1、BRITISH STANDARD BS EN 62220-1:2004 Medical electrical equipment Characteristics of digital X-ray imaging devices Part 1: Determination of the detective quantum efficiency The European Standard EN 62220-1:2004 has the status of a British Standard ICS 11.040.50 BS EN 62220-1:2004 This British Standar
2、d was published under the authority of the Standards Policy and Strategy Committee on 2 February 2004 BSI 2 February 2004 ISBN 0 580 43335 8 National foreword This British Standard is the official English language version of EN 62220-1:2004. It is identical with IEC 62220-1:2003. The UK participatio
3、n in its preparation was entrusted by Technical Committee CH/62, Electromedical equipment in medical practice, to Subcommittee CH/62/2, Diagnostic imaging equipment, which has the responsibility to: A list of organizations represented on this subcommittee can be obtained on request to its secretary.
4、 Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue o
5、r of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the tex
6、t; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cov
7、er, an inside front cover, the EN title page, pages 2 to 29 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEAN STANDARD EN 62220-1 NORME EUROPENNE EUROPISCHE NORM Januar
8、y 2004 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2004 CENELEC - All rights of exploitation in any form and by any means re
9、served worldwide for CENELEC members. Ref. No. EN 62220-1:2004 E ICS 11.040.50 English version Medical electrical equipment Characteristics of digital X-ray imaging devices Part 1: Determination of the detective quantum efficiency (IEC 62220-1:2003) Appareils lectromdicaux - Caractristiques des appa
10、reils dimagerie rayonnement X Part 1: Dtermination de lefficacit quantique de dtection (CEI 62220-1:2003) Medizinische elektrische Gerte - Merkmale digitaler Rntgenbildgerte Teil 1: Bestimmung der detektiven Quanten-Ausbeute (IEC 62220-1:2003) This European Standard was approved by CENELEC on 2003-1
11、2-01. 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 obt
12、ained 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 Cen
13、tral Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, No
14、rway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. Foreword The text of document 62B/493/FDIS, future edition 1 of IEC 62220-1, prepared by SC 62B, Diagnostic imaging equipment, of IEC TC 62, Electrical equipment in medical practice, was submitted to the IEC-C
15、ENELEC parallel vote and was approved by CENELEC as EN 62220-1 on 2003-12-01. 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) 2004-09-01 latest date by which the national stan
16、dards conflicting with the EN have to be withdrawn (dow) 2006-12-01 In this standard, terms printed in SMALL CAPITALS are used as defined in IEC 60788, in Clause 3 of this standard or other IEC publications referenced in Annex B. Where a defined term is used as a qualifier in another defined or unde
17、fined term it is not printed in SMALL CAPITALS, unless the concept thus qualified is defined or recognized as a “derived term without definition“. 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 publication
18、s listed above, a corresponding term is printed in lower-case letters. Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 62220-1:2003 was approved by CENELEC as a European Standard without any modification. In the official version, for Bibliography,
19、the following note has to be added for the standard indicated: IEC 61262-5 NOTE Harmonized as EN 61262-5:1994 (not modified). _ Page2 EN622201:2004CONTENTS INTRODUCTION.4 1 Scope.5 2 Normative references .5 3 Terminology and definitions6 4 Requirements.7 4.1 Operating conditions .7 4.2 X-RAY EQUIPME
20、NT .7 4.3 RADIATION QUALITY .8 4.4 TEST DEVICE.9 4.5 Geometry 10 4.6 IRRADIATION conditions 12 4.6.1 General conditions 12 4.6.2 Exposure measurement.12 4.6.3 Avoidance of LAG EFFECTS13 4.6.4 IRRADIATION to obtain the CONVERSION FUNCTION 13 4.6.5 IRRADIATION for determination of the NOISE POWER SPEC
21、TRUM13 4.6.6 IRRADIATION with TEST DEVICE in the RADIATION BEAM.14 5 Corrections of RAW DATA .15 6 Determination of the DETECTIVE QUANTUM EFFICIENCY 15 6.1 Definition and formula of DQE (u,v).15 6.2 Parameters to be used for evaluation 16 6.3 Determination of different parameters from the images16 6
22、.3.1 Linearization of data16 6.3.2 The NOISE POWER SPECTRUM (NPS).17 6.3.3 Determination of the MODULATION TRANSFER FUNCTION (MTF)19 7 Format of conformance statement 19 8 Accuracy 20 Annex A (normative) Determination of LAG EFFECTS22 A.1 Test of additive LAG EFFECTS22 A.2 Test of multiplicative LAG
23、 EFFECTS23 Annex B (normative) Terminology Index of defined terms25 Annex C (informative) Calculation of the input NOISE POWER SPECTRUM 26 Annex ZA (normative) Normative references to international publications with their corresponding European publications .27 Bibliography28 Page3 EN622201:2004 INT
24、RODUCTION DIGITAL X-RAY IMAGING DEVICES are increasingly used in medical diagnosis and will widely replace conventional (analogue) imaging devices such as screen-film systems or analogue X- RAY IMAGE INTENSIFIER television systems in the future. It is necessary, therefore, to define parameters that
25、describe the specific imaging properties of these DIGITAL X-RAY IMAGING DEVICES and to standardize the measurement procedures employed. There is growing consensus in the scientific world that the DETECTIVE QUANTUM EFFICIENCY (DQE) is the most suitable parameter for describing the imaging performance
26、 of an X-ray imaging device. The DQE describes the ability of the imaging device to preserve the signal-to- NOISE ratio from the radiation field to the resulting digital image data. Since in X-ray imaging, the NOISE in the radiation field is intimately coupled to the exposure level, DQE values can a
27、lso be considered to describe the dose efficiency of a given imaging device. NOTE 1 In spite of the fact that the DQE is widely used to describe the performance of imaging devices, the connection between this physical parameter and the decision performance of a human observer is not yet completely u
28、nderstood 1, 3. 1)NOTE 2 The standard IEC 61262-5 specifies a method to determine the DQE of X-RAY IMAGE INTENSIFIERS at nearly zero SPATIAL FREQUENCY. It focuses only on the electro-optical components of X-RAY IMAGE INTENSIFIERS, not on the imaging properties as this standard does. As a consequence
29、, the output is measured as an optical quantity (luminance), and not as digital data. Moreover, IEC 61262-5 prescribes the use of a RADIATION SOURCE ASSEMBLY, whereas this standard prescribes the use of an X-RAY TUBE. The scope of IEC 61262-5 is limited to X-RAY IMAGE INTENSIFIERS and does not inter
30、fere with the scope of this standard. The DQE is already widely used by manufacturers to describe the performance of their equipment. The specification of the DQE is also required by regulatory agencies (such as the Food and Drug Administration (FDA) for admission procedures. However, there is prese
31、ntly no standard governing either the measurement conditions or the measurement procedure with the consequence that values from different sources may not be comparable. This standard has therefore been developed in order to specify the measurement procedure together with the format of the conformanc
32、e statement for the DETECTIVE QUANTUM EFFICIENCY of DIGITAL X-RAY IMAGING DEVICES. In the DQE calculations proposed in this standard, it is assumed that system response is measured for objects that attenuate all energies equally (task-independent) 5. The standard will be beneficial for manufacturers
33、, users, distributors and regulatory agencies. It can be regarded as the first of a series describing all the relevant parameters of DIGITAL X- RAY IMAGING DEVICES. 1)Figures in square brackets refer to the bibliography. Page4 EN622201:2004MEDICAL ELECTRICAL EQUIPMENT CHARACTERISTICS OF DIGITAL X-RA
34、Y IMAGING DEVICES Part 1: Determination of the detective quantum efficiency 1 Scope This part of IEC 62220 specifies the method for the determination of the DETECTIVE QUANTUM EFFICIENCY (DQE) of DIGITAL X-RAY IMAGING DEVICES as a function of exposure and of SPATIAL FREQUENCY for the working conditio
35、ns in the range of the medical application as specified by the MANUFACTURER. This part of IEC 62220 is applicable to projection DIGITAL X-RAY IMAGING DEVICES producing IMAGES in digital format that are used for medical diagnosis. It is restricted to DIGITAL X-RAY IMAGING DEVICES that are used for ra
36、diographic imaging, such as CR systems, selenium-based systems, flat panel detectors, optically coupled CCD detectors, and digital X-RAY IMAGE INTENSIFIERS used for single exposures. This part of IEC 62220 is not applicable to DIGITAL X-RAY IMAGING DEVICES intended to be used in mammography or in de
37、ntal radiography; COMPUTED TOMOGRAPHY: systems in which the X-ray field is scanned across the patient; and devices for dynamic imaging (where series of images are acquired, as in fluoroscopic or cardiac imaging). NOTE The devices noted above are excluded because they contain many parameters (for ins
38、tance, beam qualities, geometry, time dependence, etc.) which differ from those important for general radiography. It is intended to treat some of these techniques in separate standards as has been done for other topics, for instance for speed and contrast, in IEC and ISO standards. 2 Normative refe
39、rences 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 60336:1993, X-ray tube assemblies for
40、medical diagnosis Characteristics of focal spots IEC 60601-2-7: Medical electrical equipment Part 2-7: Particular requirements for the safety of high-voltage generators of diagnostic X-ray generators IEC 60788:1984, Medical radiology Terminology IEC 61267:1994, Medical diagnostic X-ray equipment Rad
41、iation conditions for use in the determination of characteristics ISO 12232:1998, Photography Electronic still-picture cameras Determination of ISO speed Page5 EN622201:2004 3 Terminology and definitions For the purposes of this part of IEC 62220 the following terms and definitions apply. 3.1 CENTRA
42、L AXIS line perpendicular to the ENTRANCE PLANE passing through the centre of the entrance field 3.2 CONVERSION FUNCTION plot of the large area output level (ORIGINAL DATA) of a DIGITAL X-RAY IMAGING DEVICE versus the number of exposure quanta per unit area (Q) in the DETECTOR SURFACE plane NOTE 1 Q
43、 is to be calculated by multiplying the measured exposure excluding back scatter by the value given in column 2 of Table 2. NOTE 2 Usually AIR KERMA is substituted for exposure. NOTE 3 Many calibration laboratories, such as national metrology institutes, calibrate RADIATION METERS to measure AIR KER
44、MA. 3.3 DETECTIVE QUANTUM EFFICIENCY DQE(u,v) ratio of two NOISE POWER SPECTRUM (NPS) functions with the numerator being the NPS of the input signal at the DETECTOR SURFACE of a digital X-ray detector after having gone through the deterministic filter given by the system transfer function, and the d
45、enominator being the measured NPS of the output signal (ORIGINAL DATA) NOTE Instead of the two-dimensional DETECTIVE QUANTUM EFFICIENCY, often a cut through the two- dimensional DETECTIVE QUANTUM EFFICIENCY along a specified SPATIAL FREQUENCY axis is published. 3.4 DETECTOR SURFACE area which is clo
46、sest to the IMAGE RECEPTOR PLANE with all protecting parts (including the ANTI-SCATTER GRID and components for AUTOMATIC EXPOSURE CONTROL, if applicable) that can be safely removed out of the RADIATION BEAM without damaging the digital X-ray detector 3.5 DIGITAL X-RAY IMAGING DEVICE device consistin
47、g of a digital X-ray detector including the protective layers installed for use in practice, the amplifying and digitizing electronics, and a computer providing the ORIGINAL DATA (DN) of the image 3.6 IMAGE MATRIX arrangement of matrix elements in a preferably Cartesian coordinate system 3.7 AG EFFE
48、CT influence from a previous image on the current one 3.8 LINEARIZED DATA ORIGINAL DATA to which the inverse CONVERSION FUNCTION has been applied NOTE The LINEARIZED DATA are directly proportional to the exposure. Page6 EN622201:20043.9 MODULATION TRANSFER FUNCTION MTF(u,v) modulus of the generally
49、complex optical transfer function, expressed as a function of SPATIAL FREQUENCIES u and v 3.10 NOISE fluctuations from the expected value of a stochastic process 3.11 NOISE POWER SPECTRUM (NPS) W(u,v) modulus of the Fourier transform of the NOISE auto-covariance function. The power of NOISE, contained in a two-dimensional SPATIAL FREQUENCY interval, as a function of the two- dimensional frequency NOTE In literatur
