ASTM E2445-05(2010)
(Practice)Standard Practice for Qualification and Long-Term Stability of Computed Radiology Systems
Standard Practice for Qualification and Long-Term Stability of Computed Radiology Systems
SIGNIFICANCE AND USE
There are several factors affecting the quality of a CR image including the spatial resolution of the IP system, geometrical unsharpness, scatter and contrast sensitivity (signal/noise ratio). There are several additional factors (for example, scanning parameters), which affect the accurate reading of images on exposed IPs using an optical scanner.
The quality factors can be determined most accurately by the CR equipment manufacturer tests as described in Practice E2446. Individual test targets, which are recommended for practical user tests, are described for quality assurance. These tests can be carried out either separately or by the use of the CR phantom (Appendix X1). This CR phantom incorporates many of the basic quality assessment methods and those associated with the correct functioning of a CR system, including the scanner, for reading exposed plates and incorrectly erasing IPs for future use of each plate.
This practice is for users of industrial CR systems. This practice defines the tests to be performed, by users of CR systems, periodically to evaluate the CR systems to prove proper performance over the life-cycle of the system.
Application of Various Tests and Test Methods
Tests after Repair, Upgrade or the Use of Another IP Type:
Since modifications, such as repair or upgrade of the CR scanner and improved IP may improve the functionality of the system, specialized tests are required to prove the proper performance of the CR system.
User Tests for Long-term Stability—Quality assurance in test laboratories requires periodical tests of the CR system to prove the proper performance of the system. The time interval depends on the degree of usage of the system and shall be defined by the user and consideration of the CR equipment manufacturer’s information.
The tests described in 6.2.1 through 6.2.6 require usage of quality indicators of 5.1 or the CR test phantom shall be used regularly at user-defined intervals to test the basic performan...
SCOPE
1.1 This practice specifies the fundamental parameters of computed radiography systems to assure satisfactory and repeatable results for nondestructive testing.
1.2 This practice describes the evaluation of Computed Radiology (CR) systems for industrial radiography. It is intended to ensure that the evaluation of image quality, as far as this is influenced by the scanner/IP system, meets the needs of users and enables the test of long-term stability.
1.3 Each of the tests described may be performed with individual gages specified. The user shall decide which tests shall be used for system control using individual test objects or the CR test phantom (Appendix X1). The computed radiological tests, specified as “user tests” in this practice, may be utilized at appropriate intervals determined by the user, based on the application of the examination operations. The tests shall be appropriate for the materials and range of use of the system. Fading, uniformity, and erasure tests shall also be part of the control system. All other tests for qualification and capability are to be performed and certified by the CR equipment manufacturer.
1.4 The values stated in SI units are to be regarded as the standard. Values in inch-pound units are for information purposes.
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:E2445 −05(Reapproved 2010)
Standard Practice for
Qualification and Long-Term Stability of Computed
Radiology Systems
This standard is issued under the fixed designation E2445; 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 2. Referenced Documents
1.1 This practice specifies the fundamental parameters of 2.1 ASTM Standards:
computed radiography systems to assure satisfactory and E1316Terminology for Nondestructive Examinations
repeatable results for nondestructive testing. E1647Practice for Determining Contrast Sensitivity in Ra-
diology
1.2 This practice describes the evaluation of Computed
E2002Practice for DeterminingTotal Image Unsharpness in
Radiology (CR) systems for industrial radiography. It is
Radiology
intended to ensure that the evaluation of image quality, as far
E2007Guide for Computed Radiography
as this is influenced by the scanner/IPsystem, meets the needs
E2033Practice for Computed Radiology (Photostimulable
of users and enables the test of long-term stability.
Luminescence Method)
1.3 Each of the tests described may be performed with
E2446Practice for Classification of Computed Radiology
individual gages specified. The user shall decide which tests
Systems
shallbeusedforsystemcontrolusingindividualtestobjectsor
the CR test phantom (Appendix X1). The computed radio-
3. Terminology
logical tests, specified as “user tests” in this practice, may be
3.1 Definitions—The definition of terms relating to gamma-
utilized at appropriate intervals determined by the user, based
and X-radiology, which appear in Terminology E1316, Guide
on the application of the examination operations. The tests
E2007,andPracticeE2033shallapplytothetermsusedinthis
shall be appropriate for the materials and range of use of the
practice.
system. Fading, uniformity, and erasure tests shall also be part
of the control system. All other tests for qualification and 3.2 Definitions of Terms Specific to This Standard:
capability are to be performed and certified by the CR 3.2.1 aliasing—pre-sampled high spatial frequency signals
equipment manufacturer.
beyond the Nyquist frequency (given by the pixel distance)
reflected back into the image at lower spatial frequencies.
1.4 The values stated in SI units are to be regarded as the
3.2.2 computed radiology system (CR system)—a complete
standard. Values in inch-pound units are for information
purposes. system of a storage phosphor imaging plate (IP) and corre-
sponding read out unit (scanner or reader), which converts the
1.5 This standard does not purport to address all of the
information of the IP into a digital image (see also Guide
safety concerns, if any, associated with its use. It is the
E2007).
responsibility of the user of this standard to establish appro-
3.2.3 computed radiology system class—a particular group
priate safety and health practices and determine the applica-
of storage phosphor imaging plate systems, which is charac-
bility of regulatory limitations prior to use.
terized by a SNR (Signal-to-Noise Ratio) range shown in
Table1 and by a certain unsharpness range (for example,
MTF -value) in a specified exposure range.
This practice is under the jurisdiction of ASTM Committee E07 on Nonde-
structive Testing and is the direct responsibility of Subcommittee E07.01 on
3.2.4 CR phantom—a device containing an arrangement of
Radiology (X and Gamma) Method.
test targets to evaluate the quality of a CR system, as well as
Current edition approved June 1, 2010. Published November 2010. Originally
monitoring the quality of the chosen system.
approved in 2005. Last previous edition approved in 2005 as E2445 - 05.
DOI:10.1520/E2445–05R10.
The sole source of supply of the apparatus known to the committee at this time
is Nuclear Associates, A Division of Cardinal Health, 120 Andrews Road,
Hicksville, NY 11801, Phone: 1-888-466-8257, Catalog Number: 07-605-2435. If For referenced ASTM standards, visit the ASTM website, www.astm.org, or
you are aware of alternative suppliers, please provide this information to ASTM contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
International Headquarters. Your comments will receive careful consideration at a Standards volume information, refer to the standard’s Document Summary page on
meeting of the responsible technical committee, which you may attend. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2445−05 (2010)
3.2.5 gain/amplification—opto-electrical gain setting of the shall be defined by the user and consideration of the CR
scanning system. equipment manufacturer’s information.
4.4.1.2 The tests described in 6.2.1 through 6.2.6 require
3.2.6 ISO speed S —defines the speed of a CR system and
IPx
usage of quality indicators of 5.1 or the CR test phantom shall
iscalculatedfromthereciprocaldosevalue,measuredinGray,
be used regularly at user-defined intervals to test the basic
whichisnecessarytoobtainaspecifiedminimumSNRofaCR
performance. The documentation shall contain:
system.
(1)Spatial resolution (by duplex-wire method, optional
3.2.7 laser beam jitter—a lack of smooth movement of the
converging line pairs),
imaging plate/laser scanning device, which results in lines of
(2)Contrast (recognized contrast percentage of the mate-
the image, which consist of a series of steps.
rial to examine),
3.2.8 linearized signal intensity—a numerical signal value
(3)Slipping (yes/no),
of a picture element (pixel) of the digital image, which is
(4)Jitter (yes/no),
proportional to the radiation dose. The linearized signal inten-
(5)Shading (percentage at selected distance),
sity is zero, if the radiation dose is zero.
(6)Radiation parameters of the performed tests, and
(7)Date and operator name.
3.2.9 long-term stability—performance measurements of a
4.4.1.3 Fadingtestsshouldbeperformedonlyifthescanner
CR system over the life-cycle of the devices, used to evaluate
or IP-brand is changed without data from the CR equipment
relative system performance over time.
manufacturer, or the system is used under extreme (beyond
3.2.10 scanner slippage—the slipping of an IP in a scanner
manufacturer’s recommendation) temperature conditions. The
transport system resulting in fluctuation of intensity of hori-
fadingshouldbelessthan50%intheexpectedperiodbetween
zontal image lines.
exposure and scan.
3.2.11 signal-to-noise ratio (SNR)—quotient of mean value
4.4.1.4 The IPs shall be checked for artifacts (6.2.7) and
of the linearized signal intensity and standard deviation of the
proper erasure (6.2.6).
noise (intensity distribution) at this signal intensity. The SNR
4.4.1.5 Degradation of IPs or photo multipliers in the
depends on the radiation dose and the CR system properties.
scanner may reduce the system sensitivity after extensive
usage. For this reason, the SNR should be measured at longer
4. Significance and Use
intervals (for example, annual period) by the user or service
4.1 There are several factors affecting the quality of a CR
personnel. The SNR shall not be less than 90% of the original
image including the spatial resolution of the IP system, value.The increase of the SNR can be accepted without limits,
geometrical unsharpness, scatter and contrast sensitivity
if the system unsharpness is not increased.
(signal/noise ratio). There are several additional factors (for
example, scanning parameters), which affect the accurate
5. Apparatus—CR Quality Indicators
reading of images on exposed IPs using an optical scanner.
5.1 Description of CR Quality Indicators for User Tests—
4.2 The quality factors can be determined most accurately
The following is a description of CR quality indicators, which
by the CR equipment manufacturer tests as described in
will be identified by reference to this practice.
Practice E2446. Individual test targets, which are recom-
5.1.1 Contrast Sensitivity Quality Indicator:
mended for practical user tests, are described for quality
5.1.1.1 The description of the contrast sensitivity target
assurance.Thesetestscanbecarriedouteitherseparatelyorby
correspondstoPracticeE1647.Forusewiththispractice,three
the use of the CR phantom (Appendix X1). This CR phantom
targets are made from aluminum (Material Group 02), copper
incorporatesmanyofthebasicqualityassessmentmethodsand
(Material Group 4) and stainless steel (Material Group 1). The
those associated with the correct functioning of a CR system,
target thickness is 12.5 mm (0.50 in.) aluminum, 6.3 mm (0.25
including the scanner, for reading exposed plates and incor-
in.) copper and stainless steel. Each target contains a contrast
rectly erasing IPs for future use of each plate.
area for 1, 2, 3, and 4% wall-thickness contrast sensitivity.
4.3 This practice is for users of industrial CR systems. This
5.1.2 Duplex Wire Quality Indicator:
practice defines the tests to be performed, by users of CR
5.1.2.1 The description of the duplex wire quality indicator
systems, periodically to evaluate the CR systems to prove
corresponds to Practice E2002. The gage shall be oriented at a
proper performance over the life-cycle of the system.
5° angle to the direction of the scanned lines (fast-scan
direction) or the perpendicular direction (slow-scan-direction).
4.4 Application of Various Tests and Test Methods
5.1.3 Converging Line Pair Quality Indicator:
4.4.1 Tests after Repair, Upgrade or the Use of Another IP
5.1.3.1 The target consists of five converging strips of lead
Type: Since modifications, such as repair or upgrade of the CR
scanner and improved IPmay improve the functionality of the (0.03mm(0.001in.)thickness),whichcanbeusedforaspatial
resolutiontestbyreadingthelimitofrecognizablelinepairs.It
system, specialized tests are required to prove the proper
performance of the CR system. shall cover a range from 1.5 to 20 line pairs per mm (lp/mm).
Two quality indicators shall be used, one in parallel with the
4.4.1.1 User Tests for Long-term Stability—Quality assur-
scanned lines and the other one oriented in the perpendicular
ance in test laboratories requires periodical tests of the CR
direction.
system to prove the proper performance of the system. The
time interval depends on the degree of usage of the system and 5.1.4 Linearity Quality Indicators:
E2445−05 (2010)
5.1.4.1 Rulers of high-absorbing materials are located on as the radiation energy (keV, gamma-source type), dose (for
theperimeterofthescannedrange.Twoqualityindicatorsshall example, in mAs) and quality (prefilters, tube type and tube
be used, one parallel with the scanned lines and the other one window).
oriented in the perpendicular direction. The scaling should be
NOTE 1—High exposure time and low gain settings yield high contrast
at least in mm or tenths of inches.
resolution and SNR. Furthermore, the contrast sensitivity is higher for
largepixelsizesettings(highunsharpness)thanforsmallpixelsizesetting
5.1.5 T-target:
(low unsharpness).
5.1.5.1 This CR quality indicator consists of a thin plate of
5.2.2 Initial Assessment of CR Quality Indicators:
brassorcopper(≤0.5mm(≤0.02in.)thick)withsharpedges.
5.2.2.1 For initial quality assessment, examine the radio-
This plate is manufactured in a T-shape with 0.5 mm (0.2 in.)
graphic image(s) of the CR phantom or the separated quality
wide segments. The T should have a size of at least 50 by 70
indicators on the monitor (or hard copy) for the features
mm(2by2 ⁄4in.).Itshallbealignedperpendicularandparallel
described in 5.1.1 to 5.1.8 and 6.2.1 to 6.2.8. The results can
to the direction of the scanned lines and is used to check for
provide the basis of agreement between contracting parties.
laser jitter and may be used to measure a modulation transfer
function of the complete system (see Fig. X1.1).
5.3 Periodical Control:
5.1.6 Scanner Slipping Quality Indicator:
5.3.1 The CR quality indicators of 5.1.1 through 5.1.7
(alignment by 5.1.8) or the CR phantom shall be exposed and
5.1.6.1 The quality indicator consists of a homogeneous
the results examined at any interval agreed between the
strip of aluminum 0.5 mm (0.02 in.) in thickness. The quality
contracting parties. For periodical control, ensure that the
indicator has the shape of a rectangle (see Fig. X1.1) and shall
agreed quality values of the tests 6.1.3 and 6.2.1 to 6.2.8 are
be aligned perpendicular and parallel to the direction of the
achieved.
scanned lines.
5.1.7 Shading Quality Indicator: 5.4 Imaging Plate Fading:
5.4.1 The intensity of the stored image in the imaging plate
5.1.7.1 Different shading quality indicators may be used.
will decrease over time (called “fading”). The measurement of
Onetypeisbasedonthehomogeneousexposureofanimaging
fadingcharacteristicshallbedonebyperformingthefollowing
plate (IP) with a thinAl-plate 0.5 to 1.0 mm (0.06 to 0.04 in.)
steps:
above the IP. The exposure shall be made with low-energy
5.4.1.1 Expose a plate homogeneously using typical expo-
radiation (50 to 100 keV).
sure conditions. For documentation, the following parameters
5.1.7.2 Another type is the shading quality indicator of the
shall be recorded: kV, mAs, SDD, pre-filter and plate material,
CR test phantom (see X1.1).
and thickness. The exposed image shall have an intensity
5.1.8 Central Beam Alignment Quality Indicator (BAM-
between70and90%ofthemaximumpossibleintensityofthe
snail):
CR reader at lowest gain and under linearized condition.
5.1.8.1 Thealignmentqualityindicatorconsistsofaroll1.5
5.4.1.2 Readout the imaging plate five minutes after expo-
to 2.0 mm high (0.06 to 0.08 in.) of thin lead foil separated by
sure.
aspacerof0.1to0.2mm(0.004to0.008in.)oflow-absorbing
5.4.1.3 Set the linearized read-out intensity of this measure-
material (see X1.2).
ment as reference (=100%).
5.4.1.4 Always expose the imaging plate with the same
5.2 Application Procedures for CR Quality Indicators—The
X-ray parameters (kV, mAs, and distance).
CR quality indicators provide an evaluation of the quality of a
CR system as well as for a periodical quality control.Arrange- 5.4.1.5 Change the time between exposure and read-out.
The time interval between exposure and readout will be
ment of the CR quality indicators shall be in accordance with
this practice, or as specified by the cognizant engineering doubled for every measurement; steps are 15 min, 30 min, 1 h,
2 h, 4 h, and so forth, up to 4 days or as needed to match
organization.
application requirement for read-out.
5.2.1 Exposure of CR Quality Indicators (User Test
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.