1、Designation: E2445/E2445M 14Standard Practice forPerformance Evaluation and Long-Term Stability ofComputed Radiography Systems1This standard is issued under the fixed designation E2445/E2445M; the number immediately following the designation indicates the yearof original adoption or, in the case of
2、revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes the evaluation of ComputedRadiology (CR) systems for industrial radiolog
3、y. It is intendedto ensure that the evaluation of image quality, as far as this isinfluenced by the CR system, meets the needs of users of thisstandard, and their customers, and enables process control andlong-term stability of the CR system.1.2 This practice specifies the fundamental parameters ofC
4、R systems to be measured to determine baseline performance,and to track the long term stability of the system. These testsare for applications up to 320kV. When greater than 320kV orwhen a gamma source is used, these tests may still be used tocharacterize a system, but may need to be modified as agr
5、eedbetween the user and cognizant engineering organization(CEO).1.3 The CR system performance tests specified in thispractice shall be completed upon acceptance of the systemfrom the manufacturer and at intervals specified in this practiceto monitor long term stability of the system. The intent of t
6、hesetests is to monitor the system performance degradation and toidentify when an action needs to be taken when the systemdegrades by a certain level.1.4 The use of gauges2provided in this standard is manda-tory for each test. In the event these tests or gauges are notsufficient, the user, in coordi
7、nation with the CEO shall developadditional or modified tests, test objects, gauges, or imagequality indicators to evaluate the CR system.Acceptance levelsfor theseALTERNATE tests shall be determined by agreementbetween the user and CEO.1.5 The values stated in either SI units or inch-pound unitsare
8、 to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.6 This standard does not purport to address all
9、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:3E746 Practice for Dete
10、rmining Relative Image Quality Re-sponse of Industrial Radiographic Imaging SystemsE1316 Terminology for Nondestructive ExaminationsE1647 Practice for Determining Contrast Sensitivity in Ra-diologyE2002 Practice for Determining Total Image Unsharpness inRadiologyE2007 Guide for Computed RadiographyE
11、2033 Practice for Computed Radiology (PhotostimulableLuminescence Method)E2446 Practice for Classification of Computed RadiologySystems3. Terminology3.1 DefinitionsThe definition of terms relating to gamma-and X-radiology, which appear in Terminology E1316, GuideE2007, and Practice E2033 shall apply
12、 to the terms used in thispractice.3.2 Definitions of Terms Specific to This Standard:3.2.1 aliasingartifacts that appear in an image when thespatial frequency of the input is higher than the output iscapable of reproducing.1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-stru
13、ctive Testing and is the direct responsibility of Subcommittee E07.01 onRadiology (X and Gamma) Method.Current edition approved Oct. 1, 2014. Published October 2014. Originallyapproved in 2005. Last previous edition approved in 2010 as E2445/E2445M-05(2010). DOI:10.1520/E2445_E2445M-14.2The sole sou
14、rce of supply of the apparatus shown in Appendix X2 known to thecommittee at this time is Rockwell CollinsARINC, 1300 Thomas Drive, PanamaCity Beach, FL 32408, Phone: 405-605-7095, ARINC part number A0295224002(USAF design) or A0295224003 (NAVAIR design). The NAVAIR design includestwo additional tes
15、t targets that are not used in this test standard. If you are aware ofalternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend.13For referenced A
16、STM 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 Conshoh
17、ocken, PA 19428-2959. United States13.2.1.1 DiscussionThis will often appear as jagged orstepped sections in a line or as moir patterns (see Fig. 1).3.2.2 bandinglinear striping aligned parallel to the IPtransport direction, which may be caused by improper scannernormalization (see Fig. 2).3.2.3 com
18、puted radiology system (CR system)a completesystem of a storage phosphor imaging plate (IP) type, corre-sponding read out unit (scanner or reader) including pertinentequipment settings (for example, sampling resolution, laserpower, photomultiplier tube (PMT) gain, etc.), image acquisi-tion and proce
19、ssing software, and image display monitor.3.2.4 CR phantoma device containing an arrangement oftest targets used to evaluate the image quality of a CR system,as well as monitoring the image quality of the chosen system.3.2.5 customerthe company, government agency, or otherauthority responsible for t
20、he design, or end user, of the systemor component for which radiographic examination is required,also known as the Cognizant Engineering Organization (CEO).3.2.6 fadingthe reduction of intensity of the stored imagein the imaging plate over time.3.2.7 gainoverall signal amplification of the scannings
21、ystem.3.2.8 laser beam jittera lack of smooth movement of thelaser scanning device, which results in jagged scan lines on theimage (see Fig. 3).3.2.9 linear pixel valuea numerical value of a pictureelement (pixel) of the digital image, which is proportional tothe radiation dose.3.2.9.1 DiscussionExa
22、mple: for conversion of 12 bit logto 16 bit linear:PV16 bit linear5 65535 310SPV12 bit log10242 4D(1)The linear pixel value is zero if the radiation dose iszero.3.2.10 long-term stabilityperformance measurements of aCR system over the life-cycle of the devices, used to evaluaterelative system perfor
23、mance over time.3.2.11 manufacturerCR system manufacturer, supplier forthe user of the CR system.3.2.12 PMTphotomultiplier tube or other light capturedevice used by the specific scanner.3.2.13 PMT non-linearitydeviation from a linear responseof the PMT at high light input values or from step changes
24、 inlight.3.2.13.1 DiscussionAt high light input values the PMTmay under-respond, also the PMT may over-shoot or under-shoot in response to a step change in light (see Fig. 4).3.2.14 scan column dropouta zero PV linear image arti-fact created parallel to the transport direction when the path ofthe sc
25、anners laser beam is prevented from reaching theimaging plate, often due to an internal obstruction(contaminates, for example) (see Fig. 5).3.2.15 scan line integrity (or line ripple)fluctuation of lineintensity appearing perpendicular to the IP transport direction.3.2.16 scanner normalizationas use
26、d in this document,scanner normalization refers to a process performed to ensurea flat field image is produced when an imaging plate is exposedwithout an absorber.3.2.16.1 DiscussionScanner normalization procedures aredependent on the scanner model, and may or may not be ableto be performed by the u
27、ser.3.2.17 scanner slippagethe slipping of an IP in a scannertransport system resulting in fluctuations of PV or distortion ofgeometric linearity or both, appearing perpendicular to the IPtransport direction (see Fig. 6).3.2.18 shadingnon-uniform pixel values perpendicular tothe IP transport directi
28、on, which may also be caused byimproper alignment of the light guide or photomultiplier tubeassembly or improper scanner normalization.3.2.19 wait timetime between end of exposure and begin-ning the scan of the imaging plate.3.2.20 userthe user and operating organization of the CRsystem.NOTE 1Aliasi
29、ng is more pronounced as lines pair spacing decreases.FIG. 1 Example of Aliasing on a Line Pair Gauge ImageE2445/E2445M 142FIG. 2 Example of Banding (Parallel to IP Transport Direction) in a Computed Radiograph of a Prototype Test PhantomFIG. 3 Example of Laser Beam Jitter as Observed in a Computed
30、Radiograph of a Converging Line Pair GaugeE2445/E2445M 1434. Significance and Use4.1 This practice is intended to be used by the NDT usingorganization to measure baseline performance of the CRsystem and to monitor its performance throughout its service asan NDT imaging system. For purposes of this d
31、ocument, theCR System is defined as:4.1.1 Storage phosphor imaging plate (IP) type andmanufacturer,4.1.2 Read out unit (scanner or reader) manufacturer andmodel, including applicable scanner settings (e.g., samplingresolution, PMT gain, pixel value (PV) look up table, etc.),4.1.3 Image acquisition a
32、nd processing software, and4.1.4 Image display monitor.4.2 It is to be understood that the CR system has alreadybeen selected and purchased by the user from a manufacturerbased on the inspection needs at hand. The user shall accept theCR scanner based on manufacturers results of Practice E2446on the
33、 specific CR scanner as provided in a data sheet for thatserialized CR scanner or other acceptance test agreed tobetween the user and manufacturer (not covered in thispractice). This practice is not intended to be used as an“acceptance test” of the CR system, but rather to establish aperformance bas
34、eline that will enable tracking while in-service.FIG. 4 Example of PMT Non-Linearity as Observed in a Computed Radiograph of a USAF Process Control StandardFIG. 5 White Arrows Highlight a Simulated Example of Scan Column DropoutE2445/E2445M 1444.3 Although many of the properties listed in this stand
35、ardhave similar metrics to those found in E2446, data collectionmethods are not identical, and comparisons among valuesacquired with each standard should not be made.4.4 This practice defines the tests to be performed andrequired intervals. Also defined are the methods of tabulatingresults that CR u
36、sers will complete following the baseline ofthe CR system. These tests will also be performed periodicallyat the stated required intervals to evaluate the CR system todetermine if the system remains within acceptable operationallimits as established in this practice.4.5 There are several factors tha
37、t affect the image quality ofa CR image. Factors which are dependent on the CR systemperformance include basic spatial resolution, relative contrast,and signal-to-noise ratio (SNR) which yield the contrastsensitivity (CS), and Equivalent Penetrameter Sensitivity(EPS). There are several additional fa
38、ctors that are dependenton how well the CR system is functioning (i.e., resulting fromnormal wear and tear, inadequate maintenance, impropersetup/calibration, etc.), such as slippage, laser jitter, geometricdistortion, etc. Other factors which are related to the specificapplications (e.g., geometric
39、 unsharpness, scatter, etc.) are notevaluated in these tests.5. General Testing Procedures5.1 The tests performed herein can be completed either bythe use of the Type I CR Phantom (Appendix X1) forapplications up to 320kV, Type II CR Phantom (Appendix X2)for applications up to 160kV, or individual t
40、est targets de-scribed in Section 7. When greater than 320kV or when agamma source is used, these tests may still be used tocharacterize a system, but may need to be modified as agreedby the user and CEO. The CR phantoms incorporate many ofthe basic image quality assessment test targets into a singl
41、e testdevice, but some tests cannot be performed with both phan-toms. See Table 1 to see which tests can be performed by eachphantom.5.2 To ensure consistent PVs for calculation of test results,the wait time between end of exposure and scanning of theimaging plate should be a consistent time of at l
42、east 5 minutes.5.3 Tests are divided into two categories: (1) Core ImageQuality Tests, and (2) Supplemental (optional) Tests.5.3.1 Core Image Quality Tests shall be performed on eachCR scanner. If more than one combination of CR systemcomponents and scanner settings are used in production, theuser s
43、hall select one combination to be used for the Core ImageQuality Tests.5.3.2 Supplemental (optional) Tests may be performed atthe discretion of the user and may provide useful informationfor some applications.5.4 The technique shall be established for each test anddocumented. The technique informati
44、on shall include, at aminimum where applicable:5.4.1 Drawing sketch or photograph of the setups, showingthe location and orientation of the phantom or test target withrespect to the x-ray source, and imaging plate (IP),5.4.2 Kilovoltage (kV),5.4.3 Tube current (mA or microA),5.4.4 Exposure time,5.4.
45、5 Wait time,5.4.6 X-ray tube manufacturer, model, and focal spot sizeused (includes variable focal spot size settings),5.4.7 Focal Spot to Detector Distance (FDD),FIG. 6 Example of Scanner Slippage (Parallel to Laser Scan Direction) in a Computed Radiograph of a Prototype ProcessControl StandardE244
46、5/E2445M 1455.4.8 Focal Spot to Object Distance (FOD),5.4.9 Geometric unsharpness (Ug),5.4.10 Detector screens and filters and usage,5.4.11 Imaging plate manufacturer and type/size,5.4.12 Cassette type,5.4.13 CR scanner settings (for example, gain setting, reso-lution setting, and other parameters i
47、f available), and5.4.14 X-ray beam filtration (at tube), collimator, diaphragmand part masking.6. Application of Baseline Performance Tests and TestMethods6.1 CR System Baseline Performance Tests:6.1.1 The user shall baseline the CR scanner along with thecomplete CR system (as defined in 4.1) by per
48、forming the CoreImage Quality Tests listed in Table 1. Supplemental Tests maybe used to baseline the system if desired. Additional testsbeyond those defined in this practice are to be defined by theusing organization in terms of specific tests to perform, how thedata are presented, and the frequency
49、 of the testing. Thisapproach does the following:6.1.1.1 Provides a quantitative baseline of performance.6.1.1.2 Provides results in a defined form that can be viewedby the CEO.6.1.1.3 Offers a means to perform process checking ofperformance on a continuing basis.6.1.2 Acceptance values, and tolerances thereof, obtainedfrom these tests shall be established by this practice.6.1.3 When the test produces a result below therequirements, the CR scanner is not to be placed in serviceunless it is repaired, replaced, or some other change isinstituted that w
