IEC 62494-1:2008

Medical electrical equipment - Exposure index of digital X-ray imaging systems - Part 1: Definitions and requirements for general radiography

IEC 62494-1:2008 specifies definitions and requirements for the exposure index of images acquired with digital X-ray imaging systems. IEC 62494-1:2008 is applicable to digital X-ray imaging systems used in general radiography for producing projection X-ray images for general applications, such as, but not exclusively:
- computed radiography (CR) systems based on stimulable phosphors;
- flat-panel detector based systems;
- charge-coupled device (CCD) based systems.
Image intensifier based systems and systems for mammographic or dental application are not covered in this first edition. IEC 62494-1:2008 defines the exposure index only for images generated with a single irradiation event. Images generated from multiple irradiations (e.g., tomosynthetic or dual-energy images, multiple views on a single CR plate) are not covered.

Appareils électromédicaux - Indice d'exposition des systèmes d'imagerie numérique à rayonnement X - Partie 1: Définitions et exigences pour la radiographie générale

La CEI 62494-1:2008 spécifie les définitions et les exigences pour l'indice d'exposition des images acquises avec des systèmes d'imagerie numérique à rayonnement X. La CEI 62494-1:2008 est applicable aux systèmes d'imagerie numérique à rayonnement X utilisés en radiographie générale pour produire des images radiologiques de projection pour les applications générales, comme par exemple, mais pas exclusivement:
- les systèmes de radiographie assistée par ordinateur (CR, computed radiography) basés sur des luminophores stimulables;
- les systèmes basés sur des détecteurs à écran plat;
- les systèmes basés sur un dispositif à transfert de charge (CCD, charge-coupled device).
Les systèmes basés sur un intensificateur d'image et les systèmes utilisés en mammographie ou pour les applications dentaires ne sont pas traités dans cette première édition. La CEI 62494-1:2008 définit l'indice d'exposition uniquement pour les images produites avec un seul événement d'irradiation. Les images produites à partir d'irradiations multiples (par exemple, images tomosynthétiques ou biénergétiques, vues multiples sur une seule plaque de radiographie assistée par ordinateur) ne sont pas traitées.

General Information

• Status: Published
• Publication Date: 12-Aug-2008
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 11.040.50 - Radiographic equipment
• Technical Committee: SC 62B - Medical imaging equipment, software, and systems
• Drafting Committee: WG 43 - TC 62/SC 62B/WG 43
• Current Stage: PPUB - Publication issued
• Start Date: 31-Oct-2008
• Completion Date: 13-Aug-2008

Standards Content (Sample)

IEC 62494-1
Edition 1.0 2008-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Medical electrical equipment – Exposure index of digital X-ray imaging
systems –
Part 1: Definitions and requirements for general radiography

Appareils électromédicaux – Indice d'exposition des systèmes d’imagerie
numérique à rayonnement X –
Partie 1: Définitions et exigences pour la radiographie générale

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IEC 62494-1
Edition 1.0 2008-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Medical electrical equipment – Exposure index of digital X-ray imaging
systems –
Part 1: Definitions and requirements for general radiography

Appareils électromédicaux – Indice d'exposition des systèmes d’imagerie
numérique à rayonnement X –
Partie 1: Définitions et exigences pour la radiographie générale

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
R
CODE PRIX
ICS 11.040.50 ISBN 2-8318-9944-3
– 2 – 62494-1 © IEC:2008
CONTENTS
FOREWORD.3
INTRODUCTION.5
1 Scope.7
2 Normative references .7
3 Terms and definitions .7
4 Requirements .9
4.1 Creation of ORIGINAL DATA.9
4.2 Determination of the RELEVANT IMAGE REGION and the VALUE OF INTEREST .9
4.3 Requirements for the EXPOSURE INDEX .10
4.4 Calibration of the EXPOSURE INDEX .10
4.5 Determination of the CALIBRATION FUNCTION .11
4.6 Determination of the INVERSE CALIBRATION FUNCTION .11
4.7 Requirements for the DEVIATION INDEX.11
Annex A (informative) Details on the rationale, properties and use of the EXPOSURE
INDEX .13
Annex B (informative) Details on the rationale, properties and use of the DEVIATION
INDEX .17
Annex C (normative) Beam conditions to be used for calibration.18
Bibliography.19
Terminology – Index of defined terms .20

Figure A.1 – Example of an ORIGINAL DATA radiograph with an example of the RELEVANT
IMAGE REGION outlined .14
Figure A.2 – Histogram of the ORIGINAL DATA for the radiograph shown in Figure A.1 .15
Figure A.3 – Relative IMAGE RECEPTOR AIR KERMA required to produce a fixed detector
response for the four x-ray beam qualities defined in ISO 9236-1 .16

62494-1 © IEC:2008 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEDICAL ELECTRICAL EQUIPMENT –
EXPOSURE INDEX OF DIGITAL X-RAY IMAGING SYSTEMS –

Part 1: Definitions and requirements for general radiography

FOREWORD
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International Standard IEC 62494-1 has been prepared by subcommittee 62B: Diagnostic
imaging equipment, of IEC technical committee 62: Electrical equipment in medical practice.
The text of this standard is based on the following documents:
Enquiry draft Report on voting
62B/680/CDV 62B/703/RVC
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 – 62494-1 © IEC:2008
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;
– TERMS DEFINED IN CLAUSE 3 OF THIS STANDARD, IN IEC 60601-1 OR IN IEC 60788, AS
REFERENCED IN THE INDEX OF DEFINED TERMS: SMALL CAPITALS.
A list of all parts of the IEC 62494 series, published under the general title Medical electrical
equipment – Exposure index of digital X-ray imaging systems, can be found on the IEC
website.
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.
62494-1 © IEC:2008 – 5 –
INTRODUCTION
The direct connection between the level of detector exposure and optical density is well
established in film-screen radiology. This is not the case in digital radiography, where almost
always a constant image characteristic is achieved using automatic image processing.
Consequently, deviations from the intended exposure, i.e., over- and underexposure, are not
noticeable by a corresponding deviation in image brightness. While considerable
underexposure results in an increased level of noise, the more alarming aspect (from a
radiation protection point of view) is that overexposure cannot be recognized easily in the
displayed image.
Therefore, various manufacturers of digital radiography systems have introduced so-called
exposure indicators for their equipment. These are numbers, determined from the original
image data of each image taken, which allow conclusions about the level of the exposure at
the image receptor. However, the exposure indicators are manufacturer or system specific,
i.e. they differ for the systems of different manufacturers in their definition and scaling. A
unified EXPOSURE INDEX for all digital radiography systems is needed to simplify its usage, e.g.
for the establishment of exposure guidelines, particularly when systems of different
manufacturers
...