SIST EN 61262-7:1998

SLOVENSKI STANDARD
01-september-1998
Medical electrical equipment - Characteristics of electro-optical X-ray image
intensifiers - Part 7: Determination of the modulation transfer function (IEC 61262-
7:1995)
Medical electrical equipment - Characteristics of electro-optical X-ray image intensifiers --
Part 7: Determination of the modulation transfer function
Medizinische elektrische Geräte - Merkmale von elektronenoptischen
Röntgenbildverstärkern -- Teil 7: Bestimmung der Modulationsübertragungsfunktion
Appareils électromédicaux - Caractéristiques des intensificateurs électro-optiques
d'image radiologique -- Partie 7: Détermination de la fonction de transfert de modulation
Ta slovenski standard je istoveten z: EN 61262-7:1995
ICS:
11.040.50 Radiografska oprema Radiographic equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEI
NORME
IEC
INTERNATIONALE
1262-7
INTERNATIONAL
Première édition
STANDARD First edition
1995-09
Appareils électromédicaux –
Caractéristiques des intensificateurs
électro-optiques d'image radiologique –
Partie 7:
fonction de transfert
Détermination de la
de modulation
Medical electrical equipment –
Characteristics of electro-optical
X-ray image intensifiers –
Part 7:
Determination of the modulation transfer
function
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1262-7 © IEC:1995 - 3
CONTENTS
Page
FOREWORD 5
INTRODUCTION 7
Clause
1 Scope 9
2 Normative references 9
3 Terminology 9
3.1 Definitions 9
3.2 Degree of requirements and reading instructions 13
4 Requirements 15
4.1 Test set-up 15
4.2 X-RAY IMAGE INTENSIFIER - Operating conditions 15
RADIATION 15
4.3 Input
4.4 TEST DEVICE
4.5 Measurement equipment
5 Determination of the MODULATION TRANSFER FUNCTION 17
5.1 Preparation 17
5.2 Measurement 19
5.3 Corrections 21
5.4 Determination of the LOW-FREQUENCY DROP 23
5.5 Overall accuracy of determination 23
6 Presentation of the MODULATION TRANSFER FUNCTION
7 Statement of compliance 23
Figure 1 - Measuring arrangement 25
Annexes
A Terminology - Index of defined terms 27
TEST DEVICE 31
B Construction of the
ANALYSER 33
C Determination of the MTFA of the MTF
D Bibliography
1262-7 © IEC:1995 - 5 -
INTERNATIONAL ELECTROTECHNICAL COMMISSION
MEDICAL ELECTRICAL EQUIPMENT -
CHARACTERISTICS OF ELECTRO-OPTICAL
X-RAY IMAGE INTENSIFIERS -
7: Determination of the modulation transfer function
Part
FOREWORD
The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
1)
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote inter-
national cooperation on all questions concerning standardization in the electrical and electronic fields. To this
end and in addition to other activities, the IEC publishes International Standards. Their preparation is entrusted
to technical committees; any IEC National Committee interested in the subject dealt with may participate in this
preparatory work. International, governmental and non-governmental organizations liaising with the IEC also
participate in this preparation. The IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
The formal decisions or agreements of the IEC on technical matters, prepared by technical committees on which
2)
all the National Committees having interest therein are represented, express, as nearly as possible, an
international consensus of opinion on the subject dealt with.
They have the form of recommendations for international use published in the form of standards, technical
3)
repo s or guides and they are accepted by the National Committees in that sense.
rt
In order to promote international unification, the IEC National Committees undertake to apply IEC International
4)
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
International Standard IEC 1262-7 has been prepared by sub-committee 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:
Report on voting
DIS
62B/269/RVD
62B/250/DIS
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
Annexes A, B, C and D are for information only.
In this standard, the following print types are used:
Requirements, compliance with which can be tested, and definitions: in roman type;
-
Explanations, advice, introductions, general statements, and exceptions: in smaller type;
—
Test specifications: in italic type;
-
TERMS USED THROUGHOUT THIS STANDARD WHICH HAVE BEEN DEFINED IN 3.1 AND IN ANNEX A:
—
SMALL CAPITALS.
1262-7 © IEC:1995 - 7
INTRODUCTION
Imaging systems are often being evaluated using subjective measures of performance, such as
limiting resolution. These methods do not necessarily describe the performance appropriately
in imaging tasks that are relevant to the intended use of the system, and are susceptible to the
variability of human observers.
Linear shift-invariant imaging systems can be conveniently analysed in terms of their TRANSFER
functions. The signal TRANSFER of such systems can be specified by the OPTICAL TRANSFER
FUNCTION (OTF), which shows the response of the system to sine waves as a function of their
spatial frequency. The MODULATION TRANSFER FUNCTION (MTF), the modulus of the OTF, is
sufficient for describing the signal TRANSFER of X-RAY IMAGE INTENSIFIERS. Systems are called
does not vary with position. Note that
shift-invariant when the POINT SPREAD FUNCTION X-RAY
IMAGE INTENSIFIERS generally are shift-invariant over a limited area only: the isoplanatic region.
The MODULATION TRANSFER FUNCTION can be determined in several ways (see, for example [1]
of annex D):
- from square wave responses;
- LINE SPREAD FUNCTION;
from the Fourier transform of the
POINT SPREAD FUNCTION;
- from the Henkel transform of the
- from scanning a slit image with a spatial filter.
Any method is acceptable if performed correctly. For the purpose of simplicity, this standard
elaborates on two methods: the Fourier transform of the LINE SPREAD FUNCTION, referred to as
the LSF method, and the spatial filter method. Accurate determination of the MODULATION
TRANSFER FUNCTION requires specialized EQUIPMENT and does not generally lend itself to be
performed at field installations.
This standard only specifies methods for measurement of the MODULATION TRANSFER FUNCTION
of CENTRE OF THE ENTRANCE FIELD.
X-RAY IMAGE INTENSIFIERS near the

1262-7 © IEC:1995 - 9 -
MEDICAL ELECTRICAL EQUIPMENT -
CHARACTERISTICS OF ELECTRO-OPTICAL
X-RAY IMAGE INTENSIFIERS -
Part 7: Determination of the modulation transfer function
1 Scope
This International Standard applies to ELECTRO-OPTICAL X-RAY IMAGE INTENSIFIERS for medical
use, as components of diagnostic X-RAY EQUIPMENT.
This International Standard describes a method of determining the MODULATION TRANSFER
FUNCTION of X-RAY IMAGE INTENSIFIERS.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this International Standard. At the time of publication, the editions
indicated were valid. All normative documents are subject to revision, and parties to
agreements based on this International Standard are encouraged to investigate the possibility
of applying the most recent editions of the normative documents indicated below. Members of
IEC and ISO maintain registers of currently valid International Standards.
IEC 336: 1993, X-ray tube assemblies for medical diagnosis - Characteristics of focal spots
IEC 788: 1984, Medical radiology- Terminology
IEC 1262-4: 1994, Medical electrical equipment - Characteristics of electro-optical X-ray image
intensifiers - Part 4: Determination of the image distortion -
Optics and optical instruments - Optical transfer function - Definitions and
ISO/DIS 9334,
mathematical relationships
3 Terminology
3.1 Definitions
For the purposes of this International Standard, the following definitions apply together with
those given in IEC 788. The definitions given below take preference over those given in
IEC 788 when differences occur.
ELECTRO-OPTICAL X-RAY IMAGE INTENSIFIER.
3.1.1 XRII: An abbreviation for
The plane perpendicular to the axis of symmetry of the XRII and
3.1.2 ENTRANCE PLANE:
grazing the part of the XRII, including its housing, that protrudes most in the direction of the
RADIATION SOURCE.
1262-7 ©IEC:1995 - 11 -
3.1.3 ENTRANCE FIELD: For an XRII, the area in the ENTRANCE PLANE that can be used for the
TRANSMISSION of an X-RAY PATTERN under specific conditions.
3.1.4 ENTRANCE FIELD SIZE: For an XRII, the diameter of the field in the ENTRANCE PLANE that
can be used at a specified SED for the TRANSMISSION of an X-RAY PATTERN. For an XRII with
ENTRANCE FIELD SIZE for each of the magnification
more than one magnification mode, the
modes shall correspond to the same diameter of the XRII OUTPUT IMAGE occurring with the
largest ENTRANCE FIELD SIZE.
3.1.5 SOURCE TO ENTRANCE PLANE DISTANCE (abbreviation SED): The distance between the
FOCAL SPOT of the X-RAY TUBE and the ENTRANCE PLANE of the XRII.
The centre of the smallest circle circumscribing the
3.1.6 CENTRE OF THE OUTPUT IMAGE:
OUTPUT IMAGE.
ENTRANCE PLANE which is imaged at the
3.1.7 CENTRE OF THE ENTRANCE FIELD: That point in the
CENTRE OF THE OUTPUT IMAGE.
3.1.8 CENTRAL AXIS: The line perpendicular to the ENTRANCE PLANE passing through the CENTRE
OF THE ENTRANCE FIELD.
3.1.9 CENTRAL MAGNIFICATION: As a characteristic of XRIIs, the ratio of the length in the
OUTPUT IMAGE to the actual length of a small object placed in the ENTRANCE PLANE
symmetrically about the CENTRAL AXIS.
3.1.10 (abbreviation PSF): Normalized distribution of irradiance in the
POINT SPREAD FUNCTION
/DIS 9334.
image of a point source, see ISO
POINT SPREAD FUNCTION
3.1.11 ISOPLANATIC REGION: Region where the form of the is constant
within specified accuracy.
3.1.12 LINEARITY: Property of an imaging system in that the image of a weighted sum of
objects is identical to the similarly weighted sum of images of individual objects.
Range of input signals within which the imaging system exhibits
3.1.13 LINEAR RANGE:
LINEARITY within specified accuracy, see ISO/DIS 9334.
NOTE — The range of input signals indicating the LINEAR RANGE of the imaging system should be specified by
minimum and maximum levels.
Two-dimensional Fourier transform of
3.1.14 OPTICAL TRANSFER FUNCTION (abbreviation OTF):
the imaging system's POINT SPREAD FUNCTION, see ISO/DIS 9334.
NOTE — For the OPTICAL TRANSFER FUNCTION to have significance, it is essential that the imaging system is
working in its LINEAR RANGE, and that an ISOPLANATIC REGION is considered.
Section of the
3.1.15 ONE-DIMENSIONAL OPTICAL TRANSFER FUNCTION (abbreviation 1-OTF):
OPTICAL TRANSFER FUNCTION through the origin in a given orientation.

1262-7 ©IEC:1995 - 13 -
3.1.16 LINE SPREAD FUNCTION (abbreviation LSF): Normalised distribution of irradiance in the
image of an incoherently radiating line source. The LINE SPREAD FUNCTION only exists in an
ISOPLANATIC REGION, see ISO/DIS 9334.
NOTE – The Fourier transform of the LINE SPREAD FUNCTION is the ONE-DIMENSIONAL OPTICAL TRANSFER
FUNCTION for the orientation perpendicular to the direction of the line source.
3.1.17 MODULATION TRANSFER FUNCTION (abbreviation MTF): Modulus of the ONE-DIMENSIONAL
OPTICAL TRANSFER FUNCTION.
NOTE – The MTF is defined in ISO/DIS 9334 as the modulus of the OPTICAL TRANSFER FUNCTION. For the
purpose of this International Standard, definition 3.1.17 is more appropriate.
Instrument, including relay optics and software, capable of performing
3.1.18 MTF ANALYSER:
measurements of the MODULATION TRANSFER FUNCTION.
3.1.19 BEST FOCUS: Setting of focusing potentials resulting in maximum integrated area under
the MTF curve for the given slit orientation.
NOTE – This setting of focusing potentials is chosen to reduce ambiguity and may slightly deviate from
settings in practical use of the XRII.
3.1.20 LOW-FREQUENCY DROP (abbreviation LFD): Difference between unity and the value of
the MODULATION TRANSFER FUNCTION close to zero spatial frequency.
NOTE – With currently known XRIIs, significant veiling glare is present. This is apparent as a steep drop in
the MTF curve slightly above zero spatial frequency. For the purpose of this International Standard the
spatial frequency at which the LFD is to be determined, is chosen to be 0,1 mm-1.
sensitive to VISIBLE RADIATION (light).
3.1.21 LIGHT DETECTOR: RADIATION DETECTOR
3.2 Degree of requirements and reading instructions
In this International Standard the auxiliary verb:
- "shall" implies that compliance with a requirement is mandatory for compliance
with the standard;
implies that compliance with a requirement is strongly recommended but
- "should"
is not mandatory for compliance with the standard;
- "may" implies that compliance with a requirement is permitted to be
accomplished in a particular manner, for compliance with the standard;
and the following words have the meaning:
"specific" when used in combination with parameters or conditions: refers to a
-
particular value or standardized arrangement, usually to those required in
an IEC sandard or a legal requirement; see IEC 788, rm-74-01.
"specified" when used in combination with parameters or conditions: refers to a value
-
or arrangement to be chosen for the purpose under consider-ation and
ACCOMPANYING DOCUMENTS; see IEC 788, rm-74-02.
indicated usually in
- "designed for" when used in standards to characterize equipment, devices, com-ponents
or arrangements: designates an intended and usually apparent purpose or
use for the product.
1262-7 ©IEC:1995 - 15 -
4 Requirements
MODULATION TRANSFER FUNCTION
The methods for determining the of an XRII described in this
International Standard incorporate analyzing a slit image. In one method, the image is scanned
with a (one-dimensional) spatial filter, directly resulting in the MTF. With the second method,
called the LSF method, the LINE SPREAD FUNCTION is ob
...