ASTM E2007-10(2023)
(Guide)Standard Guide for Computed Radiography
Standard Guide for Computed Radiography
SIGNIFICANCE AND USE
4.1 This guide is intended as a source of tutorial and reference information that can be used during establishment of computed radiography techniques and procedures by qualified CR personnel for specific applications. All materials presented within this guide may not be suited for all levels of computed radiographic personnel.
4.2 This guide is intended to build upon an established basic knowledge of radiographic fundamentals (that is, film systems) as may be found in Guide E94. Similarly, materials presented within this guide are not intended as “all-inclusive” but are intended to address basic CR topics and issues that complement a general knowledge of computed radiography as described in 1.2 and 3.2.28.
4.3 Materials presented within this guide may be useful in the development of end-user training programs designed by qualified CR personnel or activities that perform similar functions. Computed radiography is considered a rapidly advancing inspection technology that will require the user maintain knowledge of the latest CR apparatus and technique innovations. Section 11 of this guide contains technical reference materials that may be useful in further advancement of knowledge associated with computed radiography.
SCOPE
1.1 This guide provides general tutorial information regarding the fundamental and physical principles of computed radiography (CR), definitions and terminology required to understand the basic CR process. An introduction to some of the limitations that are typically encountered during the establishment of techniques and basic image processing methods are also provided. This guide does not provide specific techniques or acceptance criteria for specific end-user inspection applications. Information presented within this guide may be useful in conjunction with those standards of 1.2.
1.2 CR techniques for general inspection applications may be found in Practice E2033. Technical qualification attributes for CR systems may be found in Practice E2445. Criteria for classification of CR system technical performance levels may be found in Practice E2446. Reference Images Standards E2422, E2660, and E2669 contain digital reference acceptance illustrations.
1.3 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only.
1.4 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.
1.5 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
Relations
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.
Designation: E2007 − 10 (Reapproved 2023)
Standard Guide for
Computed Radiography
This standard is issued under the fixed designation E2007; 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.
1. Scope mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.1 This guide provides general tutorial information regard-
ing the fundamental and physical principles of computed
2. Referenced Documents
radiography (CR), definitions and terminology required to
2.1 ASTM Standards:
understand the basic CR process. An introduction to some of
E94 Guide for Radiographic Examination Using Industrial
the limitations that are typically encountered during the estab-
Radiographic Film
lishment of techniques and basic image processing methods are
E746 Practice for Determining Relative Image Quality Re-
also provided. This guide does not provide specific techniques
sponse of Industrial Radiographic Imaging Systems
or acceptance criteria for specific end-user inspection applica-
E747 Practice for Design, Manufacture and Material Group-
tions. Information presented within this guide may be useful in
ing Classification of Wire Image Quality Indicators (IQI)
conjunction with those standards of 1.2.
Used for Radiology
1.2 CR techniques for general inspection applications may
E1025 Practice for Design, Manufacture, and Material
be found in Practice E2033. Technical qualification attributes
Grouping Classification of Hole-Type Image Quality In-
for CR systems may be found in Practice E2445. Criteria for
dicators (IQI) Used for Radiography
classification of CR system technical performance levels may
E1316 Terminology for Nondestructive Examinations
be found in Practice E2446. Reference Images Standards
E1453 Guide for Storage of Magnetic Tape Media that
E2422, E2660, and E2669 contain digital reference acceptance
Contains Analog or Digital Radioscopic Data
illustrations.
E2002 Practice for Determining Image Unsharpness and
1.3 The values stated in SI units are to be regarded as the
Basic Spatial Resolution in Radiography and Radioscopy
standard. The inch-pound units given in parentheses are for
E2033 Practice for Radiographic Examination Using Com-
information only.
puted Radiography (Photostimulable Luminescence
Method)
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the E2339 Practice for Digital Imaging and Communication in
Nondestructive Evaluation (DICONDE)
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter- E2422 Digital Reference Images for Inspection of Alumi-
num Castings
mine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accor- E2445 Practice for Performance Evaluation and Long-Term
Stability of Computed Radiography Systems
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the E2446 Practice for Manufacturing Characterization of Com-
puted Radiography Systems
Development of International Standards, Guides and Recom-
E2660 Digital Reference Images for Investment Steel Cast-
ings for Aerospace Applications
This guide is under the jurisdiction of ASTM Committee E07 on Nondestruc-
tive Testing and is the direct responsibility of Subcommittee E07.01 on Radiology
(X and Gamma) Method. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved June 1, 2023. Published June 2023. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1999. Last previous edition approved in 2016 as E2007 – 10 (2016). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/E2007-10R23. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2007 − 10 (2023)
E2669 Digital Reference Images for Titanium Castings image display, image storage and retrieval system and interac-
tive support software.
2.2 SMPTE Standard:
RP-133 Specifications for Medical Diagnostic Imaging Test
3.2.7 computed radiographic system class—a group of com-
Pattern for Television Monitors and Hard-Copy Recording
puted radiographic systems characterized with a standard
Cameras
image quality rating. Practice E2446, Table 1, provides such a
classification system.
3. Terminology
3.2.8 computed radiography—a radiological nondestructive
3.1 Unless otherwise provided within this guide, terminol-
testing method that uses storage phosphor imaging plates
ogy is in accordance with Terminology E1316.
(IP’s), a PSL stimulating light source, PSL capturing optics,
3.2 Definitions: optical-to-electrical conversion devices, analogue-to-digital
3.2.1 aliasing—artifacts that appear in an image when the data conversion electronics, a computer and software capable
spatial frequency of the input is higher than the output is of processing original digital image data and a means for
capable of reproducing. This will often appear as jagged or electronically displaying or printing resultant image data.
stepped sections in a line or as moiré patterns.
3.2.9 contrast and brightness—an application of digital
3.2.2 basic spatial resolution (SR )—terminology used to
image processing used to “re-map” displayed gray scale levels
b
describe the smallest degree of visible detail within a digital
of an original gray scale data matrix using different reference
image that is considered the effective pixel size.
lookup tables.
3.2.2.1 Discussion—The concept of basic spatial resolution
3.2.9.1 Discussion—This mode of image processing is also
involves the ability to separate two distinctly different image
known as “windowing” (contrast adjustment) and “leveling”
features from being perceived as a single image feature. When
(brightness adjustment) or simply “win-level” image process-
two identical image features are determined minimally distinct,
ing.
the single image feature is considered the effective pixel size.
3.2.10 contrast-to-noise ratio (CNR)—quotient of the digi-
If the physical sizes of the two distinct features are known, for
tal image contrast (see 3.2.13) and the averaged standard
example, widths of two parallel lines or bars with an included
deviation of the linear pixel values.
space equal to one line or bar, then the effective pixel size is
1 3.2.10.1 Discussion—CNR is a measure of image quality
considered ⁄2 of their sums. Example: A digital image is
that is dependent upon both digital image contrast and signal-
determined to resolve five line pairs per mm or a width of line
to-noise ratio (SNR) components. In addition to CNR, a digital
equivalent to five distinct lines within a millimetre. The basic
radiograph must also possess adequate sharpness or basic
spatial resolution is determined as 1/ [2 × 5 LP/ mm] or
spatial resolution to adequately detect desired features.
0.100 mm.
3.2.11 digital driving level (DDL)—terminology used to
3.2.3 binary/digital pixel data—a matrix of binary (0’s, 1’s)
describe displayed pixel brightness of a digital image on a
values resultant from conversion of PSL from each latent pixel
monitor resultant from digital mapping of various gray scale
(on the IP) to proportional (within the bit depth scanned)
levels within specific look-up-table(s).
electrical values. Binary digital data value is proportional to the
radiation dose received by each pixel. 3.2.11.1 Discussion— DDL is also known as monitor pixel
intensity value; thus, may not be the PV of the original digital
3.2.4 bit depth—the number “2” increased by the exponen-
image.
tial power of the analogue-to-digital (A/D) converter resolu-
tion. Example 1) In a 2-bit image, there are four (2 ) possible
3.2.12 digital dynamic range—maximum material thickness
combinations for a pixel: 00, 01, 10 and 11. If “00” represents
latitude that renders acceptable levels of specified image
black and “11” represents white, then “01” equals dark gray
quality performance within a specified pixel intensity value
and “10” equals light gray. The bit depth is two, but the number
range.
of gray scales shades that can be represented is 2 or 4.
3.2.12.1 Discussion—Digital dynamic range should not be
Example 2): A 12-bit A/D converter would have 4096 (2 )
confused with computer file bit depth.
gray scales shades that can be represented.
3.2.13 digital image contrast—pixel value difference be-
3.2.5 blooming or flare—an undesirable condition exhibited
tween any two areas of interest within a computed radiograph.
by some image conversion devices brought about by exceeding
3.2.13.1 Discussion—Digital contrast = PV2 – PV1 where
the allowable input brightness for the device, causing the
PV2 is the pixel value of area of interest “2” and PV1 is the
image to go into saturation, producing an image of degraded
pixel value of area of interest “1” on a computed radiograph.
spatial resolution and gray scale rendition.
Visually displayed image contrast can be altered via digital
3.2.6 computed radiographic system—all hardware and
re-mapping (see 3.2.11) or re-assignment of specific gray scale
software components necessary to produce a computed radio-
shades to image pixels.
graph. Essential components of a CR system consisting of: an
3.2.14 digital image noise—imaging information within a
imaging plate, an imaging plate readout scanner, electronic
computed radiograph that is not directly correlated with the
degree of radiation attenuation by the object or feature being
examined and/or insufficient radiation quanta absorbed within
Available from Society of Motion Picture and Television Engineers (SMPTE),
3 Barker Ave, 5th Floor, White Plains, NY 10601. the detector IP.
E2007 − 10 (2023)
FIG. 1 Basic Computed Radiography Process
3.2.14.1 Discussion—Digital image noise results from ran- 3.2.18 image morphing—a potentially degraded CR image
dom spatial distribution of photons absorbed within the IP and resultant from over processing (that is, over driving) an
interferes with the visibility of small or faint detail due to
original CR image.
statistical variations of pixel intensity value.
3.2.18.1 Discussion—“Morphing” can occur following sev-
3.2.15 digital image processing—the use of algorithms to eral increments of image processing where each preceding
image was “overwritten” resulting in an image that is notice-
change original digital image data for the purpose of enhance-
ment of some aspect of the image. ably altered from the original.
3.2.15.1 Discussion—Examples include: contrast,
3.2.19 look up table (LUT)—one or more fields of binary
brightness, pixel density change (digital enlargement), digital
digital values arbitrarily assigned to a range of reference gray
filters, gamma correction, and pseudo colors. Some digital
scale levels (viewed on an electronic display as shades of
processing operations such as sharpening filters, once saved,
“gray”).
permanently change the original binary data matrix (Fig. 1,
3.2.19.1 Discussion—A LUT is used (applied) to convert
Step 5).
binary digital pixel data to proportional shades of “gray” that
3.2.16 equivalent penetrameter sensitivity (EPS)—that
define the CR image. LUT’s are key reference files that allow
thickness of penetrameter, expressed as a percentage of the
binary digital pixel data to be viewed with many combinations
section thickness radiographed, in which a 2T hole would be
of pixel gray scales over the entire range of a digital image (see
visible under the same radiographic conditions. EPS is calcu-
Fig. 5-A).
lated by: EPS% = 100/ X (√ Th/2), where: h = hole diameter,
3.2.20 original digital image—a digital gray scale (see
T = step thickness and X = thickness of test object (see
3.2.17) image resultant from application of original binary
Terminology E1316 and Practices E1025, E747, and E746).
digital pixel data to a linear look-up table (see 3.2.24 and
3.2.17 gray scale—a term used to describe an image con-
3.2.19 prior to any image processing.
taining shades of gray rather than color. Gray scale is the range
3.2.20.1 Discussion—This original gray scale image is usu-
of gray shades assigned to image pixels that result in visually
ally considered the beginning of the “computed radiograph”,
perceived pixel display brightness.
since without this basic conversion (to gray scales) there would
3.2.17.1 Discussion—The number of shades is usually posi-
be no discernable radiographic image (see Fig. 5-B).
tive integer values taken from the bit depth. For example: an
8-bit gray scale image has up to 256 total shades of gray from 3.2.21 photostimulable luminescence (PSL)—photostimula-
0 to 255, with 0 representing white image areas and 255 ble luminescence (PSL) is a physical phenomenon in which a
representing black image areas with 254 shades of gray in halogenated phosphor compound emits bluish light when
between. excited by a source of red spectrum light.
E2007 − 10 (2023)
3.2.22 pixel brightness—the luminous (monitor) display 3.2.28 spatial resolution—terminology used to define a
intensity of pixel(s) that can be controlled by means of component of optical image quality associated with distinction
of closely spaced adjacent multiple features.
electronic monitor brightness level settings or changes of
digital driving level (see 3.2.11).
3.2.28.1 Discussion—The concept of optical resolution in-
volves the ability to separate multiple closely spaced
3.2.23 pixel density—the number of pixels within a digital
components, for example, optical line pairs, into two or more
image of fixed dimensions (that is, length and width).
distinctly different components within a defined unit of space.
3.2.23.1 Discussion—for digital raster images, the conven-
Example: an optical imaging system that is said to resolve two
tion is to describe pixel density in terms of the number of
line pairs within one mm of linear space (that is, 2 Lp/mm)
pixel-columns (width) and number of pixel-rows (height). An
contains five individual components: two closely spaced adja-
alternate convention is to describe the total number of pixels in
cent line components, an intervening space between the lines
the image area (typically given as t
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