1、CENELEC ENabLZb2-5 54 3404583 0350594 4T7 M BRITISH STANDARD Characteristics of electro-optical X-ray image intensifiers for medical electrical equipment Part 5. Determination of the detective quantum efficiency The European Standard EN 61262-5 : 1994 has the status of a British Standard BS EN 61262
2、-5 : 1995 IEC 1262-5 : 1994 CENELEC EN*h1262-5 94 = 3404583 0350595 333 BS EN 61262-5 : 1995 Amd. No. Committees responsible for this British Standard Date Text affected The preparation of this British Standard was entrusted to Rchnical Committee HCC/72, Image intensifiers, upon which the following
3、bodies were represented: Association of X-ray Equipment Manufacturers (BEAMA Ltd.) British Institute of Radiology College of Radiographers Institute of Physical Sciences in Medicine (Ipsm) This British Standard, having been prepared under the direction of the Health and Environment Sector Board (W-)
4、, was published under the authority of the Standards Board and comes into effect on 15 April 1995 O BSI 1995 The following BSI references relate to the work on this standard: Committee reference HCC/72 Draft for comment 94/501345 DC ISBN O 580 24035 5 Amendments issued since publication CENELEC EN*h
5、L2612-5 94 = 3404583 0350596 27T BS EN 61262-5 : 1995 Contents Committees responsible National foreword Page Inside front cover ii Foreword 2 Ext of EN 61262-5 4 i CENELEC ENabLZb2-5 94 W 3404583 0350597 106 BS EN 61262-5 : 1995 National foreword This British Standard has been prepared by Technical
6、Committee HCC/72 and is the English language version of EN 61262-5 : 1994 Medical electrical equipment - Characteristics of electro-optical X-ray image intenstyiers - Part 5 Determination of the detective quantum efficiency, published by the European Committee for Electrotechnical Standardization (C
7、ENELEC). It is identical with IEC 1262-5 : 1994 published by the International Electrotechnical Commission (IEC). Cross-references Publication referred to HD 501 S1 (IEC 788 : 1984) Additional information. The following print types are used in this standard. Requirements, with which compliance can b
8、e tested, and definitions: in roman type. Explanations, advice, general statements, exceptions and references: in smaller type. lst procedures: in italic type Terms defined in clause 3 of this standard and in annex A: in SMALL CAPITALS. For the purposes of this British Standard, any references to IE
9、C page numbers in the text should be ignored. Compliance with a British Standard does not of itself confer immunity from legal obligations. Corresponding British Standard BS 6641 1 1985 Glossary of medical radiology terms ii CENELEC EN*b12b2-5 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM 94 = 3
10、404.583 0150598 O42 H EN 61262-5 September 1994 ICs 11.040.50 Descriptors: Medical electrical equipment, image intensifier, X-ray, detection English version Medical electrical equipment - Characteristics of electro-optical X-ray image intensifiers Part 5: Determination of the detective quantum effic
11、iency (IEC 1262-5 : 1994) Appareils lectromdicaux - Caractristiques des intensificateurs electro-optiques dimage radiologique Rntgenbildverstrkern Partie 5: Dtermination de lefficacit quantique de dtection Quanten- Ausbeute Medizinische elektrische Gerte - Merkmale von elektronenoptischen Teil 5: Be
12、stimmung der detektiven (CE1 1262-5 : 1994) (IEC 1262-5 1994) This European Standard was approved by CENELEC on 1994-07-05. CENELEC members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard
13、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 la
14、nguage 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, Gre
15、ece, 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
16、: rue de Stassart 35, B-1050 Brussels O 1994 Copyright reserved to CENELEC members Ref. No. EN 61262-5 : 1994 E CENELEC ENxb3262-5 94 3404583 0350599 T89 Page 2 EN 61262-5 : 1994 Foreword The text of document 62B(C0)116, as prepared by Sub-committee 62B: Diagnostic imaging equipment, of IEC Technica
17、l Committee 62: Electrical equipment in medical practice, was submitted to the IEC-CENELEC parallel vote in January 1994. The reference document was approved by CENELEC as EN 61262-5 on 5 July 1994. The following dates were fixed: - latest date of publication of an identical national standard (dop)
18、1995-07-01 - latest date of withdrawal of conflicting national standards (dow) 1995-07-01 For products which have complied with the relevant national standard before 1995-07-01, as shown by the manufacturer or by a certification body, this previous standard may continue to apply for production until
19、 2000-07-01. Annexes designated normative are part of the body of the standard. Annexes designated informative are given only for information. In this standard, annexes A, B, C and D, are informative and annex ZA is normative. CENELEC ENa61262-5 74 m 3404583 0150600 520 Page 3 EN 61262-5 : 1994 CONT
20、ENTS FOREWORD 2 INTRODUCTION 4 clause 1 scope 5 2 Normative reference 5 3 Terminology 5 3.1 Definitions . 5 3.2 Degree of requirements and reading instructions 6 4 Requirements . 7 4.1 test set-up 7 4.2 X-RAY IMAGE INTENSIFIER . Operating conditions . 7 4.3 Input radiation 7 4.4 TESTDEVICE 8 4.5 Mea
21、surement equipment 8 5 Determination of the DETECTIVE QUANTM EFFICIENCY . 10 5.1 Preparation 10 5.2 Measurement II 5.3 Corrections 12 5.4 Determination 12 6 Presentation Of the DETECTIVE QUAMUM EFFICIENCY 13 7 Statement of compliance . 13 Figure 1 . Geometrical relationship Of RADIATION SOURCE and I
22、NPUT APERTURE . 14 Annexes A Terminology . Index of terms 15 B Representative test Set-up . 16 C Representative scintillation pulse-height spectra 17 D Bibliography . 18 ZA (normative) Other international publications quoted in this standard with the references of the relevant European publications
23、. 19 CENELEC EN*bL2b2-5 74 = 3404583 OL5ObOL 467 Page 4 EN 61262-5 : 1994 INTRODUCTION DETECTIVE QUANTUM EFFICIENCY (DQE) is a measure of the imaging quality Of a System based On a comparison of the signal-to-noise ratio (SNR) at its output to the SNR at its input. For linear imaging systems, SNR an
24、d DQE can be conveniently analysed in terms of sinusoidally varying signals. This standard gives detailed specifications for the determination of the DOE of ELECTRO-OPTICAL X-RAY IMAGE INTENSIFIERS near zero frequency for both spatial and temporal frequencies. The method employed is scintillation sp
25、ectrum analysis (SSA). The source of input radiation is the radionuclide %Am, which is preferred over an X-RAY SOURCE because of the radionuclides freedom from drift and periodic fluctuations in its output while providing gamma-rays in a radiologically interesting energy range. The signal at the out
26、put phosphor of the ELECTRO-OPTICAL X-RAY IMAGE INTENSIFIER is integrated over an area that is large compared to the image of the source. Additionally, the SSA method requires integration of essentially all of the optical photon energy at the ELEcTRo-oF)TIc implies that compliance with a requirement
27、 is strongly recommended but is not mandatory for compliance with the standard: 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 pa
28、rameters or conditions: refers to a particular value or standardized arrangement, usually to those required in an IEC Standard or a legal requirement; see IEC 788, rm-74-01. CENELEC EN*b3262-5 94 3404583 0350604 176 Page 7 EN 61262-5 : 1994 - “specified“ when used in combination with parameters or c
29、onditions: refers to a value or arrangement to be chosen for the purpose under consideration and indicated usually in ACCOMPANYING DOCUMENTS; see IEC 788, rm-74-02. - “designed for“ when used in standards to characterize equipment, devices, components or arrangements: designates an intended and usua
30、lly apparent purpose or use for the product. 4 Requirements The instrumentation characteristics and their settings needed for the determination of the DQE are given in this clause. A representative measurement set-up is shown in annex B. 4.1 Test set-up Not used. 4.2 X-RAY IMAGE INTENSIFIER - Operat
31、/hQ conditions a) The XRII shall be operated under the conditions for NORMAL USE as specified by the manufacturer. b) No ANTI-SCAmR GRID or protective cover shall be used. c) In the case of multiple-field XRllS, the measurement shall be made for the largest specified ENTRANCE FIELD. 4.3 Input radiat
32、ion a) The RADIATION SOURCE of input radiation shall be the radionuclide “Am, which emits gamma-ray photons having an energy of 59,5 keV. b) The output of the source might include quanta other than those from the decay of “Am, for example, L X-rays of neptunium and fluorescence X-rays from the mater
33、ial used in the construction of the source and its container. 1) The fluence rate of quanta with energies other than 595 keV shall be less than 1 % of the fluence rate of 59,5 keV quanta. The required level of spectral purity can be achieved by the use of a FILTER of 0,5 mm of copper. This FILTER re
34、duces the flux of 59,5 keV photons by a factor of about 2. 2) Any ADDED FILTER shall be as close as practical to the source and nearer the source than either the ENTRANCE PLANE of the XRII or the reference detector (4.5.2). c) The source ACTIVITY shall be such as to yield a count rate of 50 to 500 5
35、95 keV photonds at the INPUT APERTURE under the geometry conditions of 4.4.2. An ACTIVITY of about 1 O Bq is needed for this purpose. Page 8 EN 61262-5 : 1994 4.4 TEST DEVICE 4.4.1 INPUT APERTURE a) The cross-sectional area of the RADIATION BEAM incident on either the XRII or the reference detector
36、shall be limited by the same INPUT APERTURE. b) To avoid variations in the output due to local variations in the INPUT SCREEN thickness, the diameter of the INPUT APERTURE shall not be less than 4 mm. c) For a reference detector incorporating a well crystal, the INPUT APERTURE shall restrict the bea
37、m to an area no larger than the area of the base of the well; the incident beam shall not be allowed to strike the walls of the well. d) The INPUT APERTURE shall be cut from a sheet of lead having a thickness of at least 3 mm. 4.4.2 TEST DEVICE geometly a) To restrict both a variation of gamma-ray a
38、bsorption in the XRII INPUT SCREEN and the enlargement of the EFFECTIVE APERTURE due to obliquity of incidence, the angle 8 defined by: 9 = tan (do + d,) i 2 L shall be less than 29 (see figure 1). In the above formula, do is the source diameter d, is the INPUT APERTURE diameter L is the RADIATION S
39、OURCE to INPUT APERTURE distance. b) One set of values of do, d, and L shall be used for measurements with both the reference detector and the XRII. 4.5 Measurement equipmenf 4.5.1 Photomultiplier fube (PMT) A PMT shall be used to detect the light emitted by the XRII and the light emitted from the s
40、cintillation crystal if that is the type of reference detector employed. 4.5.1.1 PMT operating conditions a) The high-voltage supply connected to the PMT shall be set to provide a linear response of the PMT. b) The high voltage should be applied to the PMT at least 30 min before starting the measure
41、ment to achieve stabilization of the PMT response. CENELEC ENrb12b2-5 94 3404583 0350bOb T49 H Page 9 EN 61262-5 : 1994 4.5.1.2 PMT Set-up a) The PMT and the XRII shall be shielded to prevent the detection of ambient light. b) For the measurement of the scintillation pulse-height spectrum, the effic
42、iency of the optical coupling between the PMT and the OUTPUT IMAGE Of the XRII Should be Such that at least 5 % Of the photons emitted by a SINGLE GAMMA-RAY PHOTON PULSE arrive at the photocathode Of the PMT. This can be achieved either by placing the PMT directly against the output window of the XR
43、II, or by using a relay lens with a sufficiently large aperture (F/2 or better). c) When a relay lens is used, the OUTPUT IMAGE of the XRII should be out of focus on the input of the PMT to prevent possible spectral line broadening due to non-uniformities of the PMT photocat hode. d) The background
44、light emitted by the output phosphor outside the image area of the INPUT APERTURE may be prevented from reaching the PMT by appropriate masking. If such masking is used, its aperture shall be such as not to obstruct any photons emitted from an area in the OUTPUT IMAGE with a diameter of at least twi
45、ce the diameter of the image of the EFFECTIVE APERTURE. 4.5.2 Reference detector The reference detector is used to measure the flux of 59,5 keV photons incident at the ENTRANCE PLANE. The QUANTUM ABSORPTION EFFICIENCY of the reference detector at this energy shall be sufficiently high or known with
46、sufficient accuracy that its contribution to the uncertainty of the measurement does not exceed f 2 % absolute. 4.5.3 Pulse processor a) The pulse processor is an electronic device intended to supply an output signal to the multi- channel analyser (MCA). The height of which is proportional to the ma
47、gnitude of the input pulse. The pulse processor is positioned in the signal path between the ouipui of the PMT and the input may also be used when determining count rates with the reference detector. Of an MCA when meaSUring the SpeCtrUm Of SINGLE GAMMA-RAY PHOTON PULSES from the XRII; it b) For the
48、 measurement of the scintillation efficiency i (see 5.4), which is derived from the pulse- reject distorted signals due to the pile-up of two or more pulses during the measurement of a single pulse. However, at the recommended count rates pile-up rejection is generally not necessary. height SpeCtrUm
49、 Of the SINGLE GAMMA-RAY PHOTON PULSES, the processor may include elements that C) For the measurement Of the QUANTUM ABSORPTION EFFICIENCY A, (See 5.4) pile-Up rejection Should not be used. If pile-up rejection is used, it shall be coupled to the means of accumulating the effective measurement time (live time), which is accumulated only during those intervals when the processor is able to accept signals. If this is not done, errors in measuring count rates might result. CENELEC EN*bLZbZ-5 94 3404583 0150607 985 Page 10 EN 61262-5 : 1994 4.5.4 Multi-chann
