1、BRITISH STANDARD BS EN 61262-7:1996 IEC 1262-7: 1995 Characteristics of electro-optical X-ray imaging intensifiers for medical electrical equipment Part 7: Determination of the modulation transfer function The European Standard EN 61262-7:1995 has the status of a British Standard ICS 11.040.50BSEN 6
2、1262-7:1996 This British Standard, having been prepared under the directionof the Health and Environment Sector Board, waspublished under the authorityof the Standards Boardand comes into effect on 15June1996 BSI 04-2000 The following BSI references relate to the work on this standard: Committee ref
3、erence CH/72 Draft for comment 95/560960 DC ISBN 0580257061 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee CH/72, X-ray image forming components, upon which the following bodies were represented: Association of X-ray Equ
4、ipment Manufacturers (BEAMA Ltd.) College of Radiographers Amendments issued since publication Amd. No. Date CommentsBSEN 61262-7:1996 BSI 04-2000 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 Text of EN 61262-7 3 List of references Inside back coverBSEN 6
5、1262-7:1996 ii BSI 04-2000 National foreword This British Standard has been prepared by Technical Committee CH/72 and is the English language version of EN61262-7:1995 Medical electrical equipment Characteristics of electro-optical X-ray image intensifiers Part7: Determination of the modulation tran
6、sfer function published by the European Committee for Electrotechnical Standardization (CENELEC). It is identical with IEC1262-7:1995 published by the International Electrotechnical Commission (IEC). Additional information. The following print types are used in this standard. Requirements, with whic
7、h compliance can be tested, and definitions: in roman type. Explanations, advice, general statements, exceptions and references: in smaller type. Test procedures: in italic type. Terms defined in clause3 of this standard and inAnnex A: in SMALL CAPITALS. For the purposes of this British Standard, an
8、y references to IEC page numbers in the text should be ignored. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity f
9、rom legal obligations. Cross-references Publication referred to Corresponding British Standard EN 60336:1995 (IEC 336:1993) BS EN 60336:1995 X-ray tube assemblies for medical diagnosis. Characteristics of focal spots HD 501 S1:1988 (IEC 788:1984) BS 6641:1985 Glossary of medical radiology terms EN 6
10、1262-4:1994 (IEC 1262-4:1994) BS EN 61262 Characteristics of electro-optical X-ray image intensifiers for medical electrical equipment Part 4:1995 Determination of the image distortion Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, theEN title page, pa
11、ges 2 to 14, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 61262-7 November 1995 ICS 11.
12、040.50 Descriptors: Medical electrical equipment, radiology apparatus, X-ray apparatus, image intensifiers, transfer functions, modulation English version Medical electrical equipment Characteristics of electro-optical X-ray image intensifiers Part 7: Determination of the modulation transfer functio
13、n (IEC 1262-7:1995) Appareils lectromdicaux Caractristiques des intensificateurs lectro-optiques dimage radiologique Partie 7: Dtermination de la fonction de transfert de modulation (CEI 1262-7:1995) Medizinische elektrische Gerte Merkmale von elektronenoptischen Rntgenbildverstrkern Teil 7: Bestimm
14、ung der Modulationsbertragungsfunktion (IEC 1262-7:1995) This European Standard was approved by CENELEC on1995-09-20. 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 witho
15、ut 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 languag
16、e 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, Denmark, Finland, France, Germany, Greece,
17、Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue
18、 de Stassart 35, B-1050 Brussels 1995 Copyright reserved to CENELEC members Ref. No. EN 61262-7:1995EEN61262-7:1995 2 BSI 04-2000 Foreword The text of document62B/250/DIS, future edition1 of IEC1262-7, prepared by SC62B, Diagnostic imaging equipment, of IECTC62, Electrical equipment in medical pract
19、ice, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN61262-7 on 1995-09-20. The following dates were fixed: Annexes designated “normative” are part of the body of the standard. Annexes designated “informative” are given for information only. In this standard,Annex ZA
20、is normative andAnnex A, Annex B, Annex C and Annex D are informative. Annex ZA has been added by CENELEC. Contents Page Foreword 2 Introduction 3 1 Scope 3 2 Normative references 3 3 Terminology 3 3.1 Definitions 3 3.2 Degree of requirements and reading instructions 5 4 Requirements 6 4.1 Test set-
21、up 6 4.2 X-RAY IMAGE INTENSIFIER Operating conditions 6 4.3 Input RADIATION 6 4.4 TEST DEVICE 6 4.5 Measurement equipment 7 5 Determination of the MODULATION TRANSFER FUNCTION 7 5.1 Preparation 7 5.2 Measurement 7 5.3 Corrections 8 5.4 Determination of the LOW-FREQUENCY DROP 9 5.5 Overall accuracy o
22、f determination 9 6 Presentation of the MODULATION TRANSFER FUNCTION 9 7 Statement of compliance 9 Annex A (informative) Terminology Index of defined terms 11 Annex B (informative) Construction of the TEST DEVICE 12 Annex C (informative) Determination of the MTF Aof the MTF ANALYSER 13 Annex D (info
23、rmative) Bibliography 13 Annex ZA (normative) Normative references to international publications with their corresponding European publications 14 Figure 1 Measuring arrangement 10 latest date by which the EN has to be implemented at national level by publication of an identical national standard or
24、 by endorsement (dop) 1996-07-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 1996-07-01EN61262-7:1995 BSI 04-2000 3 Introduction Imaging systems are often being evaluated using subjective measures of performance, such as limiting resolution. These m
25、ethods do not necessarily describe the performance appropriately in imaging tasks that are relevant to the intended use of the system, and are susceptible to the variability of human observers. Linear shift-invariant imaging systems can be conveniently analysed in terms of their TRANSFER functions.
26、The signal TRANSFER of such systems can be specified by the OPTICAL TRANSFER FUNCTION (OTF), which shows the response of the system to sine waves as a function of their spatial frequency. The MODULATION TRANSFER FUNCTION (MTF), the modulus of the OTF, is sufficient for describing the signal TRANSFER
27、 of X-RAY IMAGE INTENSIFIERS. Systems are called shift-invariant when the POINT SPREAD FUNCTION does not vary with position. Note that X-RAY IMAGE INTENSIFIERS generally are shift-invariant over a limited area only: the isoplanatic region. The MODULATION TRANSFER FUNCTION can be determined in severa
28、l ways (see, for example 1 ofAnnex D): from square wave responses; from the Fourier transform of the LINE SPREAD FUNCTION; from the Hankel transform of the POINT SPREAD FUNCTION; from scanning a slit image with a spatial filter. Any method is acceptable if performed correctly. For the purpose of sim
29、plicity, this standard elaborates on two methods: the Fourier transform of the LINE SPREAD FUNCTION, referred to as the LSF method, and the spatial filter method. Accurate determination of the MODULATION TRANSFER FUNCTION requires specialized EQUIPMENT and does not generally lend itself to be perfor
30、med at field installations. This standard only specifies methods for measurement of the MODULATION TRANSFER FUNCTION of X-RAY IMAGE INTENSIFIERS near the CENTRE OF THE ENTRANCE FIELD. 1 Scope This International Standard applies to ELECTRO-OPTICAL X-RAY IMAGE INTENSIFIERS for medical use, as componen
31、ts of diagnostic X-RAY EQUIPMENT. This International Standard describes a method of determining the MODULATION TRANSFER FUNCTION of X-RAY IMAGE INTENSIFIERS. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of th
32、is International Standard. At the time of publication, the editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normativ
33、e documents indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. IEC 336:1993, X-ray tube assemblies for medical diagnosis Characteristics of focal spots. IEC 788:1984, Medical radiology Terminology. IEC 1262-4:1994, Medical electrical equipment Char
34、acteristics of electro-optical X-ray image intensifiers Part4: Determination of the image distortion. ISO/DIS 9334, Optics and optical instruments Optical transfer function Definitions and mathematical relationships. 3 Terminology 3.1 Definitions For the purposes of this International Standard, the
35、following definitions apply together with those given in IEC788. The definitions given below take preference over those given in IEC788 when differences occur. 3.1.1 XRII an abbreviation for ELECTRO-OPTICAL X-RAY IMAGE INTENSIFIEREN61262-7:1995 4 BSI 04-2000 3.1.2 ENTRANCE PLANE the plane perpendicu
36、lar to the axis of symmetry of the XRII and grazing the part of the XRII, including its housing, that protrudes most in the direction of the RADIATION SOURCE 3.1.3 ENTRANCE FIELD for an XRII, the area in the ENTRANCE PLANE that can be used for the TRANSMISSION of an X-RAY PATTERN under specific cond
37、itions 3.1.4 ENTRANCE FIELD SIZE for an XRII, the diameter of the field in the ENTRANCE PLANE that can be used at a specified SED for the TRANSMISSION of an X-RAY PATTERN. For an XRII with more than one magnification mode, the ENTRANCE FIELD SIZE for each of the magnification modes shall correspond
38、to the same diameter of the XRII OUTPUT IMAGE occurring with the largest ENTRANCE FIELD SIZE 3.1.5 SOURCE TO ENTRANCE PLANE DISTANCE (abbreviation SED) the distance between the FOCAL SPOT of the X-RAY TUBE and the ENTRANCE PLANE of the XRII 3.1.6 CENTRE OF THE OUTPUT IMAGE the centre of the smallest
39、 circle circumscribing the OUTPUT IMAGE 3.1.7 CENTRE OF THE ENTRANCE FIELD that point in the ENTRANCE PLANE which is imaged at the CENTRE OF THE OUTPUT IMAGE 3.1.8 CENTRAL AXIS the line perpendicular to the ENTRANCE PLANE passing through the CENTRE OF THE ENTRANCE FIELD 3.1.9 CENTRAL MAGNIFICATION a
40、s a characteristic of XRIIs, the ratio of the length in the OUTPUT IMAGE to the actual length of a small object placed in the ENTRANCE PLANE symmetrically about the CENTRAL AXIS 3.1.10 POINT SPREAD FUNCTION (abbreviation PSF) normalized distribution of irradiance in the image of a point source, see
41、ISO/DIS9334 3.1.11 ISOPLANATIC REGION region where the form of the POINT SPREAD FUNCTION is constant within specified accuracy 3.1.12 LINEARITY property of an imaging system in that the image of a weighted sum of objects is identical to the similarly weighted sum of images of individual objects 3.1.
42、13 LINEAR RANGE range of input signals within which the imaging system exhibits LINEARITY within specified accuracy, seeISO/DIS9334 NOTEThe range of input signals indicating the LINEAR RANGE of the imaging system should be specified by minimum and maximum levels. 3.1.14 OPTICAL TRANSFER FUNCTION (ab
43、breviation OTF) two-dimensional Fourier transform of the imaging systems POINT SPREAD FUNCTION, see ISO/DIS9334EN61262-7:1995 BSI 04-2000 5 NOTEFor the OPTICAL TRANSFER FUNCTION to have significance, it is essential that the imaging system is working in its LINEAR RANGE, and that an ISOPLANATIC REGI
44、ON is considered. 3.1.15 ONE-DIMENSIONAL OPTICAL TRANSFER FUNCTION (abbreviation 1-OTF) section of the OPTICAL TRANSFER FUNCTION through the origin in a given orientation 3.1.16 LINE SPREAD FUNCTION (abbreviation LSF) normalised distribution of irradiance in the image of an incoherently radiating li
45、ne source. The LINE SPREAD FUNCTION only exists in an ISOPLANATIC REGION, see ISO/DIS9334 NOTEThe Fourier transform of the LINE SPREAD FUNCTION is the ONE-DIMENSIONAL OPTICAL TRANSFER FUNCTION for the orientation perpendicular to the direction of the line source. 3.1.17 MODULATION TRANSFER FUNCTION
46、(abbreviation MTF) modulus of the ONE-DIMENSIONAL OPTICAL TRANSFER FUNCTION NOTEThe MTF is defined in ISO/DIS9334 as the modulus of the OPTICAL TRANSFER FUNCTION. For the purpose of this International Standard, definition3.1.17 is more appropriate. 3.1.18 MTF ANALYSER instrument, including relay opt
47、ics and software, capable of performing measurements of the MODULATION TRANSFER FUNCTION 3.1.19 BEST FOCUS setting of focusing potentials resulting in maximum integrated area under the MTF curve for the given slit orientation NOTEThis setting of focusing potentials is chosen to reduce ambiguity and
48、may slightly deviate from settings in practical use of the XRII. 3.1.20 LOW-FREQUENCY DROP (abbreviation LFD) difference between unity and the value of the MODULATION TRANSFER FUNCTION close to zero spatial frequency NOTEWith currently known XRIIs, significant veiling glare is present. This is appar
49、ent as a steep drop in the MTF curve slightly above zero spatial frequency. For the purpose of this International Standard the spatial frequency at which the LFD is to be determined, is chosen to be0,1mm 1 . 3.1.21 LIGHT DETECTOR RADIATION DETECTOR sensitive to VISIBLE RADIATION (light) 3.2 degree of requirements and reading instructions in this International Standard the auxiliary verb: and the following words have the meaning: “shall” implies that compliance with a requirement is mandatory for compliance with the
