IEC 62220-1-2:2007

Medical electrical equipment - Characteristics of digital X-ray imaging devices - Part 1-2: Determination of the detective quantum efficiency - Detectors used in mammography

Specifies the method for the determination of the detective quantum efficiency (DQE) of digital X-ray imaging devices as a function of air kerma and of spatial frequency for the working conditions in the range of the medical application as specified by the manufacturer. The intended users of this part of IEC 62220 are manufacturers and well equipped test laboratories. This Part 1-2 is restricted to digital X-ray imaging devices that are used for mammographic imaging such as but not exclusively, CR systems, direct and indirect flat panel detector based systems, scanning systems (CCD based or photon-counting). This part of IEC 62220 is not applicable to - digital X-ray imaging devices intended to be used in general radiography or in dental radiography; - computed tomography; and - devices for dynamic imaging (where series of images are acquired, as in fluoroscopic or cardiac imaging).

Appareils électromédicaux - Caractéristiques des dispositifs d'imagerie numérique à rayonnement X - Partie 1-2: Détermination de l'efficacité quantique de détection - Détecteurs utilisés en mammographie

Spécifie la méthode de la détermination de l'efficacite quantique de détection (EQD) des dispositifs d'imagerie numérique à rayons X en fonction du kerma dans l'air et de la fréquence spatiale pour les conditions de fonctionnement dans la gamme des applications médicales, suivant les spécifications du fabricant. Les utilisateurs prévus de la présente partie de la CEI 62220 sont les fabricants et les laboratoires d'essai bien équipés. Cette Partie 1-2 est limitée aux dispositifs d'imagerie numérique à rayonnement X utilisés dans l'imagerie mammaire, tels que, mais pas exclusivement, les systèmes à écrans photo stimulables (connus sous la désignation de "Computer Tomography", CR), les systèmes à base de détecteur à panneau plat direct ou indirect, les systèmes de balayage (à base de dispositif à transfert de charge (CCD en anglais) ou à comptage de photons). La présente partie de la CEI 62220 n'est pas applicable: - aux dispositifs d'imagerie numérique à rayonnement X destinés à être utilisés en radiographie générale ou en radiographie dentaire; - à la tomodensitométrie; et - aux dispositifs d'imagerie dynamique (où des ensembles d'images sont acquis, comme dans l'imagerie radioscopique ou cardiaque).

General Information

• Status: Published
• Publication Date: 04-Jun-2007
• ICS: 11.040.50 - Radiographic equipment
• Technical Committee: SC 62B - Medical imaging equipment, software, and systems
• Drafting Committee: WG 33 - TC 62/SC 62B/WG 33
• Current Stage: PPUB - Publication issued
• Start Date: 15-Aug-2007
• Completion Date: 05-Jun-2007

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD
CEI
62220-1-2
NORME
First edition
INTERNATIONALE
Première édition
2007-06
Medical electrical equipment –
Characteristics of digital X-ray imaging devices –
Part 1-2:
Determination of the
detective quantum efficiency –
Detectors used in mammography
Appareils électromédicaux –
Caractéristiques des dispositifs
d’imagerie numérique à rayonnement X –
Partie 1-2:
Détermination de l’efficacité
quantique de détection –
Détecteurs utilisés en mammographie
Reference number
Numéro de référence
IEC/CEI 62220-1-2:2007
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INTERNATIONAL IEC
STANDARD
CEI
62220-1-2
NORME
First edition
INTERNATIONALE
Première édition
2007-06
Medical electrical equipment –
Characteristics of digital X-ray imaging devices –
Part 1-2:
Determination of the
detective quantum efficiency –
Detectors used in mammography
Appareils électromédicaux –
Caractéristiques des dispositifs
d’imagerie numérique à rayonnement X –
Partie 1-2:
Détermination de l’efficacité
quantique de détection –
Détecteurs utilisés en mammographie
PRICE CODE
U
CODE PRIX
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
Pour prix, voir catalogue en vigueur

– 2 – 62220-1-2 © IEC:2007
CONTENTS
FOREWORD.3
INTRODUCTION.5

1 Scope.6
2 Normative references .6
3 Terminology and definitions .7
4 Requirements .9
4.1 Operating conditions .9
4.2 X-RAY EQUIPMENT .9
4.3 RADIATION QUALITY .9
4.4 TEST DEVICE .10
4.5 Geometry .11
4.6 IRRADIATION conditions.12
5 Corrections of RAW DATA .15
6 Determination of the DETECTIVE QUANTUM EFFICIENCY.16
6.1 Definition and formula of DQE(u,v) .16
6.2 Parameters to be used for evaluation .16
6.3 Determination of different parameters from the images.17
7 Format of conformance statement .21
8 Accuracy .21

Annex A (normative) Determination of LAG EFFECTS.22
Annex B (informative) Calculation of the input NOISE POWER SPECTRUM.25

Bibliography.26

Terminology – Index of defined terms .28

62220-1-2 © IEC:2007 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEDICAL ELECTRICAL EQUIPMENT –
CHARACTERISTICS OF DIGITAL X-RAY IMAGING DEVICES –

Part 1-2: Determination of the detective quantum efficiency –
Detectors used in mammography
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
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5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
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expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62220-1-2 has been prepared by subcommittee 62B: Diagnostic
imaging equipment, of IEC technical committee 62: Electrical equipment in medical practice.
The text of this standard is based on the following documents:
FDIS Report on voting
62B/649/FDIS 62B/656/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 4 – 62220-1-2 © IEC:2007
A list of all parts of the IEC 62220 series, published under the general title Medical electrical
equipment – Characteristics of digital X-ray imaging devices, can be found on the IEC
website.
In this standard, terms printed in SMALL CAPITALS are used as defined in IEC 60788, in Clause
3 of this standard or other IEC publications referenced in the Index of defined terms. Where a
defined term is used as a qualifier in another defined or undefined term it is not printed in
SMALL CAPITALS, unless the concept thus qualified is defined or recognized as a “derived term
without definition”.
NOTE Attention is drawn to the fact that, in cases where the concept addressed is not strongly confined to the
definition given in one of the publications listed above, a corresponding term is printed in lower-case letters.
In this standard, certain terms that are not printed in SMALL CAPITALS have particular
meanings, as follows:
– "shall" indicates a requirement that is mandatory for compliance;
– "should" indicates a strong recommendation that is not mandatory for compliance;
– "may" indicates a permitted manner of complying with a requirement or of avoiding the
need to comply;
– "specific" is used to indicate definitive information stated in this standard or referenced in
other standards, usually concerning particular operating conditions, test arrangements or
values connected with compliance;
– "specified" is used to indicate definitive information stated by the manufacturer in
accompanying documents or in other documentation relating to the equipment under
consideration, usually concerning its intended purposes, or the parameters or conditions
associated with its use or with testing to determine compliance.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in the
data related to the specific publication. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
62220-1-2 © IEC:2007 – 5 –
INTRODUCTION
DIGITAL X-RAY IMAGING DEVICES are increasingly used in medical diagnosis and will widely
replace conventional (analogue) imaging devices such as screen-film systems or analogue X-
RAY IMAGE INTENSIFIER television systems in the future. It is necessary, therefore, to define
parameters that describe the specific imaging properties of these DIGITAL X-RAY IMAGING
DEVICES and to standardize the measurement procedures employed.
There is growing consensus in the scientific world that the DETECTIVE QUANTUM EFFICIENCY
(DQE) is the most suitable parameter for describing the imaging performance of an X-ray
imaging device. The DQE describes the ability of the imaging device to preserve the signal-to-
NOISE ratio from the radiation field to the resulting digital image data. Since in X-ray imaging,
the NOISE in the radiation field is intimately coupled to the AIR KERMA level, DQE values can
also be considered to describe the dose efficiency of a given DIGITAL X-RAY IMAGING DEVICE.
NOTE In spite of the fact that the DQE is widely used to describe the performance of imaging devices, the
connection between this physical parameter and the decision performance of a human observer is not yet
)
completely understood [1], [3].
The DQE is already widely used by manufacturers to describe the performance of their DIGITAL
X-RAY IMAGING DEVICES. The specification of the DQE is also required by regulatory agencies
(such as the Food and Drug Administration (FDA)) for admission procedures. However, there
is presently no standard governing either the measurement conditions or the measurement
procedure with the consequence that values from different sources may not be comparable.
This standard has therefore been developed in order to specify the measurement procedure
together with the format of the conformance statement for the DETECTIVE QUANTUM EFFICIENCY
of DIGITAL X-RAY IMAGING DEVICES.
In the DQE calculations proposed in this standard, it is assumed that system response is
measured for objects that attenuate all energies equally (task-independent) [5].
This standard will be beneficial for manufacturers, users, distributors and regulatory agencies.
It is the second document out of a series of three related standards:
RADIOGRAPHY, excluding MAMMOGRAPHY and
• Part 1, which is intended to be used in
RADIOSCOPY;
• the present Part 1-2, which is intended to be used for MAMMOGRAPHY;
• Part 1-3, which is intended to be used for dynamic imaging detectors.
These standards can be regarded as the first part of the family of 62220 standards describing
the relevant parameters of DIGITAL X-RAY IMAGING DEVICES.
———————
)
Figures in square brackets refer to the bibliography.

– 6 – 62220-1-2 © IEC:2007
MEDICAL ELECTRICAL EQUIPMENT –
CHARACTERISTICS OF DIGITAL X-RAY IMAGING DEVICES –

Part 1-2: Determination of the detective quantum efficiency –
Detectors used in mammography
1 Scope
This part of IEC 62220 specifies the method for the determination of the DETECTIVE QUANTUM
EFFICIENCY (DQE) of DIGITAL X-RAY IMAGING DEVICES as a function of AIR KERMA and of SPATIAL
FREQUENCY for the working conditions in the range of the medical application as specified by
the MANUFACTURER. The intended users of this part of IEC 62220 are manufacturers and well
equipped test laboratories.
DIGITAL X-RAY IMAGING DEVICES that are used for mammographic
This Part 1-2 is restricted to
imaging such as but not exclusively, CR systems, direct and indirect flat panel detector based
systems, scanning systems (CCD based or photon-counting). This part of IEC 62220 is not
applicable to
– DIGITAL X-RAY IMAGING DEVICES intended to be used in general radiography or in dental
radiography;
– computed tomography;
and
– devices for dynamic imaging (where series of images are acquired, as in fluoroscopic or
cardiac imaging).
NOTE The devices noted above are excluded because they contain many parameters (for instance, beam
qualities, geometry, time dependence, etc.) which differ from those important for mammography. Some of these
techniques are treated in separate standards (IEC 62220-1 and IEC 62220-1-3) as has been done for other topics,
for instance for speed and contrast, in IEC and ISO standards.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60336, Medical electrical equipment – X-ray tube assemblies for medical diagnosis –
Characteristics of focal spots
IEC TR 60788:2004, Medical electrical equipment – Glossary of defined terms
IEC 60601-2-45, Medical electrical equipment – Part 2-45: Particular requirements for the
safety of mammographic X-ray equipment and mammographic stereotactic devices
IEC 61267:2005, Medical diagnostic X-ray equipment – Radiation conditions for use in the
determination of characteristics

62220-1-2 © IEC:2007 – 7 –
IEC 62220-1:2003, Medical electrical equipment – Characteristics of digital X-ray imaging
devices – Part 1: Determination of the detective quantum efficiency
ISO 12232:1998, Photography – Electronic still-picture cameras – Determination of ISO speed
3 Terms and definitions
For the purpose of this document, the terms and definitions given in IEC 60788 which are
listed in the Index of defined terms and the following apply.
3.1
CONVERSION FUNCTION
plot of the large area output level (ORIGINAL DATA) of a DIGITAL X-RAY IMAGING DEVICE versus
the number of exposure quanta per unit area (Q) in the DETECTOR SURFACE plane
NOTE 1 Q is to be calculated by multiplying the measured AIR KERMA excluding back scatter by the value given in
column 4 of Table 2.
NOTE 2 Many calibration laboratories, such as national metrology institutes, calibrate RADIATION METERS to
measure AIR KERMA.
[IEC 62220-1:2003, definition 3.2, modified]
3.2
DETECTIVE QUANTUM EFFICIENCY
DQE(u,v)
ratio of two NPS functions with the numerator being the NPS of the input signal at the
DETECTOR SURFACE of a digital X-ray detector after having gone through the deterministic filter
given by the system transfer function, and the denominator being the measured NPS of the
output signal (ORIGINAL DATA)
NOTE Instead of the two-dimensional DETECTIVE QUANTUM EFFICIENCY, often a cut through the two-
dimensional DETECTIVE QUANTUM EFFICIENCY along a specified line in the frequency plane is published.
[IEC 62220-1:2003, definition 3.3, modified]
3.3
DETECTOR SURFACE
accessible area which is closest to the IMAGE RECEPTOR PLANE
NOTE After removal of all parts (including the ANTI-SCATTER GRID and components for AUTOMATIC EXPOSURE
CONTROL, if applicable) that can be safely removed from the RADIATION BEAM without damaging the digital X-ray
detector.
[IEC 62220-1:2003, definition 3.4, modified]
3.4
DIGITAL X-RAY IMAGING DEVICE
device consisting of a digital X-ray detector including the protective layers installed for use in
practice, the amplifying and digitizing electronics, and a computer providing the ORIGINAL DATA
(DN) of the image
[IEC 62220-1:2003, definition 3.5]
3.5
IMAGE MATRIX
arrangement of MATRIX ELEMENTS preferentially in a Cartesian coordinate system
[IEC 62220-1:2003, definition 3.6, modified]

– 8 – 62220-1-2 © IEC:2007
3.6
LAG EFFECT
influence from a previous image on a current one
[IEC 62220-1:2003, definition 3.7]
3.7
LINEARIZED DATA
ORIGINAL DATA to which the inverse CONVERSION FUNCTION has been applied
NOTE The LINEARIZED DATA are directly proportional to the AIR KERMA.
[IEC 62220-1:2003, definition 3.8]
3.8
MODULATION TRANSFER FUNCTION
MTF(u,v)
modulus of the generally complex optical transfer function, expressed as a function of SPATIAL
FREQUENCIES u and v
[IEC 62220-1:2003, definition 3.9]
3.9
NOISE
fluctuations from the expected value of a stochastic process
[IEC 62220-1:2003, definition 3.10]
3.10
NOISE POWER SPECTRUM
NPS
W(u,v)
modulus of the Fourier transform of the NOISE auto-covariance function. The power of NOISE,
contained in a two-dimensional SPATIAL FREQUENCY interval, as a function of the two-
dimensional frequency
NOTE In literature, the NOISE POWER SPECTRUM is often named “Wiener spectrum” in honour of the mathematician
Norbert Wiener.
[IEC 62220-1:2003, definition 3.11]
3.11
ORIGINAL DATA
DN
RAW DATA to which the corrections allowed in this standard have been applied
[IEC 62220-1:2003, definition 3.12]
3.12
PHOTON FLUENCE
Q
mean number of photons per unit area
[IEC 62220-1:2003, definition 3.13]
3.13
RAW DATA
PIXEL values read directly after the analogue-digital-conversion from the DIGITAL X-RAY IMAGING
DEVICE or counts from photon counting systems without any software corrections
[IEC 62220-1:2003, definition 3.14, modified]

62220-1-2 © IEC:2007 – 9 –
3.14
SPATIAL FREQUENCY
u or v
inverse of the period of a repetitive spatial phenomenon. The dimension of the SPATIAL
FREQUENCY is inverse length
[IEC 62220-1:2003, definition 3.15]
4 Requirements
4.1 Operating conditions
The DIGITAL X-RAY IMAGING DEVICE shall be stored and operated according to the
MANUFACTURERS’ recommendations. The warm-up time shall be chosen according to the
recommendation of the MANUFACTURER. The operating conditions shall be the same as those
intended for clinical use and shall be maintained during evaluation as required for the specific
tests described herein.
DIGITAL X-RAY IMAGING DEVICE is operated
Ambient climatic conditions in the room where the
shall be stated together with the results.
4.2 X-RAY EQUIPMENT
For all tests described in the following subclauses, a CONSTANT POTENTIAL HIGH-VOLTAGE
GENERATOR shall be used (IEC 60601-2-45). The PERCENTAGE RIPPLE shall be equal to, or less
than, 4.
The NOMINAL FOCAL SPOT VALUE (IEC 60336) shall be not larger than 0,4.
For measuring the AIR KERMA calibrated RADIATION METERS shall be used. The uncertainty
(coverage factor 2) [2] of the measurement shall be less than 5 %.
NOTE 1 ”Uncertainty” and “coverage factor” are terms defined in the ISO Guide to the expression of uncertainty in
measurement [2].
NOTE 2 RADIATION METERS to read AIR KERMA are calibrated by many national metrology institutes.
4.3 RADIATION QUALITY
The RADIATION QUALITY shall be RQA-M 2 as specified in IEC 61267, if relevant for the clinical
use for that detector. Optionally other RADIATION QUALITIES may be used that are applied
clinically with the DIGITAL X-RAY IMAGING DEVICE, such as RQA-M 1, RQA-M 3, and RQA-M 4 or
RADIATION QUALITIES based on anode materials other than Molybdenum (see Table 1).
For the application of the RADIATION QUALITIES, refer to IEC 61267:2005-11.
NOTE According to IEC 61267 RADIATION QUALITIES RQA-M are defined by emitting TARGET of molybdenum, TOTAL
FILTRATION of 0,032 mm ± 0,002 mm molybdenum in the radiation source assembly, ADDED FILTER of 2 mm
aluminium (Table 1).
– 10 – 62220-1-2 © IEC:2007
Table 1 – RADIATION QUALITY for the determination
of DETECTIVE QUANTUM EFFICIENCY and corresponding parameters

Nominal X-RAY
Standard RADIATION ADDED FILTER
Filter
TUBE NOMINAL FIRST HALF-VALUE LAYER
QUALITY
thickness
VOLTAGE
(HVL)
characterization
mm aluminium
mm
kV
mm Al
(IEC 61267)
Mo/Mo (RQA-M 1) 0,032 25 0,56 2
Mo/Mo (RQA-M 2) 0,032 28 0,60 2
Mo/Mo (RQA-M 3) 0,032 30 0,62 2
Mo/Mo (RQA-M 4) 0,032 35 0,68 2
Mo/Rh 0,025 28 0,65 2
Rh/Rh 0,025 28 0,74 2
W/Rh 0,050 28 0,75 2
W/Al 0,500 28 0,83 2
It is noted that several mammograhy systems do not use molybdenum target and filter but
other target and/or filter materials such as but not exclusively, rhodium target with rhodium
filtration or tungsten target with aluminium filtration (Table 1). In the case that a RADIATION
QUALITY other than those mentioned in Table 1 is used it shall be explicitly stated in the
conformance statement including target material, filter material and thickness, X-RAY TUBE
VOLTAGE, HALF-VALUE LAYER (HVL) in mm Al and the used value for SNR (see also 6.2).
in
4.4 TEST DEVICE
The TEST DEVICE for the determination of the MODULATION TRANSFER FUNCTION and the
magnitude of LAG EFFECTS shall consist of a stainless steel plate (type 304 stainless steel)
with minimum dimensions: 0,8 mm thick, 120 mm long and 60 mm wide, covering half the
irradiated field (see Figure 1).
The stainless steel plate is used as an edge TEST DEVICE. Therefore, the edge which is used
for the test IRRADIATION shall be carefully polished straight and at 90° to the plate. If the edge
is irradiated by X-rays in contact with a screenless film, the image on the film shall show no
ripples on the edge larger than 5 μm.
As an alterative, it is also allowed to use the TEST DEVICE as specified in IEC 62220-1.

62220-1-2 © IEC:2007 – 11 –
Stainless steel
b
a
b
c
f
IEC  1075/07
NOTE The TEST DEVICE consists of a 0,8 mm (minimum) thick stainless steel plate
Minimum dimensions of the plate: a: 120 mm, f: 60 mm.
The region of interest (ROI) used for the determination of the MTF is defined by b × c, 25 mm × 50 mm (inner
dotted line).
The irradiated field on the detector (outer dotted line) is at least 100 mm × 100 mm
Figure 1 – TEST DEVICE
4.5 Geometry
The geometrical set-up of the measuring arrangement shall comply with Figure 2. The X-RAY
EQUIPMENT is used in that geometric configuration in the same way as it is used for normal
diagnostic applications. The distance between the FOCAL SPOT of the X-RAY TUBE and the
DETECTOR SURFACE should be between 600 mm and 700 mm. If, for technical reasons, a
distance within this range cannot be achieved, a different distance can be chosen but has to
be explicitly declared when reporting results.
The TEST DEVICE is placed immediately in front of the DETECTOR SURFACE. The centre of the
edge of the TEST DEVICE is placed 60 mm from the centre of the chest wall side of the detector.
The irradiated area of the DETECTOR SURFACE shall be 100 mm by 100 mm, with the centre of
this area 60 mm from the centre of the chest wall side of the detector.
In the set-up of Figure 2, the DIAPHRAGM B1 and the ADDED FILTER shall be positioned near the
FOCAL SPOT of the X-RAY TUBE. The DIAPHRAGM B2 should be used, but may be omitted if it is
proven that this does not change the result of the measurements.
A monitor detector should be used to assure the precision of the X-RAY GENERATOR. The
monitor detector R1 shall be placed outside of that portion of the beam that passes
DIAPHRAGM B2. The precision (standard deviation 1σ) of the monitor detector shall be better
than 2 %. The relationship between the monitor reading and the AIR KERMA at the DETECTOR
SURFACE shall be calibrated for each RADIATION QUALITY used. When calibrating this
RADIATION METER is not influenced by
relationship, care shall be taken that the reading of the
radiation back-scattered from any equipment behind the RADIATION METER. In any case, it shall

– 12 – 62220-1-2 © IEC:2007
be checked that the monitor detector does not influence the measurement of the CONVERSION
FUNCTION, of the MTF, or of the NOISE POWER SPECTRUM. To minimize the effect of back-scatter
from layers behind the detector, a minimum distance of 250 mm to other objects should be
provided.
NOTE The calibration procedure of the monitor detector may be sensitive to the positioning of the ADDED FILTER
and to the adjustment of the shutters built into the X-RAY SOURCE. Therefore, these items should not be altered
without re-measuring the calibration of the monitor detector.
This geometry is used either to irradiate the DETECTOR SURFACE uniformly for the
determination of the CONVERSION FUNCTION and the NOISE POWER SPECTRUM or to irradiate the
DETECTOR SURFACE behind a TEST DEVICE (see 4.6.6). For all measurements, the same area of
the DETECTOR SURFACE shall be irradiated.
All measurements shall be made using the same geometry.
For the determination of the NOISE POWER SPECTRUM and the CONVERSION FUNCTION, the TEST
DEVICE shall be moved out of the beam.

B1
ADDED FILTER
Monitor detector R1
B2
TEST DEVICE
DETECTOR SURFACE
IEC  1076/07
NOTE The TEST DEVICE is not used for the measurement of the CONVERSION FUNCTION and the NOISE POWER
SPECTRUM.
Figure 2 – Geometry for exposing the DIGITAL X-RAY IMAGING DEVICE in order to determine
the CONVERSION FUNCTION, the NOISE POWER SPECTRUM or the MODULATION TRANSFER FUNCTION
behind the TEST DEVICE
4.6 IRRADIATION conditions
4.6.1 General conditions
The calibration of the digital X-ray detector shall be carried out prior to any testing, i.e., all
operations necessary for corrections according to Clause 5 shall be effected. The whole
600 mm-700 mm
62220-1-2 © IEC:2007 – 13 –
series of measurements shall be done without re-calibration. Offset calibrations are excluded
from this requirement. They can be performed as in normal clinical use.
The exposure level shall be chosen as that used when the digital X-ray detector is operated
for the intended use in clinical practice. This is called the “reference“ level and shall be
specified by the MANUFACTURER. At least two additional exposure levels shall be chosen, one
2 times the “reference“ level and one at 1/2 of the “reference“ level. No change of system
settings (such as gain etc.) shall be allowed when changing exposure levels.
To cover the range of various clinical examinations, additional levels may be chosen. For
these additional levels other system settings may be chosen and kept constant during the
test procedure.
The variation of AIR KERMA shall be carried out by variation of the X-RAY TUBE CURRENT or the
IRRADIATION TIME or both. The IRRADIATION TIME shall be similar to the conditions for clinical
application of the digital X-ray detector. LAG EFFECTS shall be avoided (see 4.6.3).
The IRRADIATION conditions shall be stated together with the results (see Clause 7).
4.6.2 AIR KERMA measurement
The AIR KERMA at the DETECTOR SURFACE is measured with an appropriate RADIATION METER.
For this purpose, the digital X-ray detector is removed from the beam and the RADIATION
DETECTOR of the RADIATION METER is placed in the DETECTOR SURFACE plane. Care shall be
taken to minimize the back-SCATTERED RADIATION. The correlation between the readings of the
RADIATION METER and the monitoring detector, if used, shall be noted and shall be used for the
AIR KERMA calculation at the DETECTOR SURFACE when irradiating the DETECTOR SURFACE to
determine the CONVERSION FUNCTION, the NOISE POWER SPECTRUM and the MTF. It is
recommended that about five exposures be monitored and that the average be used for the
correct AIR KERMA.
For scanning devices with pre-patient collimator the AIR KERMA shall be measured after this
beam limiting device.
If it is not possible to remove the digital X-ray detector out of the beam, the AIR KERMA at the
DETECTOR SURFACE may be calculated via the inverse square distance law. For that purpose,
the AIR KERMA is measured at different distances from the FOCAL SPOT in front of the DETECTOR
SURFACE. For this measurement, radiation, back-scattered from the DETECTOR SURFACE, shall
be avoided. Therefore, a distance between the DETECTOR SURFACE and the RADIATION
DETECTOR of 100 mm to 200 mm is recommended.
NOTE 1 Air attenuation must be taken into account.
NOTE 2 If the pre-patient collimator is a multi-slit collimator, the exposure must be integrated during a scan.
Multi-slit collimators will result in an inhomogeneous radiation field to the RADIATION DETECTOR; therefore a longer
scan over the RADIATION DETECTOR is needed to get the correct reading.
If a monitoring detector is used, the following equation shall be plotted as a function of the
distance d between the FOCAL SPOT and the RADIATION DETECTOR:
monitor detector reading
f (d) =
radiation detector reading
By extrapolating this approximately linear curve up to the distance between the FOCAL SPOT
and the DETECTOR SURFACE r , the ratio of the readings at r can be obtained and the AIR
SID SID
KERMA at the DETECTOR SURFACE for any monitoring detector reading can be calculated.

– 14 – 62220-1-2 © IEC:2007
If no monitoring detector is used, the square root of the inverse RADIATION METER reading is
plotted as a function of the distance between the FOCAL SPOT and the RADIATION DETECTOR.
The extrapolation etc. is carried out as in the preceding paragraph.
4.6.3 Avoidance of LAG EFFECTS
LAG EFFECTS may influence the measurement of the CONVERSION FUNCTION, the NOISE POWER
SPECTRUM and the MODULATION TRANSFER FUNCTION. They may, therefore, influence the
measurement of DETECTIVE QUANTUM EFFICIENCY.
The influence may be split into an additive component (additional offset) and a multiplicative
component (change of gain). The magnitude of both components shall be estimated.
See [10, 11 and 12] for more background information.
For the determination of possible LAG EFFECTS, the digital X-ray detector shall be operated
according to the specifications of the MANUFACTURER. The minimum time interval between two
successive exposures (as determined by the tests given in Annex A) must be maintained to
prevent the contaminating LAG EFFECTS on the measurement of DETECTIVE QUANTUM
EFFICIENCY.
NOTE The following parameters may contribute to LAG EFFECTS: time of IRRADIATION relative to read-out, method
of erasure of remnants of previous IRRADIATION, time from erase to re-IRRADIATION, time from read-out to re-
IRRADIATION, or the inclusion of intervening “dummy” read-outs used to erase the effects of a previous IRRADIATION.
To test the magnitude of LAG EFFECTS, the test procedures as given in Annex A shall be used.
4.6.4 IRRADIATION to obtain the CONVERSION FUNCTION
The settings of the DIGITAL X-RAY IMAGING DEVICE shall be the same as those used when
exposing the TEST DEVICE. The IRRADIATION shall be carried out using the geometry of Figure 2
but without any TEST DEVICE in the beam. The AIR KERMA is measured according to 4.6.2. The
CONVERSION FUNCTION shall be determined from AIR KERMA level zero up to 20% greater than
the maximum AIR KERMA level tested.
The CONVERSION FUNCTION for AIR KERMA level zero shall be determined from a dark image,
realized under the same conditions as an X-ray image. The minimum X-ray AIR KERMA level
shall not be greater than one-fifth of the reference AIR KERMA level.
Depending on the evaluation procedure (see 6.3.1), the number of different exposures varies;
if only the linearity of the CONVERSION FUNCTION has to be checked, five exposures, uniformly
distributed within the desired range, are sufficient. If the complete CONVERSION FUNCTION has
to be determined, the AIR KERMA shall be varied in such a way that the maximum increment of
logarithmic (to the base 10) AIR KERMA is not greater than 0,1.
4.6.5 IRRADIATION for determination of the NOISE POWER SPECTRUM
The settings of the DIGITAL X-RAY IMAGING DEVICE shall be the same as those used when
exposing the TEST DEVICE. The IRRADIATION shall be carried out using the geometry of Figure 2
but without any TEST DEVICE in the beam. The AIR KERMA is measured according to 4.6.2.
A square area of approximately 50 mm × 50 mm located centrally in the 100 mm × 100 mm
irradiated area is used for the evaluation of an estimate for the NOISE POWER SPECTRUM to be
used later on to calculate the DQE.
For this purpose, the set of input data shall consist of at least four million independent image
PIXELS arranged in one or several independent flat-field images, each having at least 256
PIXELS in either spatial direction. If more than one image is necessary, all individual images
shall be taken at the same RADIATION QUALITY and AIR KERMA. The standard deviation of the
IRRADIATIONS used to get the different images shall be less than 10 % of the mean.

62220-1-2 © IEC:2007 – 15 –
NOTE The minimum number of required independent image PIXELS is determined by the required accuracy which
defines the minimum number of ROIs. For an accuracy of the two-dimensional NOISE POWER SPECTRUM of 5 %, a
minimum of 960 (overlapping) ROIs are needed, meaning 16 million independent image PIXELS with the given ROI
size. The averaging and binning process applied afterwards to obtain a one-dimensional cut reduces the minimum
number of required independent image PIXELS to four million, still assuring the necessary accuracy.
Care shall be taken that there is no correlation between the subsequent images (LAG EFFECT;
see 4.6.3). No change of system setting is allowed when making the IRRADIATIONS.
The images for the determination of the NOISE POWER SPECTRUM shall be taken at the AIR
KERMA levels described in 4.6.1.
4.6.6 IRRADIATION with TEST DEVICE in the RADIATION BEAM
The IRRADIATION shall be carried out using the geometry of Figure 2. The TEST DEVICE is
placed directly on the DETECTOR SURFACE. The TEST DEVICE is positioned in such a way that
the edge is tilted by an angle α relative to the axis of the PIXEL columns or PIXEL rows, where
α is between 1,5° and 3°.
NOTE The method of tilting the TEST DEVICE relative to the rows or columns of the IMAGE MATRIX is common in
other standards (ISO 15529 and ISO 12233) and reported in numerous publications when the pre-sampling
MODULATION TRANSFER FUNCTION has to be determined.
At least two IRRADIATIONS shall be made with the TEST DEVICE in the RADIATION BEAM, at least
one with the TEST DEVICE oriented approximately along the columns, and at least one with the
TEST DEVICE approximately along the rows of the IMAGE MATRIX. For CR systems, the
sharpness is known to depend on the orientation of the edge relative to the direction of the
displacement of the laser spot in the scan direction. Therefore, for CR systems 4 IRRADIATIONS
shall be made with the TEST DEVICE in the RADIATION BEAM, rotating the TEST DEVICE over 90°
between each exposure. The positions of the other components shall not be changed. For the
new position, a new adjustment of the TEST DEVICE shall be made.
The images for the determination of the MTF shall be taken at one of the three AIR KERMA
levels (see 4.6.1).
5 Corrections of RAW DATA
The following linear and image-independent corrections of the RAW DATA are allowed in
advance of the processing of the data for the determination of the CONVERSION FUNCTION, the
NOISE POWER SPECTRUM, and the MODULATION TRANSFER FUNCTION.
All the following corrections if used shall be made as in normal clinical use:
– replacement of the RAW DATA of bad or defective PIXELS by appropriate data;
– a flat-field correction comprising:
- correction of the non-uniformity of the RADIATION FIELD;
- correction for the offset of the individual PIXELS; and
- gain correction for the individual PIXELS;
- a correction for velocity variation during a scan;
– a correction for geometrical distortion
NOTE 1 Some detectors execute linear image processing due to their physical concept. As long as this image
processing is linear and image-independent, these operations are allowed as an exception.
NOTE 2 Image correction is considered image-independent if the same correction is applied to all images
independent of the image contents.

– 16 – 62220-1-2 © IEC:2007
6 Determination of the DETECTIVE QUANTUM EFFICIENCY
6.1 Definition and formula of DQE(u,v)
The equation for the frequency-dependent DETECTIVE QUANTUM EFFICIENCY DQE(u,v) is :
W (u,v)
2 2 in
DQE(u,v) = G MTF (u,v)
(1)
W (u,v)
out
The source for this equation is the Handbook of Medical Imaging Vol. 1 equation 2.153 [4].
In this standard, the NOISE POWER SPECTRUM at the output W (u, v) and the MODULATION
out
TRANSFER FUNCTION MTF(u,v) of the DIGITAL X-RAY IMAGING DEVICE shall be calculated on the
LINEARIZED DATA. The LINEARIZED DATA are calculated by applying the inverse CONVERSION
FUNCTION to the ORIGINAL DATA (according to 6.3.1) and are expressed in number of exposure
quanta per unit area. The gain G of the detector at zero SPATIAL FREQUENCY (equation 1) is
part of the conversion function and does not need to be separately determined.
Therefore the working equation for the determination of the frequency-dependent DETECTIVE
QUANTUM EFFICIENCY DQE(u,v) according to this standard is :
W (u,v)
in
DQE(u,v) = MTF (u,v) (2)
W (u,v)
out
where
MTF(u,v) is the pre-sampling MODULATION TRANSFER FUNCTION of the DIGITAL X-RAY IMAGING
DEVICE, determined according to 6.3.3;
W (u,v) is the NOISE POWER SPECTRUM of the radiation field at the DETECTOR SURFACE,
in
determined according to 6.2;
W (u,v) is the NOISE POWER SPECTRUM at the output of the DIGITAL X-RAY IMAGING DEVICE,
out
determined according to 6.3.2.

6.2 Parameters to be used for evaluation
For the determination of the DETECTIVE QUANTUM EFFICIENCY, the value of the input NOISE
POWER SPECTRUM W (u,v) shall be calculated:
in
W (u,v) = K ⋅ SNR (3)
in a in
where
K is the measured AIR KERMA, unit: µGy;
a
SNR is the squared signal-to-NOISE ratio per AIR KERMA, unit: 1/(mm ⋅µGy) as given in
in
column 4 of Table 2.
The values for SNR in Table 2 shall apply for this standard.
in
62220-1-2 © IEC:2007 – 17 –
Table 2 – Radiation parameter SNR for the application of this standard
in
(2 mm Al added filtration)
Filter thickness Nominal X-RAY TUBE
Calculated SNR in
VOLTAGE in
RADIATION QUALITY No.
mm 2
kV 1/(mm ⋅µGy)
Mo/Mo (RQA-M 1) 0,032 25 4 639
Mo/Mo (RQA-M 2) 0,032 28 4 981
Mo/Mo (RQA-M 3)
0,032 30 5 303
Mo/Mo (RQA-M 4) 0,032 35 6 325
Mo/Rh 0,025 28 5 439
Rh/Rh
0,025 28 5 944
W/Rh 0,050 28 5 975
W/Al 0,500 28 6 575
Background information on the calculation of SNR is given in Annex
...