IEC 60613:2010
(Main)Electrical and loading characteristics of X-ray tube assemblies for medical diagnosis
Electrical and loading characteristics of X-ray tube assemblies for medical diagnosis
IEC 60613:2010 applies to X-ray tube assemblies either with a rotating anode X-ray tube or a stationary anode X-ray tube, intended for use in medical diagnosis. For an X-ray tube head, its X-ray tube assembly aspects are also within the scope. IEC 60613:2010 covers performance-related definitions and conditions of electrical and loading characteristics of X-ray tube assemblies in relation to their behaviour during and after energization and, where appropriate, methods of presentation and measurement of these characteristics. This International Standard is therefore relevant for the manufacturer and the responsible organization. This third edition cancels and replaces the second edition of IEC 60613, published in 1989. It constitutes a technical revision. This third edition has been adapted to apply to the present technology.
Caractéristiques électriques et de charge des gaines équipées pour diagnostic médical
La CEI 60613:2010 s'applique aux gaines équipées à tube radiogène à anode tournante ou à tube radiogène à anode fixe, destinées à être utilisées pour le diagnostic médical. Pour une tête de tube radiogène, ses aspects concernant le tube radiogène relèvent également du domaine d'application. La CEI 60613:2010 comprend les définitions et les conditions de performance des caractéristiques électriques et de charge des gaines équipées par rapport à leur comportement pendant et après la mise sous tension avec, si besoin, des méthodes de présentation et de mesure de ces caractéristiques. La présente Norme Internationale est de ce fait utile pour le fabricant et pour l'organisme responsable. Cette troisième édition annule et remplace la deuxième édition de la CEI 60613 publiée en 1989, dont elle constitue une révision technique. Cette troisième édition a été adaptée afin d'appliquer les technologies actuelles.
General Information
Standards Content (Sample)
IEC 60613 ®
Edition 3.0 2010-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electrical and loading characteristics of X-ray tube assemblies for medical
diagnosis
Caractéristiques électriques et de charge des gaines équipées pour diagnostic
médical
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IEC 60613 ®
Edition 3.0 2010-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electrical and loading characteristics of X-ray tube assemblies for medical
diagnosis
Caractéristiques électriques et de charge des gaines équipées pour diagnostic
médical
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
S
CODE PRIX
ICS 11.040.50 ISBN 978-2-88910-235-8
– 2 – 60613 © IEC:2010
CONTENTS
FOREWORD.3
1 Scope.5
2 Normative references .5
3 Terms and definitions .5
4 Presentation of the electrical characteristic .8
4.1 X-RAY TUBE VOLTAGE .8
4.2 NOMINAL X-RAY TUBE VOLTAGE .8
4.3 X-RAY TUBE CURRENT.8
4.4 CATHODE EMISSION CHARACTERISTIC.8
4.5 ENVELOPE characteristics.9
4.5.1 ENVELOPE CURRENT .9
4.5.2 ENVELOPE VOLTAGE .9
5 LOADING of an X-RAY TUBE.9
5.1 LOADING TIME .9
5.1.1 Units.9
5.1.2 Measurement.9
5.2 CYCLE TIME .9
6 Input power .9
6.1 ANODE INPUT POWER.9
6.2 NOMINAL ANODE INPUT POWER .9
6.3 NOMINAL RADIOGRAPHIC ANODE INPUT POWER .10
6.4 NOMINAL CT ANODE INPUT POWER .10
6.5 X-RAY TUBE ASSEMBLY INPUT POWER .10
6.6 NOMINAL CONTINUOUS INPUT POWER.10
6.7 CONTINUOUS ANODE INPUT POWER .10
6.8 CT SCAN POWER INDEX (CTSPI).10
6.9 NOMINAL CT SCAN POWER INDEX (NOMINAL CTSPI) .10
7 RADIOGRAPHIC RATINGS.10
7.1 General .10
7.2 SINGLE LOAD RATING .10
7.3 SERIAL LOAD RATING .10
8 Presentation of data .11
Annex A (informative) Rationale and historical background.12
Annex B (informative) Measurement of the X-RAY TUBE CURRENT.17
Bibliography.18
Index of defined terms .19
Figure A.1 – Example: SINGLE LOAD RATING chart showing CTSPI calculation area for
scan time interval of 1 s to 25 s .14
Figure A.2 – Example: SINGLE LOAD RATING curves for two different CT tubes, both
having the same value of NOMINAL CT ANODE INPUT POWER .15
Figure B.1 – Electrical schematic of X-RAY TUBE CURRENT measurement .17
60613 © IEC:2010 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL AND LOADING CHARACTERISTICS
OF X-RAY TUBE ASSEMBLIES FOR MEDICAL DIAGNOSIS
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
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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 60613 has been prepared by subcommittee 62B: Diagnostic
imaging equipment, of IEC technical committee TC 62: Electrical equipment in medical
practice.
This third edition cancels and replaces the second edition of IEC 60613, published in 1989. It
constitutes a technical revision. This third edition has been adapted to apply to the
present technology.
The text of this standard is based on the following documents:
FDIS Report on voting
62B/774/FDIS 62B/780/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 – 60613 © IEC:2010
In this standard, the following print types are used:
– requirements and definitions: roman type.
– informative material appearing outside of tables, such as notes, examples and references: in smaller type.
Normative text of tables is also in a smaller type;
– TERMS DEFINED IN CLAUSE 3 OF THIS STANDARD OR AS NOTED: SMALL CAPS.
The committee has decided that the contents of this publication will remain unchanged until
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the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
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IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
60613 © IEC:2010 – 5 –
ELECTRICAL AND LOADING CHARACTERISTICS
OF X-RAY TUBE ASSEMBLIES FOR MEDICAL DIAGNOSIS
1 Scope
This International Standard applies to X-RAY TUBE ASSEMBLIES either with a rotating ANODE X-
RAY TUBE or a stationary ANODE X-RAY TUBE, intended for use in medical diagnosis.
For an X-RAY TUBE HEAD, its X-RAY TUBE ASSEMBLY aspects are also within the scope.
This International Standard covers performance-related definitions and conditions of electrical
and LOADING characteristics of X-RAY TUBE ASSEMBLIES in relation to their behaviour during and
after energization and, where appropriate, methods of presentation and measurement of
these characteristics. This International Standard is therefore relevant for the MANUFACTURER
and the RESPONSIBLE ORGANIZATION.
NOTE “Measurement" in this standard is always related to practical use. Consequently, “measurement" is meant
to consume only a negligible part of the life of the X-RAY TUBE ASSEMBLY.
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 60601-1:2005, Medical electrical equipment – Part 1: General requirements for basic
safety and essential performance
IEC 60601-1-3:2008, Medical electrical equipment – Part 1-3: General requirements for basic
safety and essential performance – Collateral Standard: Radiation protection in diagnostic X-
ray equipment
IEC/TR 60788:2004, Medical electrical equipment – Glossary of defined terms (available only
in English)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC/TR 60788:2004,
IEC 60601-1:2005 and IEC 60601-1-3:2008 and the following apply.
3.1
X-RAY TUBE VOLTAGE
potential difference applied to an X-RAY TUBE between the ANODE and the CATHODE. Usually X-
RAY TUBE VOLTAGE is expressed by its peak value in kilovolts (kV)
[IEC 60601-1-3:2008, 3.88]
3.2
NOMINAL X-RAY TUBE VOLTAGE
highest permitted X-RAY TUBE VOLTAGE for SPECIFIC operating conditions
[IEC 60601-1-3:2008, 3.42]
– 6 – 60613 © IEC:2010
NOTE 1 For different operating conditions of the X-RAY TUBE, for example continuous operation, intermittent
operation, short-time operation, different types of X-RAY TUBE HOUSINGS, there may be different values of the above
NOMINAL X-RAY TUBE VOLTAGE.
NOTE 2 Additionally, values may be given for the highest permitted potential difference between ANODE and earth
and between CATHODE and earth.
3.3
X-RAY TUBE CURRENT
electric current of the ELECTRON beam incident on the TARGET of an X-RAY TUBE. Usually, the
X-RAY TUBE CURRENT is expressed by its mean value in milliamperes (mA)
[IEC 60601-1-3:2008, 3.85]
NOTE See Annex B for further considerations.
3.4
CATHODE EMISSION CHARACTERISTIC
dependence of the X-RAY TUBE CURRENT on variables, for example FILAMENT CURRENT, X-RAY
TUBE VOLTAGE
3.5
ENVELOPE
vacuum-wall of the X-RAY TUBE
3.6
ENVELOPE CURRENT
electric current, flowing via a conducting part of an ENVELOPE
3.7
ENVELOPE VOLTAGE
potential difference between an X-RAY TUBE-conducting ENVELOPE part and earth
3.8
LOADING
in an X-RAY GENERATOR, act of supplying electrical energy to the ANODE of an X-RAY TUBE
[IEC 60601-1-3:2008, 3.34]
3.9
X-RAY TUBE LOAD
electrical energy supplied to an X-RAY TUBE expressed by a combination of values of LOADING
FACTORS
3.10
LOADING FACTOR
factor influencing by its value the X-RAY TUBE LOAD, for example X-RAY TUBE CURRENT, LOADING
TIME, CONTINUOUS ANODE INPUT POWER, X-RAY TUBE VOLTAGE and PERCENTAGE RIPPLE
[IEC 60601-1-3:2008, 3.35]
3.11
LOADING TIME
time determined according to a SPECIFIC method, during which the ANODE INPUT POWER is
applied to the X-RAY TUBE
[IEC 60601-1-3:2008, 3.37]
60613 © IEC:2010 – 7 –
3.12
CYCLE TIME
for a series of single LOADINGS: time interval from the beginning of a LOADING to the beginning
of the next, identical LOADING
for a series of serial LOADINGS: time interval from the beginning of a serial LOADING to the
beginning of the next, identical serial LOADING
3.13
ANODE INPUT POWER
power applied to the ANODE of an X-RAY TUBE to produce X-RADIATION
3.14
NOMINAL ANODE INPUT POWER
highest constant ANODE INPUT POWER that can be applied for a single X-RAY TUBE LOAD in a
SPECIFIC LOADING TIME and under SPECIFIED conditions
3.15
NOMINAL RADIOGRAPHIC ANODE INPUT POWER
NOMINAL ANODE INPUT POWER which can be applied for a single X-RAY TUBE LOAD with a
LOADING TIME of 0,1 s and a CYCLE TIME of 1,0 min, for an indefinite number of cycles
NOTE 1 In this application, RADIOSCOPY is not applied.
NOTE 2 With this definition mammographic and dental X-ray are included, see A.3.3 in Annex A.
3.16
NOMINAL CT ANODE INPUT POWER
NOMINAL ANODE INPUT POWER which can be applied for a single X-RAY TUBE LOAD with a
LOADING TIME of 4 s and a CYCLE TIME of 10 min, for an indefinite number of cycles
3.17
X-RAY TUBE ASSEMBLY INPUT POWER
mean power applied to an X-RAY TUBE ASSEMBLY for all purposes before, during and after
LOADING, including power applied to the stator of a rotating ANODE X-RAY TUBE, to the filament
and to any other device included in the X-RAY TUBE ASSEMBLY
3.18
NOMINAL CONTINUOUS INPUT POWER
SPECIFIED highest X-RAY TUBE ASSEMBLY INPUT POWER, which can be applied to an X-RAY TUBE
ASSEMBLY continuously
3.19
CONTINUOUS ANODE INPUT POWER
SPECIFIED highest ANODE INPUT POWER, which can be applied to the ANODE continuously
NOTE 1 CONTINUOUS ANODE INPUT POWER may be determined by subtracting all power other than the ELECTRON
beam power, such as filament heating, ANODE drive, from the NOMINAL CONTINUOUS INPUT POWER.
NOTE 2 If not SPECIFIED otherwise, CONTINUOUS ANODE INPUT POWER is the referenced LOADING FACTOR for
determining the LEAKAGE RADIATION.
3.20
CT SCAN POWER INDEX
CTSPI
characteristic of an X-RAY TUBE ASSEMBLY intended for use in COMPUTED TOMOGRAPHY for a
SPECIFIED range of LOADING TIMES for single LOADINGS, for a given CYCLE TIME, as follows
t
max
CTSPI = P()t dt
∫
(t −t )
max min
t
min
– 8 – 60613 © IEC:2010
where
t is the upper limit of the LOADING TIME in seconds,
max
t is the lower limit of the LOADING TIME in seconds, and
min
P(t) is the function representing the SINGLE LOAD RATING in kilowatts
NOTE The CTSPI represents the effective power for PATIENT throughput in CT scanning.
3.21
NOMINAL CT SCAN POWER INDEX
NOMINAL CTSPI
CTSPI, calculated for a lower limit of the LOADING TIME of 1 s, an upper of the LOADING TIME of
25 s and a CYCLE TIME of 10 min
3.22
RADIOGRAPHIC RATINGS
for the operation of an X-RAY TUBE, SPECIFIED combinations of conditions and LOADING
FACTORS, under which the SPECIFIED limits of loadability of the X-RAY TUBE are attained
3.23
SINGLE LOAD RATING
highest permitted X-RAY TUBE LOAD given by a relationship between constant ANODE INPUT
POWER and LOADING TIME for one LOADING under SPECIFIED conditions
3.24
SERIAL LOAD RATING
highest permitted X-RAY TUBE LOAD given by the relationship between ANODE INPUT POWER and
LOADING TIME for the total of a SPECIFIED series of individual X-RAY TUBE LOADS with SPECIFIED
LOADING FACTORS under SPECIFIED conditions
4 Presentation of the electrical characteristic
4.1 X-RAY TUBE VOLTAGE
The X-RAY TUBE VOLTAGE shall be given as the peak value, in kilovolts.
4.2 NOMINAL X-RAY TUBE VOLTAGE
The NOMINAL X-RAY TUBE VOLTAGE shall be given as the peak value, in kilovolts.
4.3 X-RAY TUBE CURRENT
The X-RAY TUBE CURRENT shall be given as the average value in milliamperes.
4.4 CATHODE EMISSION CHARACTERISTIC
CATHODE EMISSION CHARACTERISTICS are given as a family of curves in which the X-RAY TUBE
CURRENT is shown as a function of the FILAMENT CURRENT and, if appropriate, of further
characteristics of the CATHODE, each curve corresponding to an X-RAY TUBE VOLTAGE while
specifying its waveform, and other factors as appropriate. If appropriate, the relationship
between FILAMENT CURRENT and filament voltage shall be indicated and also its dependence
on other characteristics of the CATHODE.
60613 © IEC:2010 – 9 –
4.5 ENVELOPE characteristics
4.5.1 ENVELOPE CURRENT
If the ENVELOPE CURRENT is to be stated, it shall be given as the percentage value of X-RAY
TUBE CURRENT under SPECIFIED conditions.
4.5.2 ENVELOPE VOLTAGE
If the ENVELOPE VOLTAGE is to be stated, it shall be given in kilovolts with respect to earth.
5 LOADING of an X-RAY TUBE
5.1 LOADING TIME
5.1.1 Units
The LOADING TIME shall be given in seconds.
5.1.2 Measurement
LOADING TIME is measured as the time interval between:
– the instant that the X-RAY TUBE VOLTAGE has risen for the first time to a value of 75 % of
the peak value; and
– the instant at which it finally drops below the same value.
If LOADING is controlled by electronic switching of the HIGH VOLTAGE, using a grid in an
electronic tube or in the X-RAY TUBE, the LOADING TIME may be determined as the time interval
between the instant when the TIMING DEVICE generates the signal to start the IRRADIATION and
the instant when it generates the signal to terminate the IRRADIATION.
If LOADING is controlled by simultaneous switching in the primaries of both the high-voltage
circuit and the heating supply for the filament of the X-RAY TUBE, the LOADING TIME shall be
determined as the time interval between the instant when the X-RAY TUBE CURRENT first rises
above 25 % of its maximum value and the instant when it finally falls below the same value.
NOTE 1 See also definition 3.11.
NOTE 2 The LOADING TIME is preferably measured at the tube input to minimise the influence of HV-cable-
capacitance.
NOTE 3 For field-testing, a reasonable approximation of the LOADING TIME can be obtained by measuring the
IRRADIATION TIME, for which the SPECIFIC method according to the definition in IEC 60601-1-3:2008 is chosen in this
International Standard as the time period during which the AIR KERMA RATE exceeds 50 % of its peak value.
5.2 CYCLE TIME
The CYCLE TIME shall be given in minutes or seconds, as appropriate.
6 Input power
6.1 ANODE INPUT POWER
The ANODE INPUT POWER shall be given in kilowatts for SPECIFIED conditions of LOADING.
6.2 NOMINAL ANODE INPUT POWER
The NOMINAL ANODE INPUT POWER shall be given in kilowatts.
– 10 – 60613 © IEC:2010
6.3 NOMINAL RADIOGRAPHIC ANODE INPUT POWER
The NOMINAL RADIOGRAPHIC ANODE INPUT POWER shall be given in kilowatts.
6.4 NOMINAL CT ANODE INPUT POWER
The NOMINAL CT ANODE INPUT POWER shall be given in kilowatts.
6.5 X-RAY TUBE ASSEMBLY INPUT POWER
The X-RAY TUBE ASSEMBLY INPUT POWER shall be given in watts.
6.6 NOMINAL CONTINUOUS INPUT POWER
The NOMINAL CONTINUOUS INPUT POWER shall be given in watts.
Unless otherwise SPECIFIED, the ambient temperature shall be between 20 °C and 25 °C.
6.7 CONTINUOUS ANODE INPUT POWER
The CONTINUOUS ANODE INPUT POWER shall be given in watts.
6.8 CT SCAN POWER INDEX (CTSPI)
The CT SCAN POWER INDEX shall be given in kilowatts.
6.9 NOMINAL CT SCAN POWER INDEX (NOMINAL CTSPI)
The NOMINAL CT SCAN POWER INDEX shall be given in kilowatts.
7 RADIOGRAPHIC RATINGS
7.1 General
RADIOGRAPHIC RATINGS shall provide application-relevant parametric information on LOADING
FACTORS, in any form of presentation (tables, graphs .) which is supporting the application. If
a NOMINAL ANODE INPUT POWER is SPECIFIED, the RADIOGRAPHIC RATINGS shall at least
encompass the set of LOADING FACTORS pertinent to the SPECIFIED NOMINAL ANODE INPUT
POWER.
7.2 SINGLE LOAD RATING
The SINGLE LOAD RATING shall be presented as curves or as a table of numerical values
showing constant ANODE INPUT POWER as a function of LOADING TIME and CYCLE TIME for
appropriate LOADING FACTORS, for example NOMINAL FOCAL SPOT VALUE, ANODE SPEED and
others.
7.3 SERIAL LOAD RATING
SERIAL LOAD RATINGS shall be presented as curves or as a table of numerical values with
values of the CYCLE TIME and the appropriate LOADING FACTORS, for example, ANODE INPUT
POWER for an individual X-RAY TUBE LOAD, LOADING TIME of an individual X-RAY TUBE LOAD, total
number of LOADINGS or the duration of a series of LOADINGS, number of individual X-RAY TUBE
LOADS per second.
60613 © IEC:2010 – 11 –
8 Presentation of data
If single data values are presented in compliance with this International Standard, such values
shall be designated as follows:
IEC 60613:2010
If graphs or tables are presented in compliance with this International Standard, a reference
to IEC 60613:2010 shall be given.
– 12 – 60613 © IEC:2010
Annex A
(informative)
Rationale and historical background
A.1 Overview
The purpose of this annex is to state the general objectives and approach used in creating the
rd
3 edition of this standard, and to clarify the inclusion of those items which are substantially
new to this edition, as well as to clarify why some items are no longer described.
st nd
A.2 History: basis of 1 and 2 editions
The subject matter of these earlier editions was the electrical and thermal ratings of medical
X-RAY TUBE ASSEMBLIES and their LOADING characteristics. Therefore, the thermal/electrical
construction and operating mechanisms of X-RAY TUBES existing at the time of the earlier
editions of the standard had a significant impact on the content of those early versions.
Historically, medical X-RAY TUBES have been primarily constructed with glass ENVELOPES
which act as the insulating support between the electrically charged ANODE and CATHODE
electrodes. As such, it was not necessary or practical to define the electrical potential of this
insulating ENVELOPE, which takes on an ambiguous charge state at any particular point of its
surface. It was sufficient to state the potential difference between the ANODE and the
CATHODE, or the potential of these electrodes relative to earth. Regarding the thermal/LOADING
characteristics, most medical rotating ANODE X-RAY TUBES were constructed in such a way as
to temporarily store the heat generated in the bremsstrahlung process and then dissipate it
through the very non-linear thermal RADIATION process. Further, at the time of the earlier
editions, applications were primarily directed at RADIOGRAPHY. In the meantime, vascular and
CT applications, implying different LOADING conditions (relatively long exposures, heavy
PATIENT throughput) have to be considered.
rd
A.3 Problems and solutions: objectives of the 3 edition
A.3.1 General
Technical advancements in X-RAY TUBE design have lead to improvements, particularly in the
thermal operation of X-RAY TUBES that have made the application of the previous edition of the
standard inadequate. The main advancements and their impacts on the application of the
standard are described below.
A.3.2 Advent of metal/ceramic ENVELOPE construction
One of the advancements that have been widely adopted in the industry, especially for high-
power X-RAY TUBES, is the use of metallic ENVELOPES, often with ceramic, i.e. non-glass
insulators. These ENVELOPES can carry a substantial fraction of the overall X-RAY TUBE
CURRENT during operation as backscattered ELECTRONS from the TARGET are collected on the
inner surfaces of the metallic ENVELOPE and conducted back through to the HIGH-VOLTAGE
GENERATOR. Because it is important to know what the intended electrical connection scheme
is between the tube and generator, this edition of the standard has added a section of terms
and definitions specifically related to the ENVELOPE’S electrical configuration.
A.3.3 Thermal ratings definitions moved away from heat-content based definitions
The older editions of the standard described the tube’s thermal performance in terms of
characteristics such as the heat storage content, the heat dissipation rate, heating curves and
cooling curves. Before the widespread availability of computers integrated into X-ray imaging
systems, this data was intended to be used by the technologist to calculate the X-RAY TUBE’S
60613 © IEC:2010 – 13 –
thermal state prior to applying a given LOADING or load sequence. In modern X-RAY
EQUIPMENT, feedback algorithms track the tube’s thermal state and prevent accidental
overloading of the tube’s thermal limits, making the need for such detailed thermal information
obsolete.
At the same time, changes in tube design made these defined characteristics less useful for
estimating the thermal performance of a given X-RAY TUBE. First, rotating ANODE heat storage
ratings increased rapidly with the advent of high-throughput CT systems (and to some degree
with certain cardio-vascular X-ray applications). The nature of the construction of high storage
ANODES is such that thermal time lags within the TARGET disk are often significant and cannot
be adequately modelled by the simple heating/cooling assumptions rooted in the previous
versions of the standard. Second, in more recent years, innovations in the cooling of rotating
ANODES has lead to cooling behaviours that are quite different from those of the assumed
radiation-dominated models of the older versions of the standard. With these advancements
and others on the horizon, it became apparent that the usefulness of the older definitions was
diminished and that a new approach was called for.
Foremost, the new standard should better enable the description and comparison of the
“clinically relevant” performance of the X-RAY TUBE, as a service to the PATIENT and customer
community. With this approach in mind along with a few other “clean-up” objectives, the
rd
changes to the 3 edition of the standard were made based on the following list of goals:
• Wherever possible, eliminate definitions that take special laboratory conditions to verify,
such as heat content, and replace them with definitions that are verifiable by an end-user,
such as power and time. An example of the application of this goal is to specify the initial
thermal state of an ANODE in terms of a steady-state CYCLE TIME, which can be reproduced
in a clinical setting, instead of a thermal storage state (HU or joules), which can only be
directly verified in a laboratory setting. Heat units (HU) had been introduced in the past to
compare multipulse X-RAY GENERATORS to single or 2-pulse X-RAY GENERATORS.
• Apply definitions that represent clinically relevant conditions. Thus, for example, move
away from defining the NOMINAL ANODE INPUT POWER for a CT tube at the traditional
exposure time of 0,1 s, since this is not a common technique for typical clinical scan
sequences (hence, leading to the new definition of NOMINAL CT ANODE INPUT POWER).
Further, as “PATIENT throughput” is highly relevant for both clinical applications and for the
thermal characteristics of the X-RAY TUBE, the new term “CYCLE TIME” has been introduced.
The notion of CYCLE TIME is the new approach for defining the NOMINAL ANODE INPUT
POWER, namely defining that power for an indefinite series of PATIENTS/such LOADINGS,
hereby simulating daily practice.
• Strive for a minimum set of power-definitions, although there are many different “clinically
relevant conditions” which each could lead to a thermal rating definition tuned to the
particular condition. Ultimately, one NOMINAL radiographic rating and one NOMINAL CT-
rating appears to cover the clinical conditions sufficiently. For the radiographic rating, the
traditional exposure time of 0,1 s covers also the traditional reference exposure time of
1,0 s for certain applications, such as mammography and dental X-ray because the
loadability at 1,0 s exposure is not much different from the loadability at 0,1 s exposure for
these applications.
• Choose SPECIFIED conditions for the definitions that are clinically aggressive, but realistic.
Since the clinical usage parameters of a given type of X-RAY TUBE are wide-ranging, what
should we choose for an exposure technique to represent a particular rating? The
guidance here was to choose something that definitely falls within accepted clinical
practice, but was on the aggressive side of the distribution of clinical techniques (from the
standpoint of LOADING techniques) in order that the clinically relevant performance of
various X-RAY TUBES are better delineated.
A.3.4 CTSPI definition
ANODE HEAT CONTENT was eliminated from the standard. It has been widely used to estimate
the power-throughput capability of an imaging system, in particular of a CT system. As stated
above, ANODE HEAT CONTENT was becoming less and less useful in accurately fulfilling this
estimate. It was desirable to replace this role by defining a new characteristic which was
– 14 – 60613 © IEC:2010
based solely on clinical performance per the above-stated goals. It was also desirable that
this new defined characteristic be based on parameters which were already defined under the
rd
new 3 edition. Thus, the new term for CT, CT SCAN POWER INDEX (CTSPI), has the following
features:
rd
• is based on the SINGLE LOAD RATING curve as it is defined in the 3 edition of this standard;
• involves a “black box” approach that specifies performance which is not tied to the design
technology inside the tube itself. This approach can be used to make performance
assessments independent of how the tube is constructed, and can be verified by the end
user;
• provides a more accurate representation of the power-throughput capability of the CT tube
than the storage-based definition of the prior editions of the standard;
rd
• has units of kW in line with the overall stated goals for the 3 edition.
rd
Under the 3 edition, the NOMINAL CT ANODE INPUT POWER gives the maximum load capability
of the tube at a particular scan time (4 s) which can be repeated indefinitely during a cycle of
10 min. The CTSPI broadens this to include the tube’s load capability over a wider range of
clinically relevant scan times. It is in fact the area under the SINGLE LOAD RATING curve
normalized over the range of scan times (Figure 1). It can be considered as a single-number
representation of the SINGLE LOAD RATING curve for the purpose of estimating power
throughput under clinically relevant conditions (scan times and PATIENT CYCLE TIMES).
P (kW)
5 10 15 20 25 30 t (s)
IEC 123/10
P(kW): power
t(s): scan time
Figure A.1 – Example: SINGLE LOAD RATING chart showing CTSPI calculation area
for scan time interval of 1 s to 25 s
The CTSPI gives the advantage of capturing the essential information from the SINGLE LOAD
RATING curve and representing it as a single value. It is possible for two different CT tubes to
have the same value for the NOMINAL CT ANODE INPUT POWER while having significantly
different CTSPI values (Figure 2), so NOMINAL CT ANODE INPUT POWER alone is not sufficient to
rd
characterize the power-throughput performance of the tube. In the 3 edition, the NOMINAL CT
ANODE INPUT POWER replaces the NOMINAL ANODE INPUT POWER as a single-value estimate of
loadability of CT tubes. Likewise, the CTSPI replaces the ANODE HEAT CONTENT as a single-
value estimate of PATIENT throughput.
60613 © IEC:2010 – 15 –
P (kW)
t (s)
1 4 25
IEC 124/10
P(kW): power
t(s): scan time
The areas under each curve (representing the performance over a wide range of scan times) are different, which
would be borne out in a CTSPI calculation.
Figure A.2 – Example: SINGLE LOAD RATING curves for two different CT tubes, both having
the same value of NOMINAL CT ANODE INPUT POWER
It is noted that the definition of CTSPI was purposely kept simple by basing it upon the
defined SINGLE LOAD RATING curve for a given tube as opposed to other possibilities of using
more complex SERIAL LOAD RATING curves (this SINGLE LOAD RATING curve is the same curve
rd
from which the NOMINAL CT ANODE INPUT POWER is derived). The 3 edition standardizes the
values to be used in the calculation of CTSPI and calls this value the NOMINAL CT SCAN POWER
INDEX. The normalization conditions are: 10 min CYCLE TIME (per definition of the SINGLE LOAD
RATING curve), and lower and upper values of the scan time range of 1 s and 25 s
respectively. These were chosen using the guideline of considering clinically relevant but
aggressive scan techniques. The 10 min CYCLE TIME represents a PATIENT throughput of 6
PATIENTS per hour; the scan times of 1 s and 25 s represent realistic boundaries for scan
times on modern CT scanners, making CTSPI a simple and straightforward way of
representing the PATIENT throughput of the CT tube.
1)
For details see [1 ] .
A.3.5 MAXIMUM CONTINUOUS HEAT DISSIPATION changed names
As mentioned before, definitions will no longer be based on “heat content” and the like. In this
line of thinking, the MAXIMUM CONTINUOUS HEAT DISSIPATION is re-named into NOMINAL
CONTINUOUS INPUT POWER, thereby logically connected to the term defined in 3.17: X-RAY TUBE
ASSEMBLY INPUT POWER. The same logic for name-giving has been applied to the two terms
ANODE INPUT POWER and CONTINUOUS ANODE INPUT POWER (see A.3.6).
A.3.6 Specification of power for measurement of LEAKAGE RADIATION
The definition of NOMINAL CONTINUOUS INPUT POWER contains energy sources which are not
related to X-RADIATION, such as the stator power and the filament power, and therefore is not
precise enough for the purpose of specifying a technique for LEAKAGE RADIATION. Therefore, a
new term, the CONTINUOUS ANODE INPUT POWER, was established for this purpose. This new
—————————
1)
Figures in square brackets refer to the Bibliography.
– 16 – 60613 © IEC:2010
term represents only the power supplied to the X-RAY TUBE which goes into the production of
X-rays, and is therefore the correct one to associate with LEAKAGE RADIATION.
60613 © IEC:2010 – 17 –
Annex B
(informative)
Measurement of the X-RAY TUBE CURRENT
A
I
I a
C c
–
+
I
e
E
I
e
I
I a
c
– –
+ +
IEC 125/10
A ANODE
C CATHODE
E ENVELOPE
I ANODE current
a
I CATHODE emission current
c
I ENVELOPE CURRENT
e
Figure B.1 – Electrical schematic of X-RAY TUBE CURRENT measurement
The X-RAY TUBE CURRENT is not necessarily equivalent to the ANODE current, (Figure B.1,
current I ) due to the effects of e.g. ENVELOPE CURRENT (Figure B.1, current I ).
a e
In the case of a non-conducting ENVELOPE, e.g. glass, the ENVELOPE CURRENT is zero, and the
X-RAY TUBE CURRENT equals both I and I .
c a
– 18 – 60613 © IEC:2010
Bibliography
[1] LOUNSBERRY, Brian D.; UNGER, Christopher D. “New CT tube performance
specifications”, in Medical Imaging 2004: Physics of Medical Imaging. Edited by Yaffe,
Martin J.; Flynn, Michael J. Proceedings of the SPIE, 2004,Volume 5368, pp. 621-632
(only available in English)
60613 © IEC:2010 – 19 –
Index of defined terms
NOTE In this International Standard only terms defined either in IEC 60601-1:2005, its collateral standards, in
IEC/TR 60788:2004 or in this International Standard have been used. These defined terms can be found at the IEC
website http://std.iec.ch/glossary .
AIR KERMA RATE . IEC/TR 60788:2004, 3.15
ANODE. IEC/TR 60788:2004, 3.16
ANODE HEAT CONTENT . IEC/TR 60788:2004, 3.19
ANODE INPUT POWER . 3. 13
ANODE SPEED . IEC/TR 60788:2004, 3.22
CATHODE . IEC/TR 60788:2004, 3.57
CATHODE EMISSION CHARACTERISTIC . 3. 4
COMPUTED TOMOGRAPHY (CT) . IEC/TR 60788:2004, 3.66
CONTINUOUS ANODE INPUT POWER. 3. 19
CT SCAN POWER INDEX (CTSPI). 3. 20
CYCLE TIME.
...
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