1、Designation:E167212Standard Guide forComputed Tomography(CT)System Selection1This standard is issued under the fixed designation E1672;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
2、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.Scope*1.1 This guide covers guidelines for translating applicationrequirements into c
3、omputed tomography(CT)systemrequirements/specifications and establishes a common termi-nology to guide both purchaser and supplier in the CT systemselection process.This guide is applicable to the purchaser ofboth CT systems and scan services.Computed tomographysystems are complex instruments,consis
4、ting of many compo-nents that must correctly interact in order to yield images thatrepeatedly reproduce satisfactory examination results.Com-puted tomography system purchasers are generally concernedwith application requirements.Computed tomography systemsuppliers are generally concerned with the sy
5、stem componentselection to meet the purchasers performance requirements.This guide is not intended to be limiting or restrictive,butrather to address the relationships between application require-ments and performance specifications that must be understoodand considered for proper CT system selectio
6、n.1.2 Computed tomography(CT)may be used for newapplications or in place of radiography or radioscopy,providedthat the capability to disclose physical features or indicationsthat form the acceptance/rejection criteria is fully documentedand available for review.In general,CT has lower spatialresolut
7、ion than film radiography and is of comparable spatialresolution with digital radiography or radioscopy unless mag-nification is used.Magnification can be used in CT orradiography/radioscopy to increase spatial resolution but con-currently with loss of field of view.1.3 Computed tomography(CT)system
8、s use a set of trans-mission measurements made along a set of paths projectedthrough the object from many different directions.Each of thetransmission measurements within these views is digitized andstored in a computer,where they are subsequently conditioned(for example,normalized and corrected)and
9、 reconstructed,typically into slices of the object normal to the set of projectionpaths by one of a variety of techniques.If many slices arereconstructed,a three dimensional representation of the objectis obtained.An in-depth treatment of CT principles is given inGuide E1441.1.4 Computed tomography(
10、CT),as with conventional radi-ography and radioscopic examinations,is broadly applicable toany material or object through which a beam of penetratingradiation may be passed and detected,including metals,plastics,ceramics,metallic/nonmetallic composite materialand assemblies.The principal advantage o
11、f CT is that it has thepotential to provide densitometric(that is,radiological densityand geometry)images of thin cross sections through an object.In many newer systems the cross-sections are now combinedinto 3D data volumes for additional interpretation.Because ofthe absence of structural superposi
12、tion,images may be mucheasier to interpret than conventional radiological images.Thenew purchaser can quickly learn to read CT data becauseimages correspond more closely to the way the human mindvisualizes 3D structures than conventional projection radiol-ogy.Further,because CT images are digital,th
13、e images may beenhanced,analyzed,compressed,archived,input as data intoperformance calculations,compared with digital data fromother nondestructive evaluation modalities,or transmitted toother locations for remote viewing.3D data sets can berendered by computer graphics into solid models.The solidmo
14、dels can be sliced or segmented to reveal 3D internalinformation or output as CAD files.While many of the detailsare generic in nature,this guide implicitly assumes the use ofpenetrating radiation,specifically X rays and gamma rays.1.5 UnitsThe values stated in SI units are to be regardedas standard
15、.The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.1.6 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is the1This guide is under the jurisdicti
16、on of ASTM Committee E07 on Nondestruc-tive Testing and is the direct responsibility of Subcommittee E07.01 on Radiology(X and Gamma)Method.Current edition approved June 15,2012.Published September 2012.Originallyapproved in 1995.Last previous edition approved in 2006 as E1672-06.DOI:10.1520/E1672-12.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 responsibility of the u
