ASTM E3388-23

Standard Practice for Determining Image Unsharpness and Basic Spatial Resolution in Radiography and Radioscopy for High Energy Applications

SIGNIFICANCE AND USE
5.1 The gauge is intended to provide a means for measuring image or detector unsharpness and basic spatial image or detector resolution as independently as practicable from the imaging system and contrast sensitivity limitations. When the duplex plate gauge is positioned directly on the film or the digital detector instead on the test object, then the determined image unsharpness UIm corresponds to the inherent film or detector unsharpness (Udetector) and the determined basic spatial image resolution SRbimage corresponds to the basic spatial detector resolution SRbdetector. SRbimage provides a value which depends on the combined effect of detector unsharpness and geometric unsharpness.  
5.2 Basis of Application:  
5.2.1 The following items are subject to contractual agreement between the parties using or referencing this standard.
5.2.1.1 Personnel Qualification—Personnel performing examinations to this practice shall be qualified in accordance with NAS410, EN 4179, ANSI/ASNT CP 189, ISO 9712, or SNT-TC-1A and certified by the employer or certifying agency as applicable. Other equivalent qualification documents may be used when specified on the contract or purchase order. The applicable revision shall be the latest unless otherwise specified in the contractual agreement between parties.
5.2.1.2 If specified in the contractual agreement, NDT agencies shall be qualified and evaluated as described in Specification E543. The applicable edition of Specification E543 shall be specified in the contract.
SCOPE
1.1 This practice covers the design and basic use of a gauge used to determine the image unsharpness and the basic spatial resolution of film radiographs or of digital images taken with CR imaging plates, digital detector arrays (DDA), or radioscopic systems (for example, with X-ray image intensifiers) for applications with Se-75, Ir-192, Co-60 and high energy sources with tube potentials ≥ 300 kV. The IQI may be used at lower tube potentials too, if the expected unsharpness is > 200 µm (SRbimage or SRbdetector > 100 µm). For the measurement of lower unsharpness values, the usage of the gauge described in Practice E2002 is recommended.  
1.2 This practice is applicable to radiographic and radioscopic imaging systems utilizing X-ray and gamma ray radiation sources.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 The gauge described can be used effectively if the duplex wire IQI of Practice E2002 does not provide sufficient contrast resolution.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 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: 14-Jun-2023
• ICS: 19.100 - Non-destructive testing
• Technical Committee: E07 - Nondestructive Testing
• Drafting Committee: E07.01 - Radiography (X and Gamma) Method

Relations

• Refers: ASTM E1316-24 - Standard Terminology for <?Pub Dtl?>Nondestructive Examinations
• Effective Date: 01-Feb-2024
• Refers: ASTM E1316-19b - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2019
• Refers: ASTM E1316-19 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Mar-2019
• Refers: ASTM E1025-18 - Standard Practice for Design, Manufacture, and Material Grouping Classification of Hole-Type Image Quality Indicators (IQI) Used for Radiography
• Effective Date: 01-Feb-2018
• Refers: ASTM E1316-18 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jan-2018
• Refers: ASTM E1316-17a - Standard Terminology for Nondestructive Examinations
• Effective Date: 15-Jun-2017
• Refers: ASTM E1316-17 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Feb-2017
• Refers: ASTM E1316-16a - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Aug-2016
• Refers: ASTM E1316-16 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Feb-2016
• Refers: ASTM E1316-15a - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2015
• Refers: ASTM E1316-15 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Sep-2015
• Refers: ASTM E1316-14 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jun-2014
• Refers: ASTM E1316-14e1 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jun-2014
• Refers: ASTM E1316-13d - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2013
• Refers: ASTM E1316-13c - Standard Terminology for Nondestructive Examinations
• Effective Date: 15-Jun-2013

Overview

ASTM E3388-23: Standard Practice for Determining Image Unsharpness and Basic Spatial Resolution in Radiography and Radioscopy for High Energy Applications sets out procedures for evaluating image quality in non-destructive testing (NDT) using high energy X-ray and gamma ray sources. Developed by ASTM, this standard describes the use of a duplex plate gauge to independently measure image unsharpness and basic spatial resolution, providing essential data for maintaining the performance of radiographic and radioscopic imaging systems. This practice is critical where high energy sources such as Se-75, Ir-192, Co-60, or tube potentials ≥ 300 kV are involved, and supports both film-based and digital detector radiography.

Key Topics

• Image Unsharpness and Spatial Resolution
  The standard distinguishes between image unsharpness (U) and basic spatial resolution (SR), offering a way to assess each independently of contrast sensitivity. This separation allows for a more detailed evaluation of imaging system performance.
• Duplex Plate Gauge (IQI) Use
  Guidelines are detailed for using a duplex plate-type image quality indicator (IQI) on film, digital detectors, or within radioscopic systems, including positioning, evaluation methods, and result documentation.
• Personnel Qualification
  Practitioners must be qualified and certified according to recognized international NDT standards such as NAS410, EN 4179, ANSI/ASNT CP 189, ISO 9712, or SNT-TC-1A to ensure reliable results.
• Contrast Sensitivity Independence
  The practice recommends scenarios where this method is more effective than conventional IQIs, particularly where measurement of unsharpness below 200 µm is not required.

Applications

ASTM E3388-23 is vital for industries utilizing high energy radiography and radioscopy, especially where accurate assessment of imaging system performance is critical, such as:

• Industrial Non-Destructive Testing (NDT)
  Used for testing welds, castings, and structural components where image clarity and resolution are required for defect detection.
• Imaging System Qualification and Monitoring
  Enables baseline and ongoing performance checks of both film and digital X-ray or gamma ray imaging equipment.
• Digital Detector Assessments
  Assists in evaluating detector unsharpness and basic spatial resolution for digital detector arrays (DDA) and computed radiography (CR).
• Comparative Reference Exposures
  Supports establishing reference images to detect system degradation over time, ensuring ongoing image quality.
• Film System and Radioscopic Validation
  Useful when the duplex wire IQI is inadequate for resolution measurement, especially in high energy applications or where contrast sensitivity is not the sole limiting factor.

Related Standards

The following standards are referenced or related to ASTM E3388-23 for a comprehensive approach to image quality assessment:

• ASTM E2002 - Practice for Determining Image Unsharpness and Basic Spatial Resolution in Radiography and Radioscopy (for finer unsharpness measurements)
• ASTM E747 - Practice for Wire Image Quality Indicators (IQI) for Radiology
• ASTM E1025 - Practice for Hole-Type Image Quality Indicators (IQI)
• ASTM E543 - Specification for Agencies Performing Nondestructive Testing
• ASTM E1316 - Terminology for Nondestructive Examinations
• ISO 19232-5 - Non-destructive Testing: Image Quality of Radiographs - Duplex Wire IQI
• ISO 9712 - Qualification and Certification of NDT Personnel
• NAS410, EN 4179, ANSI/ASNT CP 189, SNT-TC-1A - Personnel Qualification and Certification

Practical Value

Applying ASTM E3388-23 ensures that image unsharpness and spatial resolution are quantified accurately and reproducibly, helping users:

• Maintain high standards in radiographic image quality
• Detect system degradation early through quantitative assessment
• Meet contractual and regulatory requirements in NDT projects
• Make informed decisions about system maintenance and upgrades

By following this standard, practitioners ensure effective quality assurance in high energy radiography and radioscopy, supporting safety, reliability, and regulatory compliance across industries such as aerospace, petrochemical, and power generation.

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: E3388 − 23
Standard Practice for
Determining Image Unsharpness and Basic Spatial
Resolution in Radiography and Radioscopy for High Energy
Applications
This standard is issued under the fixed designation E3388; 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
2.1 ASTM Standards:
1.1 This practice covers the design and basic use of a gauge
E543 Specification for Agencies Performing Nondestructive
used to determine the image unsharpness and the basic spatial
Testing
resolution of film radiographs or of digital images taken with
E747 Practice for Design, Manufacture and Material Group-
CR imaging plates, digital detector arrays (DDA), or radio-
ing Classification of Wire Image Quality Indicators (IQI)
scopic systems (for example, with X-ray image intensifiers) for
Used for Radiology
applications with Se-75, Ir-192, Co-60 and high energy sources
E1025 Practice for Design, Manufacture, and Material
with tube potentials ≥ 300 kV. The IQI may be used at lower
Grouping Classification of Hole-Type Image Quality In-
tube potentials too, if the expected unsharpness is > 200 μm
image detector dicators (IQI) Used for Radiography
(SR or SR > 100 μm). For the measurement of
b b
E1316 Terminology for Nondestructive Examinations
lower unsharpness values, the usage of the gauge described in
E1815 Test Method for Classification of Film Systems for
Practice E2002 is recommended.
Industrial Radiography
1.2 This practice is applicable to radiographic and radio-
E2002 Practice for Determining Image Unsharpness and
scopic imaging systems utilizing X-ray and gamma ray radia-
Basic Spatial Resolution in Radiography and Radioscopy
tion sources.
2.2 AIA/NAS Standard:
NAS410 NAS Certification & Qualification of Nondestruc-
1.3 The values stated in SI units are to be regarded as
tive Test Personnel
standard. No other units of measurement are included in this
2.3 ASNT Standards:
standard.
ANSI/ASNT CP-189 ASNT Standard for Qualification and
1.4 The gauge described can be used effectively if the
Certification of Nondestructive Testing Personnel
duplex wire IQI of Practice E2002 does not provide sufficient SNT-TC-1A Personnel Qualification and Certification in
contrast resolution.
Nondestructive Testing
2.4 CEN Standards:
1.5 This standard does not purport to address all of the
EN 462-5:1996 Non-destructive testing – Image quality of
safety concerns, if any, associated with its use. It is the
radiographs – Part 5: Image quality indicators (duplex
responsibility of the user of this standard to establish appro-
plate type), determination of image unsharpness value, not
priate safety, health, and environmental practices and deter-
an active standard, but still used as a reference in
mine the applicability of regulatory limitations prior to use.
companies’ procedures.
1.6 This international standard was developed in accor- 3
2.5 ISO Standards:
dance with internationally recognized principles on standard-
ISO 9712 Non-destructive testing – Qualification and certi-
ization established in the Decision on Principles for the
fication of NDT personnel
Development of International Standards, Guides and Recom-
ISO/IEC 17050-1 Conformity assessment – Supplier’s dec-
mendations issued by the World Trade Organization Technical
laration of conformity – Part 1: General requirements
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
This practice is under the jurisdiction of ASTM Committee E07 on Nonde- Standards volume information, refer to the standard’s Document Summary page on
structive Testing and is the direct responsibility of Subcommittee E07.01 on the ASTM website.
Radiology (X and Gamma) Method. Available from International Organization for Standardization, ISO Central
Current edition approved June 15, 2023. Published August 2023. DOI: 10.1520/ Secretariat, 1, ch. de la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland,
E3388-23. http://www.iso.org/iso/home/store.html.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E3388 − 23
ISO 19232-5 Non-destructive testing – Image quality of 3.2.6 image unsharpness – interpolated (iU ), n—two
Im
radiographs – Part 5: Determination of the image unsharp- times the Basic Spatial Image Resolution – interpolated (2 ×
image
ness value using duplex wire-type image quality indica-
iSR )
b
tors
3.2.7 image unsharpness – visual (vU ), n—two times the
Im
detector
Basic Spatial Image Resolution – visual (2 × vSR )
b
3. Terminology
3.2.8 linearized profile, n—a graph, generated by an image
3.1 Definitions of terms applicable to this practice may be
processing software, which shows the pixel values, which are
found in Terminology E1316.
proportional to the radiation dose vs. a spatial position as, for
3.2 Definitions of Terms Specific to This Standard:
example, duplex plate IQI length.
detector
3.2.1 basic spatial detector resolution – visual (vSR ),
b
n—determined with the duplex wire IQI directly on the 3.2.9 linepair per mm (lp/mm) value, n—determined from
the duplex plate pair values, and corresponds to 1/U (IQI on
detector with no object from the smallest number of the duplex
Im
plate pair, which is visually not separable in a film radiograph the object, beside the object or separately in the imaging plane)
on a viewing station or on a monitor image for non-film or 1/U (IQI on the detector).
detector
applications.
3.2.9.1 Discussion—The corresponding values are given in
image
Table 1.
3.2.2 basic spatial image resolution – visual (vSR ),
b
n—determined with the IQI on the object (side closest to X-ray
source), beside the object or separately in the imaging plane
4. Summary of Practice
from the smallest number of the duplex plate pair, which is
4.1 When it is determined necessary to evaluate and mea-
visually not separable in a film radiograph on a viewing station
sure the image or detector unsharpness or the basic spatial
or on a monitor image for non-film applications considering the
resolution of an imaging system or a detector separately and
magnification.
apart from contrast sensitivity measurements, a tool or gauge
3.2.3 detector unsharpness – interpolated (iU ),
detector
as described in this practice can be used. Conventional IQIs as
n—two times the Basic Spatial Image Resolution – interpolated
described in Practices E747 and E1025 combine the contrast
detector
(2 × iSR )
b
sensitivity and resolution measurements into an overall figure
3.2.4 detector unsharpness – visual (vU ), n—two
of merit. Such figures of merit may not be adequate to detect
detector
times Basic Spatial Detector Resolution – visual
subtle changes in the imaging system’s performance. For
detector
(2 × vSR )
b example, in a high-contrast image, unsharpness can increase
with almost no noticeable effect upon the overall image
3.2.5 duplex plate type image quality indicator, n—duplex
plate type IQI image quality indicator specifically designed to contrast, but the contrast sensitivity for fine details will be
reduced. Similarly, in an application in which the imaging
assess the image unsharpness and basic spatial image resolu-
tion of a radiograph or a digital image and composed of a series system provides a very sharp image, contrast can fade with
of pairs of plate elements made of high density metal. little noticeable effect upon the overall image contrast. These
TABLE 1 Duplex Plate Number, Corresponding Image Unsharpness, Basic Spatial Resolution, Linepair Readings and Plate Widths and
A
Spacings and its Tolerances
NOTE 1—All unsharpness values are rounded to two digits after the dot. For conversion of the SR -values to μm, multiply values which are given in
b
mm by 1000.
image detector
NOTE 2—If the IQI is located on the detector without object, the determined SR value is identical with the SR value and the image
b b
unsharpness U corresponds to the inherent detector unsharpness U .
Im detector
Corresponding
Corresponding Basic Spatial Reso- Tolerance of Plate
Duplex Plate Corresponding line- Plate Width and
Plate Material Unsharpness value lution Width and Plate
Number pair value (lp/mm) Spacing, d (mm)
image
U (mm) SR value Spacing (mm)
Im b
C
(mm)
B
W DP 10 0.20 0.100 5.00 0.10 ±8 %
W DP 9 0.26 0.130 3.85 0.13
W DP 8 0.32 0.160 3.13 0.16
W DP 7 0.40 0.200 2.50 0.20
W DP 6 0.50 0.250 2.00 0.25 ±7 %
W DP 5 0.64 0.320 1.56 0.32
W DP 4 0.80 0.400 1.25 0.40
W DP 3 1.00 0.500 1.00 0.50
W DP 2 1.26 0.630 0.79 0.63 ±6 %
W DP 1 1.60 0.800 0.63 0.80
A
This table is based on data provided by ISO 19232-5:2013. All unsharpness values are rounded to two digits after the dot.
B
W = Tungsten.
C
For conversion of the SR -values to μm, multiply values which are given in mm by 1000.
b
E3388 − 23
situations often develop and may go undetected until the 7. Application
system performance deteriorates below acceptable image qual-
7.1 A radiograph shall be made or an image displayed on a
ity limits.
monitor with the duplex plate placed on the source side of the
item being examined. The gauge may be placed beside the
5. Significance and Use
object, or separately in the imaging plane. The duplex plate IQI
5.1 The gauge is intended to provide a means for measuring
should be aligned, as closely as possible, normal to the axis of
image or detector unsharpness and basic spatial image or
the radiation beam. The radiation shall be directed along the
detector resolution as independently as practicable from the
gap between the plate pairs. The angle between the direction of
imaging system and contrast sensitivity limitations. When the
the radiation and the gap of interest shall be ≤ 2.5°.
duplex plate gauge is positioned directly on the film or the
NOTE 1—If the IQI is placed directly on the detector, the inherent
digital detector instead on the test object, then the determined
detector unsharpness U and the basic spatial detector resolution
detector
image unsharpness U corresponds to the inherent film or
detector
Im
SR are measured.
b
detector unsharpness (U ) and the determined basic spa-
detector
image
7.2 The evaluation of the duplex plate pair images is based
tial image resolution SR corresponds to the basic spatial
b
detector image
on a visual evaluation by an operator of films on a viewing
detector resolution SR . SR provides a value which
b b
station or images on a monitor or by measurement with a
depends on the combined effect of detector unsharpness and
profile function if digital images are available. The image
geometric unsharpness.
unsharpness U or detector unsharpness U is given by
Im detector
5.2 Basis of Application:
2d, where d is the corresponding width of the duplex plates and
5.2.1 The following items are subject to contractual agree-
is also the plate spacing distance (see Fig. 1). The value of d is
ment between the parties using or referencing this standard.
considered as the basic spatial resolution of the image or
5.2.1.1 Personnel Qualification—Personnel performing ex-
detector, depending on the IQI location (this means: IQI on the
aminations to this practice shall be qualified in accordance with
object, beside the object, separately in the imaging plane or on
NAS410, EN 4179, ANSI/ASNT CP 189, ISO 9712, or
the detector). The term 1/(2d) is considered as linepair/mm
SNT-TC-1A and certified by the employer or certifying agency
value.
as applicable. Other equivalent qualification documents may be
used when specified on the contract or purchase order. The NOTE 2—It is recommended to use the duplex plate IQI always with a
shim, close to the source or in front or behind the IQI, to avoid that
applicable revision shall be the latest unless otherwise specified
unfiltered radiation exposes the detector, because the X-ray spectrum
in the contractual agreement between parties.
changes significantly depending on the thickness and material of the
5.2.1.2 If specified in the contractual agreement, NDT
object and shim, which can influence the result of the measurement.
agencies
...