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ASTM E1695-95(2013)

(Test Method)

Standard Test Method for Measurement of Computed Tomography (CT) System Performance

Standard Test Method for Measurement of Computed Tomography (CT) System Performance

SIGNIFICANCE AND USE
4.1 Two factors affecting the quality of a CT image are geometrical unsharpness and random noise. Geometrical unsharpness limits the spatial resolution of a CT system, that is, its ability to image fine structural detail in an object. Random noise limits the contrast sensitivity of a CT system, that is, its ability to detect the presence or absence of features in an object. Spatial resolution and contrast sensitivity may be measured in various ways. ASTM specifies spatial resolution be quantified in terms of the modulation transfer function (MTF) and contrast sensitivity be quantified in terms of the contrast discrimination function (CDF) (see Guide E1441 and Practice E1570). This test method allows the purchaser or the provider of CT systems or services, or both, to measure and specify spatial resolution and contrast sensitivity.
SCOPE
1.1 This test method provides instruction for determining the spatial resolution and contrast sensitivity in X-ray and γ-ray computed tomography (CT) images. The determination is based on examination of the CT image of a uniform disk of material. The spatial resolution measurement is derived from an image analysis of the sharpness at the edge of the disk. The contrast sensitivity measurement is derived from an image analysis of the statistical noise at the center of the disk.  
1.2 This test method is more quantitative and less susceptible to interpretation than alternative approaches because the required disk is easy to fabricate and the analysis is immune to cupping artifacts. This test method may not yield meaningful results if the disk image occupies less than a significant fraction of the field of view.  
1.3 This test method may also be used to evaluate other performance parameters. Among those characteristics of a CT system that are detectable with this test method are: the mid-frequency enhancement of the reconstruction kernel, the presence (or absence) of detector crosstalk, the undersampling of views, and the clipping of unphysical (that is, negative) CT numbers (see Air Force Technical Report WL-TR-94-40212). It is highly likely that other characteristics as well can be detected with this test method.  
1.4 The values stated in SI units are to be regarded as the standard. Inch-pound units are provided for information only.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

Status
Historical
Publication Date
31-May-2013
ICS
11.040.50 - Radiographic equipment
Technical Committee
E07 - Nondestructive Testing
Drafting Committee
E07.01 - Radiology (X and Gamma) Method
Current Stage
Ref Project

Relations

Replaces
ASTM E1695-95(2006)e1 - Standard Test Method for Measurement of Computed Tomography (CT) System Performance
Effective Date
01-Jun-2013
Referred By
ASTM E1570-19 - Standard Practice for Fan Beam Computed Tomographic (CT) Examination
Effective Date
01-Jun-2013
Referred By
ASTM E3375-23 - Standard Practice for Cone Beam Computed Tomographic (CT) Examination
Effective Date
01-Jun-2013
Referred By
ASTM E543-21 - Standard Specification for Agencies Performing Nondestructive Testing
Effective Date
01-Jun-2013
Referred By
ASTM E2533-21 - Standard Guide for Nondestructive Examination of Polymer Matrix Composites Used in Aerospace Applications
Effective Date
01-Jun-2013
Referred By
ASTM E3327/E3327M-21 - Standard Guide for the Qualification and Control of the Assisted Defect Recognition of Digital Radiographic Test Data
Effective Date
01-Jun-2013
Referred By
ASTM E3166-20e1 - Standard Guide for Nondestructive Examination of Metal Additively Manufactured Aerospace Parts After Build
Effective Date
01-Jun-2013
Referred By
ASTM E1441-19 - Standard Guide for Computed Tomography (CT)
Effective Date
01-Jun-2013
Referred By
ASTM E1814-14(2022) - Standard Practice for Computed Tomographic (CT) Examination of Castings
Effective Date
01-Jun-2013

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ASTM E1695-95(2013) - Standard Test Method for Measurement of Computed Tomography (CT) System Performance
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E1695 − 95 (Reapproved 2013)
Standard Test Method for
Measurement of Computed Tomography (CT) System
1
Performance
This standard is issued under the fixed designation E1695; the number immediately following the designation indicates the year of
original adoption or, in the case of 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.1 This test method provides instruction for determining
thespatialresolutionandcontrastsensitivityinX-rayand γ-ray
2. Referenced Documents
computed tomography (CT) images. The determination is
3
2.1 ASTM Standards:
based on examination of the CT image of a uniform disk of
E1316 Terminology for Nondestructive Examinations
material. The spatial resolution measurement is derived from
E1441 Guide for Computed Tomography (CT) Imaging
an image analysis of the sharpness at the edge of the disk. The
E1570 Practice for Computed Tomographic (CT) Examina-
contrast sensitivity measurement is derived from an image
tion
analysis of the statistical noise at the center of the disk.
3. Terminology
1.2 This test method is more quantitative and less suscep-
tible to interpretation than alternative approaches because the
3.1 Definitions—The definitions of terms relating to
required disk is easy to fabricate and the analysis is immune to
Gamma- and X-Radiology, which appear in Terminology
cupping artifacts. This test method may not yield meaningful
E1316 and Guide E1441, shall apply to the terms used in this
resultsifthediskimageoccupieslessthanasignificantfraction
test method.
of the field of view.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 phantom—a part or item being used to quantify CT
1.3 This test method may also be used to evaluate other
system performance.
performance parameters. Among those characteristics of a CT
system that are detectable with this test method are: the
3.2.2 examination object—a part or specimen being sub-
mid-frequency enhancement of the reconstruction kernel, the
jected to CT examination.
presence (or absence) of detector crosstalk, the undersampling
3.3 Acronyms:
of views, and the clipping of unphysical (that is, negative) CT
3.3.1 ERF—edge response function.
2
numbers(seeAirForceTechnicalReportWL-TR-94-4021 ).It
3.3.2 PSF—point spread function.
ishighlylikelythatothercharacteristicsaswellcanbedetected
3.3.3 MTF—modulation transfer function.
with this test method.
3.3.4 CDF—contrast discrimination function.
1.4 The values stated in SI units are to be regarded as the
standard. Inch-pound units are provided for information only.
4. Significance and Use
1.5 This standard does not purport to address all of the
4.1 Two factors affecting the quality of a CT image are
safety concerns, if any, associated with its use. It is the
geometrical unsharpness and random noise. Geometrical un-
responsibility of the user of this standard to establish appro-
sharpness limits the spatial resolution of a CT system, that is,
its ability to image fine structural detail in an object. Random
noise limits the contrast sensitivity of a CT system, that is, its
1
This test method is under the jurisdiction of ASTM Committee E07 on
ability to detect the presence or absence of features in an
Nondestructive Testing and is the direct responsibility of Subcommittee E07.01 on
object. Spatial resolution and contrast sensitivity may be
Radiology (X and Gamma) Method.
measured in various ways. ASTM specifies spatial resolution
Current edition approved June 1, 2013. Published June 2013. Originally
ε1
approved in 1995. Last previous edition approved in 2006 as E1695 - 95(2006) .
DOI: 10.1520/E1695-95R13.
2 3
X-Ray Computed Tomography Standards (WL-TR-94-4021). Bossi, R. H. and For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Nelson, J. M. Air Force Contract No. F33615-88-C-5404. Source document contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
available from Air Force Research Laboratory, AFRL/MLLP Building 655, 2230 Standards volume information, refer to the standard’s Document Summary page on
Tenth Street, Suite 1, Wright-Patterson AFB, OH 45433–7814. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
E1695 − 95 (2013)
be quantified in terms of the modulation transfer function
(MTF) and contrast sensitivity be quantified in terms of the
contrast discrimination function (CDF) (see Guide E1441 and
Practi
...

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4.1 Purpose—Practices to be employed for the radiographic examination of materials and components with neutrons using digital neutron detectors are outlined herein. They are intended as a guide for the assessment of a digital neutron radiograph’s characteristics. For information on neutron beam lines for imaging and film neutron radiography, refer to Guide E748.  
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4.1 This practice provides a means to compare DDAs on a common set of technical measurements, realizing that in practice, adjustments can be made to achieve similar results even with disparate DDAs, given geometric magnification, or other industrial radiologic settings that may compensate for one shortcoming of a device.  
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4.4.1 For iSRbdetector, see 5.1, 7.7, 8.2.  
4.4.2 For Detector Efficiency, see 5.3, 7.8, 8.3.  
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4.4.5 For ISO-MTL, see 5.2 (or 7.9, if already completed), 7.10, 8.6.  
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1.1 This practice describes the evaluation of Digital Detector Arrays (DDAs), and assures that one common standard exists for quantitative comparison of DDAs so that an appropriate DDA is selected to meet NDT requirements.  
1.2 This practice is intended for use by manufacturers or integrators of DDAs to provide quantitative results of DDA characteristics for NDT user or purchaser consumption. Some of these tests require specialized test phantoms to assure consistency among results among suppliers or manufacturers. These tests 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, if so desired.
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Standard Guide for Computed Tomography (CT) System Selection

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5.1 This guide will aid the purchaser in generating a CT system specification. This guide covers the conversion of purchaser's requirements to system components that must occur for a useful CT system specification to be prepared.  
5.2 Additional information can be gained in discussions with potential suppliers or with independent consultants.  
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5.4 This guide is applicable to purchasers needing to procure a CT system for a specific examination application.
SCOPE
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1.2 Computed tomography (CT) may be used for new applications or in place of radiography or radioscopy, provided that the capability to disclose physical features or indications that form the acceptance/rejection criteria is fully documented and available for review. In general, CT has lower spatial resolution than film radiography and is of comparable spatial resolution with digital radiography or radioscopy unless magnification is used. Magnification can be used in CT or radiography/radioscopy to increase spatial resolution but concurrently with loss of field of view.  
1.3 Computed tomography (CT) systems use a set of transmission measurements made along a set of paths projected through the object from many different directions. Each of the transmission measurements within these views is digitized and stored in a computer, where they are subsequently conditioned (for example, normalized and corrected) and reconstructed, typically into slices of the object normal to the set of projection paths by one of a variety of techniques. If many slices are reconstructed, a three dimensional representation of the object is obtained. An in-depth treatment of CT principles is given in Guide E1441.  
1.4 Computed tomography (CT), as with conventional radiography and radioscopic examinations, is broadly applicable to any material or object through which a beam of penetrating radiation may be passed and detected, including metals, plastics, ceramics, metallic/nonmetallic composite material and assemblies. The principal advantage of CT is that it has the potential to provide densitometric (that is, radiological density and geometry) images of thin cross sections through an object. In many newer systems the cross-sections are now combined into 3D data volumes for additional interpretation. Because of the absence of structural superposition, images may be much easier to interpret than conventional radiological images. The new purchaser can quickly learn to read CT data because images correspond more closely to the way the human mind visualizes 3D structures than conventional projection radiology. Further, because CT images are digital, the images may be enhanced, analyzed, compressed, archived, input as data into performance calculations, compared with digital data from other nondestructive evaluation modalities, or transmitted to other locations for remote viewing. 3D data sets can be rendered ...

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ASTM
ASTM E1695-20e1(Test Method)
Standard Test Method for Measurement of Computed Tomography (CT) System Performance

SIGNIFICANCE AND USE
4.1 The major factors affecting the quality of a CT image are total image unsharpness (UTimage), contrast (Δµ), and random noise (σ). Geometrical and detector unsharpness limit the spatial resolution of a CT system, that is, its ability to image fine structural detail in an object. Random noise and contrast response limit the contrast sensitivity of a CT system, that is, its ability to detect the presence or absence of features in an object. Spatial resolution and contrast sensitivity may be measured in various ways. In this test method, spatial resolution is quantified in terms of the modulation transfer function (MTF), and contrast sensitivity is quantified in terms of the contrast discrimination function (CDF). The relationship between contrast sensitivity and spatial resolution describing the resolving and detecting capabilities is given by the contrast-detail-diagram (CDD metric, see also Guide E1441 and Practice E1570). This test method allows the purchaser or the provider of CT systems or services, or both, to measure and specify spatial resolution and contrast sensitivity and is a measure for system stability over time and performance acceptability.
SCOPE
1.1 This test method provides instruction for determining the spatial resolution and contrast sensitivity in X-ray and γ-ray computed tomography (CT) volumes. The determination is based on examination of the CT volume of a uniform cylinder of material. The spatial resolution measurement (Modulation Transfer Function) is derived from an image analysis of the sharpness at the edges of the reconstructed cylinder slices. The contrast sensitivity measurement (Contrast Discrimination Function) is derived from an image analysis of the contrast and the statistical noise at the center of the cylinder slices.  
1.2 This test method is more quantitative and less susceptible to interpretation than alternative approaches because the required cylinder is easy to fabricate and the analysis easy to perform.  
1.3 This test method is not to predict the detectability of specific object features or flaws in a specific application. This is subject of IQI and RQI standards and standard practices.  
1.4 This method tests and describes overall CT system performance. Performance tests of systems components such as X-ray tubes, gamma sources, and detectors are covered by separate documents, namely Guide E1000, Practice E2737, and Practice E2002; c.f. 2.1, which should be consulted for further system analysis.  
1.5 Units—The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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ASTM
ASTM E1570-19(Practice)
Standard Practice for Fan Beam Computed Tomographic (CT) Examination

SIGNIFICANCE AND USE
5.1 This practice establishes the basic parameters for the application and control of fan-beam CT examinations. This practice is written so it can be specified on the engineering drawing, specification, or contract. It will require a detailed procedure delineating the technique or procedure requirements and shall be approved by the Cognizant Engineering Organization (CEO).  
5.2 The requirements in this practice shall be used when placing a CT system into NDT service and establishing a baseline of system performance measures. Monitoring the system performance over time shall be performed, including calibration procedures, performance measurements, and system maintenance in accordance with Section 9.
SCOPE
1.1 This practice establishes the minimum requirements for computed tomography (CT) examination of test objects using fan beam systems (systems that generate one or a few CT cross sectional slices at a time). The examination may be used to nondestructively disclose physical features or anomalies within a test object by providing radiological density and geometric measurements. This practice implicitly assumes the use of penetrating radiation, specifically X-ray and γ-ray.  
1.2 CT is broadly applicable to any material or test object through which a beam of penetrating radiation passes. The principal advantage of CT is that it provides densitometric (that is, radiological density and geometry) images of thin cross sections through an object without the structural superposition in projection radiography.  
1.3 There are areas in this practice that may require agreement between the purchaser and the supplier, or specific direction from the cognizant engineering organization. These items should be addressed in the purchase order or the contract. Generally, the items are application specific or performance related, or both.  
1.4 Techniques and applications employed with CT are diverse. This practice is not intended to be limiting or restrictive. Refer to Guides E1441 and E1672 that provide additional information and guidance on CT fundamentals and tradeoffs in designing or purchasing a CT system, or both.  
1.5 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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ASTM
ASTM E2698-18e1(Practice)
Standard Practice for Radiographic Examination Using Digital Detector Arrays

SIGNIFICANCE AND USE
4.1 This practice establishes the basic parameters for the application and control of the digital detector array radiographic method. This practice is written so it can be specified on the engineering drawing, specification, or contract. It will require a detailed procedure delineating the technique or procedure requirements and shall be approved by the Cognizant Engineering Organization (CEO).
SCOPE
1.1 This practice establishes the minimum requirements for radiographic examination of metallic and nonmetallic materials using digital detector arrays (DDAs).  
1.2 The stated requirements of this specification are based on the use of an X-ray generating source. Additionally, some of the tests and requirements may not be applicable to X-ray energy levels >450kV.  
1.3 The requirements in this practice are intended to control the quality of radiographic examinations obtained using DDAs and are not intended to establish acceptance criteria for parts or materials.  
1.4 This practice covers the radiographic examination with DDAs including DDAs described in Practice E2597/E2597M such as a device that contains a photoconductor attached to a Thin Film Transistor (TFT) read out structure, a device that has a phosphor coupled directly to an amorphous silicon read-out structure, and devices where a phosphor is coupled to a CMOS (complementary metal–oxide–semiconductor) array, or a CCD (charge coupled device) crystalline silicon read-out structure.  
1.5 The requirements of this practice and Practice E2737 shall be used together. The requirements of Practice E2737 will provide the baseline evaluation and long term stability test procedures for the DDA system. The user of the DDA system shall establish a written procedure that addresses the specific requirements and tests to be used in their application and shall be approved by the Cognizant Radiographic Level 3 before examination of production hardware. This practice also requires the user to perform a system qualification suitable for its intended purpose and to issue a system qualification report (see 9.1).  
1.6 The DDA shall be selected for an NDT application based on knowledge of the technology described in Guide E2736, and of the selected DDA properties provided by the manufacturer in accordance with Practice E2597/E2597M.  
1.7 Techniques and applications employed with DDAs are diverse. This practice is not intended to be limiting or restrictive. Refer to Guides E94/E94M, E1000, and E2736, Terminology E1316, Practices E747 and E1025, and Federal Standards 21-CFR-1020.40 and 29-CFR-1910.96 for a list of documents that provide additional information and guidance.  
1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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