1、Designation: E 1647 09Standard 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 () 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 gauge 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. The SI units given in parentheses are for informa-tion only.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
5、 applica-bility of regulatory limitations prior to use. For specific 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:2B 139/B 139M Specification for Phosphor Bronze Rod,Bar, and ShapesB 150
6、/B 150M Specification for Aluminum Bronze Rod,Bar, and ShapesB 161 Specification for Nickel Seamless Pipe and TubeB 164 Specification for Nickel-Copper Alloy Rod, Bar, andWireB 166 Specification for Nickel-Chromium-Iron Alloys(UNS N06600, N06601, N06603, N06690, N06693,N06025, N06045, and N06696)* a
7、nd Nickel-Chromium-Cobalt-Molybdenum Alloy (UNS N06617) Rod, Bar, andWireE 747 Practice for Design, Manufacture and MaterialGrouping Classification of Wire Image Quality Indicators(IQI) Used for RadiologyE 1000 Guide for RadioscopyE 1025 Practice for Design, Manufacture, and MaterialGrouping Classif
8、ication of Hole-Type Image Quality Indi-cators (IQI) Used for RadiologyE 1255 Practice for RadioscopyE 1316 Terminology for Nondestructive ExaminationsE 1411 Practice for Qualification of Radioscopic SystemsE 2002 Practice for Determining Total Image Unsharpnessin RadiologyE 2445 Practice for Qualif
9、ication and Long-Term Stabilityof Computed Radiology Systems2.2 Federal Standards:321 CFR 1020.40 Safety Requirements for Cabinet X-raySystems29 CFR 1910.96 Ionizing Radiation2.3 NIST/ANSI Standards:NIST/ANSI Handbook 114 General Safety Standard forInstallations Using Non-Medical X-ray and SealedGam
10、ma Ray Sources, Energies to 10 MeV42.4 Other Standard:5EN 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 found in Terminology E 1316.4.
11、 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 asTest Method E 747 wire and PracticeE 1025 plaque IQIs, combine the cont
12、rast sensitivity andresolution measurements into an overall performance figure ofmerit, other methods such as included in Practice E 2002 do1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.01 onRadiology (X
13、 and Gamma) Method.Current edition approved July 1, 2009. Published August 2009. Originallyapproved in 1994. Last previous edition approved in 2003 as E 1647 03.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book o
14、f ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from U.S. Government Printing Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.4Available fromAmerican Society for N
15、ondestructiveTesting (ASNT), P.O. Box28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.5Available from British Standards Institute (BSI), 389 Chiswick High Rd.,London W4 4AL, U.K., http:/www.bsi-.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocke
16、n, PA 19428-2959, United States.not address contrast specifically. Such figures of merit are oftennot adequate to detect subtle changes in imaging systemperformance. For example, in a high contrast image, spatialresolution can degrade with almost no noticeable effect uponoverall image quality. Simil
17、arly, in an application in which theimaging system provides a very sharp image, contrast can fadewith little noticeable effect upon the overall image quality.These situations often develop and may go unnoticed until thesystem performance deteriorates below acceptable image qual-ity limits.5. Signifi
18、cance and Use5.1 The contrast sensitivity gauge measures contrast sensi-tivity independent of the imaging system spatial resolutionlimitations. The thickness recess dimensions of the contrastsensitivity gauge are large with respect to the spatial resolutionlimitations of most imaging systems. Four l
19、evels of contrastsensitivity are measured: 4 %, 3 %, 2 %, and 1 %.5.2 The contrast sensitivity gauge is intended for use inconjunction with a high-contrast resolution measuring gauge,such as the EN 462 5 Duplex Wire Image Quality Indicator.Such gauges measure spatial resolution essentially independe
20、ntof the imaging systems contrast sensitivity. Such measure-ments are appropriate for the qualification and performancemonitoring of radiographic and radioscopic imaging systemswith film, realtime devices, Computed Radiography (CR) andDigital Detector Arrays (DDA).5.3 Radioscopic/radiographic system
21、 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 gauge, the unsharpness is equal to twice the wire diameter.For the line pair gauge, the unsh
22、arpness is equal to thereciprocal of the line-pair/mm value. As an example, animaging system that exhibits 2 % contrast sensitivity andimages the 0.1 mm EN 462 5 paired wires (equivalent toimaging 5 line-pairs/millimeter resolution on a line-pair gauge)performs at a 2 %0.2 mm sensitivity level.Astan
23、dard methodof evaluating overall radioscopic system performance is givenin Practice E 1411 and in EN 130681 and for CR it can befound in Practice E 2445.6. Contrast Sensitivity Gauge Construction and MaterialSelection6.1 Contrast sensitivity gauges shall be fabricated in accor-dance with Fig. 1, usi
24、ng the dimensions given in Table 1, Table2, and Table 3.6.2 The gauge shall preferably be fabricated from theexamination 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 radi
25、ation absorption characteris-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 o
26、rder of increasing radiation 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 clari
27、fication of pertinent materials.6.3 The materials from which the contrast sensitivity gaugeis to be made is designated by group number. The gauge isapplicable to all materials in that group. Material groupings areas follows:6.3.1 Materials Group 03:6.3.1.1 The gauge shall be made of magnesium or a m
28、ag-nesium alloy, provided it is no more radio-opaque thanunalloyed magnesium, as determined by the method outlined in6.4.6.3.1.2 Use for all alloys where magnesium is the predomi-nant alloying constituent.6.3.2 Materials Group 02:FIG. 1 General Layout of the Contrast Sensitivity GaugeTABLE 1 Design
29、of the Contrast Sensitivity GaugeGaugeThicknessJ Recess K Recess L Recess M RecessT 1%ofT 2%ofT 3%ofT 4%ofTTABLE 2 Contrast Sensitivity Gauge DimensionsGaugeSizeB 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
30、. 6.000 in. 0.500 in. 1.250 in. 0.500 in.38.10 mm 152.40 mm 12.70 mm 31.75 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 Sensit
31、ivity Gauge ApplicationGauge Size Use on Thicknesses1 Up to 1.5 in. (38.1 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)E16470926.3.2.1 The gauge shall be made of aluminum or an alumi-num alloy, provided it is no more radio-opa
32、que 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 gauge shall be made of titanium or a titaniumalloy, provided it is no more radio-opaque than unalloyedtitani
33、um, 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 1:6.3.4.1 The gauge shall be made of carbon steel or Type 300series stainless steel.6.3.4.2 Use for all carbon steel, low-alloy steels, stainlessstee
34、ls, and magnesium-nickel-aluminum bronze (Superston6).6.3.5 Materials Group 2:6.3.5.1 The gauge 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
35、all nickel alumi-num bronzes.6.3.6 Materials Group 3:6.3.6.1 The gauge shall be made of nickel-chromium-ironalloy (UNS No. N06600) (Inconel7). 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 gauge shall be made of 7
36、0 to 30 nickel-copperalloy (Monel8) (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
37、leaded brasses.6.3.8 Materials Group 5:6.3.8.1 The gauge 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
38、 for some reasoncannot be obtained to fabricate a gauge, 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 thickness
39、es of both materials onone film 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 ma
40、terial, the sub-stitute material is acceptable.6.4.1 All contrast sensitivity gauges shall be suitablymarked by vibro-engraving or etching. The gauge thicknessand material type shall be clearly marked.7. Imaging System Performance Levels7.1 Imaging system performance levels are designated by atwo-pa
41、rt measurement expressed as C(%) 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 gauge expresse
42、d in terms of millimeters unsharpness.Where contrast sensitivity is measured for both thin and thicksection performance, the performance level is expressed asCmin(%)Cmax(%)U (mm) (see Practice E 1255).7.2 Each contrast sensitivity gauge has four flat-bottomrecesses that represent 1 %, 2 %, 3 %, and
43、4 % of the gaugetotal thickness. The shallowest recess that can be repeatablyand reliably imaged shall determine the limiting contrastsensitivity.7.3 Contrast sensitivity measurements shall be made underconditions as nearly identical to the actual examination aspossible. Penetrating radiation energy
44、, image formation, pro-cessing, analysis, display, and viewing variables shall accu-rately simulate the actual examination environment.8. Contrast Sensitivity Gauge Measurement Steps (seeTable 1)8.1 The gauge thickness T shall be within 65 % of theexamination object thickness value at which contrast
45、 sensitiv-ity is being determined.8.2 The gauge thickness tolerance shall be within 6 1%ofthe gauge design thickness T or 0.001 in. (0.025 mm),whichever is greater.8.3 The gauge recess depth tolerance shall be within 610 % of the design value for the shallowest recess or 0.001 in.(0.025 mm), whichev
46、er is greater.8.4 The gauge recess inside and outside corner radius shallnot exceed 0.062 in. (1.57 mm). To facilitate fabrication, thegauge may be assembled from three individually machinedcomponents: (1) the machined center section containing the1%T,2%T,3%T, and 4 % T milled slots; (2) the front r
47、ail,and (3) the rear rail. The assemblage of the three componentsforms the complete gauge similar to that shown in AppendixX1.8.5 The gauge dimensional tolerances shall be held towithin 6 0.010 in. (0.25 mm) of the dimensions specified inTable 2.9. Acceptable Performance Levels9.1 Nothing in this pr
48、actice implies a mandatory or anacceptable contrast sensitivity performance level. That deter-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
49、 will accommodate6Superstont is a registered trademark of Superston Corp., Jersey City, NJ.7Inconelt is a registered trademark of The International Nickel Co., Inc.,Huntington, WV 25720.8Monelt is a registered trademark of The International Nickel Co., Inc.,Huntington, WV 25720.E1647093many imaging system configurations. Other contrast sensitivitymeasurement points may be obtained by placing the gauge ona shim made of the gauge material. The resulting contrastsensitivity measurement expressed as a percentage is given bythe following formula:% Contrast
