of a single sample of a screen/film/filmholder/processing system in mammography.
The filmholder may be any means which ensures close screen/film contact and prevents the film from being
exposed to ambient light. In particular, the filmholder may be a light-tight vacuum bag, as often used in the
laboratory, or a radiographic cassette as used in mammography.
NOTE — Hereafter, screen/film/filmholder combinations will be referred to as “combinations”, and will be referred to as
“systems” when the processing is included.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part of
ISO 9236. At the time of publication, the editions indicated were valid. All standards are subject to revision, and
parties to agreements based on this part of ISO 9236 are encouraged to investigate the possibility of applying the
most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid
International Standards.
ISO 5-2:1991, Photography — Density measurements — Part 2: Geometric conditions for transmission density.
ISO 5-3:1995, Photography — Density measurements — Part 3: Spectral conditions.
ISO 554:1976, Standard atmospheres for conditioning and/or testing — Specifications.
3 Definitions
For the purposes of this part of ISO 9236, the following definitions apply.
3.1 air kerma, K: Energy which is transferred by ionizing radiation (for instance X-rays) to air molecules divided
by the mass of air in that volume where the energy is released. The unit is the gray (Gy).
1
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©
ISO 9236-3:1999(E) ISO
3.2 sensitometric curve: Plot of the density of a processed photographic film as a function of the logarithm of
the exposure.
3.3 speed, S: Quantitative measure of the response of the screen/film system to radiant energy for the
specified conditions of exposure, processing, and density measurement.
3.4 average gradient, G : Slope of the straight line joining two specified points on a sensitometric curve.
3.5 net density D: Density of an exposed and processed film minus the density of an unexposed and
processed sample of that film.
4 General requirements
4.1 Storage and handling conditions
The films and screens shall be stored according to the manufacturers' recommendations. Before and during
exposures, the temperatures of the films and screens shall be maintained at (23 – 2) �C (see ISO 554) and the
moisture content of the film shall be such that it will be in equilibrium at a relative humidity of (50 – 20) %.
4.2 Safelights
To eliminate the possibility of safelight illumination affecting the sensitometric results, all films shall be kept in total
darkness during handling, exposure and processing.
4.3 X-ray equipment
For all tests described in this part of ISO 9236 a 6-pulse, 12-pulse, high frequency (multipulse), or constant-potential
generator shall be used.
For dosimetry, a measuring detector shall be used that is calibrated to measure air kerma for the beam quality
applied. The accuracy of readings shall be better than – 5 % for collimated beams without scatter, and better than
– 7 % for radiation measurements behind the phantom when scattered radiation is included.
NOTE — A spherical ionization chamber is recommended for measurements where scattered radiation is involved. The centre
of the spherical chamber is to be considered the reference point; the stem of the spherical chamber should point in a direction
opposite to the focal spot direction.
4.4 Processing
Screen/film systems including either manual or automatic processing may be tested in accordance with this part of
ISO 9236. Processing should be carried out in accordance with the film manufacturer's recommendations. Nothing
shall be construed to require the disclosure of proprietary information.
No processing specifications are described in this part of ISO 9236, in recognition of the wide range of chemicals
and equipment used. Speed and average gradient values provided by film manufacturers generally apply to the
system when the film is processed in accordance with their recommendations so that the photographic
characteristics specified for the process are produced. Processing information shall be provided by the film
manufacturer or others who quote speed and average gradient values and shall specify the processing chemicals,
times, temperatures, agitation, equipment and procedures used for each of the processing steps, and any additional
information required to obtain the sensitometric results described. The values for speed and average gradient
obtained using other processing procedures may differ significantly. The processing conditions selected by a person
using this part of ISO 9236 are, in any case, part of the system being tested. Different speeds for a particular film
may be achieved by varying the processes, but the user should be aware that other changes may accompany the
speed changes.
In order to minimize any effects due to latent-image instability or process variability, all film samples shall be
processed together, neither less than 30 min nor more than 4 h after exposure. Between exposure and processing,
2
---------------------- Page: 5 ----------------------
©
ISO ISO 9236-3:1999(E)
the temperature of the film shall be maintained at (23 – 2) �C, and its moisture content shall be such that the film will
be in equilibrium at a relative humidity of (50 – 20) %.
Since films are generally processed in practice a few minutes after exposure, the speed observed in practice may
differ from that determined by this part of ISO 9236 due to latent-image fading of some films. Therefore, the speed
measured with a time delay of 30 min to 4 h between exposure and processing shall be corrected to the value one
would obtain if the film were processed soon after exposure. For the purposes of this part of ISO 9236, a time delay
of 5,0 min is used for computing speed.
NOTES
1 The information about the necessary correction may easily be gained by exposing film strips in a light sensitometer and
varying the time between exposure and processing. In the case of double-emulsion films, care should be taken that both front
and back emulsions are exposed equally by the sensitometer.
2 Since the time required for the many individual exposures to obtain the sensitometric curve is comparatively long, a time
delay of at least 30 min between exposure and processing is prescribed. That time delay is considered to be sufficient to
minimize any differences in latent-image fading for the individual exposures.
The following processing information and accuracies shall be specified:
a) trade designations of all chemicals, if proprietary; otherwise, the formula;
b) temperature of the developer to within – 0,3 �C;
c) temperature of other solutions to within – 2 �C;
d) immersion times in the developer solution to within 3 %;
e) whether the developer is fresh or "seasoned" (if "seasoned", the type and amount of film used for seasoning),
the density of the processed film and the replenishment procedure;
f) agitation specifications, in terms of volume of solution recirculated or rate at which a gas is used;
g) drying temperature to within – 5 �C;
h) trade designation of processing equipment.
NOTE — The term "seasoned developer" means that the developer is no longer unused or fresh, but is already used and in a
"normal working condition".
4.5 Densitometry
ISO standard visual diffuse transmission density of the processed images shall be measured using a densitometer
complying with the geometric conditions specified in ISO 5-2 and spectral conditions specified in ISO 5-3. Readings
shall be made in a uniform area of the image. The densities, D, shall be measured with an accuracy of
ΔD/D = – 0,02 or ΔD = – 0,02, whichever is the greater.
5 Determination of sensitometric curve shape
In this part of ISO 9236, intensity scale sensitometry is described to determine curve shape. The intensity is
modified by a change of the distance between the radiation source and the combination. As a consequence of
secondary radiation sources in the beam, and due to beam attenuation by the air, the relationship between
exposure and distance does not exactly obey the inverse-square law. Therefore that relationship shall be calibrated.
3
---------------------- Page: 6 ----------------------
©
ISO 9236-3:1999(E) ISO
5.1 Beam qualities
For the determination of the sensitometric curve shape, either of the two beam qualities specified in table 1 may be
used. The beam qualities can be achieved by an iterative procedure of half-value layer (HVL) measurements using
the specified added filtration. The approximate X-ray tube voltages are recommended as starting values for this
procedure (see 7.2.2 and figure 4).
Table 1 — Beam qualities for the determination of the sensitometric curve shape
Beam quality Anode material Approximate X-ray Inherent filtration Added filtration Half value Layer
number tube voltage
1)
kV mm Mo mm Mo + mm Al mm Al
I Mo 28 0,03 0,00 2,1 0,63 ± 0,02
II W 28 0,03 0,03 2,1 0,63 ± 0,02
1) The half-value layer is chosen to approximate the clinical exit beam from the breast. It shall be placed behind the added filtration.
Inherent and added filtration may differ from the numbers given in table 1, under the condition that the sum of the
inherent filtration and the added filtration, known as total filtration, remains unchanged. For the total filtration, the
tolerances are – 0,005 mm for molybdenum filters and – 0,1 mm for aluminium filters. The aluminium and
molybdenum used as filter materials shall have a purity of at least 99,9 %.
5.2 Geometry for curve shape determination
The geometrical set-up of the measuring arrangement shall comply with figures 1 and 2. As a consequence of the
influence of air on beam quality, the distance between the focal spot of the tube and the plane of the mammographic
film shall not be greater than 3 m.
NOTE In practice, X-ray beams emerging from mammographic tubes are usually asymmetric insofar as they extend much
more to the anode side than to the cathode side. In the laboratory, this beam asymmetry can often be reduced by changing
diaphragming directly at the tube or by rotating the tube by several degrees. Symmetric X-ray beams, as shown in all the
figures except figure 3, are not a precondition for applying the methods described in this part of ISO 9236.
The diaphragm B1 and the added filter(s) shall be positioned near the radiation source. The diaphragms B1 and B2
and the added filter(s) shall be in a fixed relation to the radiation source. The diaphragm B3 and the
screen/film/filmholder combination or the measuring detector R2 shall be in a fixed relation at each distance from
the radiation source. The incident face of the diaphragm B3 shall be (100 – 5) mm in front of the plane of the
mammographic film. If it has been confirmed that scattered radiation from walls, equipment, etc. does not influence
the results, the diaphragm B3 may be omitted. To this end, the radiation aperture of the diaphragm B2 may be made
variable so that the beam remains tightly collimated as the distance is changed.
A diaphragm B4, whose shortest dimension shall be at least 5 mm, may be positioned directly in front of the
combination in order to limit the area of the film exposed.
The attenuating properties of the diaphragms shall be such that their transmission into shielded areas does not
contribute to the results of the measurements by more than 0,1 %. The radiation aperture of the diaphragm B1 shall
be large enough so that the penumbra of the radiation beam will be outside the sensitive volume of the monitoring
detector R1 and the radiation aperture of the diaphragm B2.
The radiation aperture of the diaphragm B2 shall be small enough that no part of the beam can pass outside the
diaphragm plate of the diaphragm B3 or B4, respectively. Collimation performed by the radiation aperture of the
diaphragm B3 shall be as narrow as possible but still permit the X-ray beam to cover the radiation aperture of the
diaphragm B4 or the sensitive volume of the measuring detector R2, respectively.
4
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©
ISO ISO 9236-3:1999(E)
A monitoring detector R1 may be placed inside the beam utilized to expose the combination, if it is suitably
transparent and free of structure, otherwise it shall be placed outside the beam. The precision of the monitoring
detector R1 shall be better than – 2 %.
An attenuating protective barrier shall be at least 450 mm beyond the last area involved in the measurement. The
space between the combination or the measuring detector R2 and the protective barrier shall contain nothing but
air.
5.3 Exposure
Each exposure of the combination shall be achieved in one uninterrupted irradiation. The irradiation time shall be in
the range of 0,5 s to 1,5 s and shall be kept constant for all exposures.
NOTE 1 With the use of intensifying screens, reciprocity law failure and the intermittency effect may occur. In order to avoid
the influence of these effects, a single irradiation with a constant irradiation time in the specified range of irradiation times is
required for each exposure.
The different values of air kerma shall be obtained preferably by varying the distance from the radiation source to
the plane of the mammographic film. It shall be verified that the HVL, according to table 1, remains within the
tolerance for all distances used. Additionally, the tube current may be varied. It shall be verified that the variation of
tube current does not change the beam quality. The maximum increments of log exposure shall not be greater
10
than 0,1.
Dimen
...
SLOVENSKI STANDARD
SIST ISO 9236-3:2011
01-julij-2011
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Photography - Sensitometry of screen/film systems for medical radiography - Part 3:
Determination of sensitometric curve shape, speed and average gradient for
mammography
Photographie - Sensitométrie des ensembles film/écran pour la radiographie médicale -
Partie 3: Détermination de la forme de la courbe sensitométrique, de la sensibilité et du
contraste moyen pour la mammographie
Ta slovenski standard je istoveten z: ISO 9236-3:1999
ICS:
37.040.25 Radiografski filmi Radiographic films
SIST ISO 9236-3:2011 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST ISO 9236-3:2011
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SIST ISO 9236-3:2011
INTERNATIONAL ISO
STANDARD 9236-3
First edition
1999-02-01
Photography — Sensitometry of screen/film
systems for medical radiography —
Part 3:
Determination of sensitometric curve shape,
speed and average gradient for mammography
Photographie — Sensitométrie des ensembles film/écran pour la
radiographie médicale —
Partie 3: Détermination de la forme de la courbe sensitométrique, de la
sensibilité et du contraste moyen pour la mammographie
A
Reference number
ISO 9236-3:1999(E)
---------------------- Page: 3 ----------------------
SIST ISO 9236-3:2011
ISO 9236-3:1999(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.
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.
International Standard ISO 9236-3 was prepared by Technical Committee
ISO/TC 42, Photography.
ISO 9236 consists of the following parts, under the general title
Photography — Sensitometry of screen/film systems for medical radio-
graphy:
— Part 1: Determination of sensitometric curve shape, speed and
average gradient
— Part 2: Determination of the modulation transfer function (MTF)
— Part 3: Determination of sensitometric curve shape, speed and
average gradient for mammography
Annexes A and B of this part of ISO 9236 are for information only.
© ISO 1999
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
ii
---------------------- Page: 4 ----------------------
SIST ISO 9236-3:2011
©
ISO ISO 9236-3:1999(E)
Introduction
This part of ISO 9236 provides methods for determining the sensitometric
curve shape, the average gradient and the speed of radiographic screen/
film/filmholder/processing systems used in mammography.
The sensitometric curve, which is also needed for the determination of
other properties (as, for example, the modulation transfer function) is
measured under low-scatter conditions via intensity scale X-ray sensito-
metry, using a sensitometer which is mainly based on the photometric
inverse square law. For the determination of the sensitometric curve
shape, the irradiation of the screen/film/filmholder combination need be
measured only in relative units.
While the average gradient is determined from the sensitometric curve
shape, speed has to be measured in a separate way, since the exposure
conditions should simulate as closely as possible those which are used in
practice. Therefore, scattered radiation is included, accompanied by a
slight change of beam quality compared to the beam quality used for
intensity scale sensitometry. The clinical exposure is simulated by using
both an appropriate phantom and tube voltage. The screen/film/filmholder
combination is exposed behind the phantom. The exposure shall be
measured in absolute units (gray, Gy) in order to determine the speed.
Speed is generally dependent on X-ray energy, the amount of scattered
radiation and the exposure time. Therefore, some variation in speed values
may be expected under practical conditions. However, as the range of tube
voltages applied in screen/film mammography is small, this part of
ISO 9236 describes only one beam quality for speed measurement. The
measurement conditions described in this part of ISO 9236 provide values
for speed and average gradient which are representative of those found
under practical conditions.
iii
---------------------- Page: 5 ----------------------
SIST ISO 9236-3:2011
---------------------- Page: 6 ----------------------
SIST ISO 9236-3:2011
©
INTERNATIONAL STANDARD ISO ISO 9236-3:1999(E)
Photography — Sensitometry of screen/film systems for medical
radiography —
Part 3:
Determination of sensitometric curve shape, speed and average
gradient for mammography
1 Scope
This part of ISO 9236 specifies methods for determination of the sensitometric curve shape, average gradient and
speed of a single sample of a screen/film/filmholder/processing system in mammography.
The filmholder may be any means which ensures close screen/film contact and prevents the film from being
exposed to ambient light. In particular, the filmholder may be a light-tight vacuum bag, as often used in the
laboratory, or a radiographic cassette as used in mammography.
NOTE — Hereafter, screen/film/filmholder combinations will be referred to as “combinations”, and will be referred to as
“systems” when the processing is included.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part of
ISO 9236. At the time of publication, the editions indicated were valid. All standards are subject to revision, and
parties to agreements based on this part of ISO 9236 are encouraged to investigate the possibility of applying the
most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid
International Standards.
ISO 5-2:1991, Photography — Density measurements — Part 2: Geometric conditions for transmission density.
ISO 5-3:1995, Photography — Density measurements — Part 3: Spectral conditions.
ISO 554:1976, Standard atmospheres for conditioning and/or testing — Specifications.
3 Definitions
For the purposes of this part of ISO 9236, the following definitions apply.
3.1 air kerma, K: Energy which is transferred by ionizing radiation (for instance X-rays) to air molecules divided
by the mass of air in that volume where the energy is released. The unit is the gray (Gy).
1
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SIST ISO 9236-3:2011
©
ISO 9236-3:1999(E) ISO
3.2 sensitometric curve: Plot of the density of a processed photographic film as a function of the logarithm of
the exposure.
3.3 speed, S: Quantitative measure of the response of the screen/film system to radiant energy for the
specified conditions of exposure, processing, and density measurement.
3.4 average gradient, G : Slope of the straight line joining two specified points on a sensitometric curve.
3.5 net density D: Density of an exposed and processed film minus the density of an unexposed and
processed sample of that film.
4 General requirements
4.1 Storage and handling conditions
The films and screens shall be stored according to the manufacturers' recommendations. Before and during
exposures, the temperatures of the films and screens shall be maintained at (23 – 2) �C (see ISO 554) and the
moisture content of the film shall be such that it will be in equilibrium at a relative humidity of (50 – 20) %.
4.2 Safelights
To eliminate the possibility of safelight illumination affecting the sensitometric results, all films shall be kept in total
darkness during handling, exposure and processing.
4.3 X-ray equipment
For all tests described in this part of ISO 9236 a 6-pulse, 12-pulse, high frequency (multipulse), or constant-potential
generator shall be used.
For dosimetry, a measuring detector shall be used that is calibrated to measure air kerma for the beam quality
applied. The accuracy of readings shall be better than – 5 % for collimated beams without scatter, and better than
– 7 % for radiation measurements behind the phantom when scattered radiation is included.
NOTE — A spherical ionization chamber is recommended for measurements where scattered radiation is involved. The centre
of the spherical chamber is to be considered the reference point; the stem of the spherical chamber should point in a direction
opposite to the focal spot direction.
4.4 Processing
Screen/film systems including either manual or automatic processing may be tested in accordance with this part of
ISO 9236. Processing should be carried out in accordance with the film manufacturer's recommendations. Nothing
shall be construed to require the disclosure of proprietary information.
No processing specifications are described in this part of ISO 9236, in recognition of the wide range of chemicals
and equipment used. Speed and average gradient values provided by film manufacturers generally apply to the
system when the film is processed in accordance with their recommendations so that the photographic
characteristics specified for the process are produced. Processing information shall be provided by the film
manufacturer or others who quote speed and average gradient values and shall specify the processing chemicals,
times, temperatures, agitation, equipment and procedures used for each of the processing steps, and any additional
information required to obtain the sensitometric results described. The values for speed and average gradient
obtained using other processing procedures may differ significantly. The processing conditions selected by a person
using this part of ISO 9236 are, in any case, part of the system being tested. Different speeds for a particular film
may be achieved by varying the processes, but the user should be aware that other changes may accompany the
speed changes.
In order to minimize any effects due to latent-image instability or process variability, all film samples shall be
processed together, neither less than 30 min nor more than 4 h after exposure. Between exposure and processing,
2
---------------------- Page: 8 ----------------------
SIST ISO 9236-3:2011
©
ISO ISO 9236-3:1999(E)
the temperature of the film shall be maintained at (23 – 2) �C, and its moisture content shall be such that the film will
be in equilibrium at a relative humidity of (50 – 20) %.
Since films are generally processed in practice a few minutes after exposure, the speed observed in practice may
differ from that determined by this part of ISO 9236 due to latent-image fading of some films. Therefore, the speed
measured with a time delay of 30 min to 4 h between exposure and processing shall be corrected to the value one
would obtain if the film were processed soon after exposure. For the purposes of this part of ISO 9236, a time delay
of 5,0 min is used for computing speed.
NOTES
1 The information about the necessary correction may easily be gained by exposing film strips in a light sensitometer and
varying the time between exposure and processing. In the case of double-emulsion films, care should be taken that both front
and back emulsions are exposed equally by the sensitometer.
2 Since the time required for the many individual exposures to obtain the sensitometric curve is comparatively long, a time
delay of at least 30 min between exposure and processing is prescribed. That time delay is considered to be sufficient to
minimize any differences in latent-image fading for the individual exposures.
The following processing information and accuracies shall be specified:
a) trade designations of all chemicals, if proprietary; otherwise, the formula;
b) temperature of the developer to within – 0,3 �C;
c) temperature of other solutions to within – 2 �C;
d) immersion times in the developer solution to within 3 %;
e) whether the developer is fresh or "seasoned" (if "seasoned", the type and amount of film used for seasoning),
the density of the processed film and the replenishment procedure;
f) agitation specifications, in terms of volume of solution recirculated or rate at which a gas is used;
g) drying temperature to within – 5 �C;
h) trade designation of processing equipment.
NOTE — The term "seasoned developer" means that the developer is no longer unused or fresh, but is already used and in a
"normal working condition".
4.5 Densitometry
ISO standard visual diffuse transmission density of the processed images shall be measured using a densitometer
complying with the geometric conditions specified in ISO 5-2 and spectral conditions specified in ISO 5-3. Readings
shall be made in a uniform area of the image. The densities, D, shall be measured with an accuracy of
ΔD/D = – 0,02 or ΔD = – 0,02, whichever is the greater.
5 Determination of sensitometric curve shape
In this part of ISO 9236, intensity scale sensitometry is described to determine curve shape. The intensity is
modified by a change of the distance between the radiation source and the combination. As a consequence of
secondary radiation sources in the beam, and due to beam attenuation by the air, the relationship between
exposure and distance does not exactly obey the inverse-square law. Therefore that relationship shall be calibrated.
3
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SIST ISO 9236-3:2011
©
ISO 9236-3:1999(E) ISO
5.1 Beam qualities
For the determination of the sensitometric curve shape, either of the two beam qualities specified in table 1 may be
used. The beam qualities can be achieved by an iterative procedure of half-value layer (HVL) measurements using
the specified added filtration. The approximate X-ray tube voltages are recommended as starting values for this
procedure (see 7.2.2 and figure 4).
Table 1 — Beam qualities for the determination of the sensitometric curve shape
Beam quality Anode material Approximate X-ray Inherent filtration Added filtration Half value Layer
number tube voltage
1)
kV mm Mo mm Mo + mm Al mm Al
I Mo 28 0,03 0,00 2,1 0,63 ± 0,02
II W 28 0,03 0,03 2,1 0,63 ± 0,02
1) The half-value layer is chosen to approximate the clinical exit beam from the breast. It shall be placed behind the added filtration.
Inherent and added filtration may differ from the numbers given in table 1, under the condition that the sum of the
inherent filtration and the added filtration, known as total filtration, remains unchanged. For the total filtration, the
tolerances are – 0,005 mm for molybdenum filters and – 0,1 mm for aluminium filters. The aluminium and
molybdenum used as filter materials shall have a purity of at least 99,9 %.
5.2 Geometry for curve shape determination
The geometrical set-up of the measuring arrangement shall comply with figures 1 and 2. As a consequence of the
influence of air on beam quality, the distance between the focal spot of the tube and the plane of the mammographic
film shall not be greater than 3 m.
NOTE In practice, X-ray beams emerging from mammographic tubes are usually asymmetric insofar as they extend much
more to the anode side than to the cathode side. In the laboratory, this beam asymmetry can often be reduced by changing
diaphragming directly at the tube or by rotating the tube by several degrees. Symmetric X-ray beams, as shown in all the
figures except figure 3, are not a precondition for applying the methods described in this part of ISO 9236.
The diaphragm B1 and the added filter(s) shall be positioned near the radiation source. The diaphragms B1 and B2
and the added filter(s) shall be in a fixed relation to the radiation source. The diaphragm B3 and the
screen/film/filmholder combination or the measuring detector R2 shall be in a fixed relation at each distance from
the radiation source. The incident face of the diaphragm B3 shall be (100 – 5) mm in front of the plane of the
mammographic film. If it has been confirmed that scattered radiation from walls, equipment, etc. does not influence
the results, the diaphragm B3 may be omitted. To this end, the radiation aperture of the diaphragm B2 may be made
variable so that the beam remains tightly collimated as the distance is changed.
A diaphragm B4, whose shortest dimension shall be at least 5 mm, may be positioned directly in front of the
combination in order to limit the area of the film exposed.
The attenuating properties of the diaphragms shall be such that their transmission into shielded areas does not
contribute to the results of the measurements by more than 0,1 %. The radiation aperture of the diaphragm B1 shall
be large enough so that the penumbra of the radiation beam will be outside the sensitive volume of the monitoring
detector R1 and the radiation aperture of the diaphragm B2.
The radiation aperture of the diaphragm B2 shall be small enough that no part of the beam can pass outside the
diaphragm plate of the diaphragm B3 or B4, respectively. Collimation performed by the radiation aperture of the
diaphragm B3 shall be as narrow as possible but still permit the X-ray beam to cover the radiation aperture of the
diaphragm B4 or the sensitive volume of the measuring detector R2, respectively.
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SIST ISO 9236-3:2011
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ISO ISO 9236-3:1999(E)
A monitoring detector R1 may be placed inside the beam utilized to expose the combination, if it is suitably
transparent and free of structure, otherwise it shall be placed outside the beam. The precision of the monitoring
detector R1 shall be better than – 2 %.
An attenuating protective barrier shall be at least 450 mm beyond the last area involved in the measurement. The
space between the combination or the measuring detector R2 and the protective barrier shall contain nothing but
air.
5.3 Exposure
Each exposure of the combination shall be achieved in one uninterrupted irradiation. The irradiation time shall be in
the range of 0,5 s to 1,5 s and shall be kept constant for all exposures.
NOTE 1 With the use of intensifying screens, reciprocity law failure and the intermittency effect may occur. In order
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