1、BRITISH STANDARD Characteristics of electro-optical X-ray image intensifiers for medical electrical equipment Part 6. Determination of the contrast ratio and veiling glare index The European Standard EN 61262-6 : 1994 has the status of a British Standard BS EN 61262-6 : 1995 IEC 1262-6 : 1994 CENELE
2、C EN*bLZbZ-b 74 3404583 0350575 545 Amd. No. BS EN 61262-6 : 1995 Date Text affected This British Standard, having been prepared under the direction of the Health and Environment Sector Board (W-) , was published under the authority of the Standards Board and comes into effect on 15 April 1995 O BSI
3、 1995 The following BSI references relate to the work on this standard: Committee reference HCCi72 Draft for comment 94/501346 DC ISBN O 580 24036 3 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee HCC/72, Image intensifie
4、rs, upon which the following 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) Amendments issued since publication CENELEC EN*b1262-6 94 = 3404583 O350576 YB1 BS
5、 EN 61262-6 : 1995 Contents Committees responsible Page Inside front cover National foreword 11 Foreword 2 Rxt of EN 61262-6 4 CENELEC EN*blZbZ-b 94 3404583 0350577 318 BS EN 61262-6 : 1995 National foreword This British Standard has been prepared by Rchnical Committee HCC/72 and is the English lang
6、uage version of EN 61262-6 : 1994 Medical electrical equipment - Characteristics of electro-optical X-ray image intensa implies that compliance with a requirement is strongly recommended but is not mandatory for compliance with the standard; implies that compliance with a requirement is permitted to
7、 be accomplished in a particular manner, for compliance with the standard; and the following words have the meaning: - “specific“ - “specified“ when used in combination with parameters or conditions: refers to a particular value or standardized arrangement, usually to those required in an IEC standa
8、rd or a legal requirement; see IEC 788, rm-74-01. when used in combination with parameters or conditions: refers to a value or arrangement to be chosen for the purpose under considerati- rm-74-02. On and indicated Sally in ACCOMPANYING DOCUMENTS; see IEC 788, - “designed for“ when used in standards
9、to characterize equipment, devices, components or arrangements: designates an intended and usually apparent purpose or use for the product. CENELEC EN*b1262-6 94 3404583 0150584 558 Page 7 EN 61262-6 1994 4 Requirements The instrumentation characteristics and the settings needed for the determinatio
10、n of the CR and VGI are given here. 4.1 Test Set-up a) The SED shall be 100 cm f 1 cm. 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 exceed 33 cm. d) The X-RAY FIELD shall cover the ENTRANCE
11、FIELD entirely, but its area shall not exceed the ENTRANCE FIELD area by more than 10 %. 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 t
12、his DIAPHRAGM. The DIAPHRAGM shall provide an ATENUATION RATO Of at least 100 for the quantity AIR KERMA RATE. 4.2 X-RAY IMAGE INTENSIFIER - Ope rathg conditions a) The XRII shall be operated under the conditions for NORMAL USE as specified by the manufacturer. b) NO ANTI-SCAlTER GRID or protective
13、cover shall be used. c) In the case of multiple-field XRIIs, the measurement shall be made for the largest specified ENTRANCE FIELD. Measurements for other ENTRANCE FIELDS are OptiOflal. 4.3 Input radiation a) The RADIATION QUALITY shall be that Of an X-RAY TUBE operated at a peak X-RAY TUBE VOLTAGE
14、 of 50 kV i 2 kV, and a HALF-VALUE LAYER of 2,O mm f 0,2 mm of aluminium (99,9 % purity); this corresponds to a TOTAL FiLmATioN of approximately 3 mm of aluminium equivalent. b) It is permissible to perform an additional determination with the RADIATION QUALITY of an X-RAY of 22,5 mm i 0,5 mrn of al
15、uminium equivalent of which at least 20 mm is aluminium (99,9 % purity). These conditions require operating with a peak X-RAY TUBE VOLTAGE of approximately 75 kV. BEAM that exhibits a HALF-VALUE LAYER Of 7,O mm f O,2 mm Of aIUminUm With a TOTAL FILTRATION 1) Any ADDED FILTER shall be uniform and pos
16、itioned as close as possible to the X-ray source; see also 4.1 c). 2) The use of this RADIATION QUALITY shall be stated in the presentation Of reSUltS. CENELEC EN*bltZbZ-b i4 3404583 Olt50585 494 W Page 8 EN 61262-6 : 1994 c) The temporal fluctuations of the AIR KERMA RATE shall not impair the measu
17、rement uncertainty by more than 2 %. 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 thick
18、ness of at least 3 mm. b) One disk shall have a diameter of 10 mm i 0,5 mm. c) Other disks shall have diameters such that the area of each disk is 10 Yo f 0,5 % of the area determined by the ENTRANCE FIELD SIZE used in the measurement. Such a TEST DEVICE is referred to aS a 10 yo area TEST DEVICE. d
19、) The TEST DEVICES shall be placed tangent to the ENTRANCE PLANE. 4.5 Measurement equipment 4.5.1 Photometer a) A photometer is used to measure the luminance of the XRII OUTPUT IMAGE. The largest linear dimension of the sampling aperture of the photometer at the plane of the OUTPUT IMAGE shall not e
20、xceed one-third Of the diameter Of the NOMINAL IMAGE SIZE Of the TEST DEVICE being imaged. b) The error due to non-linearity of the photometers luminance response shall not exceed 1 %. c) The error due to dark current of the photometer shall not exceed 1 % of the smallest luminance measurement. 4.5.
21、2 X-ray fluence rate monitor a) A RADIATION DETECTOR, such as a scintillator with a photodiode, should be used to measure the relative X-ray fluence rate at the ENTRANCE PLANE. b) If a RADIATION DETECTOR is.used, it shall be capable of detecting a deviation in the fluence rate OfI3%. C) If the RADIA
22、TION DETECTOR S pOSitiOned in the X-RAY BEAM, 1) the distance from the RADIATION DETECTOR to the ENTRANCE PLANE shall not be leSS than 50 cm, 2) the projection Of the RADIATION DETECTOR shall not be within the ENTRANCE FIELD, 3) the RADIATION DETECTOR shall remain undisturbed in the X-RAY FIELD thro
23、ughout the determination. d) If measurements are made With an ADDED FILTER in the X-RAY BEAM, the RADIATION DETECTOR shall be positioned between the ADDED FILTER and the ENTRANCE PLANE. Page 9 EN 61262-6 : 1994 5 Determination Of the CONTRAST RATiO and the VEIUNG GLARE INDEX 5.1 Preparation a) The T
24、EST DEVICE shall be placed in a plane as close as possible to. but not more than 10 mm in front of, and parallel to the EMRANCE PLANE. b) The centre Of the TEST DEVICE shall be on the CENTRAL AXIS. 1) For measurements with the 10 mm TEST DEVICE, the displacement of the centre of the TEST DEVICE from
25、 the CENTRAL AXIS shall not exceed 5 mm. 2) For measurements with the 10 % area TEST DEVICE, the displacement of the centre of the TEST DMCE from the CENTRAL AXIS shall not exceed 5 mm. c) A minimum amount of supporting material should be used to suspend the TEST DEVICE in the X-RAY FIELD. The use o
26、f a plastic sheet with a thickness of only 1 mm can already produce a measurable reduction in the CONTRAST RATO. d) Measurements of luminance of the OUTPUT IMAGE shall be made at the CENTRE OF THE OUTPUT IMAGE. 1) For measurements with the 10 mm TEST DEVICE, the displacement of the centre of the pho
27、tometers sampling aperture from the CENTRE OF THE OUTPUT IMAGE shall not exceed 0.1 mm. 2) For measurements with the 10 Oh area TEST DEVICE, the displacement of the centre of the photometers sampling aperture from the CENTRE OF THE OUTPUT IMAGE shall not exceed 1,0 mm. 5.2 Measurement a) While the X
28、RII is irradiated, measure the luminance, L, at the CENTRE OF THE OUTPUT IMAGE. b) Remove the TEST DEVICE. c) Restore the X-ray fluence rate at the ENTRANCE PLANE to within I 3 % of the value in tem b). d) While the XRII is irradiated, measure the luminance, k, at the CENTRE OF THE OUTPUT IMAGE. e)
29、Measurements shall be made with the 10 mm diameter TEST DEVICE and with the 10 % area TEST DEVICE for the largest ENTRANCE FIELD SIZE Of the XRII. 5.3 Corrections In addition to the light originating from the sampled area of the image, light scattered in the optical elements of the photometer and fr
30、om structures of the test setup might contribute to the luminance measurements. If such spurious contributions exceed 3 % of the smallest luminance measured in the determination, corrections for these contributions shall be applied. A method of determining the correction is given in annex B. Page 10
31、 EN 61262-6 : 1994 5.4 Determination The CR is the quotient L, / i, and the VGI is the quotient i, / L, with L, and L, as defined in 5.2 b) and 5.2 e), respectively. 6 Presentation Of the CONTRAST RATIO and the VEILING GLARE INDEX a) The presentation of the results shall include the following inform
32、ation: - XRII identification, e.g., generic type, model name or number; - The diameter (in rnm) of the CR TEST DEVICE; and the CR as a number; and/or the VGI as a fractional number. b) Unless otherwise specified, the indicated CR or VGI or both shall refer to: - the RADIATION QUALITY Of 50 kV f 2 kV
33、 (peak X-RAY TUBE VOLTAGE) and a HALF-VALUE LAYER of 2,O mm f 0,2 mm aluminium (99,9 % purity) with no ADDED FILTER; - the largest ENTRANCE FIELD SIZE. 7 Statement of compliance if compliance with this standard for the determination of the CONTRAST RAW and the VEILING GLARE INDEX Of X-RAY IMAGE INTE
34、NSIFIERS iC to be stated, fi shall be indicated as: - - Contrast ratio: IEC 1262-6: 1994, and as Veiling glare index: IEC 1262-6: 1994. CENELEC EN*b1262-6 94 3404583 0150588 lT3 Page 11 EN 61262-6 : 1994 Annex A (informative) Terminology . Index of terms IEC788 rm. . Name of unit in the internationa
35、l System SI . Derived term without definition rm. . + Term without definition Name of earlier unit Shortened term . Subclause 3.1 of IEC 1262-6 (present publication) rm. . rm. rm. rm. . 5 3.1, ACCOMPANYING DOCUMENTS rm-82-01 AIR KERMA RATE rm-13-11 and rm-13-13 ATTENUATIONRATIO rm-13-40 ADDED FILTER
36、 rm-35-02 ANTI-SCATTER GRID . rm-3246 BEAM LIMITING DEVICE . rm-37-28 CENTRAL AXIS 3.1.8 CENTFIAL MAGNIFICATION . 3.1.9 CONTRAST RATIO 3.1.1 1 CENTRE OF THE ENTRANCE FIELD . 3.1.7 CENTRE OF THE OUTPUT IMAGE . 3.1.6 DIAPHRAGM rm-37-29 ELECTRO-OPICAL X-RAY IMAGE INTENSIFIER ENTRANCE FIELD . 3.1.3 rm-3
37、2-40 ENTRANCE FIELD SIZE . 3.1.4 ENTRANCE PLANE 3.1.2 FOCALSPOT . mi-2O-13S HALF-VALUE LAYER . rm-13-42 NORMAL USE rm-82-04 . NOMINAL FOCAL SPOT VALUE rm-20-14 NOMINAL IMAGE SIZE . : 3.1.10 OUTPUT IMAGE rm-32-49 RADIATION DETECTOR . rm-51-01 RADIATION QUALITY . rm-13-28 RADIATIONSOURCE . rm-20-01 SO
38、URCE TO ENTRANCE PLANE DISTANCE . SPECIFIC . rm-74-01 SPECIFIED . rm-74-02 3.1.5 CENELEC ENrbL262-6 94 W 3404583 0350589 03T W Page 12 EN 61262-6 : 1994 TESTDEVICE . TOTALFILTRATION . VEILINGGLAREINDEX . X-RAYBEAM X-RAYEQUIPMENT X-RAYFIELD X-RAY IMAGE INTENSIFIER . X-RAY PATTERN X-RAYSOURCEASSEMBLY
39、X-RAYTUBE X-RAYTUBEVOLTAGE . XRII . rm-71-04 rm-13-48 3.1.12 rm-37-05+ rm-20-20 rm-37-07+ rm-32-39 rm-32-01 rm-2O45-t rrn-22-03 rm-36-02 3.1.1 CENELEC ENsbLZbZ-6 94 = 3404583 0350590 851 Page 13 EN 61262-6 : 1994 Annex B (informative) Determination of a correction for photometer veiling glare The fo
40、llowing is a suggested procedure for determining the correction of luminance measurements for the veiling glare of the photometer. Set up the photometer for measuring luminance according to its ACCOMPANYING DOCUMENTS. As near as possible to the plane containing the image being analysed, position an
41、opaque mask containing an aperture. The diameter of the aperture should be variable over the range of about 0,7 to 1.4 of the diameter of the photometers sampling aperture of the image. Measure the photometers output as a function of the area of the aperture in the mask. By interpolation determine t
42、he photometer signal, S, that would be obtained if the mask aperture exactly matched the photometers sampling aperture. Obtain the photometer signal, S, with no opaque mask. This value will be larger than S, due to the photometers veiling glare. Calculate the correction factor K = S, i S,. When cond
43、ucting luminance measurements with a CR TEST DEVICE in position, under the same conditions of image content and illuminant spectrum, multiply the photometer signal by the factor K. The resulting value may then be used in the calculations as given in 5.4 of this International Standard. CENELEC EN*b12
44、62-6 99 = 3404583 0350593 798 = Page 14 EN 61262-6 1994 Annex ZA (normative) Other international publications quoted in this standard with the references of the relevant European publications This European standard incorporates by dated or undated reference, provisions from other publications. These
45、 normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated
46、 references the latest edition of the publication referred to applies. NOIX. When the international publication has been modified by CENELEC common modifications, indicated by mod), the relevant EN/HD applies. IEC publication Date Title EN/HD Date 788 i984 Medical radiology - lbrrninology HD 501 S1
47、1988 CENELEC EN*b3262-6 94 W 3404583 0350592 624 = BS EN 61262-6 1995 List of references See national foreword. BS EN 61262-6 : 1995 IEC 1262-6 1994 BSI 389 Chiswick High Road London W4 4AL 9504- 7- 0.5k-RTL BSI - British Standards Institution BSI is the independent national body responsible for pre
48、paring British Standards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Contract requirements A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible fo
49、r their correct application. Revisions British Standards are updated by amendment or revision. Users of British Standards should make sure that they possess the latest amendments or editions. Any person who finds an inaccuracy or ambiguity while using this British Standard should bring it to the attention of the Quality Manager, BSI without delay so that the matter may be investigated swiftly. BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards. Buying standards Orders for al
