BS EN 61262-6-1995 Characteristics of electro-optical X-ray image intensifiers for medical electrical equipment - Determination of the contrast ratio and veiling glare index《医用电气设备.pdf

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1、BRITISH STANDARD BS EN 61262-6:1995 IEC1262-6: 1994 Characteristics of electro-optical X-ray image intensifiers for medical electrical equipment Part6: Determination of the contrast ratio and veiling glare index The European Standard EN61262-6:1994 has the status of a BritishStandardBSEN61262-6:1995

2、 This BritishStandard, having been prepared under the directionof the Health and Environment Sector Board (H/-), was published under the authorityof the Standards Boardand comes into effect on 15April1995 BSI 01-2000 The following BSI references relate to the work on this standard: Committee referen

3、ceHCC/72 Draft for comment94/501346DC ISBN 0 580 24036 3 Committees responsible for this BritishStandard The preparation of this BritishStandard was entrusted to Technical CommitteeHCC/72, Image intensifiers, upon which the following bodies were represented: Association of X-ray Equipment Manufactur

4、ers (BEAMA Ltd.) British Institute of Radiology College of Radiographers Institute of Physical Sciences in Medicine (Ipsm) Amendments issued since publication Amd. No. Date CommentsBSEN61262-6:1995 BSI 01-2000 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2

5、Text of EN61262-6 3 List of references Inside back coverBSEN61262-6:1995 ii BSI 01-2000 National foreword This BritishStandard has been prepared by Technical CommitteeHCC/72 and is the English language version of EN61262-6:1994 Medical electrical equipment Characteristics of electro-optical X-ray im

6、age intensifiers Part6:Determination of the contrast ratio and veiling glare index, published by the European Committee for Electrotechnical Standardization (CENELEC). It is identical with IEC1262-6:1994 published by the International Electrotechnical Commission (IEC). Additional information. The fo

7、llowing print types are used in this standard. Requirements, with which 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 inAnne

8、x A: in SMALL CAPITALS. For the purposes of this BritishStandard, any 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. Com

9、pliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references Publication referred to Corresponding BritishStandard HD501S1 (IEC788:1984) BS6641:1985 Glossary of medical radiology terms Summary of pages This document comprises a front cover, an inside fr

10、ont cover, pagesi andii, theEN title page, pages2 to8, 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 EUROPI

11、SCHE NORM EN61262-6 September1994 ICS 11.040.50 Descriptors: Medical electrical equipment, image intensifier, X-ray, contrast, English version Medical electrical equipment Characteristics of electro-optical X-ray image intensifiers Part6:Determination of the contrast ratio and veiling glareindex (IE

12、C1262-6:1994) Appareils lectromdicaux Caractristiques des intensificateurs lectro-optiques dimage radiologique Partie6: Dtermination du rapport de contraste et du voile lumineux (CEI1262-6:1994) Medizinische elektrische Gerte Merkmale von elektronenoptischen Rntgenbildverstrkern Teil6: Bestimmung de

13、s Kontrastverhltnisses und des Untergrundkoeffizienten (IEC1262-6:1994) This European Standard was approved by CENELEC on1994-07-05. 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

14、 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 an

15、y 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, Denmark, Finland, France, Ge

16、rmany, Greece, 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 S

17、ecretariat: rue de Stassart 35, B-1050 Brussels 1994 Copyright reserved to CENELEC members Ref.No.EN61262-6:1994EEN61262-6:1994 BSI 01-2000 2 Foreword The text of document62B(CO)117, as prepared by Sub-Committee62B: Diagnostic imaging equipment, of IEC Technical Committee62: Electrical equipment in

18、medical practice, was submitted to the IEC-CENELEC parallel vote in January1994. The reference document was approved by CENELEC as EN61262-6 on5July1994. The following dates were fixed: For products which have complied with the relevant national standard before1995-07-01, as shown by the manufacture

19、r or by a certification body, this previous standard may continue to apply for production until2000-07-01. Annexes designated “normative” are part of the body of the standard. Annexes designated “informative” are given only for information. In this standard, Annex A andAnnex B are informative andAnn

20、ex ZA is normative. Contents Page Foreword 2 Introduction 3 1 Scope 3 2 Normative reference 3 3 Terminology 3 3.1 Definitions 3 3.2 Degree of requirements and reading instructions 4 4 Requirements 4 4.1 Test set-up 4 4.2 X-RAY IMAGE INTENSIFIER Operating conditions 4 4.3 Input radiation 5 4.4 TEST D

21、EVICE 5 4.5 Measurement equipment 5 5 Determination of the CONTRAST RATIO and the VEILING GLARE INDEX 5 5.1 Preparation 5 5.2 Measurement 6 5.3 Corrections 6 5.4 Determination 6 6 Presentation of the CONTRAST RATIO and the VEILING GLARE INDEX 6 7 Statement of compliance 6 Annex A (informative) Termi

22、nology Indexofterms 7 Annex B (informative) Determination of acorrectionfor photometer veiling glare 8 Annex ZA (normative) Other international publications quoted in this standard with the references of the relevant European publications 8 latest date of publication of an identical national standar

23、d (dop)1995-07-01 latest date of withdrawal of conflicting national standards (dow)1995-07-01EN61262-6:1994 BSI 01-2000 3 Introduction The CONTRAST RATIO (CR) and the VEILING GLARE INDEX (VGI), which is defined as the reciprocal of the CR, are measures of the spatial frequency response of an imaging

24、 system at low frequencies and, as such, complement the limiting spatial resolution, which is a measure of a systems high-frequency response. Although the CR and the VGI can, in principle, be estimated from the MODULATION TRANSFER FUNCTION, it is simpler to measure them directly. The contrast repres

25、ented by the difference in X-ray fluence between an object and its surroundings can be diminished by the imaging device. Generally, this loss of contrast is due to scattering of the image-carrying quanta away from the ideal paths. The radiance in the image due to imaging the scattered quanta is call

26、ed “veiling glare.” Processes that contribute to veiling glare include the scattering of X-RADIATION at the ELECTRO-OPTICAL X-RAY IMAGE INTENSIFIER input and the scattering of light at its output. For an ELECTRO-OPTICAL X-RAY IMAGE INTENSIFIER, the CR is the ratio of the luminance at the CENTRE OF T

27、HE OUTPUT IMAGE with no TEST DEVICE in the X-RAY BEAM to the luminance at the CENTRE OF THE OUTPUT IMAGE with a CR TEST DEVICE in the X-RAY BEAM. While the CR is unbounded, ranging from1 to infinity, the VGI is bounded between0 and1. 1 Scope This International Standard applies to ELECTRO-OPTICAL X-R

28、AY IMAGE INTENSIFIERS for medical use, as components of diagnostic X-RAY EQUIPMENT. This International Standard describes a method of determining the CONTRAST RATIO (CR) and the VEILING GLARE INDEX (VGI) of ELECTRO-OPTICAL X-RAY IMAGE INTENSIFIERS. 2 Normative reference The following standard contai

29、ns provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate

30、the possibility of applying the most recent edition of the standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. IEC788:1984, Medical Radiology Terminology. 3 Terminology 3.1 Definitions For the purposes of this International Standard, the fo

31、llowing 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 INTENSIFIER 3.1.2 ENTRANCE PLANE the plane perpendicular to the axis of symmetry of

32、 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 conditions 3.1.4 ENTRANCE FIELD SI

33、ZE 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 to the same diameter of the XR

34、II 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 circle circumscribing the OUT

35、PUT 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 FIELDEN61262-6:1994 4 BSI 01-2000 3.1.9 CENTRAL MAGNIFICATION as

36、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 NOMINAL IMAGE SIZE the product of the linear dimension of a small object in the ENTRANCE PLANE and the CENTRAL MAGNIF

37、ICATION 3.1.11 CONTRAST RATIO (ABBREVIATION CR) the ratio of the luminance at the CENTRE OF THE OUTPUT IMAGE with an unblocked X-RAY BEAM to the luminance at the CENTRE OF THE OUTPUT IMAGE when the X-RAY BEAM is blocked at the CENTRE OF THE ENTRANCE FIELD, under specific conditions 3.1.12 VEILING GL

38、ARE INDEX (ABBREVIATION VGI) the reciprocal of the CR 3.2 Degree of requirements and reading instructions In this International Standard the auxiliary verb: 4 Requirements The instrumentation characteristics and the settings needed for the determination of the CR and VGI are given here. 4.1 Test set

39、-up a) The SED shall be100cm 1cm. b) The FOCAL SPOT of the X-RAY TUBE shall be on the CENTRAL AXIS. c) The distance between the FOCAL SPOT of the X-RAY TUBE and any ADDED FILTERS shall not exceed33cm. d) The X-RAY FIELD shall cover the ENTRANCE FIELD entirely, but its area shall not exceed the ENTRA

40、NCE FIELD area by more than10%. This limitation of the X-RAY FIELD shall be made by a DIAPHRAGM placed immediately in front of the ENTRANCE PLANE. The BEAM LIMITING DEVICE of the X-RAY SOURCE ASSEMBLY shall be used to limit the X-RAY BEAM on this DIAPHRAGM. The DIAPHRAGM shall provide an ATTENUATION

41、 RATIO of at least100 for the quantity AIR KERMA RATE. 4.2 X-RAY IMAGE INTENSIFIER Operating conditions a) The XRII shall be operated under the conditions for NORMAL USE as specified by the manufacturer. b) No ANTI-SCATTER GRID or protective cover shall be used. c) In the case of multiple-field XRII

42、s, the measurement shall be made for the largest specified ENTRANCE FIELD. Measurements for other ENTRANCE FIELDS are optional. “shall” implies that compliance with a requirement is mandatory for compliance with the standard; “should” implies that compliance with a requirement is strongly recommende

43、d but is not mandatory for compliance with the standard; “may” implies that compliance with a requirement is permitted to be accomplished in a particular manner, for compliance with the standard; and the following words have the meaning: “specific” when used in combination with parameters or conditi

44、ons: refers to a particular value or standardized arrangement, usually to those required in an IEC standard or a legal requirement; see IEC788, rm-74-01. “specified” when used in combination with parameters or conditions: refers to a value or arrangement to be chosen for the purpose under considerat

45、ion and indicated usually in ACCOMPANYING DOCUMENTS; see IEC788, rm-74-02. “designed for” when used in standards to characterize equipment, devices, components or arrangements: designates an intended and usually apparent purpose or use for the product.EN61262-6:1994 BSI 01-2000 5 4.3 Input radiation

46、 a) The RADIATION QUALITY shall be that of an X-RAY TUBE operated at a peak X-RAY TUBE VOLTAGE of50kV2kV, and a HALF-VALUE LAYER of2,0mm 0,2mm of aluminium(99,9% purity); this corresponds to a TOTAL FILTRATION of approximately3mm of aluminium equivalent. b) It is permissible to perform an additional

47、 determination with the RADIATION QUALITY of an X-RAY BEAM that exhibits a HALF-VALUE LAYER of7,0mm 0,2mm of aluminium with a TOTAL FILTRATION of22,5mm 0,5mm of aluminium equivalent of which at least20mm is aluminium(99,9% purity). These conditions require operating with a peak X-RAY TUBE VOLTAGE of

48、 approximately75kV. 1) Any ADDED FILTER shall be uniform and positioned as close as possible to the X-ray source; see also4.1 c). 2) The use of this RADIATION QUALITY shall be stated in the presentation of results. 3) The temporal fluctuations of the AIR KERMA RATE shall not impair the measurement u

49、ncertainty by more than2%. As the luminance measurements are made at different time instances, the X-RAY TUBE output shall be monitored and the results of the measurements shall be corrected to meet this requirement. 4.4 TEST DEVICE a) The CR TEST DEVICES shall be lead disks having a thickness of at least3mm. b) One disk shall have a diameter of10mm 0,5mm. c) Other disks shall have diameters such that the area of each disk is10% 0,5% of the area determined by the ENTRANCE FIELD SIZE used in the measurement. Such a TEST DEVICE