1、Designation: E 1647 03Standard Practice forDetermining Contrast Sensitivity in Radiology1This standard is issued under the fixed designation E 1647; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A numbe
2、r 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 practice covers the design and material selection ofa contrast sensitivity measuring gage used to determine theminimum change in mater
3、ial thickness or density that may beimaged without regard to spatial resolution limitations.1.2 This practice is applicable to transmitted-beam radio-graphic and radioscopic imaging systems utilizing X-ray andgamma ray radiation sources.1.3 The values stated in inch-pound units are to be regardedas
4、standard.1.4 This standard 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. For s
5、pecific safetystatements, see NIST/ANSI Handbook 114 Section 8, Code ofFederal Regulations 21 CFR 1020.40 and 29 CFR 1910.96.2. Referenced Documents2.1 ASTM Standards:B 139 Specification for Phosphor Bronze Rod, Bar, andShapes2B 150 Specification for Aluminum Bronze Rod, Bar, andShapes2B 161 Specifi
6、cation for Nickel Seamless Pipe and Tube3B 164 Specification for Nickel-Copper Alloy Rod, Bar, andWire3B 166 Specification for Nickel-Chromium-Iron Alloys(UNS N06600, N06601, and N06690) and Nickel-Chromium-Cobalt-Molybdenum Alloy (UNS N06617)Rod, Bar, and Wire3E 94 Guide for Radiographic Examinatio
7、n4E 747 Practice for the Design Manufacture and MaterialGrouping Classification of Wire Image Quality Indicators(IQI) Used For Radiology4E 1025 Practice for Hole-Type Image Quality IndicatorsUsed for Radiography4E 1316 Terminology for Nondestructive Examination4E 1411 Practice for Qualification of R
8、adioscopic Systems4E 2002 Practice for Determining Total Image Unsharpnessin Radiology42.2 Federal Standards:21 CFR 1020.40 Safety Requirements for Cabinet X-raySystems529 CFR 1910.96 Ionizing Radiation52.3 NIST/ANSI Standards:NIST/ANSI Handbook 114 General Safety Standard forInstallations Using Non
9、-Medical X-ray and SealedGamma Ray Sources, Energies to 10 MeV62.4 Other Standard:7EN 462 5 Duplex Wire Image Quality IndicatorEN 130681 Radioscopic Testing-Part 1: Qualitative Mea-surement of Imaging Properties3. Terminology3.1 DefinitionsDefinitions of terms applicable to this testmethod may be fo
10、und in Terminology E 1316.4. Summary of Practice4.1 It is often useful to evaluate the contrast sensitivity of apenetrating radiation imaging system separate and apart fromspatial resolution measurements. Conventional image qualityindicators (IQIs), such as Test Method E 747 wire and PracticeE 1025
11、plaque IQIs, combine the contrast sensitivity andresolution measurements into an overall performance figure ofmerit, other methods such as included in Practice E 2002 donot address contrast specifically. Such figures of merit are oftennot adequate to detect subtle changes in imaging systemperformanc
12、e. For example, in a high contrast image, spatialresolution can degrade with almost no noticeable effect uponoverall image quality. Similarly, in an application in which theimaging system provides a very sharp image, contrast can fade1This practice is under the jurisdiction of ASTM Committee E07 on
13、Nonde-structive Testing and is the direct responsibility of Subcommittee E07.01 onRadiology (X and Gamma) Method.Current edition approved August 10, 2003. Published October 2003. Originallyapproved in 1994. Last previous edition approved in 1998 as E 1647 98a.2Annual Book of ASTM Standards, Vol 02.0
14、1.3Annual Book of ASTM Standards, Vol 02.04.4Annual Book of ASTM Standards, Vol 03.03.5Available from the Superintendent of Documents, U.S. Government PrintingOffice, Washington, DC 20402.6Available from American Society for Nondestructive Testing, 1711 ArlingatePlaza, P.O. Box 28518, Columbus, OH 4
15、3228-0518.7Available from British Standards Institute, 2 Park Street, London, EnglandW1A2B5.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.with little noticeable effect upon the overall image quality.These situations often develop a
16、nd may go unnoticed until thesystem performance deteriorates below acceptable image qual-ity limits.5. Significance and Use5.1 The contrast sensitivity gage measures contrast sensitiv-ity independent of the imaging system spatial resolutionlimitations. The thickness recess dimensions of the contrast
17、sensitivity gage are large with respect to the spatial resolutionlimitations of most imaging systems. Four levels of contrastsensitivity are measured: 4 %, 3 %, 2 %, and 1 %.5.2 The contrast sensitivity gage is intended for use inconjunction with a high-contrast resolution measuring gage,such as the
18、 EN 462 5 Duplex Wire Image Quality Indicator.Such gages measure spatial resolution essentially independentof the imaging systems contrast sensitivity. Such measure-ments are appropriate for the qualification and performancemonitoring of radiographic and radioscopic imaging systems.5.3 Radioscopic/r
19、adiographic system performance may bespecified by combining the measured contrast sensitivity ex-pressed as a percentage with the spatial resolution expressed inmillimeters of unsharpness. For the EN 462 5 spatial resolu-tion gage, the unsharpness is equal to twice the wire diameter.For the line pai
20、r gage, the unsharpness is equal to the reciprocalof the line-pair/mm value. As an example, an imaging systemthat exhibits 2 % contrast sensitivity and images the 0.1 mmEN 462 5 paired wires (equivalent to imaging 5 line-pairs/millimeter resolution on a line-pair gage) performs at a2 %0.2 mm sensiti
21、vity level. A standard method of evaluatingoverall radioscopic system performance is given in PracticeE 1411 and in EN 130681.6. Contrast Sensitivity Gage Construction and MaterialSelection6.1 Contrast sensitivity gages shall be fabricated in accor-dance with Fig. 1, using the dimensions given in Ta
22、ble 1, Table2, and Table 3.6.2 The gage shall preferably be fabricated from the exami-nation object material. Otherwise, the following materialselection guidelines are to be used:6.2.1 Materials are designated in eight groupings, in accor-dance with their penetrating radiation absorption characteris
23、-tics: groups 03, 02, and 01 for light metals and groups 1through 5 for heavy metals.6.2.2 The light metal groups, magnesium (Mg), aluminum(Al), and titanium (Ti) are identified 03, 02, and 01, respec-tively, for their predominant constituent. The materials arelisted in order of increasing radiation
24、 absorption.6.2.3 The heavy metals group, steel, copper base, nickelbase, and other alloys are identified 1 through 5. The materialsincrease in radiation absorption with increasing numericaldesignation.6.2.4 Common trade names or alloy designations have beenused for clarification of pertinent materi
25、als.6.3 The materials from which the contrast sensitivity gage isto be made is designated by group number. The gage isapplicable to all materials in that group. Material groupings areas follows:6.3.1 Material Group 03:6.3.1.1 The gage shall be made of magnesium or a magne-sium alloy, provided it is
26、no more radio-opaque than unalloyedmagnesium, as determined by the method outlined in 6.4.6.3.1.2 Use for all alloys where magnesium is the predomi-nant alloying constituent.6.3.2 Materials Group 02:6.3.2.1 The gage shall be made of aluminum or an alumi-num alloy, provided it is no more radio-opaque
27、 than unalloyedaluminum, as determined by the method outlined in 6.4.6.3.2.2 Use for all alloys where aluminum is the predomi-nant alloying constituent.6.3.3 Materials Group 01:6.3.3.1 The gage shall be made of titanium or a titaniumalloy, provided it is no more radio-opaque than unalloyedtitanium,
28、as determined by the method outlined in 6.4.6.3.3.2 Use for all alloys where titanium is the predominantalloying constituent.6.3.4 Materials Group 1:FIG. 1 General Layout of the Contrast Sensitivity GageTABLE 1 Design of the Contrast Sensitivity GageGage Thickness J Recess K Recess L Recess M Recess
29、T 1 % of T 2 % of T 3 % of T 4 % of TTABLE 2 Contrast Sensitivity Gage DimensionsGageSizeB DIM. C DIM. D DIM. E DIM. F,G DIM.1 0.750 in. 3.000 in. 0.250 in. 0.625 in. 0.250 in.19.05 mm 76.20 mm 6.35 mm 15.88 mm 6.35 mm2 1.500 in. 6.000 in. 0.500 in. 1.250 in. 0.500 in.38.10 mm 152.40 mm 12.70 mm 31.
30、75 mm 12.7 mm3 2.250 in. 9.000 in. 0.750 in. 1.875 in. 0.750 in.57.15 mm 228.60 mm 19.05 mm 47.63 mm 19.05 mm4 3.000 in. 12.000 in. 1.000 in. 2.500 in. 1.000 in.76.20 mm 304.80 mm 25.40 mm 63.50 mm 25.4 mmTABLE 3 Contrast Sensitivity Gage ApplicationGage Size Use on Thicknesses1 Up to 1.5 in. (38.1
31、mm)2 Over 1.5 in. (38.1 mm) to 3.0 in. (76.2 mm)3 Over 3.0 in. (76.2 mm) to 6.0 in. (152.4 mm)4 Over 6.0 in. (152.4 mm)E16470326.3.4.1 The gage shall be made of carbon steel or Type 300series stainless steel.6.3.4.2 Use for all carbon steel, low-alloy steels, stainlesssteels, and magnesium-nickel-al
32、uminum bronze (Superston8).6.3.5 Materials Group 2:6.3.5.1 The gage shall be made of aluminum bronze (AlloyNo. 623 of Specification B 150) or equivalent or nickel-aluminum bronze (Alloy No. 630 of Specification B 150) orequivalent.6.3.5.2 Use for all aluminum bronzes and all nickel alumi-num bronzes
33、.6.3.6 Materials Group 3:6.3.6.1 The gage shall be made of nickel-chromium-ironalloy (UNS No. N06600) (Inconel9). See Specification B 166.6.3.6.2 Use for nickel-chromium-iron alloy and 18 %nickel-maraging steel.6.3.7 Materials Group 4:6.3.7.1 The gage shall be made of 70 to 30 nickel-copperalloy (Mo
34、nel10) (Class A or B of Specification B 164) orequivalent, or 70 to 30 copper-nickel alloy, (Alloy G ofSpecification B 161) or equivalent.6.3.7.2 Use for nickel, copper, all nickel-copper series orcopper-nickel series of alloys and all brasses (copper-zincalloys) and all leaded brasses.6.3.8 Materia
35、ls Group 5:6.3.8.1 The gage shall be made of tin-bronze (Alloy D ofSpecification B 139).6.3.8.2 Use for tin bronzes including gun-metal and valvebronze and leaded-tin bronzes.6.4 Where the material to be examined is a composite,ceramic, or other non-metallic material, or for some reasoncannot be obt
36、ained to fabricate a gage, an equivalent materialmay be utilized, provided it is no more radio-opaque than theexamination object under comparable penetrating radiationenergy conditions. To determine the suitability of a substitutematerial, radiograph identical thicknesses of both materials onone fil
37、m using the lowest penetrating radiation energy to beused in the actual examination. Transmission densitometerreadings for both materials shall be in the range from 2.0 to 4.0.If the radiographic density of the substitute material iswithin + 15 % to0%oftheexamination material, the sub-stitute materi
38、al is acceptable.6.4.1 All contrast sensitivity gages shall be suitably markedby vibro-engraving or etching. The gage thickness and materialtype shall be clearly marked.7. Imaging System Performance Levels7.1 Imaging system performance levels are designated by atwo-part measurement expressed as C(%)
39、 U(mm). The firstpart of the expression C(%) refers to the depth of theshallowest flat-bottom hole that can be reliably and repeatablyimaged. The second part of the expression refers to thecompanion spatial resolution measurement made with a reso-lution gage expressed in terms of millimeters unsharp
40、ness.Where contrast sensitivity is measured for both thin and thicksection performance, the performance level is expressed asCmin(%)Cmax(%)U(mm).7.2 Each contrast sensitivity gage has four flat-bottomrecesses that represent 1 %, 2 %, 3 %, and 4 % of the gage totalthickness. The shallowest recess tha
41、t can be repeatably andreliably imaged shall determine the limiting contrast sensitiv-ity.7.3 Contrast sensitivity measurements shall be made underconditions as nearly identical to the actual examination aspossible. Penetrating radiation energy, image formation, pro-cessing, analysis, display, and v
42、iewing variables shall accu-rately simulate the actual examination environment.8. Contrast Sensitivity Gage Measurement Steps (seeTable 1)8.1 The gage thickness T shall be within 65 % of theexamination object thickness value at which contrast sensitiv-ity is being determined.8.2 The gage thickness t
43、olerance shall be within 6 1%ofthe gage design thickness T or 0.001 in., whichever is greater.8.3 The gage recess depth tolerance shall be within 6 10 %of the design value for the shallowest recess or 0.001 in.,whichever is greater.8.4 The gage recess inside and outside corner radius shallnot exceed
44、 0.062 in. To facilitate fabrication, the gage may beassembled from three individually machined components: (1)the machined center section containing the 1 % T,2%T,3%T, and 4 % T milled slots; (2) the front rail, and (3) the rear rail.The assemblage of the three components forms the completegage sim
45、ilar to that shown in Appendix X1.8.5 The gage dimensional tolerances shall be held to within6 0.010 in. (0.25 mm) of the dimensions specified in Table 2.9. Acceptable Performance Levels9.1 Nothing in this practice implies a mandatory or anacceptable contrast sensitivity performance level. That dete
46、r-mination is to be agreed upon between the supplier and user ofpenetrating radiation examination services.9.2 The recess depths specified in Table 1 provide measure-ment points at 1 %, 2 %, 3 %, and 4 % that will accommodatemany imaging system configurations. Other contrast sensitivitymeasurement p
47、oints may be obtained by placing the gage on ashim made of the gage material. The resulting contrast sensi-tivity measurement expressed as a percentage is given by thefollowing formula:% Contrast 5RT 1 S3 100 (1)where:R = recess depth,S = shim thickness, andT = gage thickness.If other recess depths
48、are required to document radioscopicor radiographic system performance, special contrast sensitiv-ity gages may be fabricated by changing the recess depthsspecified in Table 1 to suit the need.8Superstont is a registered trademark of Superston Corp., Jersey City, NJ.9Inconelt is a registered tradema
49、rk of The International Nickel Co., Inc.,Huntington, WV 25720.10Monelt is a registered trademark of The International Nickel Co., Inc.,Huntington, WV 25720.E164703310. Performance Measurement Records10.1 The results of the contrast sensitivity measurementshould be recorded and maintained as a part of the initialqualification and performance monitoring records for theimaging system. Changes in contrast sensitivity can be an earlyindicator of deteriorating imaging system performance.11. Precision and Bias11.1 No statement is made about the precision or bias forindicati
