ASTM E2736-17(2022)
(Guide)Standard Guide for Digital Detector Array Radiography
Standard Guide for Digital Detector Array Radiography
SIGNIFICANCE AND USE
4.1 This standard provides a guide for the other DDA standards (see Practices E2597, E2698, and E2737). It is not intended for use with computed radiography apparatus. Figure 1 describes how this standard is interrelated with the aforementioned standards.
FIG. 1 Flow Diagram Representing the Connection Between the Four DDA Standards
4.2 This guide is intended to assist the user to understand the definitions and corresponding performance parameters used in related standards as stated in 4.1 in order to make an informed decision on how a given DDA can be used in the target application.
4.3 This guide is also intended to assist cognizant engineering officers, prime manufacturers, and the general service and manufacturing customer base that may rely on DDAs to provide advanced radiological results so that these parties may set their own acceptance criteria for use of these DDAs by suppliers and shops to verify that their parts and structures are of sound integrity to enter into service.
4.4 The manufacturer characterization standard for DDA (see Practice E2597) serves as a starting point for the end user to select a DDA for the specific application at hand. DDA manufacturers and system integrators will provide DDA performance data using standardized geometry, X-ray beam spectra, and phantoms as prescribed in Practice E2597. The end user will look at these performance results and compare DDA metrics from various manufacturers and will decide on a DDA that can meet the specification required for inspection by the end user. See Sections 5 and 8 for a discussion on the characterization tests and guidelines for selection of DDAs for specific applications.
4.5 Practice E2698 is designed to assist the end user to set up the DDA with minimum requirements for radiological examinations. This standard will also help the user to get the required SNR, to set up the required magnification, and provides guidance for viewing and storage of radiographs. Discussion is also...
SCOPE
1.1 This standard is a user guide, which is intended to serve as a tutorial for selection and use of various digital detector array systems nominally composed of the detector array and an imaging system to perform digital radiography. This guide also serves as an in-detail reference for the following standards: Practices E2597, E2698, and E2737.
1.2 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.
1.3 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: E2736 − 17 (Reapproved 2022)
Standard Guide for
Digital Detector Array Radiography
This standard is issued under the fixed designation E2736; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope amination by Using Representative Quality Indicators
(RQIs)
1.1 This standard is a user guide, which is intended to serve
E2002Practice for Determining Image Unsharpness and
as a tutorial for selection and use of various digital detector
Basic Spatial Resolution in Radiography and Radioscopy
arraysystemsnominallycomposedofthedetectorarrayandan
E2422Digital Reference Images for Inspection of Alumi-
imagingsystemtoperformdigitalradiography.Thisguidealso
num Castings
serves as an in-detail reference for the following standards:
E2445Practice for Performance Evaluation and Long-Term
Practices E2597, E2698, and E2737.
Stability of Computed Radiography Systems
1.2 This standard does not purport to address all of the
E2446Practice for Manufacturing Characterization of Com-
safety concerns, if any, associated with its use. It is the
puted Radiography Systems
responsibility of the user of this standard to establish appro-
E2597Practice for Manufacturing Characterization of Digi-
priate safety, health, and environmental practices and deter-
tal Detector Arrays
mine the applicability of regulatory limitations prior to use.
E2660Digital Reference Images for Investment Steel Cast-
1.3 This international standard was developed in accor-
ings for Aerospace Applications
dance with internationally recognized principles on standard-
E2669Digital Reference Images for Titanium Castings
ization established in the Decision on Principles for the
E2698Practice for Radiographic Examination Using Digital
Development of International Standards, Guides and Recom-
Detector Arrays
mendations issued by the World Trade Organization Technical
E2737Practice for Digital Detector Array Performance
Barriers to Trade (TBT) Committee.
Evaluation and Long-Term Stability
2.2 ISO Document:
2. Referenced Documents
ISO 17636-2 Non-Destructive Testing of Welds—
2.1 ASTM Standards:
Radiographic Testing - Part 2: X- and Gamma-Ray Tech-
E94Guide for Radiographic Examination Using Industrial
niques with Digital Detector
Radiographic Film
E155Reference Radiographs for Inspection of Aluminum 3. Terminology
and Magnesium Castings
3.1 Definitions of Terms Specific to This Standard:
E192Reference Radiographs of Investment Steel Castings
3.1.1 achievable contrast sensitivity (CSa)—best contrast
for Aerospace Applications
sensitivity (see Terminology E1316 for a definition of contrast
E1000Guide for Radioscopy
sensitivity)obtainableusingastandardphantomwithanX-ray
E1316Terminology for Nondestructive Examinations
technique that has little contribution from scatter.
E1320Reference Radiographs for Titanium Castings
3.1.2 bad pixel—a bad pixel is a pixel identified with a
E1815Test Method for Classification of Film Systems for
performance outside of the specification for a pixel of a DDA
Industrial Radiography
as defined in Practice E2597.
E1817Practice for Controlling Quality of Radiological Ex-
3.1.3 burn-in—change in gain of the scintillator or photo-
conductor that persists well beyond the exposure.
1 3.1.4 effıciency—SNR (see 3.1.6 of Practice E2597) di-
This guide is under the jurisdiction of ASTM Committee E07 on Nondestruc- n
tive Testing and is the direct responsibility of Subcommittee E07.01 on Radiology vided by the square root of the dose (in mGy) and is used to
(X and Gamma) Method.
measuretheresponseofthedetectoratdifferentbeamenergies
Current edition approved Dec. 1, 2022. Published December 2022. Originally
and qualities.
approved in 2010. Last previous edition approved in 2017 as E2736–17. DOI:
10.1520/E2736-17R22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available from International Organization for Standardization (ISO), ISO
Standards volume information, refer to the standard’s Document Summary page on Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
the ASTM website. Geneva, Switzerland, http://www.iso.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2736 − 17 (2022)
3.1.5 grooved wedge—awedgewithonegroove,thatis5% 3.1.10 specific material thickness range (SMTR)—material
of the base material thickness and that is used for achievable thickness range within which a given image quality is
contrast sensitivity measurement in Practice E2597.
achieved.
3.1.6 internal scatter radiation (ISR)—scattered radiation
4. Significance and Use
within the detector (from scintillator, photodiodes, electronics,
shielding, or other detector hardware).
4.1 This standard provides a guide for the other DDA
3.1.7 lag—residual signal in the DDA that occurs shortly
standards (see Practices E2597, E2698, and E2737). It is not
after the exposure is completed.
intended for use with computed radiography apparatus. Figure
3.1.8 phantom—a part or item being used to quantify DDA 1 describes how this standard is interrelated with the afore-
mentioned standards.
characterization metrics.
3.1.9 SNR —SNR, normalized by the basic spatial resolu-
N
4.2 This guide is intended to assist the user to understand
tion SR as measured directly in the digital image and/or
b
thedefinitionsandcorrespondingperformanceparametersused
calculated from measured SNR by:
measured
in related standards as stated in 4.1 in order to make an
88.6 µm informed decision on how a given DDA can be used in the
SNR 5SNR 3 (1)
S D
N measured
SR target application.
b
FIG. 1 Flow Diagram Representing the Connection Between the Four DDA Standards
E2736 − 17 (2022)
4.3 This guide is also intended to assist cognizant engineer- 5.1.3 Area—DDAs are area imaging devices and as such
ing officers, prime manufacturers, and the general service and can capture much more information in a single exposure than
manufacturing customer base that may rely on DDAs to a Linear Detector Array (LDA), or a linear-DDA. For the
provide advanced radiological results so that these parties may balance of this standard, the term LDA shall be considered a
set their own acceptance criteria for use of these DDAs by linear detector array, while a DDAshall be considered an area
suppliers and shops to verify that their parts and structures are device.Whencapturinganareaofinterest,aDDAmaycapture
of sound integrity to enter into service. a full area in a single exposure, while an LDAcaptures only a
single line in an exposure. To capture an area of interest, the
4.4 The manufacturer characterization standard for DDA
LDAneeds a series of adjacent line scans and thereby a series
(see Practice E2597) serves as a starting point for the end user
of exposures.
to select a DDA for the specific application at hand. DDA
5.1.4 Despite the advantages in 5.1.3, there is a tradeoff in
manufacturers and system integrators will provide DDA per-
that the DDA devices are prone to higher levels of Compton
formance data using standardized geometry, X-ray beam
scatter. For example, the use of a fan beam over the use of a
spectra, and phantoms as prescribed in Practice E2597. The
cone beam will inherently produce less Compton scatter from
end user will look at these performance results and compare
the object, or from the side walls of an X-ray cabinet.
DDAmetrics from various manufacturers and will decide on a
Secondly, the LDA can more effectively collimate this scatter
DDAthat can meet the specification required for inspection by
using a narrow slit.That said, the DDAcan be configured with
the end user. See Sections 5 and 8 for a discussion on the
a set of adjustable jaws both about the detector and/or the
characterization tests and guidelines for selection of DDAs for
sourcetoreducethescatterfield,butthebenefitofitsprojected
specific applications.
coverage is diminished.
4.5 Practice E2698 is designed to assist the end user to set
5.1.5 When considering the SNR as a tradeoff, the LDAhas
up the DDA with minimum requirements for radiological
an advantage compared to DDA’s. LDA’s have significantly
examinations. This standard will also help the user to get the
thicker scintillators, and thereby require a lower radiation dose
required SNR, to set up the required magnification, and
toproduceasuccessfulimageperlinecomparedtoaDDA.For
provides guidance for viewing and storage of radiographs.
a given overall exposure time, because of the thicker scintil-
Discussion is also added to help the user with marking and
lator in an LDA, there could be situations where it produces a
identification of parts during radiological examinations.
higher SNR compared to the thinner scintillator in a DDA.
Also, for a given SNR, there could be situations where more
4.6 Practice E2737 is designed to help the end user with a
overall exposure time is needed for a DDA.
set of tests so that the stability of the performance of the DDA
5.1.6 DDAsalsoenableafacilecorrectionfordifferencesin
can be confirmed. Additional guidance is provided in this
pixel value response (gain) across the DDA, X-ray beam
document to support this standard.
shading, offset levels of the device, and bad pixels. These
4.7 Figure 1 provides a summary of the interconnectivity of
correctionsresultinahighlyuniformandlinearresponsetothe
these four DDA standards.
X-ray beam and provides the capability to provide very high
4.8 DDAs may be used with significant success under a
and uniform signal to noise response with respect to the X-ray
wide energy range, i.e. from 10 kV to 20 MeV if configured beam incident on the DDA. These corrections are not neces-
appropriately. However in this document some phantoms such
sarily simple to perform with film or computed radiography
as the duplex wire gauge (Practice E2002) may not give an systems where the SNR might be limited by a structure noise
accurate representation of the basic spatial resolution at ener-
inherent in the imaging medium, or the shading of the X-ray
gies above 600 kV. beam.
5.1.7 Unlike film or computed radiography (CR) systems,
5. DDA Technology Description
theabilitytoflexthesensor,forexamplearoundapipehasnot
yet been realized, and is certainly one of the advantages of
5.1 General Discussion:
these other imaging media over DDA devices.
5.1.1 DDAs are seeing increased use in industries to en-
5.1.8 Another difference between film/CR is that these
hanceproductivityandqualityofnondestructivetesting.DDAs
devices/media will enable very long exposure times. For
are being used for in-service nondestructive testing, as a
example unlike a DDA there is not any restriction on frame
diagnostic tool in the manufacturing process, and for inline
rate. That said, a DDAcan overcome this shortfall by averag-
testing on production lines. DDAs are also being used as hand
ing frames to achieve the desired image quality. All X-ray
held, or scanned devices for pipeline inspections, in industrial
imaging devices will suffer from poor SNR if the dynamic
computed tomography systems, and as part of large robotic
nature of the inspection is too fast to capture enough photons
scanning systems for imaging of large or complex structures.
as an object transits the beam.
Because of the digital nature of the data, a variety of new
applications and techniques have emerged recently, enabling 5.2 DDA architecture:
quantitative inspection and automatic defect recognition.
5.2.1 A common aspect of the different forms of this
5.1.2 DDAs can be used to detect various forms of electro- technology is the use of discrete sensors (position-sensitive)
magneticradiation,orparticles,includinggammarays,X-rays, where, the data from each discrete location is read out into a
neutrons,orotherformsofpenetratingradiation.Thisstandard file structure to form pixels of a digital image file. In all its
focuses on X-rays and gamma rays. simplicity, the device has an X-ray capture material as its
E2736 − 17 (2022)
primary means for detecting X-rays, which is then coupled to for each of these steps, and the reader is referred to (1, 2, 3)
a solid-state pixelized structure, where such a structure is for further discussion on this topic.
similar to the imaging chips used in visible-wavelength digital
5.3 Digitization Methods:
photography and videography devices. Figure 2 shows a block
5.3.1 Digitization techniques typically convert the analog
diagram of a typical digital X-ray imaging system.
signal to discrete pixel values. For DDAs the digitization is
5.2.2 An important difference between X-ray imaging and
typically, 8-bit (256 pixel values), 12-bits (4096 pixel values),
visible-light imaging is the size of the read-out device. The
14-bits (16,384 pixel values) or 16-bits (65,536 pixel values),
imagers found in cameras and for visible-light are typically on
and 20-bits (1,048,576). The higher the bit depth, the more
the order of 1 to 2 cm in area. Since X-rays are not easily
finely the signal intensity is sampled.
focused, as is the case for visible light, the imaging medium
5.3.2 The digitization does not necessarily define the pixel
must be the size of the object. Hence, the challenge lies in
value range of the DDA. The useful range of performance is
meeting the requirement of a large uniform imaging area
defined by the ability of the read device to capture signal in a
without loss of spatial information. This in turn requires high
linear relation to the signal generated by the primary conver-
pixel densities of the read-out device over the object under
sion device.Awide linear range warrants the use of a high bit
examination, as well a primary sensing medium that also
depthdigitizer.Itshouldbenotedthatifdigitizationisnothigh
retains the radiologic pattern in its structure. Therefore, each enough to cover the information content from the read device,
DDA consists of a primary X-ray or gamma ray capture digitization noise might result. This can be manifested as a
medium followed by a pixelized read structure, with various posterization effect, where discrete bands of pixel values are
meansoftransferringtheabovesaidcapturedpattern.Foreach observed in the image.
of these elements, there are numerous options that can
...
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