SIST EN 60336:2006

SLOVENSKI SIST EN 60336:2006
STANDARD
januar 2006
Medicinska električna oprema – Rentgenske naprave za medicinsko
diagnostiko – Značilnosti žariščnih točk (IEC 60336:2005)
(istoveten EN 60336:2005)
Medical electrical equipment - X-ray tube assemblies for medical diagnosis -
Characteristics of focal spots (IEC 60336:2005)
ICS 11.040.50; 11.040.55 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

EUROPEAN STANDARD EN 60336
NORME EUROPÉENNE
EUROPÄISCHE NORM July 2005
ICS 11.040.50 Supersedes EN 60336:1995

English version
Medical electrical equipment –
X-ray tube assemblies for medical diagnosis –
Characteristics of focal spots
(IEC 60336:2005)
Appareils électromédicaux –  Medizinische elektrische Geräte -
Gaines équipées pour diagnostic médical - Röntgenstrahler für medizinische
Caractéristiques des foyers Diagnostik –
(CEI 60336:2005) Kennwerte von Brennflecken
(IEC 60336:2005)
This European Standard was approved by CENELEC on 2005-06-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60336:2005 E
Foreword
The text of document 62B/554/FDIS, future edition 4 of IEC 60336, prepared by SC 62B, Diagnostic
imaging equipment, of IEC TC 62, Electrical equipment in medical practice, was submitted to the
IEC-CENELEC parallel vote and was approved by CENELEC as EN 60336 on 2005-06-01.
This European Standard supersedes EN 60336:1995.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-03-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-06-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60336:2005 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 60601-2-28 NOTE Harmonized as EN 60601-2-28:1993 (not modified).
__________
- 3 - EN 60336:2005
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
IEC 60417 database Graphical symbols for use on - -
equipment
1) 2)
IEC 60613 - Electrical, thermal and loading EN 60613 1990
characteristics of rotating anode X-ray
tubes for medical diagnosis
IEC/TR 60788 2004 Medical electrical equipment - - -
Glossary of defined terms
1)
Undated reference.
2)
Valid edition at date of issue.

NORME CEI
INTERNATIONALE
IEC
INTERNATIONAL
Quatrième édition
STANDARD
Fourth edition
2005-04
Appareils électromédicaux –
Gaines équipées pour diagnostic médical –
Caractéristiques des foyers
Medical electrical equipment –
X-ray tube assemblies for medical diagnosis –
Characteristics of focal spots

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For price, see current catalogue

60336  IEC:2005 – 3 –
CONTENTS
FOREWORD.7

1 Scope.11
2 Normative references .11
3 Terms and definitions .11
4 Determinations for the evaluation of the FOCAL SPOT characteristics.11
4.1 Statement of the FOCAL SPOT characteristics .11
4.2 Longitudinal axis of the X-RAY TUBE ASSEMBLY.11
4.3 REFERENCE AXIS of the X-RAY TUBE ASSEMBLY .13
4.4 Direction of evaluation for the FOCAL SPOT length.13
4.5 Direction of evaluation for the FOCAL SPOT width .13
5 FOCAL SPOT camera set-up .13
5.1 Overview .13
5.2 Test equipment .13
5.3 Test arrangement .17
5.4 Total uncertainty of the camera set-up .23
6 Production of RADIOGRAMS .23
6.1 Overview .23
6.2 Operating conditions .23
6.3 Production of FOCAL SPOT SLIT RADIOGRAMS or FOCAL SPOT PINHOLE
RADIOGRAMS.25
6.4 Statement of compliance .27
7 Determination of the LINE SPREAD FUNCTION.27
7.1 Overview .27
7.2 Measuring equipment and measuring arrangement.27
7.3 Measurement of the density distribution .29
7.4 Determination of the LINE SPREAD FUNCTION .29
7.5 Statement of compliance .29
8 Determination of FOCAL SPOT dimensions.31
8.1 Overview .31
8.2 Measurement and determination .31
8.3 Specified NOMINAL FOCAL SPOT VALUES .33
8.4 Statement of compliance .37
8.5 Marking of compliance.37
9 Determination of the MODULATION TRANSFER FUNCTION .37
9.1 Overview .37
9.2 Specified MODULATION TRANSFER FUNCTION.37
9.3 Calculation of the MODULATION TRANSFER FUNCTION .39
9.4 Evaluation of compliance of the MTF.41
9.5 Statement of compliance .41
10 FOCAL SPOT STAR RADIOGRAMS.41
10.1 Overview .41
10.2 Test equipment .43
11 STAR PATTERN RESOLUTION LIMIT .47
11.1 Overview .47

60336  IEC:2005 – 5 –
11.2 Specified STAR PATTERN RESOLUTION LIMIT .47
11.3 Measurement .49
11.4 Determination of the STAR PATTERN RESOLUTION LIMIT .49
11.5 Evaluation and statement of compliance.51
12 BLOOMING VALUE.53
12.1 Overview .53
12.2 Determination of the BLOOMING VALUE .53
12.3 Evaluation and statement of compliance.53
13 Alternate measurement methods .55

Annex A (informative) Alignment to the REFERENCE AXIS.57
Annex B (informative) Application of digital X-ray image detectors for determination of
the FOCAL SPOT characteristics .61
Annex C (informative) Historical background.63

Bibliography.73
Index of defined terms .75

Figure 1 – Essential dimensions of the slit diaphragm.15
Figure 2 – Essential dimensions of the pinhole diaphragm .17
Figure 3 − Position of the centre of the slit or pinhole diaphragm (marked as x in the
figure) with respect to the REFERENCE AXIS .19
Figure 4 – Reference dimensions and planes.21
Figure 5 − Alignment of the optical densitometer slit .29
Figure 6 – LINE SPREAD FUNCTION.31
Figure 7 – Essential dimensions of the star test pattern .43
Figure 8 – Essential dimensions of the star test pattern .45
Figure 9 – Illustration of the zones of minimum modulation .49
Figure A.1 – The REFERENCE AXIS and directions of evaluation .57
Figure A.2 – Projection of the ACTUAL FOCAL SPOT on the IMAGE RECEPTION PLANE.59
Figure C.1 – The LSFs for a typical X-RAY TUBE with small FOCAL SPOT (< 0,3 mm) .65
Figure C.2 – The LSFs for a typical X-RAY TUBE with large FOCAL SPOT (≥0,3 mm).65
Figure C.3 – The corresponding MTFs for the LSFs in Figure C.2 .67

Table 1 – Enlargement for FOCAL SPOT RADIOGRAMs .23
Table 2 − LOADING FACTORS .25
Table 3 − Maximum permissible values of FOCAL SPOT dimensions for NOMINAL FOCAL
SPOT VALUES.35
Table 4 − Standard magnifications for MODULATION TRANSFER FUNCTIONS.39
Table 5 – Standard magnifications for STAR PATTERN RESOLUTION LIMIT.51
Table 6 – LOADING FACTORS for the determination of the BLOOMING VALUE.53
Table C.1 − Methods for evaluation of specific aspects characterising the FOCAL SPOT.71

60336  IEC:2005 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEDICAL ELECTRICAL EQUIPMENT –
X-RAY TUBE ASSEMBLIES FOR MEDICAL DIAGNOSIS –
CHARACTERISTICS OF FOCAL SPOTS

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
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). 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. IEC collaborates closely
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
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
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
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
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 60336 has been prepared by subcommittee 62B: Diagnostic
imaging equipment, of IEC technical committee 62: Electrical equipment in medical practice.
This fourth edition cancels and replaces the third edition published in 1993 and constitutes a
technical revision. The significant changes of this fourth edition are detailed in Annex C (see
Clause C.6).
The text of this standard is based on the following documents:
FDIS Report on voting
62B/554/FDIS 62B/569/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.

60336  IEC:2005 – 9 –
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
In this standard, the following conventions apply.
a) Terms printed in small capitals are used as defined in IEC 60788 and in Clause 3 of this
standard. 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”.
b) Certain terms that are not printed in small capitals have particular meanings, as follows
− "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.
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.
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.
The contents of the corrigendum of May 2006 have been included in this copy.

60336  IEC:2005 – 11 –
MEDICAL ELECTRICAL EQUIPMENT –
X-RAY TUBE ASSEMBLIES FOR MEDICAL DIAGNOSIS –
CHARACTERISTICS OF FOCAL SPOTS

1 Scope
This International Standard applies to FOCAL SPOTs in medical diagnostic X-RAY TUBE
assemblies for medical use, operating at X-RAY TUBE VOLTAGEs up to and including 200 kV.
This International Standard describes the test methods for evaluating FOCAL SPOT character-
istics and the means for indicating compliance.
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.
1)
IEC 60417-DB:2002: Graphical symbols for use on equipment
IEC 60613, Electrical, thermal and loading characteristics of rotating anode X-ray tubes for
medical diagnosis
IEC 60788:2004, Medical electrical equipment – Glossary of defined terms
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60788 together with
the following apply.
3.1
STAR PATTERN RESOLUTION LIMIT
characteristic of the FOCAL SPOT of an X-RAY TUBE; highest spatial frequency that can be
resolved under specific measuring conditions
4 Determinations for the evaluation of the FOCAL SPOT characteristics
4.1 Statement of the FOCAL SPOT characteristics
The FOCAL SPOT characteristics shall be stated for two normal directions of evaluation referred
to as the length direction and width direction. An illustration for this clause can be found in
Figure A.1.
4.2 Longitudinal axis of the X-RAY TUBE ASSEMBLY
Generally, the longitudinal axis can be identified unambiguously. If the X-RAY TUBE ASSEMBLY
does not have an identifiable longitudinal axis or if it is specified otherwise by the
MANUFACTURER, the longitudinal axis shall be specified together with the FOCAL SPOT
characteristics.
———————
1)
"DB" refers to the IEC on-line database.

60336  IEC:2005 – 13 –
4.3 REFERENCE AXIS of the X-RAY TUBE ASSEMBLY
If not specified otherwise, the REFERENCE AXIS is normal to the longitudinal axis and intersects
both the centre of the ACTUAL FOCAL SPOT and the longitudinal axis of the X-RAY TUBE
ASSEMBLY.
4.4 Direction of evaluation for the FOCAL SPOT length
The direction of evaluation for the FOCAL SPOT length is normal to the REFERENCE AXIS in the
plane given by the REFERENCE AXIS and the longitudinal axis of the X-RAY TUBE ASSEMBLY.
4.5 Direction of evaluation for the FOCAL SPOT width
The direction of evaluation for the FOCAL SPOT width is normal to the longitudinal axis of the X-
RAY TUBE ASSEMBLY and normal to the REFERENCE AXIS.
5 FOCAL SPOT camera set-up
5.1 Overview
This clause deals with the design requirements of a camera for the production of FOCAL SPOT
SLIT RADIOGRAMs to be used for the determination of FOCAL SPOT dimensions in accordance
with Clause 8, and the determination of the modulation transfer function in accordance with
Clause 9.
This clause deals also with the design requirements of a camera for the production of FOCAL
SPOT PINHOLE RADIOGRAMs.
5.2 Test equipment
5.2.1 SLIT CAMERA
The diaphragm of the SLIT CAMERA shall be made from materials with high ATTENUATION
properties and shall have dimensions as given in Figure 1.
Suitable materials are for example:
– tungsten;
– tantalum;
– alloy of gold and 10 % platinum;
– alloy of tungsten and 10 % rhenium;
– alloy of platinum and 10 % iridium;

60336  IEC:2005 – 15 –
Dimensions in millimetres
Not drawn to scale
Axis of symmetry
0,01 ± 0,002
8° ± 1°
≥ 5
0,002
// 0,002
IEC  526/05
Figure 1 – Essential dimensions of the slit diaphragm
≥ 1,5
≤ 0,015
≥ 5
60336  IEC:2005 – 17 –
5.2.2 PINHOLE CAMERA
The diaphragm of the PINHOLE CAMERA shall be constructed from materials with high
ATTENUATION and shall have dimensions as given in Figure 2.
Suitable materials are for example:
– tungsten;
– tantalum;
– alloy of gold and 10 % platinum;
– alloy of tungsten and 10 % rhenium;
– alloy of platinum and 10 % iridium.
Dimensions in millimetres
Not drawn to scale
Axis of symmetry
0,03 ± 0,005
8° ± 1°
≥ 5
IEC  527/05
Figure 2 – Essential dimensions of the pinhole diaphragm
5.2.3 RADIOGRAPHIC FILM
FOCAL SPOT SLIT RADIOGRAMS or FOCAL SPOT PINHOLE RADIOGRAMS shall be made using fine-
grain radiographic film, for example dental radiographic film, without INTENSIFYING SCREENS.
5.3 Test arrangement
5.3.1 Position of the slit or pinhole diaphragm normal to the REFERENCE AXIS
The slit or pinhole diaphragm shall be positioned in such a way that the distance from its
centre to the REFERENCE AXIS is within 0,2 mm per 100 mm of m (as indicated in Figure 3).
≥ 1,5
≤ 0,075
60336  IEC:2005 – 19 –
EFFECTIVE FOCAL SPOT
REFERENCE PLANE
m
(100 mm min.)
REFERENCE AXIS
Incident face of the slit
or pinhole diaphragm
∅0,4 per
x
100 mm
Centre of diaphragm
n
IMAGE RECEPTION PLANE
IEC  528/05
Figure 3 − Position of the centre of the slit or pinhole diaphragm (marked as x
in the figure) with respect to the REFERENCE AXIS
5.3.2 Position of the slit or pinhole diaphragm along the REFERENCE AXIS
The incident face of the slit or pinhole diaphragm shall be placed at a distance from the
REFERENCE PLANE sufficient to ensure that the variation of the enlargement over the extension
of the ACTUAL FOCAL SPOT does not exceed ± 5 % along the REFERENCE AXIS (see Figure 4).
This is met when
p < 5 mm and k < 5 mm per 100 mm of distance m;
where
k is the distance from the REFERENCE PLANE to the edge of the ACTUAL FOCAL SPOT farthest
away from the slit or pinhole diaphragm;
p is the distance from the REFERENCE PLANE to the edge of the ACTUAL FOCAL SPOT closest to
the slit or pinhole diaphragm;
m is the distance from the REFERENCE PLANE to the incident face of the diaphragm;
n is the distance from the incident face of the diaphragm to the IMAGE RECEPTION PLANE;
E is the enlargement given by n/m .
The distance from the FOCAL SPOT to the slit or pinhole diaphragm shall not be less than
100 mm.
60336  IEC:2005 – 21 –
EFFECTIVE FOCAL SPOT
k
p
REFERENCE PLANE
m
Incident face of the slit
or pinhole diaphragm
REFERENCE AXIS
n
IMAGE RECEPTION PLANE
IEC  529/05
Figure 4 – Reference dimensions and planes
5.3.3 Orientation of the slit or pinhole diaphragm
The axis of symmetry (see Figures 1 and 2) shall be aligned with the REFERENCE AXIS forming
an angle that is smaller than 1° .
For the production of a pair of FOCAL SPOT SLIT RADIOGRAMs, the slit diaphragm shall be
orientated such that the length of the slit is normal to the direction of evaluation within ±1°.
5.3.4 Position of the RADIOGRAPHIC FILM
The RADIOGRAPHIC FILM should be placed in the IMAGE RECEPTION PLANE normal to the
REFERENCE AXIS within ±1° and at a distance from the incident face of the slit or pinhole
diaphragm determined from the appropriate enlargement according to Table 1. The
enlargement E shall be determined with an accuracy to within ±3 %.

60336  IEC:2005 – 23 –
Table 1 – Enlargement for FOCAL SPOT RADIOGRAMs
a
Enlargement
NOMINAL FOCAL SPOT VALUE (f)
b
(E = n / m)
f < 0,4 E > 3
0,4 < f < 1,1 E > 2
1,1 < f E ≥ 1
a
See 8.3.
b
See Figure 4.
5.4 Total uncertainty of the camera set-up
The uncertainty in the FOCAL SPOT measurement contributed by the set-up of the FOCAL SPOT
camera shall not exceed ±5 %.
6 Production of RADIOGRAMS
6.1 Overview
This clause deals with production of FOCAL SPOT SLIT RADIOGRAMS and FOCAL SPOT PINHOLE
RADIOGRAMS.
A method of indicating compliance with this standard of FOCAL SPOT SLIT RADIOGRAMS and
FOCAL SPOT PINHOLE RADIOGRAMS is included.
6.2 Operating conditions
6.2.1 FOCAL SPOT SLIT RADIOGRAMS and FOCAL SPOT PINHOLE RADIOGRAMS
FOCAL SPOT SLIT RADIOGRAMS and FOCAL SPOT PINHOLE RADIOGRAMS shall be produced using a
FOCAL SPOT camera according to Clause 5. Requirements for determining FOCAL SPOT
dimensions from FOCAL SPOT SLIT RADIOGRAMS are described in Clause 8; requirements for
determining the MODULATION TRANSFER FUNCTION are described in Clause 9.
FOCAL SPOT PINHOLE RADIOGRAMs are used only for showing the orientation, the symmetry and
the distribution of radiant intensity over the FOCAL SPOT.
6.2.2 X-RAY TUBE ASSEMBLY
The X-RAY TUBE shall be installed in an X-RAY TUBE HOUSING of the type for which it is
specified for NORMAL USE or it shall be placed under equivalent mounting and operating
conditions as far as these can influence the results of the test.
No ADDITIONAL FILTRATION shall be used to decrease the X-ray output flux unless it is verified
that the ADDITIONAL FILTRATION has no significant effect on the LINE SPREAD FUNCTION.
However, all the materials belonging to the X-RAY TUBE ASSEMBLY in NORMAL USE shall be
installed.
6.2.3 LOADING FACTORS
FOCAL SPOT SLIT RADIOGRAMS or FOCAL SPOT PINHOLE RADIOGRAMS for X-ray tube assemblies
used in projection radiography or in COMPUTED TOMOGRAPHY shall be obtained with constant
LOADING FACTORS in accordance with Table 2.

60336  IEC:2005 – 25 –
For ROTATING ANODE X-RAY TUBEs, the ANODE shall be rotated at the highest ANODE SPEED
specified in the applicable RADIOGRAPHIC RATINGs.
Table 2 − LOADING FACTORS
NOMINAL X-RAY Required X-RAY TUBE Exposure time Required X-RAY
TUBE VOLTAGE VOLTAGE TUBE power

kV
RADIOGRAPHY NOMINAL X-RAY TUBE
U < 75
other than VOLTAGE
50 % of the
COMPUTED As required to meet the
NOMINAL ANODE
75 < U < 150 75 kV
optical density
TOMOGRAPHY
INPUT POWER as
requirement, see 6.3.3
50 % of the NOMINAL
specified by
150 < U < 200
X-RAY TUBE VOLTAGE
IEC 60613
COMPUTED TOMOGRAPHY 120 kV
6.2.4 Special LOADING FACTORS
If the LOADING FACTORs according to Table 2 do not fall within the RADIOGRAPHIC RATINGs for
the X-RAY TUBE concerned or if they otherwise do not cover the typical special applications of
specified NORMAL USE of the X-RAY TUBE, LOADING FACTORs shall be chosen to correspond to
those specific conditions. In this case, the LOADING FACTORs under which the FOCAL SPOT SLIT
RADIOGRAMs or FOCAL SPOT PINHOLE RADIOGRAMs were obtained shall be stated together with
the characteristics.
In particular cases, it may be appropriate to state the characteristics of a FOCAL SPOT under
multiple LOADING conditions.
6.2.5 Special arrangements
If, for the purpose of production of suitable FOCAL SPOT RADIOGRAMs, special arrangements
were made for the adjustment and alignment of either the SLIT CAMERA and X-RAY TUBE
ASSEMBLY or if special electrical or LOADING conditions prevailed, details shall be stated
together with the characteristics in the statement of compliance.
6.3 Production of FOCAL SPOT SLIT RADIOGRAMS or FOCAL SPOT PINHOLE RADIOGRAMS
6.3.1 Production of FOCAL SPOT SLIT RADIOGRAMS
A pair of FOCAL SPOT SLIT RADIOGRAMs shall be made with the operating conditions described
in 6.2.
6.3.2 Production of FOCAL SPOT PINHOLE RADIOGRAMS
FOCAL SPOT PINHOLE RADIOGRAMs shall be made with the operating conditions described in 6.2.
6.3.3 RADIOGRAPHIC FILM exposure
The RADIOGRAPHIC FILM shall be exposed so that, after development, a local diffuse density
between 1,0 and 1,4 is obtained in areas of greatest blackening. The blackening of the film
due to fog and base shall not exceed a diffuse density of 0,25.

60336  IEC:2005 – 27 –
6.4 Statement of compliance
If compliance with this standard is to be stated for a pair of FOCAL SPOT SLIT RADIOGRAMs or for
a FOCAL SPOT PINHOLE RADIOGRAM, it shall be stated as follows:
2)
FOCAL SPOT SLIT RADIOGRAM with enlargement of…. according to IEC 60336 or FOCAL SPOT
3)
PINHOLE RADIOGRAM with enlargement of … according to IEC 60336
and as appropriate: Subclause
REFERENCE AXIS 4.3
LOADING FACTORS 6.2.3
Special arrangements 6.2.5
Description of the longitudinal axis of the X-RAY TUBE ASSEMBLY 4.2

7 Determination of the LINE SPREAD FUNCTION
7.1 Overview
This clause deals with the determination of a pair of LINE SPREAD FUNCTIONS to be used for the
determination of FOCAL SPOT dimensions in accordance with Clause 8 and the determination of
the MODULATION TRANSFER FUNCTION in accordance with Clause 9. These LINE SPREAD
FUNCTIONs shall be deduced from FOCAL SPOT SLIT RADIOGRAMs.
A method of indicating compliance with this standard of a pair of LINE SPREAD FUNCTIONS is
included.
7.2 Measuring equipment and measuring arrangement
The FOCAL SPOT SLIT RADIOGRAMs obtained in accordance with Clause 5 and Clause 6 shall be
scanned by means of an optical densitometer. The aperture of the optical densitometer shall
have a width b not exceeding the width of the slit diaphragm used for the production of the
FOCAL SPOT SLIT RADIOGRAMs.
The length of the aperture of the optical densitometer shall be limited, so that it can be
aligned with the direction of the diaphragm slit projected on the RADIOGRAM in such a way that
the effective width b of the optical densitometer aperture normal to the direction of the
eff
projected diaphragm slit will be smaller than twice the width b of the optical densitometer
aperture, as shown in Figure 5.
———————
2)
Enlargement used and determined in accordance with Clause 5.
3)
Enlargement used and determined in accordance with Clause 5.

60336  IEC:2005 – 29 –
b
Longitudinal direction of the
diaphragm slit projected
on the RADIOGRAM
Direction of the optical
densitometer aperture
Scanning direction
b
eff
b < 2b
eff
IEC  530/05
Figure 5 − Alignment of the optical densitometer slit
7.3 Measurement of the density distribution
The density distribution of each FOCAL SPOT SLIT RADIOGRAM shall be scanned normal to its
longitudinal direction at the centre half of its length. The scanning direction shall be aligned
normal to the direction of the diaphragm slit to within ±2°.
The total range scanned divided by the enlargement E used to acquire the FOCAL SPOT SLIT
RADIOGRAM shall be at least four times the maximum allowed value relating to the claimed
NOMINAL FOCAL SPOT VALUE.
The results of this measurement shall be presented as a curve showing density over the width
of the RADIOGRAM.
7.4 Determination of the LINE SPREAD FUNCTION
The values of density above base and fog shall be transformed into a curve showing the
linear distribution over the width of the RADIOGRAM of the radiant intensity, by means of a
densitometric curve showing the relation between radiant intensity and density.
The densitometric curve shall be established using an identical RADIOGRAPHIC FILM processed
under the same conditions as those used for the FOCAL SPOT SLIT RADIOGRAM.
The LINE SPREAD FUNCTION shall be deduced from the curve showing the linear distribution of
the radiant intensity over the width of the RADIOGRAM, where the axis values in the scanning
direction are divided by the enlargement E used to acquire the FOCAL SPOT SLIT RADIOGRAM.
7.5 Statement of compliance
If compliance with this standard for a LINE SPREAD FUNCTION is to be stated, this shall be done
as follows:
60336  IEC:2005 – 31 –
LINE SPREAD FUNCTION according to IEC 60336
and as appropriate: Subclause
REFERENCE AXIS 4.3
LOADING FACTORS 6.2.3
Special arrangements 6.2.5
Description of the longitudinal axis of the X-RAY TUBE ASSEMBLY 4.2

8 Determination of FOCAL SPOT dimensions
8.1 Overview
This clause deals with the determination of the FOCAL SPOT dimensions on the basis of a pair
of LINE SPREAD FUNCTIONs. These functions shall be obtained from a pair of FOCAL SPOT SLIT
RADIOGRAMs as described in Clause 6.
Criteria for compliance with this standard and the method of indicating NOMINAL FOCAL SPOT
VALUEs in compliance with this standard are included.
8.2 Measurement and determination
The actual dimension of the FOCAL SPOT shall be determined as the size of the related LINE
SPREAD FUNCTION according to Clause 7 measured at 15 % of the peak value, as shown in
Figure 6.
100 %
80 %
60 %
40 %
At 15 % actual dimension
20 %
Linear distribution
IEC  531/05
Figure 6 – LINE SPREAD FUNCTION
Radiant intensity
60336  IEC:2005 – 33 –
8.3 Specified NOMINAL FOCAL SPOT VALUES
8.3.1 Nominal values
The FOCAL SPOTs of each type of X-ray tube assembly, NOMINAL FOCAL SPOT VALUEs shall be
assigned, being the numbers
– from 0,1 to 0,25 in steps of 0,05,
– from 0,3 to 2,0 in steps of 0,1, and
– from 2,2 and upwards in steps of 0,2.
The FOCAL SPOTs of X-RAY TUBE assemblies specified for special applications (such as for CT)
shall be stated in NOMINAL FOCAL SPOT VALUEs consisting of a pair of numbers, for example
1,0 × 1,6, where the first number refers to the width of the EFFECTIVE FOCAL SPOT in the
direction normal to the REFERENCE AXIS or the axis of the X-RAY TUBE ASSEMBLY, and the
second to the length of the EFFECTIVE FOCAL SPOT in the direction parallel to that axis. This
pair of values shall be stated in the same steps as given above.
8.3.2 Actual values
The NOMINAL FOCAL SPOT VALUE shall be related to the dimensions in the two directions of
evaluation over the FOCAL SPOT so that the actual values for the width and the length of the
FOCAL SPOT determined in accordance with 8.2 are smaller than the maximum permissible
values for width and length given in Table 3.
Each number of a pair of FOCAL SPOT values for special applications such as for CT shall be
related to the NOMINAL FOCAL SPOT VALUE in Table 3 using the column of maximum permissible
values for width only.
For these determinations, no correction is required for measurement errors.

60336  IEC:2005 – 35 –
Table 3 − Maximum permissible values of FOCAL SPOT dimensions
for NOMINAL FOCAL SPOT VALUES
FOCAL SPOT dimensions,
NOMINAL FOCAL SPOT
Maximum permissible values
VALUE
mm
f Width Length
0,1 0,15 0,15
0,15 0,23 0,23
0,2 0,30 0,30
0,25 0,38 0,38
0,3 0,45 0,65
0,4 0,60 0,85
0,5 0,75 1,10
0,6 0,90 1,30
0,7 1,10 1,50
0,8 1,20 1,60
0,9 1,30 1,80
1,0 1,40 2,00
1,1 1,50 2,20
1,2 1,70 2,40
1,3 1,80 2,60
1,4 1,90 2,80
1,5 2,00 3,00
1,6 2,10 3,10
1,7 2,20 3,20
1,8 2,30 3,30
1,9 2,40 3,50
2,0 2,60 3,70
2,2 2,90 4,00
2.4 3,10 4,40
2,6 3,40 4,80
2,8 3,60 5,20
3,0 3,90 5,60
NOTE For NOMINAL FOCAL SPOT VALUES 0,3 to 3,0, the maximum
permissible values for the length have been adjusted with the factor 0,7
(see Annex C).
60336  IEC:2005 – 37 –
8.4 Statement of compliance
If compliance with this standard for one or more NOMINAL FOCAL SPOT VALUEs is to be stated,
this shall be done:
− as plain numbers (no units to be quoted), for example:
NOMINAL FOCAL SPOT VALUE 0,6 in accordance with IEC 60336 Ed.4.
− or as a pair of plain numbers for special application X-RAY TUBE ASSEMBLIES (see 8.3.1), no
units to be quoted, for example:
NOMINAL FOCAL SPOT VALUEs 1,0 x 0,6 in accordance with IEC 60336 Ed.4.
and as appropriate: Subclause
REFERENCE AXIS 4.3
LOADING FACTORS 6.2.3
Special arrangements 6.2.5
Description of the longitudinal axis of the X-RAY TUBE ASSEMBLY 4.2

8.5 Marking of compliance
If compliance with this standard for one or more specified NOMINAL FOCAL SPOT VALUEs is to be
marked on X-RAY TUBE assemblies, or otherwise to be stated in a shortened form, this shall be
done as follows, using graphical symbols of IEC 60417, for example:
Symbol IEC 60417-5325  Symbol IEC 60417-5326 Symbol IEC 60417-5327
(DB:2002-10) (DB:2002-10) (DB:2002-10)

0,6 IEC 60336 1,0 x 1,6 IEC 60336 1,8 x 1,2 IEC 60336

9 Determination of the MODULATION TRANSFER FUNCTION
9.1 Overview
This clause deals with the determination of the one-dimensional MODULATION TRANSFER
FUNCTIONs belonging to the FOCAL SPOT of an X-RAY TUBE ASSEMBLY on the basis of a pair of
LINE SPREAD FUNCTIONs.
Criteria for compliance with this standard and a method of indicating modulation transfer
functions in compliance with this standard are included.
9.2 Specified MODULATION TRANSFER FUNCTION
If the statement of the modulation transfer function is required, a pair of one-dimensional
modulation transfer functions of the geometry of each FOCAL SPOT shall be specified for each
type of X-RAY TUBE ASSEMBLY.
If compliance for an individual X-RAY TUBE ASSEMBLY is to be stated with this standard, it shall
be evaluated in accordance with 9.4.

60336  IEC:2005 – 39 –
9.3 Calculation of the MODULATION TRANSFER FUNCTION
9.3.1 Calculation for the theoretical magnification approaching infinity
The one-dimensional MODULATION TRANSFER FUNCTION of the geometry of a FOCAL SPOT shall
be calculated by means of the magnitude of the Fourier transform.
The input values for carrying out the Fourier transform shall be the DIGITISED LINE SPREAD
FUNCTION obtained in Clause 7, which shall be scanned over a range of at least three times
the FOCAL SPOT size. The distance between the measurement points along the abscissa shall
be chosen so that the extent and the structures of the linear distribution of radiant intensity
over the FOCAL SPOT will be taken into account, and a further reduction of the distance shall
not result in a significant change in the stated values, i.e. the distance between measuring points
is such that a further 50 % reduction of the distance does not change the reported MTF at any point by
more than 5 %.
NOTE In most cases, it is sufficient if the step between two measuring points divided by the enlargement (E) used
to acquire the FOCAL SPOT SLIT RADIOGRAM is less than 10 % of the related NOMINAL FOCAL SPOT VALUE if this value
is smaller than or equal to 0,15, and is less than 5 % of the related NOMINAL FOCAL SPOT VALUE if this value is
greater than 0,15.
9.3.2 Calculation for the standard magnification
The values of spatial frequency obtained in accordance with 9.3.1 shall be transformed in
accordance with the formula:
f = f · M / (M -1)
s i s s
where
M is the standard magnification given in Table 4;
s
f is the spatial frequency in the object plane determined by the standard magnification M ;
s s
f is the spatial frequency obtained in accordance with 9.3.1.
i
Table 4 − Standard magnifications for MODULATION TRANSFER FUNCTIONS
NOMINAL FOCAL SPOT VALUE Standard magnification
f M
s
f < 0,6 2
1,3
0,6 ≤ f
NOTE In general the magnification M for any object is given by M = (n + m)/m (analogous to Figures 3 and 8).
9.3.3 Calculation for finite magnification
For the application of the MODULATION
...