1、Designation: E 2002 98 (Reapproved 2009)Standard Practice forDetermining Total Image Unsharpness in Radiology1This standard is issued under the fixed designation E 2002; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast 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 unsharpness of radiographsand
3、 radioscopic systems.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 values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 The gauge described c
4、an be used effectively withradiation energies up to 400 kv. When using energies in themegavolt range the results may not be completely satisfactory.1.5 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 st
5、andard 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:2E 747 Practice for Design, Manufacture and MaterialGrouping Classification of Wire Image Quality Indicators(IQI) Used for Ra
6、diologyE 1025 Practice for Design, Manufacture, and MaterialGrouping Classification of Hole-Type Image Quality Indi-cators (IQI) Used for RadiologyE 1316 Terminology for Nondestructive ExaminationsE 1647 Practice for Determining Contrast Sensitivity inRadiology2.2 EN Standard:EN-462-5:1994 Nondestru
7、ctive TestingImage Quality ofRadiographsPart 5: Image Quality Indicators (DuplexWire Type)Determination of Total Image UnsharpnessValue33. Terminology3.1 DefinitionsDefinitions of terms applicable to thispractice may be found in Terminology E 1316.4. Summary of Practice4.1 When it is determined nece
8、ssary to evaluate and mea-sure the Total Image Unsharpness (Spatial Resolution) of animaging system separately and apart from contrast sensitivitymeasurements, a tool or gauge as described in this practice canbe used. Conventional IQIs described in Practices E 747 andE 1025 combine the contrast sens
9、itivity and resolution mea-surements into an overall figure of merit. Such figures of meritmay not be adequate to detect subtle changes in the imagingsystems performance. For example, in a high-contrast image,spatial resolution can degrade with almost no noticeable effectupon the overall image quali
10、ty. Similarly, in an application inwhich the imaging system provides a very sharp image,contrast can fade with little noticeable effect upon the overallimage quality, as determined using conventional IQIs. Thesesituations often develop and may go undetected until thesystem performance deteriorates b
11、elow acceptable image qual-ity limits.5. Significance and Use5.1 The gauge is intended to provide a means for measuringtotal image unsharpness as independently as practicable fromthe imaging system contrast sensitivity limitations. Furtherdescription and details of the gauge are provided in EN-462-5
12、:1994.5.2 The gauge can be used in conjunction with a contrastsensitivity measuring gauge, as described in Practice E 1647.6. Gauge Construction6.1 The gauge shall be fabricated in accordance with Fig. 1,using the tolerances given in Table 1. This gauge is identical to1This practice is under the jur
13、isdiction 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 June 1, 2009. Published July 2009. Originally approvedin 1998. Last previous edition approved in 2003 as E 2002 - 98 (2003).2Fo
14、r 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 Document Summary page onthe ASTM website.3Available from British Standards Institute (BSI), 389 Chiswick
15、High Rd.,London W4 4AL, U.K., http:/www.bsi-.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.the gauge described in EN-462-5:1994 and if necessary,EN-462-5:1994 should be reviewed for additional detailedinformation.6.2 The gauge shal
16、l consist of 13 elements. Each elementshall 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.6.3 The gauge shall be identified by marking “EN-46
17、2-5:1994”. Marking shall be performed by any suitable means.6.4 The gauge manufacturer shall provide a certificate ofconformance with each gauge.7. Application7.1 A radiograph shall be made or an image displayed on amonitor with the gauge placed on the source side of the itembeing examined, or the g
18、auge may be placed on a blockrepresenting the material and total thickness of the item beingexamined. The gauge should be aligned, as closely as possible,normal to the axis of the radiation beam.7.2 The image of the gauge shall be examined usingmagnification up to 43. The largest element, (that is,
19、pair ofwires), of which the image has just merged into single formwithout an identifiable space between the images of the twowires, is taken as the limit of discernibility. The total imageunsharpness Utotalis given as 2d where d is the diameter of thewire and also is the spacing between the pair of
20、wires (see Fig.1 and Table 1).7.3 Performance levels of unsharpness of images are rela-tive to the users applications and shall be specified in thepurchaser/supplier agreement.NOTE 1Not to Scale.FIG. 1 Total Image Unsharpness gauge (see EN-462-5:1994)TABLE 1 Element Number, Corresponding Unsharpness
21、 andWire DiameterAElementNumberCorrespondingUnsharpness(mm)Wire Diameterand Spacing,d (mm)Tolerance of WireDiameter and WireSparing (mm)PtB13 0.10 0.0560.005Pt 12 0.13 0.063Pt 11 0.16 0.08Pt 10 0.20 0.10Pt 9 0.26 0.13Pt 8 0.32 0.1660.01Pt 7 0.40 0.20Pt 6 0.50 0.25Pt 5 0.64 0.32Pt 4 0.80 0.40WC3 1.00
22、 0.5060.02W 2 1.26 0.63W 1 1.60 0.80AThis table is based on data provided in EN-462-5:1994.BPt = Platinum.CW = Tungsten.E 2002 98 (2009)28. Records8.1 The results of the image unsharpness measurementshould be recorded along with the imaging parameters andmaintained as a part of the initial qualifica
23、tion and performancemonitoring records for the imaging system. Changes in imageunsharpness can be an early indicator of deteriorating imagingsystem performance.9. Precision and Bias9.1 No statement is made about the precision and bias forindicating the total image unsharpness of a imaging systemusin
24、g the gauge as described in this practice.10. Keywords10.1 contrast sensitivity gauge; gamma ray; imaging sys-tem; radiation; radiation energy; spatial resolution; total imageunsharpness; x-rayASTM International takes no position respecting the validity of any patent rights asserted in connection wi
25、th any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible tech
26、nical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful considerat
27、ion at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Ha
28、rbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).E 2002 98 (2009)3
