1、Designation: E 746 07Standard Practice forDetermining Relative Image Quality Response of IndustrialRadiographic Imaging Systems1This standard is issued under the fixed designation E 746; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This standard provides a practice whereby industrialradiographic imaging systems may be comparatively
3、 assessedusing the concept of relative image quality response (RIQR).The RIQR method presented within this practice is based uponthe use of equivalent penetrameter sensitivity (EPS) describedwithin Practice E 1025 and subsection 5.2 of this practice.Figure 1 illustrates a relative image quality indi
4、cator (RIQI)that has four different steel plaque thicknesses (.015, .010,.008, and .005 in.) sequentially positioned (from top to bottom)on a34-in. thick steel plate. The four plaques contain a total of14 different arrays of penetrameter-type hole sizes designed torender varied conditions of thresho
5、ld visibility ranging from1.92 % EPS (at the top) to .94 % EPS (at the bottom) whenexposed to nominal 200 keV X-ray radiation. Each “EPS”array consists of 30 identical holes; thus, providing the userwith a quantity of threshold sensitivity levels suitable forrelative image qualitative response compa
6、risons.1.2 This practice is not intended to qualify the performanceof a specific radiographic technique nor for assurance that aradiographic technique will detect specific discontinuities in aspecimen undergoing radiographic examination. This practiceis not intended to be used to classify or derive
7、performanceclassification categories for radiographic imaging systems. Forexample, performance classifications of radiographic film sys-tems may be found within Test Method E 1815.1.3 This practice contains an alternate provision wherebyindustrial radiographic imaging systems may be comparativelyass
8、essed using Lucite plastic material exposed to nominal 30keV X-ray radiation. The RIQI for this alternate evaluation isalso illustrated in Fig. 1, except the plaque and base platematerials are constructed of Lucite plastic in lieu of steel. EPSvalues for Lucite plastic are provided in Section 5 base
9、d uponthe use of a 138-in. thick Lucite base plate. For high-energyX-ray applications (4 to 25 MeV), Test Method E 1735provides a similar RIQR standard practice.1.4 The values stated in SI are to be regarded as thestandard.1.5 This standard does not purport to address all of thesafety concerns, if a
10、ny, 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 ASTM Standards:2B 152/B 152M Specification for Copper Sheet, Stri
11、p, Plate,and Rolled BarE 999 Guide for Controlling the Quality of Industrial Ra-diographic Film ProcessingE 1025 Practice for Design, Manufacture, and MaterialGrouping Classification of Hole-Type Image Quality Indi-cators (IQI) Used for RadiologyE 1079 Practice for Calibration of Transmission Densit
12、om-etersE 1316 Terminology for Nondestructive ExaminationsE 1735 Test Method for Determining Relative Image Qual-ity of Industrial Radiographic Film Exposed toX-Radiation from 4 to 25 MeVE 1815 Test Method for Classification of Film Systems forIndustrial RadiographyE 2002 Practice for Determining To
13、tal Image Unsharpnessin Radiology2.2 ANSI Standard3:ANSI PH2.19 Photography Density Measurements-Part 2:Geometric Conditions for Transmission Density2.3 ISO Standards3:ISO 5-2 Photography Density Measurements-Part 2: Geo-metric Conditions for Transmission DensityISO 7004 Photography- Industrial Radi
14、ographic Film, De-termination of ISO Speed, ISO average gradient, and ISO1This 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) Method.Current edition approved Dec. 1, 2007. Published
15、 January 2008. Originallyapproved in 1980. Last previous edition approved in 2002 as E746 - 02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Documen
16、t Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Copyright by ASTM Intl (
17、all rights reserved); Mon Mar 10 23:10:39 EST 2008Downloaded/printed byGuo Dehua (CNIS) pursuant to License Agreement. No further reproductions authorized.gradients G2 and G4 when exposed to X- and gamma-radiation3. Terminology3.1 DefinitionsThe definitions of terms relating to gammaand X-radiology
18、in Terminology E 1316 shall apply to termsused in this practice.3.2 Definitions of Terms Specific to This Standard:3.2.1 detectoran imaging device used to store a radio-graphic latent image or directly convert ionizing radiation intoelectrical signals in proportion to the quantity of radiationabsorb
19、ed.3.2.2 cassettea device that is either flexible or rigid usedto hold or protect a detector3.2.3 Relative Image Quality Indicator (RIQI)an imagequality measuring device that is capable of determining mean-ingful differences between two or more radiographic imagingsystems or changes of individual co
20、mponents of radiographicimaging systems.3.2.4 pixel intensity value (PV)a positive integer numeri-cal value of gray scale level of a picture data element (pixel)directly proportional with originating digital image data values.3.2.4.1 DiscussionPV is directly related to radiation dosereceived by a di
21、gital detector, that is, PV is “0” if radiation dosewas “0”. The number of available PV integers is associatedwith gray scale bit depth of the digital image. For example: a12-bit gray scale image will have a range from “0” to “4095”levels (shades) of gray (4096 total pixel value integers) andwill be
22、come saturated when PV reaches “4095”.4. Significance and Use4.1 This standard provides a practice for RIQR evaluationsof film and non-film imaging systems when exposed throughsteel or plastic materials. Three alternate data evaluationmethods are provided in Section 9. Determining RIQR requiresthe c
23、omparison of at least two radiographs or radiographicprocesses whereby the relative degree of image quality differ-ence may be determined using the EPS plaque arrangement ofStep Identification Shim Thickness, mm (in.) Hole Identification Hole Size, mm (in.)15 0.38 6 0.012 (0.015 6 0.0005) 32 0.81 6
24、0.025 (0.032 6 0.001)10 0.25 6 0.012 (0.010 6 0.0005) 31 0.79 6 0.025 (0.031 6 0.001)8 0.20 6 0.012 (0.008 6 0.0005) 28 0.71 6 0.025 (0.028 6 0.001)5 0.13 6 0.012 (0.005 6 0.0005) 25 0.64 6 0.025 (0.025 6 0.001)23 0.58 6 0.025 (0.023 6 0.001)20 0.50 6 0.025 (0.020 6 0.001)Hole Spacing (horizontal):
25、5 6 0.1mm(0.26 0.004 in.) NonaccumulativeRow Spacing: 3 6 0.1mm(0.26 0.004 in.)Spacing between hole sets: 5 6 0.1mm(0.26 0.004 in.)All other dimensions shall be in accordance with standard engineering practice.FIG. 1 Relative Image Quality IndicatorE746072Copyright by ASTM Intl (all rights reserved)
26、; Mon Mar 10 23:10:39 EST 2008Downloaded/printed byGuo Dehua (CNIS) pursuant to License Agreement. No further reproductions authorized.Fig. 1 as a relative image quality indicator (RIQI). In conjunc-tion with the RIQI, a specified radiographic technique ormethod must be established and carefully con
27、trolled for eachradiographic process. This practice is designed to allow thedetermination of subtle changes in EPS that may arise toradiographic imaging system performance levels resultant fromprocess improvements/changes or change of equipment at-tributes. This practice does not address relative un
28、sharpness ofa radiographic imaging system as provided in Practice E 2002.The common element with any relative comparison is the useof the same RIQI arrangement for both processes underevaluation.4.2 In addition to the standard evaluation method describedin Section 9, there may be other techniques/me
29、thods in whichthe basic RIQR arrangement of Fig. 1 might be utilized toperform specialized assessments of relative image qualityperformance. For example, other radiographic variables can bealtered to facilitate evaluations provided these differences areknown and documented for both processes. Where
30、multipleradiographic process variables are evaluated, it is incumbentupon the user of this practice to control those normal processattributes to the degree suitable for the application. SpecializedRIQR techniques may also be useful with micro focus X-ray,isotope sources of radiation or with the use
31、of non-filmradiographic imaging systems. RIQR may also be useful inevaluating imaging systems with alternate materials (RIQI andbase plate) such as copper-nickel or aluminum. When usingany of these specialized applications, the specific method ortechniques used shall be as specified and approved by
32、thecognizant engineering authority.5. Relative Image Quality Indicator5.1 The relative image quality indicator (RIQI) illustrated inFig. 1 shall be fabricated from mild steel plate for the 200 keVevaluation method and Lucite plastic for the 30 keV evaluationmethod. The RIQI steps may be fabricated a
33、s a single multi-step unit or separately and taped together to form the penet-rameter type hole arrays shown in Fig. 1. If tape is used, thetape shall not cover or interfere with any of the holes in theRIQI. All dimensions of the RIQI shall conform to Fig. 1.5.2 The RIQI shown in Fig. 1 consists of
34、14 arrays of 30holes where all hole diameters are the same for each array.Hole diameters are based upon a “multiple” of each respectivestep thickness; therefore, each array of 30 holes has a unique“equivalent” penetrameter sensitivity (EPS) as defined by thefollowing relationship (E 1025):EPS,%5100X
35、3Th2(1)where:h = hole diameter, mmT = step thickness of IQI, mmX = thickness of test object, mmHole diameters within each EPS array are progressivelysmaller from the top to the bottom of Fig. 1; thus, providingdescending EPS values ranging from 1.92 % to 0.94 % for thesteel method and 1.05 % to .51
36、% for the plastic method (Fig.1 illustrates EPS values for the steel method). Descending EPSvalues for Lucite plastic are: 1.05 %, 1.00 %, .96 %, .91 %,.86 %, .81 %, .77 %, .73 %, .70 %, .65 %, .61 %, .58 %, .55 %and .51 % for the plaque steps of Fig. 1.5.3 The absorber base plate shall be made of m
37、ild steel forthe 200 keV method and Lucite plastic for the 30 keV method.Both base plates shall be at least 200 by 250 mm (8 by 10 in.)wide and long. The steel plate shall be 19 6 0.12 mm (0.7506 0.005 in.) thick and the plastic plate shall be 36 6 0.12 mm(1.375 6 0.005 in.) thick. The surface finis
38、h of both absorberbase plates shall be a maximum of 6.3 m (250 in.) Ra,ground finish (both faces).5.4 The RIQI shown in Fig. 1 shall be placed on theradiation source side and within the approximate center of theappropriate absorber base plate as illustrated in Fig. 2(B).6. Calibration of X-Ray Sourc
39、e6.1 Use a target to detector distance at least 750 mm (29.5in.) for all exposures.6.2 The voltage calibration of the X-ray source for 200keVis based on ISO 7004. With an 8-mm (0.32-in.) copper filter atthe X-ray tube, adjust the kilovoltage until the half value layer(HVL) in copper is 3.5 mm (0.14
40、in.) (see SpecificationB 152/B 152M). Using a calibrated ionization chamber orsimilar radiation measurement device, make a reading of thedetector with 8 mm (0.32 in.) of copper at the tube, and then,make a second reading with a total of 11.5 mm (0.45 in.) ofcopper at the tube as shown in Fig. 2(A).6
41、.3 The voltage calibration of the X-ray source for 30keVis based on ISO 7004 method for 100keV calibration, modi-fied for 30keV. With a 7.62-mm (0.30-in.) aluminum filter atthe X-ray tube port, adjust the kilovoltage until the half valuelayer (HVL) in aluminum is 1.52 mm (0.06 in.). That is, theinte
42、nsity of the X-ray beam with 9.14mm (0.36in.) alumi-num at the tube port shall be one-half that with 7.62mm(0.30in.) aluminum at the tube port.6.4 For both 200keV and 30keV X-ray beam calibrationmethods, calculate the ratio of the two readings. If this ratio isnot 2, adjust the kilovoltage up or dow
43、n and repeat themeasurement until a ratio of 2 (within 5 %) is obtained. Recordthe X-ray machine voltage settings and use these same valuesfor the RIQR evaluations. Prior to RIQR performance evalua-tions for both 200keV and 30keV methods, remove all HVLand filter materials at the X-ray tube port.7.
44、Procedure7.1 BasicUse the physical set up as shown in Fig. 2(B).Position the X-ray tube directly over the approximate center ofthe RIQI and detector cassette. The plane of the detector andRIQI must be normal to the central ray of the X-ray beam. Usea diaphragm at the tube to limit the field of radia
45、tion to the filmarea.7.2 Source-to-detector distance (SDD) is based uponachieving a geometrical unsharpness (Ug) of 0.05 mm (0.002in.) or less on a 36 mm (1.375 in.) thick plastic plate for30keV and a 19 mm (0.750 in.) thick absorber plate for200keV. Calculate the minimum SDD, in millimetres, asfoll
46、ows:SDD 5 381 fE746073Copyright by ASTM Intl (all rights reserved); Mon Mar 10 23:10:39 EST 2008Downloaded/printed byGuo Dehua (CNIS) pursuant to License Agreement. No further reproductions authorized.where:SDD = source-to-detector distance, mm, andf = focal spot size, mm.The SDD shall be not less t
47、han 1 m (39.4 in.).7.3 Detector Cassettes and ScreensLow absorption cas-settes shall be used to maximize the effectiveness of the RIQIand only a single detector shall be used within the cassette. Forthe 200keV method, place the detector between lead-foilscreens, the front screen being 0.130 6 0.013
48、mm (0.005 60.0005 in.) thick and the back screen 0.250 6 0.025 mm (0.0106 0.001 in.) thick. The cassette shall provide a means for gooddetector-screen contact. No lead screens shall be used with the30 keV method. The same type cassette and screens (absorp-tion characteristics and thicknesses) shall
49、be used to produceall exposures required for the relative image quality responseevaluations. When using this practice with computed radiog-raphy systems, it is recommended that a minimum of 0.020 in.(.5 mm) steel plate be positioned between the backing lead andcassette.7.4 Backing LeadUse a 6.3 6 0.8 mm (14 6132 in.) thicklead “backup” behind the cassette. The backup lead shallexceed each edge of the cassette by at least 25 mm (1 in.).7.5 Identify the detector number, type, exposure, and othertechnique data by means of lead letters, or numerals, place
