1、Designation: E1165 12 (Reapproved 2017)Standard Test Method forMeasurement of Focal Spots of Industrial X-Ray Tubes byPinhole Imaging1This standard is issued under the fixed designation E1165; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 The image quality and the resolution of X-ray imageshighly depend on the characteristics of the
3、focal spot. Theimaging qualities of the focal spot are based on its twodimensional intensity distribution as seen from the detectorplane.1.2 This test method provides instructions for determiningthe effective size (dimensions) of standard and mini focal spotsof industrial x-ray tubes. This determina
4、tion is based on themeasurement of an image of a focal spot that has beenradiographically recorded with a “pinhole” technique.1.3 This standard specifies a method for the measurement offocal spot dimensions from 50 m up to several mm of X-raysources up to 1000 kV tube voltage. Smaller focal spots sh
5、ouldbe measured using EN 12543-5 using the projection of an edge.1.4 This test method may also be used to determine thepresence or extent of focal spot damage or deterioration thatmay have occurred due to tube age, tube overloading, and thelike. This would entail the production of a focal spot radio
6、-graph (with the pinhole method) and an evaluation of theresultant image for pitting, cracking, and the like.1.5 Values stated in SI units are to be regarded as thestandard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibili
7、ty of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accor-dance with internationally recognized principles on standard-ization es
8、tablished in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E1000 Guide for RadioscopyE1255 Practice for RadioscopyE2002
9、 Practice for Determining Total Image Unsharpnessand Basic Spatial Resolution in Radiography and Radios-copyE2033 Practice for Computed Radiology (PhotostimulableLuminescence Method)E2698 Practice for Radiological Examination Using DigitalDetector Arrays2.2 European Standards:3EN 12543-2 Non-destruc
10、tive testingCharacteristics of fo-cal spots in industrial X-ray systems for use in non-destructive testingPart 2: Pinhole camera radiographicmethodEN 12543-5 Non-destructive testingCharacteristics of fo-cal spots in industrial X-ray systems for use in non-destructive testingPart 5: Measurement of th
11、e effectivefocal spot size of mini and micro focus X-ray tubes2.3 Papers:Klaus Bavendiek, Uwe Heike, Uwe Zscherpel, Uwe EwertAnd Adrian Riedo, “New measurement methods of focalspot size and shape of X-ray tubes in digital radiologicalapplications in comparison to current standards,” WC-NDT 2012, Dur
12、ban, South Africa3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 actual focal spotthe X-ray producing area of thetarget as viewed from a position perpendicular to the targetsurface (see Fig. 1).3.1.2 effective focal spotthe X-ray producing area of thetarget as viewed from a po
13、sition perpendicular to the tube axisin the center of the X-ray beam (see Fig. 1).1This test method is under the jurisdiction of ASTM Committee E07 onNondestructive Testing and is the direct responsibility of Subcommittee E07.01 onRadiology (X and Gamma) Method.Current edition approved Nov. 1, 2017.
14、 Published December 2017. Originallyapproved in 1987. Last previous edition approved in 2012 as E1165 12. DOI:10.1520/E1165-12R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informat
15、ion, refer to the standards Document Summary page onthe ASTM website.3Available from European Committee for Standardization (CEN), AvenueMarnix 17, B-1000, Brussels, Belgium, http:/www.cen.eu.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United S
16、tatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to
17、Trade (TBT) Committee.13.1.3 effective size of focal spotfocal spot size measured inaccordance with this standard.4. Summary of Test Method4.1 This method is based on a projection image of the focalspot using a pinhole camera. This image shows the intensitydistribution of the focal spot. From this i
18、mage the effective sizeof the focal spot is computed. A double integration of a profileacross the pinhole image transforms the pinhole image into anedge profile. The X- and Y-dimension of the edge unsharpnessis used for calculation of the size of the focal spot. This methodprovides similar results a
19、s the method described in EN 12543-5using an edge target instead of a pinhole camera. The measuredeffective spot sizes correspond to the geometrical imageunsharpness values at given magnifications as measured withthe ASTM E2002 duplex wire gauge in practical images usingequation:uG5 v 2 1! (1)with g
20、eometrical unsharpness uG, focal spot size andmagnification v (seeASTM E1000 for details of this equation).For a full description see Reference 2.3.4.2 Additionally, a simplified test method is described in theannex A for users of X-ray tubes who may not intend to use apinhole camera. This alternati
21、ve method is based on the edgemethod in accordance with EN 12543-5 using a plate hole IQIas described in ASTM E1025 or E1742 instead of a pinholecamera.5. Significance and Use5.1 One of the factors affecting the quality of radiologicimages is the geometric unsharpness. The degree of geometricunsharp
22、ness is dependent on the focal spot size of the radiationsource, the distance between the source and the object to beradiographed, and the distance between the object to beradiographed and the detector (imaging plate, Digital DetectorArray (DDA) or film). This test method allows the user todetermine
23、 the effective focal size of the X-ray source. Thisresult may then be used to establish source to object and objectto detector distances appropriate for maintaining the desireddegree of geometric unsharpness and/or maximum magnifica-tion for a given radiographic imaging application. SomeASTMstandard
24、s require this value for calculation of a requiredmagnification, for example, E1255, E2033, and E2698.6. Apparatus6.1 Pinhole DiaphragmThe pinhole diaphragm shall con-form to the design and material requirements of Table 1 andFig. 3.6.2 CameraThe pinhole camera assembly consists of thepinhole diaphr
25、agm, the shielding material to which it is affixed,and any mechanism that is used to hold the shield/diaphragm inposition (jigs, fixtures, brackets, and the like).6.3 Alignment and Position of the Pinhole CameraTheangle between the beam direction and the pinhole axis (see Fig.4) shall be smaller tha
26、n 61.5. When deviating from Fig. 4, thedirection of the beam shall be indicated. The incident face ofthe pinhole diaphragm shall be placed at a distance m from thefocal spot so that the variation of the magnification over theextension of the actual focal spot does not exceed 65 % in thebeam directio
27、n. In no case shall this distance be less than 100mm.FIG. 1 Actual/Effective Focal SpotTABLE 1 Pinhole Diaphragm Design Requirements (Dimension)ANOTE 1The pinhole diaphragm shall be made from one of thefollowing materials: (1) An alloy of 90 % gold and 10 % platinum,(2) Tungsten, (3) Tungsten carbid
28、e, (4) Tungsten alloy, (5) Platinum and10 % Iridium Alloy, or (6) Tantalum.Focal Spot SizemmDiameter PmHeight Hm0.05 to 0.3 10 5 50 50.3to0.8 305 75100.8 100 5 500 10ASee Fig. 3.E1165 12 (2017)26.4 Position of the Radiographic Image DetectorTheradiographic image detector (film, imaging plate or DDA)
29、 shallbe placed normal to the beam direction at a distance n from theincident face of the pinhole diaphragm determined from theapplicable magnification according to Fig. 5 and Table 2.6.5 Radiographic Image DetectorAnalogue or digital ra-diographic image detectors may be used, provided sensitivity,d
30、ynamic range and detector unsharpness allow capturing of thefull spatial size of the focal spot image without detectorsaturation. The maximum allowed detector unsharpness is(a) Image of a double line Focal Spot with the Location and Size of the Line Profile in Length Direction.(b) Line Profile in th
31、e direction of the large arrow averaged over the dotted rectangle of Fig. 2a.(c) Integrated Line Profile with Markers (blue) for 16 % and 84 % of the Profile Intensity, Markers (green) for 0 % and 100 %Extrapolation and the Extrapolation Line(dotted black), corresponding to the Klasens method of E10
32、00.(d) Pseudo 3D Image of the Focal Spot; the large arrow points in the direction of the Line Profile.(e) Image of a double line Focal Spot with the Location and Size of the Line Profile in Width Direction.(f) Integrated Line Profile with Markers (blue) for 16 % and 84 % of the Profile Intensity, Ma
33、rkers (green) for 0 % and 100 %Extrapolation and the Extrapolation Line(dotted black) for the Width Direction.FIG. 2 Example for the Measurement of Effective Focal Spot Length and Width with the Integrated Line Profile (ILP) MethodE1165 12 (2017)3given by the geometrical unsharpness uGof the pinhole
34、 and thepinhole diameter P. It is calculated according to (see Fig. 5).uG5 P11n/m! (2)6.5.1 The detector unsharpness shall be determined with theduplex wire IQI in accordance with ASTM E2002. Theminimum projected length and width of the focal spot imageshould be covered always by at least 20 detecto
35、r pixels indigital images. The signal-to-noise ratio of the focal spot image(ratio of the maximum intensity value inside the focal spot andthe standard deviation of the background signal outside) shouldbe at least 50. The maximum intensity inside the focal spotshould be above 30 %, but lower than 90
36、 % of the maximumlinear detector output value. The grey value resolution of thedetector shall be in minimum 12 Bit.(e) Image of a double line Focal Spot with the Location and Size of the Line Profile in Width Direction.(f) Integrated Line Profile with Markers (blue) for 16 % and 84 % of the Profile
37、Intensity, Markers (green) for 0 % and 100 % Extrapolation and the Extrapolation Line(dotted black) for the Width Direction.FIG. 2 Example for the Measurement of Effective Focal Spot Length and Width with the Integrated Line Profile (ILP) Method (continued)E1165 12 (2017)46.5.2 Imaging plate systems
38、 (Computed Radiography, CR)or digital detector arrays (DDA) may be used as digital imagedetectors following practices E2033 or E2698. The pixelvalues shall be linear to the dose.6.5.3 If radiographic film is used as image detector, it shallmeet the requirements of E1815 film system class I or Specia
39、land shall be packed in low absorption cassettes using noscreens. The film shall be exposed to a maximum opticaldensity between 1.5 and 2.5. The film shall be digitized with amaximum pixel of 50 m or a smaller size, which fulfills therequirements of the above unsharpness conditions and beevaluated a
40、ccording to Eq 2. If the user has no digitalequipment the film may be evaluated visually; the procedure isshown in 7.9. The film shall be processed in accordance withGuide E999.6.6 Image Processing EquipmentThis apparatus is used tocapture the images and to measure the intensity profile of thefocal
41、spot in the projected image. The image shall be a positiveimage (more dose shows higher grey values) and linearproportional to the dose. The equipment shall be able:FIG. 3 Essential Dimensions of the Pinhole DiaphragmFIG. 4 Alignment of the Pinhole DiaphragmE1165 12 (2017)5(1) to calibrate the pixel
42、 size with a precision of 2 m or1 % of the pixel size,(2) to draw line profiles and average the line profiles overa preset area,(3) to integrate line profiles by the length of the line profile,(4) to subtract the background using a linear interpolation(straight line) of both ends of the line profile
43、 using at least theaverage of 10 % of the line profile as support on both ends, and(5) to calculate the X- and Y-dimension of the focal spot inthe image with two threshold values of 16 % and 84 % of theintegrated line profile and extrapolate the width to 100 % (seeFig. 2).NOTE 1The software for this
44、 calculation can be downloaded fromhttp:/dir.bam.de/ic (or http:/www.kb.bam.de/alex/ic/index.html).6.6.1 When using CR technology or digitized film whereoutliner pixel may occur, a median 33 filter shall be available.7. Procedure7.1 If possible, use a standard 1 m (40 in.) focal spot todetector dist
45、ance (FDD = m+n) for all exposures. If themachine geometry or accessibility limitations will not permittheuseofa1mFDD, use the maximum attainable FDD (inthese instances adjust the relative distances between focal spot,FIG. 5 Beam Direction Dimensions and PlanesTABLE 2 Magnification for Focal Spot Pi
46、nhole ImagesAnticipatedFocalSpot Sized mmMinimumMagnificationn/mDistance betweenFocal Spot andPinhole mADistance betweenPinhole andDetector nA0.05 to 2.0 3 : 1 0.25 0.752.0 1 : 1 0.5 0.5AWhen using a technique that entails the use of enlargement factors anda1mfocal spot to detector distance (FDD = m
47、+n) is not possible (see 7.1), the distancebetween the focal spot and the pinhole (m) shall be adjusted to suit the actual focalspot to detector distance (FDD) used (for example, if a 600 mm FDD is used, mshall be 150 mm for 3:1 enlargement, 300 mm for 1:1 enlargement, and the like).E1165 12 (2017)6
48、pinhole, and detector accordingly to suit the image enlarge-ment factors specified in Table 2). For small focal spots FDDmay be larger than 1 m (40 in.) to meet the requirements in 6.5and 7.5. The distance between the focal spot and the pinhole isbased on the anticipated size of the focal spot being
49、 measuredand the desired degree of image enlargement (see Fig. 5). Thespecified focal spot to pinhole distance (m) for the differentfocal spot size ranges is provided in Table 2. Position thepinhole such that it is within 61.5 of the central axis of theX-ray beam.NOTE 2The accuracy of the pinhole system is highly dependent uponthe relative distances between (and alignment of) the focal spot, thepinhole, and the detector.Accordingly, a specially designed apparatus maybe necessary in order to assure compliance with the above req
