1、Designation: E2002 2015Standard Practice forDetermining Total Image Unsharpness and Basic SpatialResolution in Radiography and Radioscopy1This standard is issued under the fixed designation E2002; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、 of 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 This practice covers the design and basic use of a gaugeused to determine the total image un
3、sharpness and the basicspatial resolution of film radiographs or of digital images takenwith CR imaging plates, digital detector arrays, or radioscopicsystems.1.2 This practice is applicable to radiographic and radio-scopic imaging systems utilizing X-ray and gamma ray radia-tion sources.1.3 The val
4、ues stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 The gauge described can be used effectively with tubevoltages up to 600 kV. When using source voltages in themegavolt range the results may not be completely satisfactory.1.5 This sta
5、ndard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1
6、ASTM Standards:2E747 Practice for Design, Manufacture and Material Group-ing Classification of Wire Image Quality Indicators (IQI)Used for RadiologyE1025 Practice for Design, Manufacture, and MaterialGrouping Classification of Hole-Type Image Quality In-dicators (IQI) Used for RadiologyE1316 Termino
7、logy for Nondestructive ExaminationsE1815 Test Method for Classification of Film Systems forIndustrial Radiography2.2 ISO Standards3ISO 192321 Non-destructive TestingImage Quality ofRadiographsPart 1: Image Quality Indicators (WireType)Determination of Image Quality ValueISO 192322 Non-destructive T
8、estingImage Quality ofRadiographsPart 2: Image Quality Indicators (Step/Hole Type)Determination of Image Quality ValueISO 192325 Non-destructive TestingImage Quality ofRadiographsPart 5: Determination of Image Unsharp-ness Value Using Duplex Wire Type Image QualityIndicatorsISO/IEC 170501 Conformity
9、 AssessmentSuppliersDeclaration of ConformityPart 1: General Require-ments2.3 CEN Standard:EN-462-5:1996 Nondestructive TestingImage Quality ofRadiographsPart 5: Image Quality Indicators (DuplexWire Type)Determination of Total Image UnsharpnessValue43. Terminology3.1 DefinitionsDefinitions of terms
10、applicable to this prac-tice may be found in Terminology E1316.3.2 Definitions of Terms Specific to This Standard:3.2.1 basic spatial image resolution (SRbimage) valuedetermined from the smallest number of the duplex wire pair,which is not separable by visual inspection or from the smallestnumber of
11、 the duplex wire pair with less than 20% modulationdepth in a linearized profile, and corresponds to12 UT.UTmaybe UTvisualor UT20%.3.2.2 duplex wire type image quality indicatorduplex wiretype image quality indicator (IQI) specifically designed toassess the total image unsharpness and basic spatial
12、imageresolution of a radiograph or a digital image and composed ofa series of pairs of wire elements made of high density metal.1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.01 onRadiology (X and Gamma)
13、Method.Current edition approved July 1, 2015. Published September 2015. Originallyapproved in 1998. Last previous edition approved in 2009 as E2002 - 98 (2009).DOI: 10.1520/E2002-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.o
14、rg. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from International Organization for Standardization (ISO), ISOCentral Secretariat Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,Switzerland, http:/www.iso.org.4A
15、vailable from British Standards Institute (BSI), 389 Chiswick High Rd.,London W4 4AL, U.K., http:/www.bsi-.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.3 interpolated basic spatial image resolution (iSRbimage)valuedetermined fr
16、om the modulation values of differentneighbored duplex wire pairs by interpolation, which corre-sponds to12 iUT20%.3.2.4 interpolated total image unsharpness (iUT=iUT20%)value determined from a profile function in a digitalimage by interpolation is determined from a linearized profilefunction and ob
17、tained by interpolation to 20% modulationdepth from neighbored element modulations.3.2.5 linepair per mm (lp/mm) valuedetermined from theduplex wire pair values or the interpolated values, and corre-sponds to 1/UT.UTmay be UTvisual,UT20%,oriUT20%.3.2.6 total image unsharpness (UT=UTvisual)determined
18、visuallyis determined from the smallest number of theduplex wire pair, which is visually not separable in a filmradiograph on a viewing station or on a monitor image.NOTE 1The corresponding unsharpness values are given in Table 1.3.2.7 total image unsharpness (UT=UT20%)value, deter-mined from a prof
19、ile function in a digital image is determinedfrom the smallest number of the duplex wire pair, which isseparable by a profile function with less than 20% modulationdepth in a linearized profile.4. Summary of Practice4.1 When it is determined necessary to evaluate and mea-sure the total image unsharp
20、ness or the basic spatial resolutionof an imaging system separately and apart from contrastsensitivity measurements, a tool or gauge as described in thispractice can be used. Conventional IQIs as described inPractices E747 and E1025, or ISO 19232-1 and ISO 19232-2.Combine the contrast sensitivity an
21、d resolution measurementsinto an overall figure of merit. Such figures of merit may not beadequate to detect subtle changes in the imaging systemsperformance. For example, in a high-contrast image, unsharp-ness can increase with almost no noticeable effect upon theoverall image contrast, but the con
22、trast sensitivity for finedetails will be reduced. Similarly, in an application in whichthe imaging system provides a very sharp image, contrast canfade with little noticeable effect upon the overall imagecontrast. These situations often develop and may go undetecteduntil the system performance dete
23、riorates below acceptableimage quality limits.5. Significance and Use5.1 The gauge is intended to provide a means for measuringtotal image unsharpness and basic spatial image resolution asindependently as practicable from the imaging system contrastsensitivity limitations. A similar description of t
24、he gaugesconstruction may be found in ISO 19232-5. When the duplexgauge is positioned directly on the film or the digital detectorwithout any test object between them, the total image unsharp-ness or basic spatial image resolution is equivalent to theinherent film or detector unsharpness (Ui) and th
25、e basic spatialdetector resolution (SRbdetector). Alternatively, line pair gaugeswith constant bar thickness of high attenuating material can beused to determine total image unsharpness and basic spatialresolution of radiologic imaging systems. They may producedifferent results up to one wire pair a
26、s compared to duplex wiremeasurements as described in this standard.6. Gauge Construction6.1 The standard duplex wire IQI shall be fabricated inaccordance with Fig. 1, using the tolerances given in Table 1.NOTE 1Not to Scale.1 space for identification marking2 rigid plastic mountingwire diameter (d)
27、 equals spacing between the wiresFIG. 1 Total Image Unsharpness Gauge (see ISO 19232-5: 2013)E2002 20152This gauge is identical to that described in ISO 19232-5: 2013,and if necessary, ISO 19232-5: 2013 may be reviewed foradditional information.6.2 The gauge shall consist of 13 elements. Each elemen
28、tshall consist of a pair of wires with circular cross-section.Elements 1 through 3 are of tungsten material and elements 4through 13 are of platinum material. The 13 elements aremounted in a rigid plastic holder. Gauges with more elementsthan 13 can be used (see Section 8). These shall be used ifuns
29、harpness values lower than 0.1 mm or basic spatial resolu-tion values lower than 0.05 mm need to be determined (seeSections 7 and 8).6.3 The gauge shall be identified by marking “ISO D (orISO 19232-5 or ASTM E2002) and a serial number.” Markingshall be performed by any suitable means. IQIs with the
30、letters“EN D (or EN 462-5)” are considered to be identical to IQIswith the letters “ISO” or “ASTM.”6.4 The gauge manufacturer shall provide a certificate ofconformance with each gauge. Each IQI should be deliveredwith a declaration of conformity according to ISO/IEC 1750-1.For identification, the IQ
31、I should be numbered and marked bythe producer.7. Application7.1 A radiograph shall be made or an image displayed on amonitor with the duplex wire placed on the source side of theitem being examined or the gauge may be placed on a blockrepresenting the material and total thickness of the item beinge
32、xamined. The duplex wire IQI should be aligned, as closely aspossible, normal to the axis of the radiation beam.NOTE 2If the IQI is placed directly on the detector, the inherentdetector unsharpness and SRbdetectoris measured.7.2 The evaluation of the duplex wire pair images are basedon a visual eval
33、uation by an operator of films on a viewingstation or images on a monitor, or by measurement with aprofile function if digital images are available. The total imageunsharpness UTis given as 2d, where d is the correspondingdiameter of the duplex wires and is also the wire spacingdistance (see Fig. 1)
34、. The value of d is considered as the basicspatial resolution of the image.The term 1/(2d) is considered aslinepair/mm value.7.2.1 Visual EvaluationThe image of the duplex wire IQIshall be examined using magnification up to4onfilmorona monitor. For evaluation of D12 and higher on films, amagnificati
35、on lens2shall be used. The element withsmallest wire number, (that is pair of wires), of which theimage has just merged into single form without an identifiablespace between the images of the two wires, is taken as the limitof visual discernibility for radiography and radioscopy.NOTE 3Visual determi
36、nation of the first unresolved wire pair maydepend on the contrast-to-noise ratio (CNR) and signal-to-noise ratio(SNR) for digital systems or radioscopic systems, or may depend on thefilm system class and tube kV. Therefore, the visual evaluation ofreference images should be performed at CNR or SNR
37、values (for digitalsystems) or using the film system class and kV values typically used forthe production radiographs.7.2.2 Evaluation of Digital Images with ProfileFunctionIf digital images are evaluated with a profilefunction, the element with smallest wire number, of the duplexwire pair, which is
38、 separable by a profile function with lessthan 20% modulation depth, is taken as the limit of discern-ibility for digital radiography. See Fig. 2. The profile functionshall be evaluated from linearized pixel profiles.7.2.2.1 The duplex wire IQI shall be positioned at an angleof approximately 2 to 5
39、towards the pixel line or columnorientation as shown in Fig. 2a in order to reduce aliasingeffects in the digital images.7.2.2.2 The total unsharpness or the basic spatial resolutionof digital images is based on the determination of the firstduplex wire pair (smallest number) with less than 20%modul
40、ation depth (dip).TABLE 1 Duplex Wire Number, Corresponding Total Unsharpness, Basic Spatial Resolution, Linepair Readings, and Wire Diametersand their TolerancesAWire MaterialDuplex WireNumberCorrespondingUnsharpness Value(UT) (mm)CorrespondingBasic SpatialResolution SRbValue (mm)DCorrespondingLine
41、pair Value(lp/mm)Wire Diameterand Spacing,d (mm)Tolerance of WireDiameter and WireSpacing (mm)PtBD13 0.10 0.050 10.0 0.050.005Pt D12 0.13 0.063 7.94 0.063Pt D11 0.16 0.080 6.25 0.08Pt D10 0.20 0.100 5.00 0.10Pt D9 0.26 0.130 3.85 0.13Pt D8 0.32 0.160 3.13 0.160.01Pt D7 0.40 0.200 2.50 0.20Pt D6 0.50
42、 0.250 2.00 0.25Pt D5 0.64 0.320 1.56 0.32Pt D4 0.80 0.400 1.25 0.40WCD3 1.00 0.500 1.00 0.500.02W D2 1.26 0.630 0.79 0.63W D1 1.60 0.800 0.63 0.80AThis table is based on data provided in ISO 19232-5:2013. All unsharpness values are rounded to two decimal places.BPt = Platinum.CW = Tungsten.DFor con
43、version of the SRb-values to m, multiply values which are given in mm by 1000.E2002 201537.2.2.3 The measurement shall be done with a profilefunction of an image processing software across the middlearea of the IQI image integrating along the wires of about30-60% of the duplex wires length in order
44、to obtain a robustrepeatable value, but shall use a minimum of an 11 pixel widthline profile (or the average of 11 single width line profiles) toavoid variability along the length of the wires (Fig. 2b).7.2.3 Evaluation of Digital Images with Profile Function byInterpolationFor more accurate measure
45、ment of the totalunsharpness (iUT) or the basic spatial resolution of digitalimages (iSRb) the measurement of the 20% modulation depthshould be performed by interpolation or approximation. Thismay be required for manufacturer qualification or if specifiedby contracting parties. See Fig. 3. The profi
46、le function shall beevaluated from linearized pixel profiles.7.2.3.1 The duplex wire IQI shall be positioned at an angleof approximately 2 to 5 towards the pixel line or columnorientation as shown in Fig. 2a in order to reduce aliasingeffects in the digital images.7.2.3.2 The measurement shall be do
47、ne with a profilefunction of an image processing software across the middlearea of the IQI image integrating along the wires of about 30to 60 % of the duplex wires length in order to obtain a robustrepeatable value, but shall use a minimum of an 11 pixel widthline profile (or the average of 11 singl
48、e width line profiles) toavoid variability along the length of the wires (Fig. 3a-b).FIG. 2 Wire-pair Image Analysis for Calculation of Basic Spatial Resolution (SRb) and Total Unsharpness (UT) of Digital Images. Thelowest wire pair value shall be determined which has a modulation depth (dip) 450 kV
49、.10.2 Digital images should be taken with high contrast-to-noise ratio for the wire pairs to enhance the visibility of thewire pairs. The procedure of 7.2.2 improves the precisioncompared to the visual evaluation. The procedure of 7.2.2provides a precision of 6 0.5 duplex wire numbers if thecontrast-to-noise ratio of the evaluated wire pair is CNR 20in the integrated profile line. This means that the IQI readingscatters typically between two neighboring duplex wire num-bers if different operators do the evaluation.1
