Evaluation and routine testing in medical imaging departments - Part 2-6: Constancy tests - Imaging performance of computed tomography X-ray equipment (IEC 61223-2-6:2006)

This part of IEC 61223 provides assistance in performing CONSTANCY TESTS on a CT SCANNER. It applies to those components of CT SCANNERS which influence the image quality, PATIENT dose and positioning. This standard - defines the essential parameters which describe the performance of CT SCANNERS with regard to image quality, PATIENT dose and positioning; the list of parameters to be tested can be found in section 4.5; - defines the methods of testing the essential parameters; - provides criteria to be applied in the evaluation of data for compliance with the tolerances of the parameters specified by the ACCOMPANYING DOCUMENTS and with respect to BASELINE VALUES. These methods rely on non-invasive measurements, using appropriate test equipment, performed to ensure that the functional performance of EQUIPMENT meets ESTABLISHED CRITERIA or to enable the early recognition of changes in the properties of components of the EQUIPMENT. The aim is to verify compliance with specifications affecting the image quality, PATIENT dose and PATIENT positioning. It is not intended to consider: - aspects of mechanical and electrical safety nor - aspects of mechanical, electrical and software performance, unless they are essential for performing the CONSTANCY TESTS and directly affect image quality, PATIENT dose and positioning.

Bewertung und routinemäßige Prüfung in Abteilungen für medizinische Bildgebung - Teil 2-6: Konstanzprüfungen - Röntgeneinrichtungen für die Computertomographie (IEC 61223-2-6:2006)

Essais d'évaluation et de routine dans les services d'imagerie médicale - Partie 2-6: Essais de constance - Performance d'imagerie des équipements de tomodensitométrie à rayonnement X (CEI 61223-2-6:2006)

La présente partie de la CEI 61223 fournit une aide à la réalisation des essais de constance des tomodensitomètres. Elle s'applique aux composants des tomodensitomètres qui influencent la qualité de l'image, la dose patient et le positionnement. La présente norme - définit les paramètres essentiels qui décrivent les performances des tomodensitomètres concernant la qualité de l'image, la dose patient et le positionnement; la liste des paramètres à soumettre aux essais peut être trouvée au paragraphe 4.5; - définit les méthodes d'essai des paramètres essentiels; - fournit les critères à appliquer lors de l'évaluation des données pour établir la conformité aux tolérances des paramètres spécifiés par les documents d'accompagnement et concernant les valeurs de base. Ces méthodes reposent sur des mesurages non invasifs, utilisant des équipements d'essai appropriés, réalisés pour s'assurer que la performance fonctionnelle de l'équipement satisfait aux critères établis ou pour permettre une reconnaissance précoce des variations des propriétés des composants de l'équipements. Le but recherché est la vérification de la conformité aux spécifications concernant la qualité de l'image, la dose patient et le positionnement du patient.

Vrednotenje in rutinsko preskušanje v oddelkih za medicinsko slikanje - 2-6. del: Preskus konstantnosti - Rentgenska oprema za računalniško tomografijo (IEC 61223-2-6:2006)

Ta del IEC 61223 predpisuje pomoč pri izvajanju PRESKUSOV KONSTANTNOSTI pri RENTGENU ZA RAČUNALNIŠKO TOMOGRAFIJO. Velja za tiste komponente RENTGENOV ZA RAČUNALNIŠKE TOMOGRAFIJE, ki vplivajo na kvaliteto slike, odmerek na PACIENTA in pozicioniranje. Ta standard opredeljuje bistvene parametre, ki opisujejo zmogljivost RENTGENOV ZA RAČUNALNIŠKO TOMOGRAFIJO glede  kvalitete slike, odmerka za PACIENTA in pozicioniranja; seznam parametrov, ki se jih preskuša, se nahaja v Razdelku 4.5.; - opredeljuje metode preskušanja bistvenih parametrov; zagotavlja merila za uporabo pri vrednotenju podatkov za skladnost z odstopanji parametrov, ki jih določajo SPREMNI DOKUMENTI in ob upoštevanju SREDNJIH VREDNOSTI. Te metode se opirajo na neinvazivna merjenja z uporabo primerne preskusne opreme in delujejo tako, da se za funkcionalno zmogljivost OPREME zagotovi, da izpolnjuje VZPOSTAVLJENA MERILA ali da omogoča zgodnje prepoznavanje sprememb lastnosti komponent OPREME. Cilj je potrditi skladnost s specifikacijami, ki vplivajo na kakovost slike, odmerka za PACIENTA in pozicioniranje PACIENTA. Njegov namen ni, da upošteva: - vidike mehanske in električne varnosti, niti - vidike mehanske in električne zmogljivosti ter zmogljivosti programske opreme, razen če so le-ti bistveni za izvajanje PRESKUSOV KONSTANTNOSTI in neposredno vplivajo na kakovost slike, odmerka za PACIENTA in njegovo pozicioniranje.

General Information

Status
Published
Publication Date
12-Jul-2010
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
22-Jun-2010
Due Date
27-Aug-2010
Completion Date
13-Jul-2010

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Evaluation and routine testing in medical imaging departments - Part 2-6: Constancy

tests - Imaging performance of computed tomography X-ray equipment (IEC 61223-2-
6:2006)

Bewertung und routinemäßige Prüfung in Abteilungen für medizinische Bildgebung - Teil

2-6: Konstanzprüfungen - Röntgeneinrichtungen für die Computertomographie (IEC
61223-2-6:2006)

Essais d'évaluation et de routine dans les services d'imagerie médicale - Partie 2-6:

Essais de constance - Performance d'imagerie des équipements de tomodensitométrie à

rayonnement X (CEI 61223-2-6:2006)
Ta slovenski standard je istoveten z: EN 61223-2-6:2007
ICS:
11.040.50 Radiografska oprema Radiographic equipment
35.240.80 Uporabniške rešitve IT v IT applications in health care
zdravstveni tehniki technology
SIST EN 61223-2-6:2010 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN 61223-2-6:2010
---------------------- Page: 2 ----------------------
SIST EN 61223-2-6:2010
EUROPEAN STANDARD
EN 61223-2-6
NORME EUROPÉENNE
May 2007
EUROPÄISCHE NORM
ICS 11.040.50 Supersedes EN 61223-2-6:1994
English version
Evaluation and routine testing in medical imaging departments -
Part 2-6: Constancy tests -
Imaging performance of computed tomography X-ray equipment
(IEC 61223-2-6:2006)
Essais d'évaluation et de routine Bewertung und routinemäßige Prüfung
dans les services d'imagerie médicale - in Abteilungen
Partie 2-6: Essais de constance - für medizinische Bildgebung -
Performance d'imagerie des équipements Teil 2-6: Konstanzprüfungen -
de tomodensitométrie à rayonnement X Röntgeneinrichtungen
(CEI 61223-2-6:2006) für die Computertomographie
(IEC 61223-2-6:2006)

This European Standard was approved by CENELEC on 2007-03-01. 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, Bulgaria, Cyprus, the

Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,

Sweden, Switzerland and the 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

© 2007 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 61223-2-6:2007 E
---------------------- Page: 3 ----------------------
SIST EN 61223-2-6:2010
EN 61223-2-6:2007 - 2 -
Foreword

The text of document 62B/629/FDIS, future edition 2 of IEC 61223-2-6, 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 61223-2-6 on 2007-03-01.

This European Standard supersedes EN 61223-2-6:1994.

EN 61223-2-6:2007 is harmonized with the content of EN 60601-2-44:2001 + A1:2003 and with

EN 61223-3-5:2004. Instead of harmonizing test procedures for all modalities of X-ray equipment, as

intended in EN 61223-2-6:1994, this EN 61223-2-6:2007 comprises part of a set of standards covering all

of the particular requirements for CT scanners.
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) 2007-12-01
– latest date by which the national standards conflicting
(dow) 2010-03-01
with the EN have to be withdrawn
In this standard, the following print types are used:

– requirements, compliance with which can be tested, and definitions: in roman type;

– explanations, advice, notes, general statements, exceptions and references: in smaller type;

– test specifications: in italic type;

– TERMS DEFINED IN EN 60601-1, IN EN 60788, IN EN 61223-1 OR IN OTHER PUBLICATIONS REFERENCED IN

THE INDEX OF DEFINED TERMS: SMALL CAPITALS.
Annex ZA has been added by CENELEC.
__________
Endorsement notice

The text of the International Standard IEC 61223-2-6:2006 was approved by CENELEC as a European

Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards indicated:

IEC 61223-2-5 NOTE Harmonized as EN 61223-2-5:1994 (not modified).
IEC 61223-2-4 NOTE Harmonized as EN 61223-2-4:1994 (not modified).
IEC 60336 NOTE Harmonized as EN 60336:2005 (not modified).
IEC 60522 NOTE Harmonized as EN 60522:1999 (not modified).
IEC 60601-1 NOTE Harmonized as EN 60601-1:2006 (not modified).
IEC 60601-2-28 NOTE Harmonized as EN 60601-2-28:1993 (not modified).
IEC 60601-2-32 NOTE Harmonized as EN 60601-2-32:1994 (not modified).
IEC 61267 NOTE Harmonized as EN 61267:2006 (not modified).
__________
---------------------- Page: 4 ----------------------
SIST EN 61223-2-6:2010
- 3 - EN 61223-2-6:2007
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 When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD

applies.
Publication Year Title EN/HD Year
IEC 60601-2-44 2001 Medical electrical equipment - EN 60601-2-44 2001
A1 2002 Part 2-44: Particular requirements for the A1 2003
safety of X-ray equipment for computed
tomography
IEC/TR 60788 2004 Medical electrical equipment - Glossary of - -
defined terms
IEC 61223-3-5 2004 Evaluation and routine testing in medical EN 61223-3-5 2004
imaging departments -
Part 3-5: Acceptance tests - Imaging
performance of computed tomography X-ray
equipment
---------------------- Page: 5 ----------------------
SIST EN 61223-2-6:2010
---------------------- Page: 6 ----------------------
SIST EN 61223-2-6:2010
NORME CEI
INTERNATIONALE
IEC
61223-2-6
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2006-11
Essais d’évaluation et de routine dans
les services d’imagerie médicale –
Partie 2-6:
Essais de constance –
Performance d’imagerie des équipements
de tomodensitométrie à rayonnement X
Evaluation and routine testing in
medical imaging departments –
Part 2-6:
Constancy tests –
Imaging performance of computed
tomography X-ray equipment
© IEC 2006 Droits de reproduction réservés ⎯ Copyright - all rights reserved

Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any

utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including

électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from

microfilms, sans l'accord écrit de l'éditeur. the publisher.

International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland

Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch

CODE PRIX
PRICE CODE
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue
---------------------- Page: 7 ----------------------
SIST EN 61223-2-6:2010
61223-2-6 © IEC:2006 – 3 –
CONTENTS

FOREWORD...........................................................................................................................5

INTRODUCTION.....................................................................................................................9

1 Scope and object............................................................................................................11

2 Normative references .....................................................................................................11

3 Terms and definitions .....................................................................................................13

4 General aspects of CONSTANCY TESTS .............................................................................21

4.1 Preconditions ........................................................................................................21

4.2 General conditions affecting test procedures .........................................................21

4.3 Establishment of BASELINE VALUES .........................................................................23

4.4 Identification of equipment, instrumentation and test conditions ............................23

4.5 Scope of the CONSTANCY TESTS..............................................................................25

4.6 Test equipment, including PHANTOMS and TEST DEVICES .........................................25

4.7 Frequency of CONSTANCY TESTS .............................................................................27

5 Test methods for CT SCANNERS.......................................................................................27

5.1 Positioning of the PATIENT SUPPORT........................................................................27

5.2 PATIENT positioning accuracy .................................................................................29

5.3 TOMOGRAPHIC SECTION THICKNESS ..........................................................................33

5.4 Dose .....................................................................................................................37

5.5 NOISE, UNIFORMITY AND MEAN CT NUMBERS ..............................................................39

5.6 SPATIAL RESOLUTION...............................................................................................43

Annex A (informative) Guidance on action to be taken .........................................................47

Annex B (informative) Alternate test methods for SPATIAL RESOLUTION ..................................51

Annex C (informative) TOMOGRAPHIC SECTION THICKNESS for helical scanning .......................57

Annex D (informative) Visual method for LOW CONTRAST RESOLUTION ....................................59

Bibliography..........................................................................................................................61

Index of terms.......................................................................................................................65

Figure 1 – Coordinate system used for CT SCANNERS............................................................21

Table B.1 − Comparison of SPATIAL RESOLUTION test procedures ...........................................51

---------------------- Page: 8 ----------------------
SIST EN 61223-2-6:2010
61223-2-6 © IEC:2006 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
EVALUATION AND ROUTINE TESTING
IN MEDICAL IMAGING DEPARTMENTS –
Part 2-6: Constancy tests – Imaging performance
of computed tomography X-ray equipment
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 61223-2-6 has been prepared by subcommittee 62B: Diagnostic

imaging equipment, of IEC technical committee 62: Electrical equipment in medical practice.

This second edition cancels and replaces the first edition published in 1994. It constitutes a

technical revision. This second edition is harmonized with the content of IEC 60601-2-44:2001

and its Amendment 1 (2002) and with IEC 61223-3-5. Instead of harmonizing test procedures

for all modalities of X-ray equipment, as intended in the first edition, this second edition

comprises part of a set of standards covering all of the particular requirements for CT

scanners.
---------------------- Page: 9 ----------------------
SIST EN 61223-2-6:2010
61223-2-6 © IEC:2006 – 7 –
The text of this standard is based on the following documents:
FDIS Report on voting
62B/629/FDIS 62B/639/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.

A list of all parts of the IEC 61223 series, published under the general title Evaluation and routine

testing in medical imaging departments, can be found on the IEC website.
In this standard, the following print types are used:

– requirements, compliance with which can be tested, and definitions: in roman type;

– explanations, advice, notes, general statements, exceptions and references: in smaller type;

– test specifications and headings of subclauses: in italic type;

– TERMS DEFINED IN IEC 60601-1, IN IEC 60788, IN IEC 61223-1 OR IN OTHER IEC PUBLICATIONS

REFERENCED IN THE INDEX OF DEFINED TERMS: SMALL CAPITALS.

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.
---------------------- Page: 10 ----------------------
SIST EN 61223-2-6:2010
61223-2-6 © IEC:2006 – 9 –
INTRODUCTION
The second edition of this standard is harmonized with the content of

– IEC 60601-2-44:2001, Particular requirements for the safety of X-ray equipment for

computed tomography and its Amendment 1 (2002), and

– IEC 61223-3-5, Evaluation and routine testing in medical imaging departments –

Part 3-5, Acceptance tests – Imaging performance of computed tomography X-ray
equipment.

In case the CT SCANNER does not offer an integrated, automated evaluation of the test

images, attention shall be given to the proper function and setting of the IMAGE DISPLAY

DEVICE. It is strongly recommended to assure its proper functioning prior to the constancy

1)

testing of the CT SCANNER, applying IEC 61223-2-5 [1] on IMAGE DISPLAY DEVICES or the

related in-house procedure. Some provisions or statements in this standard require additional

information, which is presented in the annexes. An asterisk in the left margin of a clause or

subclause indicates the presence of such additional information.

With regard to the measurements, reference is made to methods described in related

publications, which for practical reasons should be carried out prior to the application of the

methods described in this standard.

This standard forms Part 2-6 of IEC 61223, which includes the following parts of particular

interest in the context of this standard:
Part 1: General aspects [2]
Part 2-4: Constancy tests – Hard copy cameras [3]
Part 2-5: Constancy tests – Image display devices
———————
Figures in square brackets refer to the Bibliography.
---------------------- Page: 11 ----------------------
SIST EN 61223-2-6:2010
61223-2-6 © IEC:2006 – 11 –
EVALUATION AND ROUTINE TESTING
IN MEDICAL IMAGING DEPARTMENTS –
Part 2-6: Constancy tests – Imaging performance
of computed tomography X-ray equipment
1 Scope and object

This part of IEC 61223 provides assistance in performing CONSTANCY TESTS on a CT SCANNER.

It applies to those components of CT SCANNERS which influence the image quality, PATIENT

dose and positioning.
This standard

– defines the essential parameters which describe the performance of CT SCANNERS with

regard to image quality, PATIENT dose and positioning; the list of parameters to be tested

can be found in section 4.5;
– defines the methods of testing the essential parameters;

– provides criteria to be applied in the evaluation of data for compliance with the tolerances

of the parameters specified by the ACCOMPANYING DOCUMENTS and with respect to BASELINE

VALUES.

These methods rely on non-invasive measurements, using appropriate test equipment,

performed to ensure that the functional performance of EQUIPMENT meets ESTABLISHED

CRITERIA or to enable the early recognition of changes in the properties of components of the

EQUIPMENT.

The aim is to verify compliance with specifications affecting the image quality, PATIENT dose

and PATIENT positioning.
It is not intended to consider:
– aspects of mechanical and electrical safety nor

– aspects of mechanical, electrical and software performance, unless they are essential for

performing the CONSTANCY TESTS and directly affect image quality, PATIENT dose and

positioning.
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 60788:2004, Medical electrical equipment – Glossary of defined terms

IEC 61223-3-5:2004, Evaluation and routine testing in medical imaging departments –

Part 3-5: Acceptance tests – Imaging performance of computed tomography X-ray equipment

---------------------- Page: 12 ----------------------
SIST EN 61223-2-6:2010
61223-2-6 © IEC:2006 – 13 –

IEC 60601-2-44:2001, Medical electrical equipment – Part 2-44: Particular requirements for

the safety of X-ray equipment for computed tomography
Amendment 1 (2002)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60788:2004 and the

following apply.

NOTE 1 An index of defined terms used in this standard is given following the annexes

NOTE 2 Attention is drawn to the fact that in cases where the concept addressed is not strongly confined to the

definition given in IEC 61223-1 or IEC 60788, a corresponding term is printed in lower case letters.

3.1
CT CONDITIONS OF OPERATION

all selectable parameters governing the operation of a CT SCANNER, for example NOMINAL

TOMOGRAPHIC SECTION THICKNESS, CT PITCH FACTOR, FILTRATION, peak X-RAY TUBE VOLTAGE and

either X-RAY TUBE CURRENT and LOADING TIME or CURRENT TIME PRODUCT
[IEC 60601-2-44:2001, definition 2.102]
3.2
CT SCANNER
X-RAY EQUIPMENT for COMPUTED TOMOGRAPHY (CT)

diagnostic X-ray system intended to generate cross-sectional images of the body by computer

reconstruction of X-ray transmission data obtained at different angles. This generic type of

device may include signal analysis and display equipment, PATIENT SUPPORT, support parts

and accessories
NOTE Secondary imaging processing is not included in the scope of this standard.
[IEC 60601-2-44, Amend.1:2002, definition 2.101]
3.3
COMPUTED TOMOGRAPHY DOSE INDEX 100
CTDI
100

integral of the DOSE PROFILE produced in a single axial scan along a line perpendicular to

the TOMOGRAPHIC PLANE from – 50 mm to + 50 mm, divided by the product of the number of

TOMOGRAPHIC SECTIONS N and the NOMINAL TOMOGRAPHIC SECTION THICKNESS T
+50 mm
D (z)
= dz
CTDI
100
N ⋅ T
-50 mm
where

D(z) is the DOSE PROFILE along a line z perpendicular to the TOMOGRAPHIC PLANE, where

dose is reported as ABSORBED DOSE to air;

N is the number of TOMOGRAPHIC SECTIONS produced in a single axial scan of the X-ray

source;
T is the NOMINAL TOMOGRAPHIC SECTION THICKNESS.

NOTE 1 The term CTDI has been introduced as a more representative value for dose than the traditional CTDI

100
integrated from – 7 T to + 7 T as defined by the FDA in 21 CFR 1020.33 [31].

NOTE 2 The dose is reported as ABSORBED DOSE to air. This is required in order to avoid present confusion, as

some MANUFACTURERS of CT SCANNERS express dose values calculated as ABSORBED DOSE to air and others as

ABSORBED DOSE to polymethyl-methacrylate (PMMA).
---------------------- Page: 13 ----------------------
SIST EN 61223-2-6:2010
61223-2-6 © IEC:2006 – 15 –

Although CTDI refers to ABSORBED DOSE to air, for practical purposes the evaluation of ABSORBED DOSE to air

100

within a PMMA dosimetry PHANTOM is well approximated by measurement of the AIR KERMA with an ionization

chamber in the PHANTOM.
NOTE 3 This definition assumes that the DOSE PROFILE is centred on z = 0.
NOTE 4 A single axial scan is typically a 360° rotation of the X-ray source.
[IEC 60601-2-44, Amendment 1:2002, definition 2.106]
3.4
WEIGHTED CTDI
100
The WEIGHTED CTDI (CTDI ) is defined as
100 w
1 2
CTDI = CTDI + CTDI
W 100(centre ) 100(periphe ral)
3 3
where
CTDI is the value measured in the centre of the CT DOSIMETRY PHANTOM and
100(centre)
CTDI is the average value measured in the periphery of the CT DOSIMETRY
100(peripheral)
PHANTOM
3.5
COMPUTED TOMOGRAPHY NUMBER (CT NUMBER)

number used to represent the mean X-ray ATTENUATION associated with each elemental area

of the COMPUTED TOMOGRAPHY image

NOTE The CT NUMBER is normally expressed in Hounsfield units. MEASURED VALUES of the linear ATTENUATION

coefficients are transformed into CT NUMBERS using the international Hounsfield scale, using the expression:

μ − μ
material water
CT number of material = ⋅1 000
water
where
μ is the linear ATTENUATION coefficient.

The CT NUMBER scale is defined so that water has a value of 0 and air a value of -1000 (μ is assumed to be 0).

air
3.6
COMPUTED TOMOGRAPHY DOSE INDEX FREE IN AIR
CTDI
free air
CTDI measured at isocentre in the absence of a PHANTOM and the PATIENT SUPPORT
100
3.7
CT PITCH FACTOR

in helical scanning the ratio of the PATIENT SUPPORT travel Δd along the z direction per rotation

of the X-RAY SOURCE divided by the product of the NOMINAL TOMOGRAPHIC SECTION THICKNESS T

and the number of TOMOGRAPHIC SECTIONS N:
CT pitch factor =
N ⋅T
where

Δd is the PATIENT SUPPORT travel along the z direction per rotation of the X-RAY SOURCE;

T is the NOMINAL TOMOGRAPHIC SECTION THICKNESS;
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SIST EN 61223-2-6:2010
61223-2-6 © IEC:2006 – 17 –

N is the number of TOMOGRAPHIC SECTIONS produced in a single axial scan of the X-RAY

SOURCE.
[IEC 60601-2-44, Amend.1:2002, definition 2.107]
3.8
DOSE PROFILE
representation of the dose as a function of position along a line.
[IEC 60601-2-44:2001, definition 2.103]
3.9
MEAN CT NUMBER

mean value of the CT NUMBERS of all pixels within a certain defined REGION OF INTEREST

3.10
NOISE

variation of CT NUMBERS from a mean value in a defined area in the image of a uniform

substance

NOTE The magnitude of NOISE is indicated by the standard deviation of the CT NUMBERS of a uniform substance in

the REGION OF INTEREST.
3.11
NOMINAL TOMOGRAPHIC SECTION THICKNESS

in CT SCANNERS the TOMOGRAPHIC SECTION THICKNESS which is selected and indicated on the

CONTROL PANEL

NOTE In helical scanning the thickness of a reconstructed image depends on the helical reconstruction algorithm

NOMINAL TOMOGRAPHIC SECTION THICKNESS. The thickness of
and pitch, and hence this thickness may not equal the
the reconstructed image may be indicated or selected prior to the helical scan.
[IEC 60601-2-44, Amend.1:2002, definition 2.110]
3.12
SENSITIVITY PROFILE

relative response of a system for COMPUTED TOMOGRAPHY as a function of position along a line

perpendicular to the TOMOGRAPHIC PLANE
[IEC 60601-2-44:2001, definition 2.104]
3.13
SPATIAL RESOLUTION

in EQUIPMENT for COMPUTED TOMOGRAPHY, the ability to resolve different objects in the

displayed image, when the difference in ATTENUATION between the objects and the back-

ground is large compared to NOISE

NOTE 1 Normally a difference in ATTENUATION coefficient between the object and the background resulting in a

difference of the respective CT NUMBERS of several hundred Hounsfield units is regarded as large enough.

NOTE 2 HIGH-CONTRAST RESOLUTION is an alternative name for SPATIAL RESOLUTION.
3.14
TOMOGRAPHIC PLANE
geometric plane perpendicular to the axis of rotation
[IEC 60601-2-44:2001, definition 2.105]
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SIST EN 61223-2-6:2010
61223-2-6 © IEC:2006 – 19 –
3.15
TOMOGRAPHIC SECTION

volume over which TRANSMISSION data of X-RADIATION are collected in a single axial scan

NOTE In a CT SCANNER with multiple detector elements along the z-axis, it is the volume over which data are

collected by a single acquisition channel (selected grouping of elements) and not the total volume irradiated.

[IEC 60601-2-44, Amendment 1:2002, definition 2.108]
3.16
TOMOGRAPHIC SECTION THICKNESS

FULL WIDTH AT HALF MAXIMUM of the SENSITIVITY PROFILE taken at the isocentre of a

TOMOGRAPHIC SECTION
[IEC 60601-2-44, Amendment 1:2002, definition 2.109]
3.17
UNIFORMITY

consistency of the CT NUMBERS of the image of a homogeneous material across the scan field

3.18
VOLUME CTDI
CTDI
vol

average dose over the total volume scanned for the selected CT CONDITIONS OF OPERATION

The CTDI is defined as follows:
vol
a) for axial scanning
N ⋅T
CTDI = ⋅CTDI
vol w
where

N is the number of TOMOGRAPHIC SECTIONS produced in a single axial scan of the X-RAY

SOURCE;
T is the NOMINAL TOMOGRAPHIC SECTION THICKNESS;
Δd is the PATIENT SUPPORT travel in z-direction between consecutive scans.
b) for helical scanning
CTDI
CTDI =
vol
CT pitch factor
c) for scanning without pre-programmed movement of the PATIENT SUPPORT
CTDI = n ⋅CTDI
vol w
where n is equal to the maximum number of pre-programmed rotations.

NOTE 1 The displayed CTDI given by the MANUFACTURER may be a representative figure for that model and not

vol
the value measured on the particular CT SCANNER
NOTE 2 The definition of CTDI in section c) will li
...

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