1、Designation: E2446 05 (Reapproved 2010)E2446 15Standard Practice forClassification Manufacturing Characterization of ComputedRadiologyRadiography Systems1This standard is issued under the fixed designation E2446; the number immediately following the designation indicates the year oforiginal adoption
2、 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.1. Scope1.1 This practice describes the evaluation and classification of a manufacturing
3、 characterization of computed radiography (CR)system, systems, consisting of a particular phosphor imaging plate (IP), system scanner and software, scanner, software, and animage display monitor, in combination with specified metal screens for industrial radiography. It is intended to ensure that th
4、eevaluation of image quality, as far as this is influenced by the scanner/IP system, meets the needs of users.1.2 The practice defines system tests to be used to classifycharacterize the systems of different suppliers and make themcomparable for users.1.3 This practice is intended for use by manufac
5、turers of CR systems or certification agencies to provide quantitative results ofCR system characteristics for nondestructive testing (NDT) user or purchaser consumption. Some of these tests require specializedtest phantoms to ensure consistency of results among suppliers or manufacturers.These test
6、s are not intended for users to complete,nor are they intended for long term stability tracking and lifetime measurements. However, they may be used for this purpose, ifso desired.1.4 The CR system performance is described by the basic spatial resolution, contrast, signal and noise parameters. For f
7、ilmsystems, the signal is represented by gradient and the noise by granularity. The signal-to-noise ratio is normalized by the basicspatial resolution of the system and is part of classification. The normalizationparameters, and the equivalent penetrametersensitivity (EPS). Some of these parameters
8、are used to compare with DDA characterization and film characterization data (seePractice E2597 is given by the scanning aperture of 100 m diameter for the micro-photometer, which is defined in and TestMethod E1815 for ).NOTE 1For film system characterization, the signal is represented by the optica
9、l density of 2 (above fog and base) and the noise as granularity. Thesignal-to-noise ratio is normalized by the aperture (similar to the basic spatial resolution) of the system and is part of characterization. This normalizationis given by the scanning circular aperture of 100 m of the micro-photome
10、ter, which is defined in Test Method E1815 for film system characterization.film system classification. This practice describes how the parameters shall be measured for CR systems.1.5 The measurement of CR systems in this practice is restricted to a selected radiation quality to simplify the procedu
11、re. Theproperties of CR systems will change with radiation energy but not the ranking of CR system performance. Users of this practicemay carry out the tests at different or additional radiation qualities (X-ray or gamma ray) if required.1.6 The values stated in SI are to be regarded as the standard
12、.1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatorylimitations prior to use.2. Referenced
13、 Documents2.1 ASTM Standards:2E746 Practice for Determining Relative Image Quality Response of Industrial Radiographic Imaging SystemsE1165 Test Method for Measurement of Focal Spots of Industrial X-Ray Tubes by Pinhole ImagingE1316 Terminology for Nondestructive Examinations1 This practice is under
14、 the jurisdiction ofASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.01 on Radiology (X andGamma) Method.Current edition approved June 1, 2010July 1, 2015. Published August 2010November 2015. Originally approved in 2005. Last previous edition approved
15、 in 20052010as E2446 05.E2446 05(2010). DOI: 10.1520/E2446-05R10.10.1520/E2446-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page
16、 on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that us
17、ers consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E1815 Test Method for Class
18、ification of Film Systems for Industrial RadiographyE2002 Practice for Determining Total Image Unsharpness and Basic Spatial Resolution in Radiography and RadioscopyE2007 Guide for Computed RadiographyE2033 Practice for Computed Radiology (Photostimulable Luminescence Method)E2445 Practice for Perfo
19、rmance Evaluation and Long-Term Stability of Computed Radiography SystemsE2597 Practice for Manufacturing Characterization of Digital Detector ArraysE2903 Test Method for Measurement of the Effective Focal Spot Size of Mini and Micro Focus X-ray Tubes2.2 ISO Standard:3ISO 17636-2 Non-Destructive Tes
20、ting of WeldsRadiographic TestingPart 2: X- and Gamma Ray Technologies with DigitalDetectors3. Terminology3.1 DefinitionsThe definition of terms relating to gamma- and X-radiology,X-radiography, which appear in TerminologyE1316, Guide E2007, and Practice E2033, shall apply to the terms used in this
21、practice.3.2 Definitions of Terms Specific to This Standard:3.2.1 computed radiologyradiography system (CR system)A complete system of a storage phosphor imaging plate (IP), acorresponding read out unit (scanner or reader) and software, reader), software and an image display monitor, which converts
22、theinformation of the IP into a digital image (see also Guide E2007).3.2.2 computed radiologyradiography system classperformance levelA particular group of storage phosphor imaging platesystems, CR performance levels, which is characterized by a SNRN (signal-to-noise ratio) range shownrange, an inte
23、rpolated basicspatial resolution range iSRbdetector inand Table 1 and by a certain unsharpness range equivalent penetrameter sensitivity (EPS)shown in Table 4 in a specified exposure range.3.2.3 gain/amplificationOpto-electrical gain setting of the scanning system.3.2.4 ISO speed SIPxDefines the spe
24、ed of a CR system and is calculated from the reciprocal dose value, measured in gray, Gray(Gy), which is necessary to obtain a specified minimum SNRN of a CR system.system performance level.3.2.4 signal-to-noise ratio (SNR)Quotient of mean value of the linearized signal intensity and standard deviat
25、ion of the noise(intensity distribution) at this signal intensity. The SNR depends on the radiation dose and the CR system properties.3.2.5 modulation transfer function (MTF)The normalized magnitude of the Fourier-transform (FT) of the differentiated edgespread function (ESF) of the linearized PSL (
26、photo stimulated luminescence) intensity, measured perpendicular to a sharp edge.3 Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http:/www.iso.org.TABLE 1 CR System Classificationcolwidth=“1.74in“CR SystemClassif
27、icationMinimumSignal-Noise RatioASTM IP Special/Y 130ASTM IP I/Y 65ASTM IP II/Y 52ASTM IP III/Y 43TABLE 1 EPS Values on Standard 19-mm (-in.) Absorber Plateas a Function of Step and Hole SizePlaque Number Step Sizemm (in.) Hole Sizemm (in.) EPS%15 0.38 (0.015)0.71 (0.028) 1.920.64 (0.025) 1.820.58 (
28、0.023) 1.7110 0.25 (0.010)0.79 (0.031) 1.660.71 (0.028) 1.570.64 (0.025) 1.498 0.20 (0.008)0.71 (0.028) 1.410.64 (0.025) 1.330.58 (0.023) 1.255 0.13 (0.005)0.81 (0.032) 1.190.71 (0.028) 1.120.64 (0.025) 1.050.58 (0.023) 1.000.50 (0.020) 0.94E2446 152MTF describes the contrast transmission as a funct
29、ion of the object size. In this practice, the MTF characterizes the unsharpnessof the CR system. This depends on the scanning system itself and IP-type and cassette employed.3.2.6 gain/amplificationOpto-electrical gain setting of the scanning system.3.2.5 linearized signal intensitya numerical signa
30、l value of a picture element (pixel) of the digital image, which is proportionalto the radiation dose. The linearized signal intensity is zero, if the radiation dose is zero.3.2.8 basic spatial resolutionthe read-out value of unsharpness measured with duplex wire IQI in accordance with PracticeE2002
31、 divided by 2 as effective pixel size of the CR system.4. Significance and Use4.1 There are several factors affecting the quality of a CR image including the basic spatial resolution of the IP system,geometrical unsharpness, scatter and contrast sensitivity (signal-to-noise ratio), as well as softwa
32、re. sensitivity. There are severaladditional factors (for example, scanning parameters), whichsoftware and scanning parameters) that affect the accurate reading ofimages on exposed IPs using an optical scanner.4.2 This practice is to be used to establish a classificationcharacterization of CR system
33、 classes by performance levels on thebasis of a normalized SNR. Due to the difference between the methods, it is required to specify the CR system classes with spatialresolution values. SNR, interpolated basic spatial detector resolution and EPS. The CR system classes performance levels in thisdocum
34、entpractice do not refer to any particular manufacturersimaging plates. A CR system class performance level results fromthe use of a particular imaging plate together with the exposure conditions, particularly total exposure, standardized phantom, thescanner type, and software and the scanning param
35、eters. This classificationcharacterization system provides a means to comparediffering CR technologies, as is common practice with film systems, which guides the user to the appropriate configuration, IP, andtechnique for the application at hand. The class performance level selected may not match th
36、e imaging performance of acorresponding film class due tobecause of the difference in the spatial resolution and scatter sensitivity. Therefore, the practiceusershould always use IQIs for proof of contrast sensitivity and basic spatial resolution.4.3 The measured performance parameters are presented
37、 in a characterization chart. This enables users to select specific CRsystems by the different characterization data to find the best system for his specific application.4.4 The quality factors can be determined most accurately by the tests described in this practice. Some of the system testsrequire
38、 special tools, which may not be available in user laboratories. Simpler tests are described for quality assurance inPracticeand long E2445, which are designed forterm stability tests in Practice E2445a fast test of the quality of CR systems andlong-term stability and are recommended as practical us
39、er tests, should the user not have the special tools available as needed forthe tests in this practice4.5 Manufacturers of industrial CR systems or certification agencies will use this practice. Users of industrial CR systems mayalso use Practice E2445 or perform some of the described tests and meas
40、urements outlined in this practice, provided that therequired test equipment is used and the methodology is strictly followed. Any alternative methods or radiation qualities may beapplied if equivalence to the methods of this practice is proven to the appropriate Cognizant Engineering Organization.c
41、ognizantengineering organization.4.6 The publication of CR system classes performance levels will enable specifying bodies and contracting parties to agree toparticular system class, performance level, as a first step in arriving at the appropriate settings of a system, or the selection of asystem.
42、Confirmation of necessary image quality shall be achieved by using Practice E2033.5. Apparatus5.1 CR system evaluation depends on the combined properties of the phosphor imaging plate (IP) type, the scanner and softwareused, and the selected scan parameters. parameters and image display monitor. The
43、refore, documentation for each test shall includethe IP type, scanner, software and software, scan parameters, and image display monitor, and the results shall be calculated andtabulated prior to before arriving at a classperformance assignment. The applied test equipment for SNR measurement (Fig. 1
44、) andalgorithm 6.1.1 correspond to Test Method E1815. The recommended thickness for aperture test object (diaphragm) is10.2-mm10.2 mm (0.4 in.) of Pb. The SDD shall be at least 1 m (39 in.). Do not use any material (for example, lead) behind thecassette and leave a free space of at least 1 m (39 in.
45、) behind the cassette or use a steel screen of about 0.5 mm (0.02 in.) and alead plate of 2 mm (0.08 in.) just behind the cassette (steel screen is positioned between cassette and lead) and in contact withthe cassette.5.2 The step wedge method (Fig. 2) describes a simpler procedure for SNR measureme
46、nt than described in Test Method E1815,which permits obtaining similar results with less expense, and less accuracy.6. Procedure for quantitative measurement of image quality parametersQuantitative Measurement of Image QualityParameters6.1 Measurement of the Normalized Signal-to-Noise Ratio (SNR)(SN
47、RN)6.1.1 Step Exposure MethodFor measurement of the SNR, the following steps are taken (see also Test Method E1815):E2446 1536.1.1.1 The IP, with front and back lead screens of 0.1 mm (0.004 in.) thickness in the typical exposure cassette, IP shall bepositioned in front of an X-ray tube with tungste
48、n anode. Make the exposures with an 8 mm (0.32 in.) (0.32 in.) copper filter atthe X-ray tube and the kilovoltage set such that the half value layer in copper is 3.5 mm (0.14 in.). The kilovoltage setting willbe approximately 220 kV. Metal screens can be used in the cassette if the manufacturer reco
49、mmends its application. The focal spotsize is not relevant for SNR measurements.6.1.1.2 Determine the required exact kilovoltage setting by making an exposure (or an exposure rate) measurement with thedetector placed at a distance of at least 750 mm (29.5 in.) from the tube target and an 8 mm (0.32 in.) copper filter at the tube.Then make a second measurement with a total of 11.5 mm 11.5 mm (0.45 in.) of copper at the tube. These filters should be madeof 99.9 % pure copper.6.1.1.3 Calculate the ratio of the first and second readings. If this ratio is not 2,
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