ASTM E2737-10
(Practice)Standard Practice for Digital Detector Array Performance Evaluation and Long-Term Stability
Standard Practice for Digital Detector Array Performance Evaluation and Long-Term Stability
SIGNIFICANCE AND USE
This practice is intended to be used by the NDT using organization to measure the baseline performance of the DDA and to monitor its performance throughout its service as an NDT imaging system.
It is to be understood that the DDA has already been selected and purchased by the user from a manufacturer based on the inspection needs at hand. This practice is not intended to be used as an “acceptance test” of the DDA, but rather to establish a performance baseline that will enable periodic performance tracking while in-service.
Although many of the properties listed in this standard have similar metrics to those found in Practice E2597, data collection methods are not identical, and comparisons among values acquired with each standard should not be made.
This practice defines the tests to be performed and required intervals. Also defined are the methods of tabulating results that DDA users will complete following initial baselining of the DDA system. These tests will also be performed periodically at the stated required intervals to evaluate the DDA system to determine if the system remains within acceptable operational limits as established in this practice or defined between user and customer (CEO).
There are several factors that affect the quality of a DDA image including the spatial resolution, geometrical unsharpness, scatter, signal to noise ratio, contrast sensitivity (contrast/noise ratio), image lag, and burn in. There are several additional factors and settings (for example, integration time, detector parameters or imaging software), which affect these results. Additionally, calibration techniques may also have an impact on the quality of the image. This practice delineates tests for each of the properties listed herein and establishes standard techniques for assuring repeatability throughout the lifecycle testing of the DDA.
SCOPE
1.1 This practice describes the evaluation of DDA systems for industrial radiology. It is intended to ensure that the evaluation of image quality, as far as this is influenced by the DDA system, meets the needs of users, and their customers, and enables process control and long term stability of the DDA system.
1.2 This practice specifies the fundamental parameters of Digital Detector Array (DDA) systems to be measured to determine baseline performance, and to track the long term stability of the DDA system.
1.3 The DDA system performance tests specified in this practice shall be completed upon acceptance of the system from the manufacturer and at intervals specified in this practice to monitor long term stability of the system. The intent of these tests is to monitor the system performance for degradation and to identify when an action needs to be taken when the system degrades by a certain level.
1.4 The use of the gages provided in this standard is mandatory for each test. In the event these tests or gages are not sufficient, the user, in coordination with the cognizant engineering organization (CEO) may develop additional or modified tests, test objects, gages, or image quality indicators to evaluate the DDA system. Acceptance levels for these ALTERNATE tests shall be determined by agreement between the user, CEO and manufacturer.
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
Relations
Standards Content (Sample)
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: E2737 − 10
Standard Practice for
Digital Detector Array Performance Evaluation and Long-
Term Stability
This standard is issued under the fixed designation E2737; 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 2. Referenced Documents
1.1 This practice describes the evaluation of DDA systems 2.1 ASTM Standards:
for industrial radiology. It is intended to ensure that the E1025 Practice for Design, Manufacture, and Material
evaluation of image quality, as far as this is influenced by the Grouping Classification of Hole-Type Image Quality In-
DDA system, meets the needs of users, and their customers, dicators (IQI) Used for Radiology
and enables process control and long term stability of the DDA E1316 Terminology for Nondestructive Examinations
system. E1742 Practice for Radiographic Examination
E2002 Practice for DeterminingTotal Image Unsharpness in
1.2 This practice specifies the fundamental parameters of
Radiology
Digital Detector Array (DDA) systems to be measured to
E2445 Practice for Performance Evaluation and Long-Term
determine baseline performance, and to track the long term
Stability of Computed Radiography Systems
stability of the DDA system.
E2597 Practice for Manufacturing Characterization of Digi-
1.3 The DDA system performance tests specified in this
tal Detector Arrays
practice shall be completed upon acceptance of the system
E2698 Practice for Radiological Examination Using Digital
fromthemanufacturerandatintervalsspecifiedinthispractice
Detector Arrays
to monitor long term stability of the system.The intent of these
E2736 Guide for Digital Detector Array Radiology
tests is to monitor the system performance for degradation and
3. Terminology
to identify when an action needs to be taken when the system
degrades by a certain level.
3.1 Definitions—the definition of terms relating to gamma
1.4 The use of the gages provided in this standard is andX-radiology,whichappearinTerminologyE1316,Practice
mandatory for each test. In the event these tests or gages are E2597, Guide E2736, and Practice E2698 shall apply to the
not sufficient, the user, in coordination with the cognizant terms used in this practice.
engineering organization (CEO) may develop additional or
3.2 Definitions of Terms Specific to This Standard:
modified tests, test objects, gages, or image quality indicators
3.2.1 digital detector array (DDA) system—an electronic
to evaluate the DDA system. Acceptance levels for these
device that converts ionizing or penetrating radiation into a
ALTERNATE tests shall be determined by agreement between
discrete array of analog signals which are subsequently digi-
the user, CEO and manufacturer.
tized and transferred to a computer for display as a digital
1.5 This standard does not purport to address all of the
image corresponding to the radiologic energy pattern imparted
safety concerns, if any, associated with its use. It is the
upon the input region of the device. The conversion of the
responsibility of the user of this standard to establish appro-
ionizing or penetrating radiation into an electronic signal may
priate safety and health practices and determine the applica-
transpire by first converting the ionizing or penetrating radia-
bility of regulatory limitations prior to use.
tion into visible light through the use of a scintillating material.
1 2
This practice is under the jurisdiction of ASTM Committee E07 on Nonde- For referenced ASTM standards, visit the ASTM website, www.astm.org, or
structive Testing and is the direct responsibility of Subcommittee E07.01 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Radiology (X and Gamma) Method. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved April 15, 2010. Published June 2010. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2737 − 10
These devices can range in speed from many seconds per 3.2.19 saturationgrayvalue—themaximumpossibleusable
image to many images per second, up to and in excess of gray value of the DDA after offset correction.
real-time radioscopy rates (usually 30 frames per seconds).
NOTE 1—Saturation may occur because of a saturation of the pixel
3.2.2 active DDA area—the active pixelized region of the
itself, the amplifier, or digitizer, where the DDA encounters saturation
gray values as a function of increasing exposure levels.
DDA, which is recommended by the manufacturer as usable.
3.2.20 user—the user and operating organization of the
3.2.3 signal-to-noise ratio (SNR)—quotient of mean value
DDA system.
of the intensity (signal) and standard deviation of the intensity
(noise). The SNR depends on the radiation dose and the DDA
3.2.21 customer—the company, government agency, or
system properties.
other authority responsible for the design, or end user, of the
system or component for which radiologic examination is
3.2.4 contrast-to-noise ratio (CNR)—quotient of the differ-
required, also known as the CEO. In some industries, the
ence of the signal levels between two material thicknesses, and
customer is frequently referred to as the “Prime”.
standard deviation of the intensity (noise) of the base material.
The CNR depends on the radiation dose and the DDA system
3.2.22 manufacturer—DDA system manufacturer, supplier
properties.
for the user of the DDA system.
3.2.5 contrast sensitivity—recognized contrast percentage
4. Significance and Use
of the material to examine. It depends on 1/CNR.
4.1 This practice is intended to be used by the NDT using
3.2.6 spatial resolution (SR)—the spatial resolution indi-
organization to measure the baseline performance of the DDA
cates the smallest geometrical detail, which can be resolved
and to monitor its performance throughout its service as an
using the DDA with given geometrical magnification. It is the
NDT imaging system.
half of the value of the detector unsharpness divided by the
magnification factor of the geometrical setup and is similar to
4.2 It is to be understood that the DDA has already been
the effective pixel size.
selected and purchased by the user from a manufacturer based
3.2.7 material thickness range (MTR)—the wall thickness ontheinspectionneedsathand.Thispracticeisnotintendedto
be used as an “acceptance test” of the DDA, but rather to
range within one image of a DDA, whereby the thinner wall
establish a performance baseline that will enable periodic
thickness does not saturate the DDA and at the thicker wall
performance tracking while in-service.
thickness, the signal is significantly higher than the noise.
3.2.8 frame rate—number of frames acquired per second. 4.3 Although many of the properties listed in this standard
have similar metrics to those found in Practice E2597, data
3.2.9 lag—residual signal in the DDA that occurs shortly
collection methods are not identical, and comparisons among
after detector read-out and erasure.
values acquired with each standard should not be made.
3.2.10 burn-in—change in gain of the scintillator that per-
4.4 This practice defines the tests to be performed and
sists well beyond the exposure.
required intervals. Also defined are the methods of tabulating
3.2.11 bad pixel—a pixel identified with a performance
results that DDAusers will complete following initial baselin-
outside of the specification range for a pixel of a DDA as
ing of the DDA system. These tests will also be performed
defined in Practice E2597.
periodically at the stated required intervals to evaluate the
3.2.12 five-groove wedge—a continuous wedge with five
DDA system to determine if the system remains within
long grooves on one side (see Fig. 1).
acceptable operational limits as established in this practice or
3.2.13 phantom—a part or item being used to quantify DDA
defined between user and customer (CEO).
characterization metrics.
4.5 ThereareseveralfactorsthataffectthequalityofaDDA
3.2.14 duplex plate phantom—two plates of the same mate-
image including the spatial resolution, geometrical
rial; Plate 2 has same size in x- and half the size in v- direction
unsharpness, scatter, signal to noise ratio, contrast sensitivity
of Plate 1; the thickness of Plate 1 matches the minimum
(contrast/noise ratio), image lag, and burn in.There are several
thickness of the material for inspection; the thickness of Plate
additional factors and settings (for example, integration time,
1 plus Plate 2 matches the maximum thickness of the material
detector parameters or imaging software), which affect these
for inspection (see Fig. 2).
results. Additionally, calibration techniques may also have an
3.2.15 DDA offset image—image of the DDAin the absence
impact on the quality of the image. This practice delineates
of x-rays providing the background signal of all pixels.
tests for each of the properties listed herein and establishes
standard techniques for assuring repeatability throughout the
3.2.16 DDAgain image—image obtained with no structured
lifecycle testing of the DDA.
object in the x-ray beam to calibrate pixel response in a DDA.
3.2.17 calibration—correction applied for the offset signal
5. General Testing Procedures
and the non-uniformity of response of any or all of the X-ray
5.1 The tests performed herein can be completed either by
beam, scintillator, and the read out structure.
the use of the five-groove wedge phantom (see Fig. 1) or with
3.2.18 gray value—the numeric value of a pixel in the DDA
separate IQIs on the Duplex Plate Phantom (see Fig. 2).
image. This is typically interchangeable with the term pixel
value, detector response, Analog-to-Digital unit and detector 5.2 DDA Calibration Method—Prior to testing, the DDA
signal. shall be calibrated for offset and, or gain to generate corrected
E2737 − 10
FIG. 1 5-Groove-Wedge (steel) – see Appendix
images per manufacturer’s recommendation. It is important under similar conditions as in production. Some parameters to
that the calibration procedure be completed as would be done controlarelistedbelow.Ifseveraldifferentenergiesareusedin
in production during routine calibration procedures, and that production, the complete settings with the highest energy level
these same procedures be used throughout the periodic testing shall be used for these tests.
of the DDA after it is in-service. 5.3.1 X-ray tube voltage [kV]
5.3.2 tube current [mA]
5.3 Bad Pixel Standardization for DDAs—Images collected
5.3.3 focus detector distance (FDD) [mm]
for testing shall be corrected for bad pixels as would be done
5.3.4 object detector distance (ODD) [mm]
in production during routine bad pixel correction procedures
5.3.5 total exposure time per image [ms]
per manufacturer’s recommendation wherever required. A
5.3.6 detector corrections (calibration and bad pixel substi-
standardized nomenclature is presented in Practice E2597. The
tution)
identification and correction of bad pixels in a delivered DDA
5.3.7 detector settings
remain in the purview of agreement between the user and the
system manufacturer. The various tests shall be completed
5.3.8 image acquisition software and image processing
E2737 − 10
FIG. 2 Duplex Plate Phantom with IQIs positioned; one ASTM E1025 or E1742 Penetrameter on each plate and one ASTM E2002 Duplex
Wire IQI on the thinner plate. The boxes ROI 1 to ROI 4 are for evaluation of signal level and SNR.
6. Application of Baseline Tests and Test Methods zation in terms of the specific tests to perform, how the data is
presented, and the frequency of testing.This approach does the
6.1 DDA System Baseline Performance Tests
following:
6.1.1 The user shall accept the DDA system based on
manufacturer’s results of Practice E2597 on the specific 6.1.1.1 Provides a quantitative baseline of performance,
detector as provided in a data sheet for that serialized DDAor
6.1.1.2 provides results in a defined form that can be
other agreed to acceptance test between the user and manufac-
reviewed by the CEO and
turer(notcoveredinthispractice).TheuserbaselinestheDDA
6.1.1.3 offers a means to perform process checking of
using the tests defined in Table 1. Additional tests are to be
performance on a continuing basis.
defined in agreement between the CEO and the using organi-
E2737 − 10
TABLE 1 System Performance Tests and Process Check of the DDA System
System Performance Test System Performance Test Process Check
Base Software Tube Detector Short Long Usage Duplex
Line Update Change Change/ Version Version of Plate
Unit
Parameter Repair Five-Phantom
Hole
Wedge
Spatial Resolution SR µm x xxxx xx
Contrast Sensitivity CS % x x xxxx xx
Material Thickness Range MTR mm x x xxxx xx
Signal to Noise Ratio SNR x x xxxx xx
Signal Level SL x x x x x x x
Image Lag Lag % x x x
Burn In BI % x x x x x
Offset Level OL x x x x x
BadPixelDistribution x x xxxx
6.1.2 Acceptance values, and tolerances thereof obtained performance of the system. The time interval depends on the
from these tests shall also be in agreement between the CEO degree of usage of the system and shall be defined by the user
and the using organization. with consideration of the DDA system manufacturer’s infor-
6.1.3 Acceptance levels for individual bad pixels, bad mation.Theremaybetwoversionsofthelongversionstability
clusters, relevant bad clusters, and bad lines, and their statis- tests, the complete program and a short version. The intervals
tical distribution within the DDA, as well as proximity to said for the performance checks shall not exceed ten days. The
anomalies is to be determined by agreement between the user check for bad pixel shall be done daily. Details shall be agreed
and the CEO. The user and or CEO may refer to the Guide for upon between the customer and the user.
DDAs (E2736), Practice E2597, as well as consult with the
manufacturer on how the prevalence of these anomalous pixels
7. Apparatus
might impact a specific application. This practice does not set
7.1 The tests described in Table 1 and in Section 6 require
limits, but does offer a means for tracking such anomalous
the usage of either the five-groove wedge (see Fig. 1); or the
pixels in the table templates provided herein.
Duplex Plate Phantom with separate IQIs—E2002 Duplex
6.1.4 Given that the other elements of the DDA system are
Wire and proper E1025 or E1742 penetrameters (see Fig. 2).
withintheirtolerancesincl
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.