ASTM E3168-20a

Standard Practice for Determining Low-Contrast Visual Acuity of Radiographic Interpreters

SIGNIFICANCE AND USE
4.1 This practice is used to evaluate the ability of a radiographic interpreter to discriminate low contrast slit images in a radiographic interpretation environment. A radiographic viewer, as described in Specification E1390, and a viewing environment, as described in Guide E94, are strongly recommended. The minimum acceptable test score in any given application depends on the requirements of the application. Using parties should develop and maintain records of their test results to guide the establishment of acceptable test scores for their applications. (See Note 1.)  
Note 1: During round robin testing with experienced radiographic interpreters, 76 % of the interpreters achieved a score of 85 % or higher, and 95 % achieved a score of 80 % or higher. The average score was 90.7 %, and the standard deviation was 6.7 %. In a second study from 2017, with both certified radiographers and uncertified personnel, the average and standard deviation among certified radiographers was 90.4 ± 4.0 % and among uncertified personnel was 88.4 ± 4.9 %. It was found that on each test page there are 3 or 4 images where the average score for each was less than 80 % correct and the remainder of the images all individually scored greater than 80 % on average. A limited number of the general public was examined, and the average score among these was 75.0 ± 3.3 %.  
4.2 Administration of the Test  
4.2.1 The test procedure described in this practice is intended to determine the ability of a radiographic interpreter to detect low contrast images in a low light level environment. Appropriate dark adaptation time should be permitted. A minimum of 1 min is recommended; however, longer dark adaptation times may be required by some users.  
4.2.2 The test shall be administered by or under the direction of a test administrator (see 3.2.4). The individual being tested shall not know the identification of the plate or orientation prior to the test.  
4.2.3 The interpretation of each of the ...
SCOPE
1.1 This practice details the procedure for determining the low-contrast visual acuity of a radiographic interpreter by evaluating the ability of the individual to detect linear images of varying radiographic noise, contrast, and sharpness. No statement is made regarding the applicability of these images to evaluate the competence of a radiographic interpreter. There is no correlation between these images of slit phantoms and the ability to detect cracks or other linear features in an actual radiographic examination. The test procedure follows from work performed by the National Institute of Standards and Technology presented in NBS Technical Note 1143, issued June 1981.  
1.2 The visual acuity test set consists of five individual plates, each containing a series of radiographic images of 0.5 in. (12.7 mm) long slits in thin metal shims. The original radiographs used to prepare the illustrations were generated using various absorbers, geometric parameters (unsharpness, slit widths), and source parameters (kV, mA, time) to produce images of varying noise, contrast, and sharpness. Each radiographic image has a background density of 1.8 ± 0.15. The images are viewed in a radiographic interpretation environment as used for the evaluation of production radiographic films, for example, illuminators and background lighting as described in Guide E94 and Specification E1390, and without optical magnification.  
1.3 Each visual acuity test plate consists of 25 individual image areas. The images are arranged in 5 rows and 5 columns as shown in Fig. 1. Each image area is 2 in. x 2 in. (51 mm x 51 mm). All identification is on the back side of the plate. Each plate can be viewed from any of the four orientations (that is, it can be viewed with any of the four edges “up” on the illuminator). Since there are five different plates in the set, this makes for a total of 20 different patterns that can be viewed. The identification of whi...

General Information

• Status: Published
• Publication Date: 30-Nov-2020
• ICS: 19.100 - Non-destructive testing
• Technical Committee: E07 - Nondestructive Testing
• Drafting Committee: E07.02 - Reference Radiological Images

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: E3168 − 20a
Standard Practice for
Determining Low-Contrast Visual Acuity of Radiographic
1
Interpreters
This standard is issued under the fixed designation E3168; 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* makes for a total of 20 different patterns that can be viewed.
The identification of which of the five plates and which of the
1.1 This practice details the procedure for determining the
four orientations were viewed in any given test can be
low-contrast visual acuity of a radiographic interpreter by
determined from the designation on the back side.
evaluating the ability of the individual to detect linear images
1.4 Within the image areas, the slit image may appear in any
of varying radiographic noise, contrast, and sharpness. No
statement is made regarding the applicability of these images to of five locations, that is, in any of the four corners of the image
area, or near the center. No more than one slit image will
evaluate the competence of a radiographic interpreter. There is
no correlation between these images of slit phantoms and the appear in any one image area. The slit image may be
horizontal, vertical, slant left, or slant right. Several of the
ability to detect cracks or other linear features in an actual
radiographic examination. The test procedure follows from plates include one or more image areas in which there is no slit
image.
work performed by the National Institute of Standards and
Technology presented in NBS Technical Note 1143, issued
1.5 Use of this standard requires procurement of the adjunct
June 1981.
test plates.
1.2 The visual acuity test set consists of five individual
1.6 This standard does not purport to address all of the
plates, each containing a series of radiographic images of
safety concerns, if any, associated with its use. It is the
0.5 in. (12.7 mm) long slits in thin metal shims. The original
responsibility of the user of this standard to establish appro-
radiographs used to prepare the illustrations were generated
priate safety, health, and environmental practices and deter-
using various absorbers, geometric parameters (unsharpness,
mine the applicability of regulatory limitations prior to use.
slit widths), and source parameters (kV, mA, time) to produce
1.7 This international standard was developed in accor-
images of varying noise, contrast, and sharpness. Each radio-
dance with internationally recognized principles on standard-
graphic image has a background density of 1.8 6 0.15. The
ization established in the Decision on Principles for the
images are viewed in a radiographic interpretation environment
Development of International Standards, Guides and Recom-
as used for the evaluation of production radiographic films, for
mendations issued by the World Trade Organization Technical
example, illuminators and background lighting as described in
Barriers to Trade (TBT) Committee.
Guide E94 and Specification E1390, and without optical
2. Referenced Documents
magnification.
2
2.1 ASTM Standards:
1.3 Each visual acuity test plate consists of 25 individual
E94 Guide for Radiographic Examination Using Industrial
image areas. The images are arranged in 5 rows and 5 columns
Radiographic Film
as shown in Fig. 1. Each image area is 2 in. x 2 in. (51 mm x
E1316 Terminology for Nondestructive Examinations
51 mm). All identification is on the back side of the plate. Each
E1390 Specification for Illuminators Used for Viewing In-
plate can be viewed from any of the four orientations (that is,
dustrial Radiographs
it can be viewed with any of the four edges “up” on the
3
2.2 ASTM Adjuncts:
illuminator). Since there are five different plates in the set, this
5 Visual Acuity Test Plates and Answer Key
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 E07.02 on contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Reference Radiological Images. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Dec. 1, 2020. Published January 2021. Originally the ASTM website.
3
approved in 2020. Last previous edition approved in 2020 as E3168 – 20. DOI: Available from ASTM International Headquarters. Order Reference Radio-
10.1520/E3168-20A. graph RRE3168.
*A Summary of Changes s
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E3168 − 20 E3168 − 20a
Standard Practice for
Determining Low-Contrast Visual Acuity of Radiographic
1
Interpreters
This standard is issued under the fixed designation E3168; 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 Scope*
1.1 This practice details the procedure for determining the low-contrast visual acuity of a radiographic interpreter by evaluating
the ability of the individual to detect linear images of varying radiographic noise, contrast, and sharpness. No statement is made
regarding the applicability of these images to evaluate the competence of a radiographic interpreter. There is no correlation between
these images of slit phantoms and the ability to detect cracks or other linear features in an actual radiographic examination. The
test procedure follows from work performed by the National Institute of Standards and Technology presented in NBS Technical
Note 1143, issued June 1981.
1.2 The visual acuity test set consists of five individual plates, each containing a series of radiographic images of 0.5 in. (12.7 mm)
long slits in thin metal shims. The original radiographs used to prepare the illustrations were generated using various absorbers,
geometric parameters (unsharpness, slit widths), and source parameters (kV, mA, time) to produce images of varying noise,
contrast, and sharpness. Each radiographic image has a background density of 1.8 6 0.15. The images are viewed in a radiographic
interpretation environment as used for the evaluation of production radiographic films, for example, illuminators and background
lighting as described in Guide E94 and Specification E1390, and without optical magnification.
1.3 Each visual acuity test plate consists of 25 individual image areas. The images are arranged in 5 rows and 5 columns as shown
in Fig. 1. Each image area is 2 in. x 2 in. (51 mm x 51 mm). All identification is on the back side of the plate. Each plate can be
viewed from any of the four orientations (that is, it can be viewed with any of the four edges “up” on the illuminator). Since there
are five different plates in the set, this makes for a total of 20 different patterns that can be viewed. The identification of which
of the five plates and which of the four orientations were viewed in any given test can be determined from the designation on the
back side.
1.4 Within the image areas, the slit image may appear in any of five locations, that is, in any of the four corners of the image area,
or near the center. No more than one slit image will appear in any one image area. The slit image may be horizontal, vertical, slant
left, or slant right. Several of the plates include one or more image areas in which there is no slit image.
1.5 Use of this standard requires procurement of the adjunct test plates.
1.6 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
This practice is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.02 on Reference
Radiological Images.
Current edition approved Feb. 1, 2020Dec. 1, 2020. Published March 2020January 2021. Originally approved in 2020. Last previous edition approved in 2020 as
E3168 – 20. DOI: 10.1520/3168-20.10.1520/E3168-20A.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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E3168 − 20a
FIG. 1 Layout of Visual Acuity Test Plate
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E3168 − 20a
1.7 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.
2. Referenced Documents
2
2.1 ASTM Standards:
E94 Guide for Radiographic Examination Using Industrial Radiographic Film
E1316 Terminology
...