ASTM_E_1695_-_95_2013.pdf

Designation:E169595(Reapproved 2013)Standard Test Method forMeasurement of Computed Tomography(CT)SystemPerformance1This standard is issued under the fixed designation E1695;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method provides instruction for determiningthe spatial resolution and contrast sensitivity in X-ray and-raycomputed tomography(CT)images.The determination isbased on examination of the CT image of a uniform disk ofmaterial.The spatial resolution measurement is derived froman image analysis of the sharpness at the edge of the disk.Thecontrast sensitivity measurement is derived from an imageanalysis of the statistical noise at the center of the disk.1.2 This test method is more quantitative and less suscep-tible to interpretation than alternative approaches because therequired disk is easy to fabricate and the analysis is immune tocupping artifacts.This test method may not yield meaningfulresults if the disk image occupies less than a significant fractionof the field of view.1.3 This test method may also be used to evaluate otherperformance parameters.Among those characteristics of a CTsystem that are detectable with this test method are:themid-frequency enhancement of the reconstruction kernel,thepresence(or absence)of detector crosstalk,the undersamplingof views,and the clipping of unphysical(that is,negative)CTnumbers(seeAir Force Technical Report WL-TR-94-40212).Itis highly likely that other characteristics as well can be detectedwith this test method.1.4 The values stated in SI units are to be regarded as thestandard.Inch-pound units are provided for information only.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 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:3E1316 Terminology for Nondestructive ExaminationsE1441 Guide for Computed Tomography(CT)ImagingE1570 Practice for Computed Tomographic(CT)Examina-tion3.Terminology3.1 DefinitionsThe definitions of terms relating toGamma-and X-Radiology,which appear in TerminologyE1316 and Guide E1441,shall apply to the terms used in thistest method.3.2 Definitions of Terms Specific to This Standard:3.2.1 phantoma part or item being used to quantify CTsystem performance.3.2.2 examination objecta part or specimen being sub-jected to CT examination.3.3 Acronyms:3.3.1 ERFedge response function.3.3.2 PSFpoint spread function.3.3.3 MTFmodulation transfer function.3.3.4 CDFcontrast discrimination function.4.Significance and Use4.1 Two factors affecting the quality of a CT image aregeometrical unsharpness and random noise.Geometrical un-sharpness limits the spatial resolution of a CT system,that is,its ability to image fine structural detail in an object.Randomnoise limits the contrast sensitivity of a CT system,that is,itsability to detect the presence or absence of features in anobject.Spatial resolution and contrast sensitivity may bemeasured in various ways.ASTM specifies spatial resolution1This test method is under the jurisdiction of ASTM Committee E07 onNondestructive Testing and is the direct responsibility of Subcommittee E07.01 onRadiology(X and Gamma)Method.Current edition approved June 1,2013.Published June 2013.Originallyapproved in 1995.Last previous edition approved in 2006 as E1695-95(2006)1.DOI:10.1520/E1695-95R13.2X-Ray Computed Tomography Standards(WL-TR-94-4021).Bossi,R.H.andNelson,J.M.Air Force Contract No.F33615-88-C-5404.Source documentavailable from Air Force Research Laboratory,AFRL/MLLP Building 655,2230Tenth Street,Suite 1,Wright-Patterson AFB,OH 454337814.3For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 be quantified in terms of the modulation transfer function(MTF)and contrast sensitivity be quantified in terms of thecontrast discrimination function(CDF)(see Guide E1441 andPractice E1570).This test method allows the purchaser or theprovider of CT systems or services,or both,to measure andspecify spatial resolution and contrast sensitivity.5.Apparatus5.1 Disk PhantomThe disk phantom shall be a rightcylinder of uniform material conforming to the design andmaterial requirements in Table 1 and Fig.1.Since spatialresolution and contrast sensitivity depend on the examination