ASTM E1695-20e1

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.

General Information

• Status: Published
• Publication Date: 31-May-2020
• ICS: 11.040.50 - Radiographic equipment
• Technical Committee: E07 - Nondestructive Testing
• Drafting Committee: E07.01 - Radiology (X and Gamma) Method

Standards Content (Sample)

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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Designation: E1695 − 20
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.
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ε NOTE—Added research report footnote to Section 10 editorially in June 2022.
1. Scope responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.1 This test method provides instruction for determining
mine the applicability of regulatory limitations prior to use.
thespatialresolutionandcontrastsensitivityinX-rayand γ-ray
1.7 This international standard was developed in accor-
computed tomography (CT) volumes. The determination is
dance with internationally recognized principles on standard-
based on examination of the CT volume of a uniform cylinder
ization established in the Decision on Principles for the
of material. The spatial resolution measurement (Modulation
Development of International Standards, Guides and Recom-
Transfer Function) is derived from an image analysis of the
mendations issued by the World Trade Organization Technical
sharpness at the edges of the reconstructed cylinder slices. The
Barriers to Trade (TBT) Committee.
contrast sensitivity measurement (Contrast Discrimination
Function) is derived from an image analysis of the contrast and
2. Referenced Documents
the statistical noise at the center of the cylinder slices.
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2.1 ASTM Standards:
1.2 This test method is more quantitative and less suscep-
E177 Practice for Use of the Terms Precision and Bias in
tible to interpretation than alternative approaches because the
ASTM Test Methods
required cylinder is easy to fabricate and the analysis easy to
E691 Practice for Conducting an Interlaboratory Study to
perform.
Determine the Precision of a Test Method
1.3 This test method is not to predict the detectability of E1000 Guide for Radioscopy
specific object features or flaws in a specific application. This
E1316 Terminology for Nondestructive Examinations
is subject of IQI and RQI standards and standard practices. E1441 Guide for Computed Tomography (CT)
E1570 Practice for Fan Beam Computed Tomographic (CT)
1.4 This method tests and describes overall CT system
Examination
performance. Performance tests of systems components such
E2002 Practice for Determining Image Unsharpness and
as X-ray tubes, gamma sources, and detectors are covered by
Basic Spatial Resolution in Radiography and Radioscopy
separatedocuments,namelyGuideE1000,PracticeE2737,and
E2737 Practice for Digital Detector Array Performance
Practice E2002; c.f. 2.1, which should be consulted for further
Evaluation and Long-Term Stability
system analysis.
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2.2 ISO Standard:
1.5 Units—The values stated in SI units are to be regarded
15708 NDT – Radiation Methods – Computed Tomography
as standard. The values given in parentheses after SI units are
– Part 1: Terminology, Part 2: Principles, Equipment and
provided for information only and are not considered standard.
Samples, Part 3: Operation and Interpretation, Part 4:
1.6 This standard does not purport to address all of the
Qualification
safety concerns, if any, associated with its use. It is the
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
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This test method is under the jurisdiction of ASTM Committee E07 on contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Nondestructive Testing and is the direct responsibility of Subcommittee E07.01 on Standards volume information, refer to the standard’s Document Summary page on
Radiology (X and Gamma) Method. the ASTM website.
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Current edition approved June 1, 2020. Published August 2020. Originally Available from International Organization for Standardization (ISO), ISO
approved in 1995. Last previous edition approved in 2013 as E1695 – 95(2013). Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
DOI: 10.1520/E1695-20E01. Geneva, Switzerland, http://www.iso.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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E1695 − 20
3. Terminology design and material requirements in Table 1 and Fig. 1. For fan
beam CT apparatus with LDA, a disk-shaped phantom as
3.1 Defi
...