1、Designation: E 2002 98 (Reapproved 2003)e1Standard 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
2、 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.e1NOTEEditorial corrections were made throughout in June 2003.1. Scope1.1 This practice covers the design and basic use of a gag
3、eused to determine the total image unsharpness of radiographsand 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.1.4 The gage describe
4、d can be used effectively with radia-tion 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 th
5、is 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:E 747 Practice for Design, Manufacture and MaterialGrouping Classification of Wire Image Quality Indicators(IQI) Used fo
6、r Radiology2E 1025 Practice for Design, Manufacture and MaterialGrouping Classification of Hole-Type Image Quality Indi-cators (IQI) used for Radiology2E 1316 Terminology for Nondestructive Examinations2E 1647 Practice for Determining Contrast Sensitivity inRadioscopy22.2 EN Standard:EN-462-5:1994 N
7、ondestructive 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 determi
8、ned necessary to evaluate and mea-sure the Total Image Unsharpness (Spatial Resolution) of animaging system separately and apart from contrast sensitivitymeasurements, a tool or gage as described in this practice canbe used. Conventional IQIs described in Practices E 747 andE 1025 combine the contra
9、st sensitivity 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 imag
10、e quality. 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 deterio
11、rates below acceptable image qual-ity limits.5. Significance and Use5.1 The gage 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 gage are provided in EN-
12、462-5.5.2 The gage can be used in conjunction with a contrastsensitivity measuring gage, as described in Practice E 1647.6. Gage Construction6.1 The gage shall be fabricated in accordance with Fig. 1,using the tolerances given in Table 1. This gage is identical to1This practice is under the jurisdic
13、tion 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 10, 2003. Published August 2003. Originallyapproved in 1998. Last previous edition approved in 1998 as E 2002 - 98.2Annual Book
14、 of ASTM Standards, Vol 03.03.3Available from British Standards Institution, British Standards House, 389Chiswick High Road, London, W4 4AL United Kingdom.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.the gage described in EN-462-5
15、 and if necessary, EN-462-5should be reviewed for additional detailed information.6.2 The gage shall 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 1
16、3 elements aremounted in a rigid plastic holder.6.3 The gage shall be identified by marking “EN-462-5.”Marking shall be performed by any suitable means.6.4 The gage manufacturer shall provide a certificate ofconformance with each gage.7. Application7.1 A radiograph shall be made or an image displaye
17、d on amonitor with the gage placed on the source side of the itembeing examined, or the gage may be placed on a blockrepresenting the material and total thickness of the item beingexamined. The gage should be aligned, as closely as possible,normal to the axis of the radiation beam.7.2 The image of t
18、he gage shall be examined using magni-fication up to 43. The largest element, (that is, pair of wires),of which the image has just merged into single form without anidentifiable space between the images of the two wires, is takenas the limit of discernibility. The total image unsharpness Utotalis gi
19、ven as 2d where d is the diameter of the wire and also isthe spacing between the pair of wires (see Fig. 1 and Table 1).NOTE 1Not to Scale.FIG. 1 Total Image Unsharpness Gage (see EN-462-5)TABLE 1 Element Number, Corresponding Unsharpness andWire DiameterAElementNumberCorrespondingUnsharpness(mm)Wir
20、e 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 0.5060.02W 2 1.26 0.63W 1 1.60 0.80AThis table is based on da
21、ta provided in EN 462-5.BPt = Platinum.CW = Tungsten.E 2002 98 (2003)e127.3 Performance levels of unsharpness of images are rela-tive to the users applications and shall be specified in thepurchaser/supplier agreement.8. Records8.1 The results of the image unsharpness measurementshould be recorded a
22、long with the imaging parameters andmaintained as a part of the initial qualification 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 pre
23、cision and bias forindicating the total image unsharpness of a imaging systemusing the gage as described in this practice.10. Keywords10.1 contrast sensitivity gage; gamma ray; imaging system;radiation; radiation energy; spatial resolution; total imageunsharpness; x-rayASTM International takes no po
24、sition respecting the validity of any patent rights asserted in connection with 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 responsibi
25、lity.This standard is subject to revision at any time by the responsible technical 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 A
26、STM International Headquarters. Your comments will receive careful consideration 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 addres
27、s shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor 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 (2003)e13
