ASTM E1000-16

Standard Guide for Radioscopy

SIGNIFICANCE AND USE
4.1 Radioscopy is a versatile nondestructive means for examining an object. It provides immediate information regarding the nature, size, location, and distribution of imperfections, both internal and external. It also provides a rapid check of the dimensions, mechanical configuration, and the presence and positioning of components in a mechanism. It indicates in real-time the presence of structural or component imperfections anywhere in a mechanism or an assembly. Through manipulation, it may provide three-dimensional information regarding the nature, sizes, and relative positioning of items of interest within an object, and can be further employed to check the functioning of internal mechanisms. Radioscopy permits timely assessments of product integrity, and allows prompt disposition of the product based on acceptance standards. Although closely related to the radiographic method, it has much lower operating costs in terms of time, manpower, and material.  
4.2 Long-term records of the radioscopic image may be obtained through motion-picture recording (cinefluorography), video recording, or “still” photographs using conventional cameras, or direct digital streaming and storage of image stacks to internal or external hard drives, or directly to RAM locations, if sufficient RAM is present in the computer. The radioscopic image may be electronically enhanced, digitized, or otherwise processed for improved visual image analysis or automatic, computer-aided analysis, or both.  
4.3 Computer systems enable image or frame averaging for noise reduction. For some applications image integration or averaging is required to get the required image quality. As an add-on, an automatic defect recognition system (ADR) may be used with the radioscopic image.  
4.4 Personnel Qualification—Personnel performing examinations to this standard shall be qualified in accordance with a nationally or internationally recognized NDT personnel qualification practice or standard such as ANSI/...
SCOPE
1.1 This guide is for tutorial purposes only and to outline the general principles of radioscopic imaging.  
1.2 This guide describes practices and image quality measuring systems for real-time, and near real-time, nonfilm detection, display, and recording of radioscopic images. These images, used in materials examination, are generated by penetrating radiation passing through the subject material and producing an image on the detecting medium. Although the described radiation sources are specifically X-ray and gamma-ray, the general concepts can be used for other radiation sources such as neutrons. The image detection and display techniques are nonfilm, but the use of photographic film as a means for permanent recording of the image is not precluded.  
Note 1: For information purposes, refer to Terminology E1316.  
1.3 This guide summarizes the state of radioscopic technology prior to the advent of Digital Detector Arrays (DDAs), which may also be used for radioscopic imaging. For a summary of DDAs, see E2736, Standard Guide for Digital Detector Array Radiology. It should be noted that some detector configurations listed herein have similar foundations to those described in Guide E2736.  
1.4 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. For specific safety precautionary statements, see Section 6.

General Information

• Status: Published
• Publication Date: 30-Nov-2016
• ICS: 19.100 - Non-destructive testing
• Technical Committee: E07 - Nondestructive Testing
• Drafting Committee: E07.01 - Radiography (X and Gamma) Method

Relations

• Replaces: ASTM E1000-98(2009) - Standard Guide for Radioscopy
• Effective Date: 01-Dec-2016
• 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

Overview

ASTM E1000-16 – Standard Guide for Radioscopy provides a comprehensive framework for the nondestructive examination of materials and components using radioscopic techniques. Radioscopy, often termed real-time radiography, utilizes penetrating radiation (such as X-rays or gamma rays) to generate immediate visual information about the internal and external features of an object. Unlike traditional film-based radiography, radioscopy enables real-time imaging, rapid inspection, and immediate assessment of product integrity, making it a valuable tool in quality control, failure analysis, and maintenance across various industries.

This standard, developed by ASTM International, outlines general principles, recommended practices, and image quality systems for real-time and near real-time radioscopic imaging. It is intended for tutorial purposes and supports users in understanding the benefits, limitations, and appropriate applications of radioscopy within a nondestructive testing (NDT) program.

Key Topics

• Immediate Detection of Imperfections: Radioscopy allows for the real-time identification of internal and external flaws such as cracks, voids, and inclusions, as well as assessment of component placement and configuration.
• Dimensional and Assembly Verification: The technology offers rapid verification of dimensions and assembly correctness, ensuring proper mechanical function.
• Real-Time and Three-Dimensional Visualization: Radioscopy can present defects as they occur and, when combined with manipulation, provides three-dimensional information about structures and assemblies.
• Digital Image Recording and Enhancement: Long-term records can be made using video recording, digital storage, or traditional photography. Advanced digital processing enables enhanced image analysis and supports computer-aided interpretation.
• Noise Reduction and Defect Recognition: Computer systems can average images to reduce noise or implement automatic defect recognition (ADR) for improved reliability.
• Personnel Qualification: Operators must be qualified according to recognized NDT personnel standards (e.g., ANSI/ASNT CP-189, ISO 9712, EN 4179).

Applications

Radioscopic examination is widely used across diverse sectors, offering practical value in:

• Manufacturing: In-process quality control for welds, castings, microcircuits, and mechanical assemblies, especially where fast disposition and high throughput are priorities.
• Aerospace and Automotive: Inspection of structural components, detection of material uniformity, verification of safety-critical assemblies, and automatic defect recognition in production lines.
• Electronics: Nonfilm-based testing and analysis of printed circuit boards, semiconductor packages, and intricate connectors.
• Materials Science: Evaluation of internal features in research and testing, with real-time feedback for process optimization.
• Maintenance and Field Inspection: Mobile radioscopic systems provide on-site, real-time inspection for pipelines, pressure vessels, and machinery, reducing downtime and maintenance costs.

Radioscopy offers particular value when quick decision-making, high productivity, and lower operational costs compared to traditional radiography are desired. It supports immediate feedback and minimizes delays associated with film processing, thus streamlining workflows in dynamic manufacturing or service environments.

Related Standards

The use of ASTM E1000-16 is complemented by several national and international standards relevant to nondestructive testing and radioscopic image quality:

• ASTM E747: Practice for Wire Image Quality Indicators (IQI)
• ASTM E1025: Practice for Hole-Type Image Quality Indicators (IQI)
• ASTM E1316: Terminology for Nondestructive Examinations
• ASTM E1742: Practice for Radiographic Examination
• ASTM E2002: Practice for Determining Image Unsharpness and Spatial Resolution
• ASTM E2736: Guide for Digital Detector Array Radiology
• ISO 9712: Qualification and certification of NDT personnel
• EN 4179: Aerospace - Qualification and approval of personnel for NDT
• ANSI/ASNT CP-189: Qualification and Certification of NDT Personnel

Safety requirements and radiation protection practices must be observed, in accordance with local regulations and referenced standards like Fed. Std. No. 21-CFR 1020.40 and NCRP guidelines.

---

By adhering to ASTM E1000-16, organizations can ensure reliable, cost-effective, and efficient radioscopic examinations, resulting in improved product quality, reduced inspection time, and enhanced safety in critical applications.

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: E1000 − 16
Standard Guide for
Radioscopy
This standard is issued under the fixed designation E1000; 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 ing Classification of Wire Image Quality Indicators (IQI)
Used for Radiology
1.1 Thisguideisfortutorialpurposesonlyandtooutlinethe
E1025Practice for Design, Manufacture, and Material
general principles of radioscopic imaging.
Grouping Classification of Hole-Type Image Quality In-
1.2 This guide describes practices and image quality mea-
dicators (IQI) Used for Radiology
suring systems for real-time, and near real-time, nonfilm
E1316Terminology for Nondestructive Examinations
detection, display, and recording of radioscopic images. These
E1742Practice for Radiographic Examination
images, used in materials examination, are generated by
E2002Practice for Determining Total Image Unsharpness
penetrating radiation passing through the subject material and
and Basic Spatial Resolution in Radiography and Radios-
producing an image on the detecting medium. Although the
copy
described radiation sources are specifically X-ray and gamma-
E2736Guide for Digital Detector Array Radiology
ray, the general concepts can be used for other radiation
2.2 National Council on Radiation Protection and Measure-
sources such as neutrons. The image detection and display
ment (NCRP) Standards:
techniques are nonfilm, but the use of photographic film as a
NCRP49 Structural Shielding Design and Evaluation for
means for permanent recording of the image is not precluded.
Medical Use of X-rays and Gamma Rays of Energies up
to 10 MeV
NOTE 1—For information purposes, refer to Terminology E1316.
NCRP 51 Radiation Protection Design Guidelines for
1.3 This guide summarizes the state of radioscopic technol-
0.1–100 MeV Particle Accelerator Facilities
ogy prior to the advent of Digital Detector Arrays (DDAs),
NCRP91,(supercedes NCRP 39) Recommendations on
which may also be used for radioscopic imaging. For a
Limits for Exposure to Ionizing Radiation
summary of DDAs, see E2736, Standard Guide for Digital
2.3 Federal Standard:
Detector Array Radiology. It should be noted that some
Fed. Std. No.21-CFR1020.40 Safety Requirements for
detector configurations listed herein have similar foundations
Cabinet X-Ray Machines
to those described in Guide E2736.
2.4 Aerospace Industries Association Document:
1.4 This standard does not purport to address all of the
NAS 410Certification & Qualification of Nondestructive
safety concerns, if any, associated with its use. It is the 5
Test Personnel
responsibility of the user of this standard to establish appro-
2.5 ASNT Documents:
priate safety and health practices and determine the applica-
SNT-TC-1ARecommended Practice for Personnel Qualifi-
bility of regulatory limitations prior to use. For specific safety
cation and Certification in Nondestructive Testing
precautionary statements, see Section 6.
ANSI/ASNT-CP-189ASNT Standard for Qualification and
Certification of Nondestructive Testing Personnel
2. Referenced Documents
2.6 CEN Documents:
2.1 ASTM Standards:
EN 4179Aerospace Series—Qualification and Approval of
E747Practice for Design, Manufacture and Material Group-
Personel for Non-Destructive Testing
Available from NCRP Publications, 7010 Woodmont Ave., Suite 1016,
This guide is under the jurisdiction ofASTM Committee E07 on Nondestruc- Bethesda, MD 20814.
tive Testing and is the direct responsibility of Subcommittee E07.01 on Radiology AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
(X and Gamma) Method. Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
Current edition approved Dec. 1, 2016. Published January 2017. Originally Available fromAerospace IndustriesAssociation ofAmerica, Inc. (AIA), 1000
approved in 1989. Last previous edition approved in 2009 as E1000-98 (2009). WilsonBlvd.,Suite1700,Arlington,VA22209-3928,http://www.aia-aerospace.org.
DOI: 10.1520/E1000-16.
2 6
For referenced ASTM standards, visit the ASTM website, www.astm.org, or AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Standards volume information, refer to the standard’s Document Summary page on AvailablefromCEN-EuropeanCommitteeforStandardization,RueDeStassart
the ASTM website. 36, Bruxelles, Belgium B-1050, http://www.cen.eu
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1000 − 16
2.7 ISO Documents: 5. Background
ISO 9712Non-destructive Testing—Qualification and Cer-
5.1 Fluorescence was the means by which X-rays were
tification of NDT Personnel
discovered, but industrial fluoroscopy began some years later
with the development of more powerful radiation sources and
3. Summary of Guide
improvedFluoroscopicscreens.Fluoroscopicscreenstypically
3.1 This guide outlines the practices for the use of radio-
consist of phosphors that are deposited on a substrate. They
scopicmethodsandtechniquesformaterialsexaminations.Itis
emit light in proportion to incident radiation intensity, and as a
intended to provide a basic understanding of the method and
function of the composition, thickness, and grain size of the
the techniques involved. The selection of an imaging device,
phosphor coating. Screen brightness is also a function of the
radiation source, and radiological and optical techniques to
wavelength of the impinging radiation. Screens with coarse-
achieve a specified quality in radioscopic images is described.
grained or thick coatings of phosphor, or both, are usually
brighter but have lower spatial resolution than those with fine
4. Significance and Use
grains or thin coatings, or both. In the past, conventional
4.1 Radioscopy is a versatile nondestructive means for
fluorescent screens limited the industrial applications of fluo-
examining an object. It provides immediate information re-
roscopy.Thelightoutputofsuitablescreenswasquitelowand
garding the nature, size, location, and distribution of
required about 30 min for an examiner to adapt his eyes to the
imperfections, both internal and external. It also provides a
dim image. To protect the examiner from radiation, the
rapid check of the dimensions, mechanical configuration, and
fluoroscopic image had to be viewed through leaded glass or
thepresenceandpositioningofcomponentsinamechanism.It
indirectlyusingmirroroptics.Suchsystemswereusedprimar-
indicates in real-time the presence of structural or component
ily for the examination of light-alloy castings, the detection of
imperfections anywhere in a mechanism or an assembly.
foreign material in foodstuffs, cotton and wool, package
Through manipulation, it may provide three-dimensional in-
inspection, and checking weldments in thin or low-density
formation regarding the nature, sizes, and relative positioning
metal sections. The choice of fluoroscopy over radiography
of items of interest within an object, and can be further
was generally justified where time and cost factors were
employed to check the functioning of internal mechanisms.
important and other nondestructive methods were not feasible.
Radioscopy permits timely assessments of product integrity,
and allows prompt disposition of the product based on accep-
5.2 It was not until the early 1950s that technological
tance standards. Although closely related to the radiographic
advances set the stage for widespread uses of industrial
method, it has much lower operating costs in terms of time,
fluoroscopy. The development of the X-ray image intensifier
manpower, and material.
provided the greatest impetus. It had sufficient brightness gain
tobringfluoroscopicimagestolevelswhereexaminationcould
4.2 Long-term records of the radioscopic image may be
be performed in rooms with somewhat subdued lighting, and
obtained through motion-picture recording (cinefluorography),
without the need for dark adaption. These intensifiers con-
video recording, or “still” photographs using conventional
tained an input phosphor to convert the X-rays to light, a
cameras,ordirectdigitalstreamingandstorageofimagestacks
photocathode (in intimate contact with the input phosphor) to
to internal or external hard drives, or directly to RAM
convert the light image into an electronic image, electron
locations, if sufficient RAM is present in the computer. The
accelerating and focusing electrodes, and a small output
radioscopic image may be electronically enhanced, digitized,
or otherwise processed for improved visual image analysis or phosphor.Intensifierbrightnessgainresultsfromboththeratio
of input to output phosphor areas and the energy imparted to
automatic, computer-aided analysis, or both.
the electrons. Early units had brightness gains of around 1200
4.3 Computer systems enable image or frame averaging for
to 1500 and resolutions somewhat less than high-resolution
noise reduction. For some applications image integration or
conventional screens. Modern units utilizing improved phos-
averaging is required to get the required image quality. As an
phors and electronics have brightness gains in excess of
add-on,anautomaticdefectrecognitionsystem(ADR)maybe
10 000× and improved resolution. For example, welds in steel
used with the radioscopic image.
thicknesses up to 28.6 mm (1.125 in.) can be examined at 2%
4.4 Personnel Qualification—Personnel performing exami-
plaque penetrameter sensitivity using a 160 constant potential
nations to this standard shall be qualified in accordance with a
X-ray generator (kVcp) source. Concurrent with image-
nationally or internationally recognized NDT personnel quali-
intensifier developments, direct X-ray to television-camera
fication practice or standard such as ANSI/ASNT CP-189,
tubes capable of high sensitivity and resolution on low-density
SNT-TC-1A, NAS 410, ISO 9712, EN 4179 or similar docu-
materialsweremarketed.Becausetheyrequireacomparatively
ment and certified by the employer or certifying agency, as
high X-ray flux input for proper operation, however, their use
applicable. The practice or standard used and its applicable
has been limited to examination of low-density electronic
revision shall be identified in the contractual agreement be-
components, circuit boards, and similar applications. The
tween the using parties.
development of low-light level television (LLLTV) camera
tubes, such as the isocon, intensifier orthicon, and secondary
electron conduction (SEC) vidicon, and the advent of
Available from International Organization for Standardization (ISO), ISO
advanced, low-noise video circuitry have made it possible to
Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
Geneva, Switzerland, http://www.iso.org. use television cameras to scan conventional, high-resolution,
E1000 − 16
low-light-output fluorescent screens directly. The results are 6. Safety Precautions
comparable to those obtained with the image intensifier.
6.1 The safety procedures for the handling and use of
ionizing radiation sources must be followed. Mandatory rules
5.3 In the 1980s new digital radiology techniques were
and regulations are published by governmental licensing
developed.These methods produce directly digitized represen-
agencies, and guidelines for control of radiation are available
tationsoftheX-rayfieldtransmittedbyanexaminationarticle.
in publications such as the Fed. Std. No.21-CFR 1020.40.
Directdigitizationenhancesthesignal-to-noiseratioofthedata
Careful radiation surveys should be made in accordance with
and presents the information in a form directly suitable for
regulations and codes and should be conducted in the exami-
electronic image processing and enhancement, and storage.
nation area as well as adjacent areas under all possible
Digital radioscopic systems use scintillator-photodetector and
operating conditions.
phosphor-photodetector sensors in flying spot (pencil beam),
fan beam-detector, or cone beam array arrangements.
7. Interpretation and Reference Standards
5.4 All of these techniques employ live monitor display
7.1 Reference radiographs produced by ASTM and accep-
presentation and can utilize various electronic techniques for
tance standards written by other organizations may be em-
image enhancement, image storage, and video or data record-
ployed for radioscopic examination as well as for radiography,
ing. These imaging devices, along with video and data stream
provided appropriate adjustments are made to accommodate
processing and analysis techniques, have greatly expanded the
for the differences in the fluoroscopic images.
versatility of radioscopic imaging. Industrial applications have
become wide-spread: production examination of the longitudi-
8. Radioscopic Devices, Classification
nal fusion welds in line pipe, welds in rocket-motor housings,
8.1 The most commonly used electromagnetic radiation in
castings, transistors, microcircuits, circuit-boards rocket pro-
radioscopy is produced by X-ray sources. X-rays are affected
pellant uniformity, solenoid valves, fuses, relays, tires and
in various modes and degrees by passage through matter. This
reinforced plastics are typical examples. Additionally the use
providesveryusefulinformationaboutthematterthathasbeen
of full automatic defect recognition systems for automotive
traversed. The detection of these X-ray photons in such a way
casting inspection using integrated or averaged images and an
that the information they carry can be used immediately is the
appropriately powered computer leads to a large cost reduc-
prime requisite of radioscopy. Since there are many ways of
tion.
detecting the presence of X-rays, their energy and flux density,
5.5 Limitations—Despite the numerous advances in radio-
there are a number of possible systems. Of these, only a few
scopic imaging technology, the sensitivity and resolution of
deserve more than the attention caused by scientific curiosity.
real-time systems usually are not as good as can be obtained
For our purposes here, only these few are classified and
with longer exposures obtained with film. In radiography the
described.
time exposures and close contact between the film and the
8.2 Basic Classification of Radioscopic Systems—All com-
subject, the control of scatter, and the use of metallic screens
monly used systems depend on two basic processes for
make it relatively simple to obtain better than 2% penetram-
detecting X-ray photons: X-ray to light conversion and X-ray
eter sensitivity in most cases. Inherently, because of statistical
to electron conversion.
limitations dynamic scenes require a higher X-ray flux level to
develop a suitable image than static scenes. In addition, the 8.3 X-ray to Light Conversion–Radioscopic Systems—In
these systems X-ray photons are converted into visible light
product-handling considerations in a dynamic imaging system
mandate that the image plane be separated from the surface of photons, which are then used in various ways to produce
images. The processes are fluorescence and scintillation. Cer-
the product resulting in perceptible image unsharpness. Geo-
metric unsharpness can be minimized by employing small tain materials have the property of emitting visible light when
excited by X-ray photons. Those used most commonly are as
focal spot (fractions of a millimetre) X-ray sources, but this
requirement is contrary to the need for the high X-ray flux follows (see section 10.6.3.1 for additional discussion on
density cited previously. An alternative may be a micro-focus image intensifiers):
source and image integration with a computer system; the 8.3.1 Phosphors—These include the commonly used fluo-
limitationinspatialresolutionwillbethesizeofthefocalspot, rescent screens, composed of relatively thin, uniform layers of
andincontrast-to-noiseratio,theavailableintegrationtimefor phosphor crystals spread upon a suitable support. Zinc cad-
one resulting image. Furthermore, limitations imposed by the mium sulfide, gadolinium oxysulfide, lanthanum oxybromide,
dynamic system make control of scatter and geometry more and calcium tungstate are in common use. Coating weights
2 2
difficult than in conventional radiographic systems. Finally, vary from approximately 50 mg/cm to 200 mg/cm.
dynamic radioscopic systems require careful alignment of the 8.3.2 Scintillators—These are materials which are transpar-
source, subject, and detector and often expensive product- ent and emit visible light when excited by X-rays. The
handling mechanisms. These, along with the radiation safety emission occurs very rapidly for each photon capture event,
requirements peculiar to dynamic systems usually result in andconsistsofapulseoflightwhosebrightnessisproportional
capital equipment costs considerably in excess of that for totheenergyofthephoton.Sincethematerialsaretransparent,
conventional film radiography. The costs of expendables, theylendthemselvestoopticalconfigurationsnotpossiblewith
manpower, product-handling and time, however, are usually the phosphors used in ordinary fluorescent screens. Typical
significantly lower for radioscopic systems. materials used are sodium iodide (thallium-activated), cesium
E1000 − 16
FIG. 1 Basic Fluoroscope
iodide (thallium-activated) and sodium iodide (cesium- formed over thin film transistor (TFT) arrays, and are read-out
activated). These single crystal, transparent or translucent directlyinsolidstateimagingdevices.Theselaterdeviceswith
ceramic materials can be obtained in very large sizes (up to solid state read-out circuitry are more appropriately defined as
45-cmor17-in.diameterisnowpossible)andcanbemachined Digital Detector Arrays (DDAs), see E2736. Whereas the
intovarioussizesandshapesasrequired.Thicknessesof0.1to former devices where the direct converter is coupled with
100 mm (0.08 to 4 in.) are customary. camera tube technology are treated as radioscopic devices.
8.4.3 Microchannel Plates—These consist of an array or
8.4 X-ray to Electron Conversion—Radioscopic Systems—
bundle of very tiny, short tubes, each of which, under proper
X-ray photons of sufficient energy have the ability to release
conditions, can emit a large number of electrons from one end
loosely bound electrons from the inner shells of atoms with
when an X-ray photon strikes the other end. The number of
which they collide. These photoelectrons have energies pro-
electrons emitted depends upon the X-ray flux per unit area,
portional to the original X-ray photon and can be utilized in a
and thus an electron image can be produced. These devices
variety of ways to produce images, including the following
mustoperateinavacuum,sothatapracticalimagingdeviceis
useful processes.
possible only with careful packaging. Usually, this will mean
8.4.1 Energizing of Semiconductor Junctions—The resis-
that a combination of processes is required, as described more
tance of a semiconductor, or of a semiconductor junction in a
completely in 8.5.
device such as a diode or transistor, can be altered by adding
free electrons. The energy of an X-ray photon is capable of
8.5 Combinations of Detecting Processes—Radioscopic
freeing electrons in such materials and can profoundly affect
Systems—A variety of practical systems can be produced by
the operation of the device. For example, a simple silicon
various combinations of the basic mechanisms described,
“solar cell” connected to a microammeter will produce a
together with other devices for transforming patterns of light,
substantial current when exposed to an X-ray source.
electrons, or resistance changes into an image visible to the
8.4.1.1 If an array of small semiconductor devices is ex-
human eye, or which can be analyzed for action decision in a
posedtoanX-raybeam,andtheperformanceofeachdeviceis
completely automated system. Since the amount of light or
sampled, then an image can be produced by a suitable display
electrical energy produced by the detecting mechanism is
of the data. Such arrays can be linear or two-dimensional.
normally orders of magnitude below the range of human
Linear arrays normally require relative motion between the
senses, some form of amplification or intensification is com-
object and the array to produce a useful real-time image. The
mon. Figs. 1-11 illustrate the basic configuration of practical
choice depends upon the application.
systemsinuse.Fordetailsoftheirperformanceandapplication
8.4.2 Affecting Resistance of Semiconductors—Onetechnol-
see Section 10. Table 1 compares several common imaging
ogy used for direct X-ray-to-electron device is the X-ray
systems in terms of general performance, complexity, and
sensitive vidicon camera tube. Here the target layer of the
relative costs.
vidicontube,anditssupport,aremodifiedtohaveanimproved
sensitivity to X-ray photons. The result is a change in conduc-
9. Radiation Sources
tivity of the target layer corresponding to the pattern of X-ray
9.1 General:
flux falling upon the tube, and this is directly transformed by
the scanning beam into a video signal which can be used in a 9.1.1 The sources of radiation for radioscopic imaging
variety of ways. systems described in this guide are X-ray machines and
8.4.2.1 Photoconductive materials that exhibit X-ray sensi- radioactive isotopes. The energy range available extends from
tivity include cadmium telluride (CdTe), zinc cadmium tellu- a few keV to 32 MeV. Since examination systems in general
ride (CdZnTe), cadmium selenide, lead oxide, selenium, gal- require high dose rates, X-ray machines are the primary
lium arsenide, and silicon. Some of these have been used in radiation source. The types of X-ray sources available are
X-ray sensitive TV camera tubes. Cadmium sulfide is com- conventional X-ray generators that extend in energy up to 750
monly used as an X-ray detector, but not usually for image keV.Energysourcesfrom1MeVandabovemaybetheVande
formation. Selenium, CdTe, and CdZnTe (CZT) have been Graaff generator, linear accelerator, or the betatron. High
E1000 − 16
FIG. 2 Fluoroscope with Optics
FIG. 3 Light-Intensified Fluoroscope
FIG. 4 Light-Intensified Fluoroscope with Optics
FIG. 5 LLLTV Fluoroscope
energy sources with large flux outputs make possible the have an adjustable energy range so that they are applicable to
real-time examination of greater thicknesses of material. a wide range of materials. Specifically, 50-keV units operate
9.1.2 Usable isotope sources have energy levels from
down to a few keV, 160-keV equipment operates down to
84keV (Thulium-170, Tm ) up to 1.25 MeV (Cobalt-60, 20keV, and 450-keV equipment operates down to about 25
Co ). With high specific activities, these sources should be
keV.Aguide to the use of radiation sources for some materials
considered for special application where their field mobility
is given in Table 2.
and operational simplicity can be of significant advantage.
9.2.2 High-Energy Sources—The increased efficiency of
9.1.3 The factors to be considered in determining the
X-ray production at higher accelerating potentials makes
desiredradiationsourceareenergy,focalgeometry,dutycycle,
available a large radiation flux, and this makes possible the
wave form, half life, and radiation output.
examination of greater thicknesses of material. High-radiation
9.2 Selection of Sources: energies in general produce lower image contrast, so that as a
guide the minimum thickness of material examined should not
9.2.1 Low Energy—The radiation source selected for a
specific examination system depends upon the material being be less than three-half value layers of material. The maximum
examined, its mass, its thickness, and the required rate of thickness of material can extend up to ten-half value layers.
examination.Intheenergyrangeupto750keV,theX-rayunits Table 3 is a guide to the selection of high-energy sources.
E1000 − 16
FIG. 6 Light-Intensified LLLTV Fluoroscope
FIG. 7 Scintillator Arrays, TV Readout
FIG. 8 X-ray Image Intensifier
9.3 Source Geometry: 9.3.2 The small source geometry of microfocus X-ray tubes
9.3.1 While an X-ray tube with a focal spot of 3 mm permits small target-to-detector spacings and object projection
(0.12in.) operating at a target to detector distance of 380 mm magnification for the detection of small anomalies. The selec-
(15 in.) and penetrating a 25-mm (1-in.) thick material would tion of detectors with low unsharpness is of particular advan-
contribute an unsharpness of 0.2 mm (0.008 in.), a detector tageinthesecasestothereducethefocalspot-detectordistance
unsharpness of 0.5 to 0.75 mm would still be the principal (FDD). With high magnification, the focal spot size would be
source of unsharpness. the principal source of unsharpness.
E1000 − 16
FIG. 9 X-ray Sensitive Vidicon
FIG. 10 Microchannel Plates
FIG. 11 Flying Spot Scanner
9.3.3 Where isotopes are to be evaluated for radioscopic by the design of the real-time systems. Other lower energy
systems, the highest specific activities that are economically
X-ray generators operate with pulse rates of more than 10,000
practical should be available so that source size is minimized. pulses/sec, thus the influence on real-time imaging is negli-
gible.
9.4 Radiation Source Rating Requirements:
9.4.3 The radiation flux is a major consideration in the
9.4.1 The X-ray equipment selected for examination should
selection of the radiation source. For stationary or slow-
be evaluated at its continuous duty ratings, because the
moving objects, radiation sources with high outputs at a
economy of radioscopic examination is realized in continuous
production examination. X-ray units with target cooling by continuousdutycyclearedesired.X-rayequipmentatthesame
nominal kilovolt and milliampere ratings may have widely
fluids are usually required.
9.4.2 High-energy sources, for example linear accelerators, different radiation outputs.Therefore in a specific examination
which can operate at pulse rates up to 400 pulses per second, requirement of radiation output through the material thickness
may produce interference lines. These lines can be minimized being examined should be measured.
E1000 − 16
TABLE 1 Comparison of Several Imaging Devices
(new instrumentation and configurations to meet a similar need are continually being invented and commercialized)
NOTE 1—The data presented are for general guidance only, and must be used circumspectly. There are many variables inherent in combining such
devices that can affect results significantly, and that cannot be covered adequately in such a simple presentation. These data are based upon the personal
experiences of the authors and may not reflect the experiences of others.
X-ray
Fluorescent X-ray Image X-ray Microchannel Flying Spot/Line
Scintillating
Phosphors Intensifier Vidicon Plates Scanners
Crystals
Availability excellent excellent excellent good fair fair
Auxiliary
A A
equipment shielding glass, shielding glass, CCTV, optics CCTV fluorescent fluorescent phos-
needed optics optics screen, phor or
A
LLLTV special pack- scintillating
aging, crystals,
CCTV, special
output phos- electronics,
phor digitizers
Usual readout Visual computer moni- computer moni- computer monitor(s) computer electronic/visual
methods tor(s) tor(s) monitor(s)
Other readout none none direct none none none
methods
Practical up to 4.5 10 4 20 20 10
resolution, usual
readout, lp/mm
Minimum large-21 25 5 1
area contrast sen-
sitivity, %
Useful keVcp
range, min 25 25 5 20 15 25
range, max 300 10 MeV 10 MeV 250 2 MeV 15 MeV
Optimum keVcp 120 200 100 75 100 NA
Field of view, maxi- no practical 229-mm (9-in.) 305-mm (12- 9.53 × 12.7 76-mm (3-in.) no limit
mum limit dia in.) dia mm ( ⁄8 dia
× ⁄2 in.)
Relative sensitivity low medium high low medium high
to X-rays
Relative cost low high medium low high high
Approximate useful 10 years indefinite 3 years 5 years 5 years 5 years
life
Special remarks very simple high quality very practical limited to small Rarely used No longer used
image thin, objects
A
Low-light level television (LLLTV) is a sensitive form of closed circuit television (CCTV) designed to produce usable images at illumination levels equivalent to starlight
−1 −4 2 −4 −7 2
(10 to 10 lm/m or 0.343 × 10 to 0.343 × 10 cd/m ).
A
TABLE 2 Radiation Sources for Aluminum and Steel TABLE 3 High-Energy Radiation Sources for Solid Propellant and
Steel
Aluminum, Steel,
kV or Isotope
mm (in.) mm (in.)
Steel, Solid Propellant,
MeV
40 5.1–12.8 (0.2–0.5) . mm (in.) mm (in.)
70 12–30 (0.5–1.2) 3–7.5 (0.12–0.3)
1.0 46.0–107.0 (1.8–4.2) 198.0–462.0
100 20–50 (0.8–2) 6.25–15.6
(7.8–18.2)
(0.25–0.62)
2.0 57.0–133.0 (2.24–5.24) 267.0–620.0
200 33.5–83.8 (1.3–3.3) 8–20 (0.32–0.8)
(10.5–24.4)
300 . 15–45 (0.6–1.8)
4.0 76.0–178.0 (3–7) 358.0–836.0
420 . 18–45 (0.71–1.8)
(14.1–32.9)
A
Thulium 170 . 3 (0.12)
10.0 99.0–231.0 (3.9–9.1) 495.0–1156.0
Ytterbium 169 . 4 -15 (0.15 – 0.59)
(19.7–45.5)
Selenium 75 . 8 - 20 (0.31 – 0.78)
15.0 99.0–231.0 (3.9–9.1) 553.0–1290.0
Iridium 192 . 26 (1.02)
(21.8–50.8)
A Cobalt-60 57.0 (2.24)–180 (7.08) 267.0–620.0
The minimum thickness of material at a given energy represents two-half value
(10.5-24.4)
layers of material while the maximum thickness represents five-half value layers.
The use of a selected energy at other material thicknesses depends upon the A
There is no significant difference in the half-value layers for steel from 10 to 15
specific radiation flux and possible image processing in the radioscope system.
MeV.
10. Imaging Devices
10.1 Animagingdevicecanbedescribedasacomponentor
caused primarily by photoelectric absorption, or Compton
sub-system that transforms an X-ray flux field into a prompt
scattering. At high energies, scattering is by pair production
response optical or electronic signal.
(over1MeV)andphotonuclearprocesses(atabout11.5MeV).
10.2 When X-ray photons pass through an object, they are As a result of attenuation, the character of the flux field in a
attenuated. At low-to-medium energies this attenuation is cross-section of the X-ray beam is changed. Variations in
E1000 − 16
photon flux density and energy are most commonly sensitivity and resolution. Careful filtering and collimation of
encountered, and are caused by photoelectric absorption and the X-ray beam, control of backscatter, and appropriate use of
Compton scatterings. lightabsorbingmaterialsintheopticalsystemarevitaltogood
radioscopy. The low-resolution, low-contrast visible light im-
10.3 By analyzing this flux field, deductions can be made
agesproducedbythedetectormayposespecialproblemsinthe
about the composition of the object being examined, since the
choice of optical components. For example, a lens that would
attenuation process depends on the number of atoms encoun-
be an excellent choice for photography may be a poor choice
tered by the original X-ray beam, and their atomic number.
to couple a low-light-level imaging camera to a fluorescent
10.4 The attenuation process is quite complex, since the
screen.
X-ray beam is usually composed of a mixture of photons of
10.4.2.1 This brief treatment just touches on a complex
many different energies, and the object composed of atoms of
subject.When designing an imaging system, the reader should
many different kinds. Exact prediction of the flux field falling
consult other references.
upontheimagingdeviceistherefore,difficult.Approximations
10.5 Physical Factors—The selection of a radioscopic im-
can be made, since the mathematics and data are available to
aging system for any specific application may be affected by a
treat any single photon energy and atomic type, but in practice
number of factors. Environmental conditions such as extremes
great reliance must be placed on the experience of the user. In
of temperature and humidity, the presence of strong magnetic
spite of these difficulties, many successful imaging devices
fields in the proximity of image intensifiers and cameras, the
havebeendeveloped,andperformwell.Thecriteriaforchoice
presence of loose dirt and scale and oily vapors can all limit
depend on many factors, which, depending on the application,
their use, or even preclude some applications. In production-
may, or may not be critical. Obviously, these criteria will
line applications, system reliability, ease of adjustment, mean-
include the following devices.
time-between-failures, and ease and cost of maintenance are
10.4.1 Field of View of Imaging Device—The field of view
significantfactors.Furthermore,thesizeandweightofimaging
of the imaging device, its resolution, and the dynamic inspec-
systemcomponentsaswellaspositioningandhandlingmecha-
tion speed are interrelated. The resolution of the detector is
nism requirements must be considered in system design, and
fixed by its physical characteristics, so if the X-ray image is
interact with cost factors in selection of a system.
projected upon it full-size (the object and image planes in
contact),theresultantresolutionwillbeapproximatelyequalto 10.6 X-ray to Light Conversion—Radioscopic Systems—For
that of the detector. When detector resolution becomes the the purpose of radioscopy, a fluorescent screen can be de-
limiting factor, the object may be moved away from the scribed as a sheet of material that converts X-ray photons into
detector,andtowardsthesourcetoenlargetheprojectedimage visible light through energy transitions in the material as the
and thus allow smaller details to be resolved by the same X-ray energy is absorbed and cascades to lower energy
radiation. At these lower discrete energies in the screen, the
detector. As the image is magnified, however, the detail
contrast is reduced and its outlines are less distinct. (See 11.3.) material goes into an excited state, that upon relaxation emits
someofthatenergyaslight.Screenmaterialswereknowneven
It is apparent, also, that when geometric magnification is used,
the area of the object that is imaged on the detector is before the discovery of X-rays or radioactive materials, since
substances which “glow in the dark” have been known for
proportionally reduced. Consequently the area that can be
examined per unit time will be reduced. As a general rule, centuries. In fact, it was a fluorescent screen that was the key
to the discovery of X-rays. However, enormous improvements
X-ray magnifications should not exceed 5× except when using
X-ray sources with very small (microfocus) anodes. In such havebeenmadeinunderstanding,manufacturing,andapplying
screens. Although the basic physical phenomena involved are
cases, magnifications in the order of 10 to 20× are useful.
When using conventional focal-spot X-ray sources, magnifica- similar, it is convenient for our purposes to divide screens into
tions from 1.2 to 1.5 provide a good compromise between two groups, fluorescent phosphors and scintillating crystals.
contrast and resolution in the magnified image. 10.6.1 Fluorescent Phosphors:
10.4.2 Inherent Sensitivity of Imaging Device—The basic 10.6.1.1 Afluorescent screen is a layer of phosphor crystals
sensitivity of the detector may be defined as its ability to deposited on a suitable support backing, with a transparent
respond to small, local variations in radiant flux to display the protective coating or cover. The crystals used have the ability
featuresofinterestintheobjectbeingexamined.Itwouldseem to absorb energy from an X-ray photon and re-emit some of
that a detector that can display density changes on the order of that energy in the form of visible light. The amount of light
1 to 2% at resolutions approaching that of radiography would produced for a given X-ray flux input is termed the brightness
satisfy all of the requirements for successful radioscopic (luminance)ofthescreen.Thenumberoflightphotonsemitted
imaging. It is not nearly that simple. Often good technique is perunitexposureisthe conversion effıciency. Resolutionisthe
more important than the details of the imaging system itself. ability to show fine detail (for high contrast objects), and
The geometry of the system with respect to field of view, contrastisthedetectablediscerniblechangeinbrightnesswith
resolution, and contrast is a very important consideration as is a specified change in input flux. This is often specified as the
thecontrolofscatteredradiation.ScatteredX-raysenteringthe minimum percentage thickness change in the object which can
imaging system and scattered light in the optical system bedetected.Imagequalityindicators(IQI)arecommonlyused
produce background similar to fogging in a radiograph. This to make these tests. Most phosphors used in screens have
scatter not only introduces radiant energy containing no useful limited ability to transmit the light they produce without
information into the imaging system but also impairs system scattering or refraction due to their size, shape, coatings, and
E1000 − 16
A
TABLE 4 Properties of Some Common Fluorescent Screens
B
Relative Brightness With Attenuation
C
Resolution Color
Medium Hard Hardest
Soft Spectrum Harder Spectrum
No. Formula Name Spectrum Spectrum
50 100 150 100 150 100 150 150 lp/mm nm
keVp keVp keVp keVp keVp keVp keVp keVp (in.)
1 CaWO calcium 6 13 2 8 1 2 0.5 1.2 (30) violet ;420
tungstate
2 ZnCdS zinc cadmium 3.5 46 120 22 65 7 25 3 2.0 (50) green ;540
sulfide
3 ZnCdS zinc cadmium 8 122 320 50 160 16 60 5 0.8 (20) green ;540
sulfide
4Gd O S gadolinium 5 89 250 43 150 16 65 12 1.6 (40) yellow-green
2 2 j
oxysulfide ;550
5 LaOBr lanthanum 1 19 50 8 29 3.5 13 2 1.2 (30) blue ;460
oxybromide
A
These are for illustrative purposes only. The X-ray tube used had beryllium window and fractional focal spot.
B
All these measurements were made under identical conditions.
C
The higher numbers indicate better resolution. These are approximately lp/mm (lp/in.).
other factors, and are not truly transparent. Thus the light that and5in Table 4. Two thicknesses of the ZnCdS and Gd O S
2 2
is produced by the lowermost layers is somewhat distorted by screens are shown to illustrate the range of sensitivity (bright-
passage through the layers above. Consequently thicker phos- ness) and resolution available. As would be expected, the
phors that have, in general, increased ability to absorb X-rays, brightest screen, No. 3, has the lowest resolution except when
and thus produce more light, usually produce brighter images the X-ray beam is strongly attenuated (see data for ⁄4-in.
with lower resolution, as compared to thin screens of the same (6.2-mm) steel, for example). Then, screens 4 and 5 are
material. preferable. As these few examples show, the choice of screen
10.6.1.2 The contrast of a fluorescent screen is influenced foraparticularapplicationisnotsimple,andthebestavailable
by the scattering of light and X-rays within the structure of the data from various suppliers should be studied before making a
screen itself, and to a larger extent by the relative response of choice.
thescreentodirectandscatteredX-rays.ThescatteredX-rays, 10.6.1.6 Inusingfluorescentscreens,historicallytherehave
particularly those scattered at large angles, consist of lower beentwooptionsforviewingtheimage.Directopticalviewing
energyphotons,towhichthescreenismoresensitive.Thishas can be as simple as covering the screen with a sheet of leaded
the effect of reducing the contrast. glass of the required thickness and looking directly at the
10.6.1.3 Inusualapplications,thecontrastofthefluorescent image. (See Fig. 1.) This option has since given way to fully
image for large areas (such as the outline of an IQI) is limited electronic viewing. This older methodology employed optical
by the contrast capability of the eye. Practical experience is viewing systems with the use of mirrors or lenses, or both, to
that the lower observable limit is that change in brightness position the operator out of the direct path of the X-ray beam
caused by a 1% change in thickness of the object. Smaller orevenatsomedistance.(SeeFig.2.)Thequalityoftheimage
differences may be possible with digitization and image in direct viewing is not degraded if reasonable care is taken in
processing techniques. the choice of the optical components used, but the light level
10.6.1.4 All fluorescent screens exhibit some persistence or must be high and this may be difficult to achieve, unless some
afterglow.Thisisafunctionofthephosphorandactivatorused form of light intensification is used (see Fig. 3 and Fig. 4).
and to this extent may be somewhat controlled by the manu- 10.6.1.7 Most modern systems employ electronic readout,
−5
facturer. It is usually of the order of 10 s for calcium with a camera and lens taking the place of the human eye (see
−2
tungstate (CaWO ) screens and 10 for zinc sulfide (ZnS). Fig. 5). These are very flexible and convenient systems. Some
3 3 3+ 3+
Rare earth screens with terbium (Tb ) and europium (Eu ) loss of original signal quality inevitably occurs, but the
−2
activators have about the same persistence (10 s), but other convenience, the possibility of increased brightness and the
3+
activators such as Ce can produce characteristic decay times possibility of manipulation of the electronic image usually
−6 −9
asshortas10 to10 s.Therelationshipbetweenbrightness morethancompensateforthisloss.VarioustypesofCCTVand
and resolution is clearly shown in Table 4. LLLTV systems are used, including those with light intensifi-
10.6.1.5 These screens are commercially available and the cation added (see Fig. 6). Fluorescent screens are rugged and
choice of screen will be governed by the requirements of the durable and have useful lives of several years with reasonable
user,whomustmakeacompromisechoicebetweenbrightness, care. They should not be exposed to mechanical abrasion, or
resolution, keV range, and apparent color of the image. The hightemperatures.Theirconversionefficiencyincreasesmark-
apparentcolorofthefluorescentimageisimportantbothinthe edly as the temperature is reduced. These factors should be
directly viewed and electronically scanned systems. Matching considered for the specified operating environment.
of spectral content to the response of the human eye or that of 10.6.2 Scintillation Crystals:
a detector such as a camera is significant in low-light-level 10.6.2.1 Scintillators are generally understood to be opti-
systems, and can affect both sensitivity and “noise” figures. cally clear crystals, transparent or transluscent ceramics of a
Those most commonly used are phosphors numbered 2, 3, 4, material which fluoresces when irradiated by X-rays, with
E1000 − 16
TABLE 5 Properties of Single Crystal Fluorescent Screens
A
Diameter, mm Brightness
Material Thickness, mm (in.) Resolution
(in.) Contrast 100 keV 120 keV 140 keV
Cesium Iodide (Thallium), CsI (Tl) 0.5–6.5 25–230 10 lp/mm 1 % 1.6 1.9 2.1
(0.020–0.250) (1–9)
A
Factors relative to gadolinium oxysulfide (Gd O S) with 13 mm ( ⁄2 in.) aluminum absorber.
2 2 j
short pulses of light being emitted for each photon absorbed. but visible light opaque cover or window on the source side,
The practical difference between fluorescent screens and scin- and an optical grade thick glass window on the viewing side.
tillation screens is that the latter are bulk solids and are Overall thickness of the package is approximately 25.4 mm (1
normally much thicker than phosphors. in.).
10.6.2.2 Since we have noted that larger or thicker crystals 10.6.2.6 The scintillators must be protected against tem-
orceramicsinascreenmorereadilyabsorbX-rayphotons,and peratureextremes,thermalshock,andmechanicalabuse.Some
that the thickness of such screens must be limited by practical screens (for example, sodium iodide) are hygroscopic and
considerations of particle size and thus resolution, the advan- should be hermetically sealed. The larger sizes are expensive
tage of a thicker screen that is still capable of good resolution due to the high cost of the raw material.
and contrast is evident. They have high efficiencies, particu- 10.6.2.7 Arrays of smaller scintill
...

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: E1000 − 98 (Reapproved 2009) E1000 − 16
Standard Guide for
Radioscopy
This standard is issued under the fixed designation E1000; 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
1.1 This guide is for tutorial purposes only and to outline the general principles of radioscopic imaging.
1.2 This guide describes practices and image quality measuring systems for real-time, and near real-time, nonfilm detection,
display, and recording of radioscopic images. These images, used in materials examination, are generated by penetrating radiation
passing through the subject material and producing an image on the detecting medium. Although the described radiation sources
are specifically X-ray and gamma-ray, the general concepts can be used for other radiation sources such as neutrons. The image
detection and display techniques are nonfilm, but the use of photographic film as a means for permanent recording of the image
is not precluded.
NOTE 1—For information purposes, refer to Terminology E1316.
1.3 This guide summarizes the state of radioscopic technology prior to the advent of Digital Detector Arrays (DDAs), which
may also be used for radioscopic imaging. For a summary of DDAs, see E2736, Standard Guide for Digital Detector Array
Radiology. It should be noted that some detector configurations listed herein have similar foundations to those described in Guide
E2736.
1.4 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. For specific safety precautionary statements, see Section 6.
2. Referenced Documents
2.1 ASTM Standards:
E142 Method for Controlling Quality of Radiographic Testing (Withdrawn 2000)
E747 Practice for Design, Manufacture and Material Grouping Classification of Wire Image Quality Indicators (IQI) Used for
Radiology
E1025 Practice for Design, Manufacture, and Material Grouping Classification of Hole-Type Image Quality Indicators (IQI)
Used for Radiology
E1316 Terminology for Nondestructive Examinations
E1742 Practice for Radiographic Examination
E2002 Practice for Determining Total Image Unsharpness and Basic Spatial Resolution in Radiography and Radioscopy
E2736 Guide for Digital Detector Array Radiology
2.2 National Council on Radiation Protection and Measurement (NCRP) Standards:
NCRP 49 Structural Shielding Design and Evaluation for Medical Use of X Rays X-rays and Gamma Rays of Energies up
to 10 MeV
NCRP 51 Radiation Protection Design Guidelines for 0.1–100 MeV Particle Accelerator Facilities
NCRP 91, (supercedes NCRP 39) Recommendations on Limits for Exposure to Ionizing Radiation
2.3 Federal Standard:
Fed. Std. No. 21-CFR 1020.40 Safety Requirements for Cabinet X-Ray Machines
This guide is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.01 on Radiology (X and
Gamma) Method.
Current edition approved June 1, 2009Dec. 1, 2016. Published July 2009January 2017. Originally approved in 1989. Last previous edition approved in 20032009 as
E1000 - 98 (2003).(2009). DOI: 10.1520/E1000-98R09.10.1520/E1000-16.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from NCRP Publications, 7010 Woodmont Ave., Suite 1016, Bethesda, MD 20814.
Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700 Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1000 − 16
2.4 Aerospace Industries Association Document:
NAS 410 Certification & Qualification of Nondestructive Test Personnel
2.5 ASNT Documents:
SNT-TC-1A Recommended Practice for Personnel Qualification and Certification in Nondestructive Testing
ANSI/ASNT-CP-189 ASNT Standard for Qualification and Certification of Nondestructive Testing Personnel
2.6 CEN Documents:
EN 4179 Aerospace Series—Qualification and Approval of Personel for Non-Destructive Testing
2.7 ISO Documents:
ISO 9712 Non-destructive Testing—Qualification and Certification of NDT Personnel
3. Summary of Guide
3.1 This guide outlines the practices for the use of radioscopic methods and techniques for materials examinations. It is intended
to provide a basic understanding of the method and the techniques involved. The selection of an imaging device, radiation source,
and radiological and optical techniques to achieve a specified quality in radioscopic images is described.
4. Significance and Use
4.1 Radioscopy is a versatile nondestructive means for examining an object. It provides immediate information regarding the
nature, size, location, and distribution of imperfections, both internal and external. It also provides a rapid check of the dimensions,
mechanical configuration, and the presence and positioning of components in a mechanism. It indicates in real-time the presence
of structural or component imperfections anywhere in a mechanism or an assembly. Through manipulation, it may provide
three-dimensional information regarding the nature, sizes, and relative positioning of items of interest within an object, and can
be further employed to check the functioning of internal mechanisms. Radioscopy permits timely assessments of product integrity,
and allows prompt disposition of the product based on acceptance standards. Although closely related to the radiographic method,
it has much lower operating costs in terms of time, manpower, and material.
4.2 Long-term records of the radioscopic image may be obtained through motion-picture recording (cinefluorography), video
recording, or “still” photographs using conventional cameras. cameras, or direct digital streaming and storage of image stacks to
internal or external hard drives, or directly to RAM locations, if sufficient RAM is present in the computer. The radioscopic image
may be electronically enhanced, digitized, or otherwise processed for improved visual image analysis or automatic, computer-aided
analysis, or both.
4.3 Computer systems enable image or frame averaging for noise reduction. For some applications image integration or
averaging is required to get the required image quality. As an add-on, an automatic defect recognition system (ADR) may be used
with the radioscopic image.
4.4 Personnel Qualification—Personnel performing examinations to this standard shall be qualified in accordance with a
nationally or internationally recognized NDT personnel qualification practice or standard such as ANSI/ASNT CP-189,
SNT-TC-1A, NAS 410, ISO 9712, EN 4179 or similar document and certified by the employer or certifying agency, as applicable.
The practice or standard used and its applicable revision shall be identified in the contractual agreement between the using parties.
5. Background
5.1 Fluorescence was the means by which X rays X-rays were discovered, but industrial fluoroscopy began some years later
with the development of more powerful radiation sources and improved Fluoroscopic screens. Fluoroscopic screens typically
consist of phosphors that are deposited on a substrate. They emit light in proportion to incident radiation intensity, and as a function
of the composition, thickness, and grain size of the phosphor coating. Screen brightness is also a function of the wavelength of
the impinging radiation. Screens with coarse-grained or thick coatings of phosphor, or both, are usually brighter but have lower
spatial resolution than those with fine grains or thin coatings, or both. In the past, conventional fluorescent screens limited the
industrial applications of fluoroscopy. The light output of suitable screens was quite low (on the order of 0.1 millilambert or
−3
0.343 × 10 cd/m ) and required about 30 min for an examiner to adapt his eyes to the dim image. To protect the examiner from
radiation, the fluoroscopic image had to be viewed through leaded glass or indirectly using mirror optics. Such systems were used
primarily for the examination of light-alloy castings, the detection of foreign material in foodstuffs, cotton and wool, package
inspection, and checking weldments in thin or low-density metal sections. The choice of fluoroscopy over radiography was
generally justified where time and cost factors were important and other nondestructive methods were not feasible.
Available from Aerospace Industries Association of America, Inc. (AIA), 1000 Wilson Blvd., Suite 1700, Arlington, VA 22209-3928, http://www.aia-aerospace.org.
Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Available from CEN-European Committee for Standardization, Rue De Stassart 36, Bruxelles, Belgium B-1050, http://www.cen.eu
Available from International Organization for Standardization (ISO), ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Switzerland, http://www.iso.org.
E1000 − 16
5.2 It was not until the early 1950’s1950s that technological advances set the stage for widespread uses of industrial fluoroscopy.
The development of the X-ray image intensifier provided the greatest impetus. It had sufficient brightness gain to bring fluoroscopic
images to levels where examination could be performed in rooms with somewhat subdued lighting, and without the need for dark
adaption. These intensifiers contained an input phosphor to convert the X rays X-rays to light, a photocathode (in intimate contact
with the input phosphor) to convert the light image into an electronic image, electron accelerating and focusing electrodes, and
a small output phosphor. Intensifier brightness gain results from both the ratio of input to output phosphor areas and the energy
imparted to the electrons. Early units had brightness gains of around 1200 to 1500 and resolutions somewhat less than
high-resolution conventional screens. Modern units utilizing improved phosphors and electronics have brightness gains in excess
of 10 000× and improved resolution. For example, welds in steel thicknesses up to 28.6 mm (1.125 in.) can be examined at 2 %
plaque penetrameter sensitivity using a 160 constant potential X-ray generator (keVcp)(kVcp) source. Concurrent with
image-intensifier developments, direct X ray X-ray to television-camera tubes capable of high sensitivity and resolution on
low-density materials were marketed. Because they require a comparatively high X-ray flux input for proper operation, however,
their use has been limited to examination of low-density electronic components, circuit boards, and similar applications. The
development of low-light level television (LLLTV) camera tubes, such as the isocon, intensifier orthicon, and secondary electron
conduction (SEC) vidicon, and the advent of advanced, low-noise video circuitry have made it possible to use television cameras
to scan conventional, high-resolution, low-light-output fluorescent screens directly. The results are comparable to those obtained
with the image intensifier.
5.3 In recent years (circa 1980’s) the 1980s new digital radiology techniques have been were developed. These methods produce
directly digitized representations of the X-ray field transmitted by an examination article. Direct digitization enhances the
signal-to-noise ratio of the data and presents the information in a form directly suitable for electronic image processing and
enhancement, and storage on magnetic tape. storage. Digital radioscopic systems use scintillator-photodetector and phosphor-
photodetector sensors in flying spot and fan beam-detector (pencil beam), fan beam-detector, or cone beam array arrangements.
5.4 All of these techniques employ television live monitor display presentation and can utilize various electronic techniques for
image enhancement, image storage, and video or data recording. These advanced imaging devices, along with modern video video
and data stream processing and analysis techniques, have greatly expanded the versatility of radioscopic imaging. Industrial
applications have become wide-spread: production examination of the longitudinal fusion welds in line pipe, welds in rocket-motor
housings, castings, transistors, microcircuits, circuit-boards rocket propellant uniformity, solenoid valves, fuses, relays, tires and
reinforced plastics are typical examples. Additionally the use of full automatic defect recognition systems for automotive casting
inspection using integrated or averaged images and an appropriately powered computer leads to a large cost reduction.
5.5 Limitations—Despite the numerous advances in RRTI radioscopic imaging technology, the sensitivity and resolution of
real-time systems usually are not as good as can be obtained with longer exposures obtained with film. In radiography the time
exposures and close contact between the film and the subject, the control of scatter, and the use of metallic screens make it
relatively simple to obtain better than 2 % penetrameter sensitivity in most cases. Inherently, because of statistical limitations
dynamic scenes require a higher X-ray flux level to develop a suitable image than static scenes. In addition, the product-handling
considerations in a dynamic imaging system mandate that the image plane be separated from the surface of the product resulting
in perceptible image unsharpness. Geometric unsharpness can be minimized by employing small focal spot (fractions of a
millimetre) X-ray sources, but this requirement is contrary to the need for the high X-ray flux density cited previously. An
alternative may be a micro-focus source and image integration with a computer system; the limitation in spatial resolution will be
the size of the focal spot, and in contrast-to-noise ratio, the available integration time for one resulting image. Furthermore,
limitations imposed by the dynamic system make control of scatter and geometry more difficult than in conventional radiographic
systems. Finally, dynamic radioscopic systems require careful alignment of the source, subject, and detector and often expensive
product-handling mechanisms. These, along with the radiation safety requirements peculiar to dynamic systems usually result in
capital equipment costs considerably in excess of that for conventional film radiography. The costs of expendables, manpower,
product-handling and time, however, are usually significantly lower for radioscopic systems.
6. Safety Precautions
6.1 The safety procedures for the handling and use of ionizing radiation sources must be followed. Mandatory rules and
regulations are published by governmental licensing agencies, and guidelines for control of radiation are available in publications
such as the Fed. Std. No. 21-CFR 1020.40. Careful radiation surveys should be made in accordance with regulations and codes
and should be conducted in the examination area as well as adjacent areas under all possible operating conditions.
7. Interpretation and Reference Standards
7.1 Reference radiographs produced by ASTM and acceptance standards written by other organizations may be employed for
radioscopic examination as well as for radiography, provided appropriate adjustments are made to accommodate for the differences
in the fluoroscopic images.
E1000 − 16
8. Radioscopic Devices, Classification
8.1 The most commonly used electromagnetic radiation in radioscopy is produced by X-ray sources. X rays X-rays are affected
in various modes and degrees by passage through matter. This provides very useful information about the matter that has been
traversed. The detection of these X-ray photons in such a way that the information they carry can be used immediately is the prime
requisite of radioscopy. Since there are many ways of detecting the presence of X rays, X-rays, their energy and flux density, there
are a number of possible systems. Of these, only a few deserve more than the attention caused by scientific curiosity. For our
purposes here, only these few are classified and described.
8.2 Basic Classification of Radioscopic Systems—All commonly used systems depend on two basic processes for detecting
X-ray photons: X-ray to light conversion and X-ray to electron conversion.
8.3 X Ray X-ray to Light Conversion–Radioscopic Systems—In these systems X-ray photons are converted into visible light
photons, which are then used in various ways to produce images. The processes are fluorescence and scintillation. Certain materials
have the property of emitting visible light when excited by X-ray photons. Those used most commonly are as follows:follows (see
section 10.6.3.1 for additional discussion on image intensifiers):
8.3.1 Phosphors—These include the commonly used fluorescent screens, composed of relatively thin, uniform layers of
phosphor crystals spread upon a suitable support. Zinc cadmium sulfide, gadolinium oxysulfide, lanthanum oxybromide, and
2 2
calcium tungstate are in common use. Coating weights vary from approximately 50 mg/cm to 100200 mg/cm.
8.3.2 Scintillators—These are materials which are transparent and emit visible light when excited by X rays. X-rays. The
emission occurs very rapidly for each photon capture event, and consists of a pulse of light whose brightness is proportional to
the energy of the photon. Since the materials are transparent, they lend themselves to optical configurations not possible with the
phosphors used in ordinary fluorescent screens. Typical materials used are sodium iodide (thallium-activated), cesium iodide
(thallium-activated) and sodium iodide (cesium-activated). These single crystal crystal, transparent or translucent ceramic
materials can be obtained in very large sizes (up to 30-cm45-cm or 12-in.17-in. diameter is not uncommon)now possible) and can
be machined into various sizes and shapes as required. ThicknessThicknesses of 20.1 to 100 mm (0.08 to 4 in.) are customary.
8.4 X Ray X-ray to Electron Conversion—Radioscopic Systems—X-ray photons of sufficient energy have the ability to release
loosely bound electrons from the inner shells of atoms with which they collide. These photoelectrons have energies proportional
to the original X-ray photon and can be utilized in a variety of ways to produce images, including the following useful processes.
8.4.1 Energizing of Semiconductor Junctions—The resistance of a semiconductor, or of a semiconductor junction in a device
such as a diode or transistor, can be altered by adding free electrons. The energy of an X-ray photon is capable of freeing electrons
in such materials and can profoundly affect the operation of the device. For example, a simple silicon “solar cell” connected to
a microammeter will produce a substantial current when exposed to an X-ray source.
8.4.1.1 If an array of small semiconductor devices is exposed to an X-ray beam, and the performance of each device is sampled,
then an image can be produced by a suitable display of the data. Such arrays can be linear or two-dimensional. Linear arrays
normally require relative motion between the object and the array to produce a useful real-time image. The choice depends upon
the application.
8.4.2 Affecting Resistance of Semiconductors—The most common example of this One technology used for direct X-ray-to-
electron device is the X-ray sensitive vidicon camera tube. Here the target layer of the vidicon tube, and its support, are modified
to have an improved sensitivity to X-ray photons. The result is a change in conductivity of the target layer corresponding to the
pattern of X-ray flux falling upon the tube, and this is directly transformed by the scanning beam into a video signal which can
be used in a variety of ways.
8.4.2.1 Photoconductive materials that exhibit X-ray sensitivity include cadmium sulfide, cadmium telluride (CdTe), zinc
cadmium telluride (CdZnTe), cadmium selenide, lead oxide, and selenium. The latter twoselenium, gallium arsenide, and silicon.
Some of these have been used in X-ray sensitive TV camera tubes. Cadmium sulfide is commonly used as an X-ray detector, but
not usually for image formation. Selenium, CdTe, and CdZnTe (CZT) have been formed over thin film transistor (TFT) arrays, and
are read-out directly in solid state imaging devices. These later devices with solid state read-out circuitry are more appropriately
defined as Digital Detector Arrays (DDAs), see E2736. Whereas the former devices where the direct converter is coupled with
camera tube technology are treated as radioscopic devices.
8.4.3 Microchannel Plates—These consist of an array or bundle of very tiny, short tubes, each of which, under proper
conditions, can emit a large number of electrons from one end when an X-ray photon strikes the other end. The number of electrons
emitted depends upon the X-ray flux per unit area, and thus an electron image can be produced. These devices must operate in a
vacuum, so that a practical imaging device is possible only with careful packaging. Usually, this will mean that a combination of
processes is required, as described more completely in 8.5.
8.5 Combinations of Detecting Processes—Radioscopic Systems—A variety of practical systems can be produced by various
combinations of the basic mechanisms described, together with other devices for transforming patterns of light, electrons, or
resistance changes into an image visible to the human eye, or which can be analyzed for action decision in a completely automated
system. Since the amount of light or electrical energy produced by the detecting mechanism is normally orders of magnitude below
the range of human senses, some form of amplification or intensification is common. Figs. 1-1311 illustrate the basic configuration
E1000 − 16
FIG. 1 Basic Fluoroscope
FIG. 2 Fluoroscope with Optics
FIG. 3 Light-Intensified Fluoroscope
FIG. 4 Light-Intensified Fluoroscope with Optics
of practical systems in use. For details of their performance and application see Section 10. Table 1 compares several common
imaging systems in terms of general performance, complexity, and relative costs.
9. Radiation Sources
9.1 General:
9.1.1 The sources of radiation for radioscopic imaging systems described in this guide are X-ray machines and radioactive
isotopes. The energy range available extends from a few keV to 32 MeV. Since examination systems in general require high dose
rates, X-ray machines are the primary radiation source. The types of X-ray sources available are conventional X-ray generators
that extend in energy up to 420750 keV. Energy sources from 1 MeV and above may be the Van de Graaff generator and the linear
accelerator. generator, linear accelerator, or the betatron. High energy sources with large flux outputs make possible the real-time
examination of greater thicknesses of material.
E1000 − 16
FIG. 5 LLLTV Fluoroscope
FIG. 6 Light-Intensified LLLTV Fluoroscope
FIG. 7 Scintillator Arrays, TV Readout
170 60
9.1.2 Usable isotope sources have energy levels from 84 KeV 84 keV (Thulium-170, Tm ) up to 1.25 MeV (Cobalt-60, Co ).
With high specific activities, these sources should be considered for special application where their field mobility and operational
simplicity can be of significant advantage.
9.1.3 The factors to be considered in determining the desired radiation source are energy, focal geometry, duty cycle, wave form,
half life, and radiation output.
9.2 Selection of Sources:
9.2.1 Low Energy—The radiation source selected for a specific examination system depends upon the material being examined,
its mass, its thickness, and the required rate of examination. In the energy range up to 420 keV, 750 keV, the X-ray units have an
adjustable energy range so that they are applicable to a wide range of materials. Specifically, 50-keV units operate down to a few
keV, 160-keV equipment operates down to 20 keV, 20 keV, and 420-keV450-keV equipment operates down to about 8525 keV.
A guide to the use of radiation sources for some materials is given in Table 2.
9.2.2 High-Energy Sources—The increased efficiency of X-ray production at higher accelerating potentials makes available a
large radiation flux, and this makes possible the examination of greater thicknesses of material. High-radiation energies in general
produce lower image contrast, so that as a guide the minimum thickness of material examined should not be less than three-half
value layers of material. The maximum thickness of material can extend up to ten-half value layers. Table 3 is a guide to the
selection of high-energy sources.
E1000 − 16
FIG. 8 X-ray Image Intensifier
FIG. 119 X-ray Sensitive Vidicon
FIG. 1210 Microchannel Plates
9.3 Source Geometry:
9.3.1 The physical size of the source of radiation is a parameter that may vary considerably. One reason is the dominating
unsharpness in the radiation detector, which can be of the order of 0.5 to 0.75 mm (0.02 to 0.03 in.). Thus, while While an X-ray
tube with a focal spot of 3 mm (0.12 in.) (0.12 in.) operating at a target to detector distance of 380 mm (15 in.) and penetrating
E1000 − 16
FIG. 1311 Flying Spot Scanner
a 25-mm (1-in.) thick material would contribute an unsharpness of 0.2 mm (0.008 in.), a detector unsharpness of 0.5 to 0.75 mm
would still be the principal source of unsharpness.
9.3.2 The small source geometry of microfocus X-ray tubes permits small target-to-detector spacings and object projection
magnification for the detection of small anomalies. The selection of detectors with low unsharpness is of particular advantage in
these cases. Where isotopes are to be evaluated for radioscopic systems, the highest specific activities that are economically
practical should be available so that source size is minimized.cases to the reduce the focal spot-detector distance (FDD). With high
magnification, the focal spot size would be the principal source of unsharpness.
9.3.3 Where isotopes are to be evaluated for radioscopic systems, the highest specific activities that are economically practical
should be available so that source size is minimized.
9.4 Radiation Source Rating Requirements:
9.4.1 The X-ray equipment selected for examination should be evaluated at its continuous duty ratings, because the economy
of radioscopic examination is realized in continuous production examination. X-ray units with target cooling by fluids are usually
required.
9.4.2 The wave form of X-ray units up to 420 keV are mostly of the full-wave rectified or the constant potential type. The
full-wave rectified units give 120 pulses per second which can present interference lines on the television monitor. Similarly the
high-energy sources which can High-energy sources, for example linear accelerators, which can operate at pulse rates up to 300400
pulses per second second, may produce interference lines. These lines can be minimized by the design of the real-time systems.
Other lower energy X-ray generators operate with pulse rates of more than 10,000 pulses/sec, thus the influence on real-time
imaging is negligible.
9.4.3 The radiation flux is a major consideration in the selection of the radiation source. For stationary or slow-moving objects,
radiation sources with high outputs at a continuous duty cycle are desired. X-ray equipment at the same nominal kilovolt and
milliampere ratings may have widely different radiation outputs. Therefore in a specific examination requirement of radiation
output through the material thickness being examined should be measured.
10. Imaging Devices
10.1 An imaging device can be described as a component or sub-system that transforms an X-ray flux field into a prompt
response optical or electronic signal.
10.2 When X-ray photons pass through an object, they are attenuated. At low-to-medium energies this attenuation is caused
primarily by photoelectric absorption, or Compton scattering. At high energies, scattering is by pair production (over 1 MeV) and
photonuclear processes (at about 11.5 MeV). As a result of attenuation, the character of the flux field in a cross-section of the X-ray
beam is changed. Variations in photon flux density and energy are most commonly encountered, and are caused by photoelectric
absorption and Compton scatterings.
10.3 By analyzing this flux field, wedeductions can make deductionsbe made about the composition of the object being
examined, since the attenuation process depends on the number of atoms encountered by the original X-ray beam, and their atomic
number.
10.4 The attenuation process is quite complex, since the X-ray beam is usually composed of a mixture of photons of many
different energies, and the object composed of atoms of many different kinds. Exact prediction of the flux field falling upon the
imaging device is therefore, difficult. Approximations can be made, since the mathematics and data are available to treat any single
photon energy and atomic type, but in practice great reliance must be placed on the experience of the user. In spite of these
difficulties, many successful imaging devices have been developed, and perform well. The criteria for choice depend on many
factors, which, depending on the application, may, or may not be critical. Obviously, these criteria will include the following
devices.
10.4.1 Field of View of Imaging Device—The field of view of the imaging device, its resolution, and the dynamic inspection
speed are interrelated. The resolution of the detector is fixed by its physical characteristics, so if the X-ray image is projected upon
E1000 − 16
TABLE 1 Comparison of Several Imaging Devices
(circa 1980’s)(new instrumentation and configurations to meet a similar need are continually being invented and commercialized)
NOTE 1—The data presented are for general guidance only, and must be used circumspectly. There are many variables inherent in combining such
devices that can affect results significantly, and that cannot be covered adequately in such a simple presentation. These data are based upon the personal
experiences of the authors and may not reflect the experiences of others.
X-ray
Fluorescent X-ray Image Semiconductor X-ray Microchannel Flying Spot/Line
Scintillating
Phosphors Intensifier Arrays Vidicon Plates Scanners
Crystals
Availability excellent good excellent good good fair (1980) fair (1983)
Availability excellent excellent excellent good fair fair
Auxiliary
A A
equipment shielding glass, shielding glass, CCTV, optics fluorescent screen, CCTV fluorescent fluorescent phosphor
needed optics optics optics special screen, scintillating
A A
LLLTV LLLTV electronics special pack- special electronics,
aging, CCTV, digitizers
output phos-
phor
A A
equipment shielding glass, shielding glass, CCTV, optics CCTV fluorescent fluorescent phos-
needed optics optics screen, phor or
A
LLLTV special pack- scintillating
aging, crystals,
CCTV, special
output phos- electronics,
phor digitizers
Usual readout Visual LLLTV LLLTV CCTV CCTV CCTV CCTV electronic/visual
methods
Usual readout Visual computer moni- computer moni- computer monitor(s) computer electronic/visual
methods tor(s) tor(s) monitor(s)
Other readout none none direct none none none none
methods
Other readout none none direct none none none
methods
Practical up to 4.5 10 4 20 20 20 10
resolution, usual
readout, lp/mm
Practical up to 4.5 10 4 20 20 10
resolution, usual
readout, lp/mm
Minimum large- 2 1 2 10 5 10 1
area contrast sen-
sitivity, %
Minimum large- 2 1 2 5 5 1
area contrast sen-
sitivity, %
Useful keVcp
range, min 25 25 5 20 20 15 25
range, max 300 10 MeV 10 MeV 150 250 2 MeV 15 MeV
range, min 25 25 5 20 15 25
range, max 300 10 MeV 10 MeV 250 2 MeV 15 MeV
Optimum keVcp 120 200 100 100 75 100 NA
Optimum keVcp 120 200 100 75 100 NA
Field of view, maxi- no practical 229-mm (9-in.) 305-mm (12- 25.4 × 25.4 mm 9.53 × 12.7 76-mm (3-in.) dia no limit
mum limit dia in.) dia (1 × 1 in.) mm ( ⁄8
× ⁄2 in.)
Field of view, maxi- no practical 229-mm (9-in.) 305-mm (12- 9.53 × 12.7 76-mm (3-in.) no limit
mum limit dia in.) dia mm ( ⁄8 dia
× ⁄2 in.)
Relative sensitivity low medium high medium low medium high
to X-rays
Relative sensitivity low medium high low medium high
to X-rays
Relative cost low high medium medium low high high
Relative cost low high medium low high high
Approximate useful 10 years indefinite 3 years indefinite 5 years 5 years 5 years
life
Approximate useful 10 years indefinite 3 years 5 years 5 years 5 years
life
Special remarks very simple high quality very practical new limited to small new new
image thin, objects
Special remarks very simple high quality very practical limited to small Rarely used No longer used
image thin, objects
A
Low-light level television (LLLTV) is a sensitive form of closed circuit television (CCTV) designed to produce usable images at illumination levels equivalent to starlight
−1 −4 2 −4 −7 2
(10 to 10 lm/m or 0.343 × 10 to 0.343 × 10 cd/m ).
E1000 − 16
TABLE 2 Low-Energy Radiation Sources for Aluminum and
A
Steel
Aluminum, Steel,
keVkV or Isotope
mm (in.) mm (in.)
40 5.1–12.8 (0.2–0.5) .
70 12–30 (0.5–1.2) 3–7.5 (0.12–0.3)
100 20–50 (0.8–2) 6.25–15.6
(0.25–0.62)
200 33.5–83.8 (1.3–3.3) 8–20 (0.32–0.8)
300 . 15–45 (0.6–1.8)
420 . 18–45 (0.71–1.8)
Thulium 170 . 3 (0.12)
Ytterbium 169 . 4 -15 (0.15 – 0.59)
Selenium 75 . 8 - 20 (0.31 – 0.78)
Iridium 192 . 26 (1.02)
A
The minimum thickness of material at a given energy represents two-half value
layers of material while the maximum thickness represents five-half value layers.
The use of a selected energy at other material thicknesses depends upon the
specific radiation flux and possible image processing in the real time radioscope
system.
TABLE 3 High-Energy Radiation Sources for Solid Propellant and
Steel
Steel, Solid Propellant,
MeV
mm (in.) mm (in.)
1.0 46.0–107.0 (1.8–4.2) 198.0–462.0
(7.8–18.2)
2.0 57.0–133.0 267.0–620.0
(2.24–5.24) (10.5–24.4)
4.0 76.0–178.0 (3–7) 358.0–836.0
(14.1–32.9)
A
10.0 99.0–231.0 (3.9–9.1) 495.0–1156.0
(19.7–45.5)
15.0 99.0–231.0 (3.9–9.1) 553.0–1290.0
(21.8–50.8)
Cesium-137 51.0 (2) .
Cobalt-60 57.0 (2.24) .
TABLE 3 High-Energy Radiation Sources for Solid Propellant and
Steel
Steel, Solid Propellant,
MeV
mm (in.) mm (in.)
1.0 46.0–107.0 (1.8–4.2) 198.0–462.0
(7.8–18.2)
2.0 57.0–133.0 (2.24–5.24) 267.0–620.0
(10.5–24.4)
4.0 76.0–178.0 (3–7) 358.0–836.0
(14.1–32.9)
A
10.0 99.0–231.0 (3.9–9.1) 495.0–1156.0
(19.7–45.5)
15.0 99.0–231.0 (3.9–9.1) 553.0–1290.0
(21.8–50.8)
Cobalt-60 57.0 (2.24)–180 (7.08) 267.0–620.0
(10.5-24.4)
A
There is no significant difference in the half-value layers for steel from 10 to 15
MeV.
it full-size (the object and image planes in contact), the resultant resolution will be approximately equal to that of the detector.
When detector resolution becomes the limiting factor, the object may be moved away from the detector, and towards the source
to enlarge the projected image and thus allow smaller details to be resolved by the same detector. As the image is magnified,
however, the detail contrast is reduced and its outlines are less distinct. (See 11.3.) It is apparent, also, that when geometric
magnification is used, the area of the object that is imaged on the detector is proportionally reduced. Consequently the area that
can be examined per unit time will be reduced. As a general rule, X-ray magnifications should not exceed 5× except when using
X-ray sources with very small (microfocus) anodes. In such cases, magnifications in the order of 10 to 20× are useful. When using
conventional focal-spot X-ray sources, magnifications from 1.2 to 1.5 provide a good compromise between contrast and resolution
in the magnified image.
E1000 − 16
10.4.2 Inherent Sensitivity of Imaging Device—The basic sensitivity of the detector may be defined as its ability to respond to
small, local variations in radiant flux to display the features of interest in the object being examined. It would seem that a detector
that can display density changes on the order of 1 to 2% at resolutions approaching that of radiography would satisfy all of the
requirements for successful radioscopic imaging. It is not nearly that simple. Often good technique is more important than the
details of the imaging system itself. The geometry of the system with respect to field of view, resolution, and contrast is a very
important consideration as is the control of scattered radiation. Scattered X rays X-rays entering the imaging system and scattered
light in the optical system produce background similar to fogging in a radiograph. This scatter not only introduces radiant energy
containing no useful information into the imaging system but also impairs system sensitivity and resolution. Careful filtering and
collimation of the X-ray beam, control of backscatter, and appropriate use of light absorbing materials in the optical system are
vital to good radioscopy. The low-resolution, low-contrast visible light images produced by the detector may pose special problems
in the choice of optical components. For example, a lens that would be an excellent choice for photography may be a poor choice
to couple a low-light-level television (LLLTV)imaging camera to a fluorescent screen.
10.4.2.1 This brief treatment just touches on a complex subject. When designing an imaging system, the reader should consult
other references.
10.5 Physical Factors—The selection of a radioscopic imaging system for any specific application may be affected by a number
of factors. Environmental conditions such as extremes of temperature and humidity, the presence of strong magnetic fields in the
proximity of image intensifiers and television cameras, the presence of loose dirt and scale and oily vapors can all limit their use,
or even preclude some applications. In production-line applications, system reliability, ease of adjustment, mean-time-between-
failures, and ease and cost of maintenance are significant factors. Furthermore, the size and weight of imaging system components
as well as positioning and handling mechanism requirements must be considered in system design, and interact with cost factors
in selection of a system.
10.6 X Ray X-ray to Light Conversion—Radioscopic Systems—For the purpose of radioscopy, a fluorescent screen can be
described as a sheet of material that converts X-ray photons into visible light, without use of external energy sources. light through
energy transitions in the material as the X-ray energy is absorbed and cascades to lower energy radiation. At these lower discrete
energies in the screen, the material goes into an excited state, that upon relaxation emits some of that energy as light. Screen
materials were known even before the discovery of X rays X-rays or radioactive materials, since substances which “glow in the
dark” have been known for centuries. In fact, it was a fluorescent screen that was the key to the discovery of X-rays. However,
enormous improvements have been made in understanding, manufacturing, and applying screens. Although the basic physical
phenomena involved are similar, it is convenient for our purposes to divide screens into two groups, fluorescent phosphors and
scintillating crystals.
10.6.1 Fluorescent Phosphors:
10.6.1.1 A fluorescent screen is a layer of phosphor crystals deposited on a suitable support backing, with a transparent
protective coating or cover. The crystals used have the ability to absorb energy from an X-ray photon and re-emit some of that
energy in the form of visible light. The amount of light produced for a given X-ray flux input is termed the brightness (luminance)
of the screen. The number of light photons emitted per unit exposure is the conversion effıciency. Resolution is the ability to show
fine detail (for high contrast objects), and contrast is the detectable discernible change in brightness with a specified change in input
flux. This is often specified as the minimum percentage thickness change in the object which can be detected. Image quality
indicators (IQI) are commonly used to make these tests. Most phosphors used in screens have limited ability to transmit the light
they produce without scattering or refraction due to their size, shape, coatings, and other factors, and are not truly transparent. Thus
the light that is produced by the lowermost layers is somewhat distorted by passage through the layers above. Consequently thicker
phosphors that have, in general, increased ability to absorb X-rays, and thus produce more light, usually produce brighter images
with lower resolution, as compared to thin screens of the same material.
10.6.1.2 The contrast of a fluorescent screen is influenced by the scattering of light and X rays X-rays within the structure of
the screen itself, and to a larger extent by the relative response of the screen to direct and scattered X rays. X-rays. The scattered
X rays, X-rays, particularly those scattered at large angles, consist of lower energy photons, to which the screen is more sensitive.
This has the effect of reducing the contrast.
10.6.1.3 In usual applications, the contrast of the fluorescent image for large areas (such as the outline of an IQI) is limited by
the contrast capability of the eye. Practical experience is that the lower observable limit is that change in brightness caused by a
1 % change in thickness of the object. Smaller differences may be possible with digitization and image processing techniques.
10.6.1.4 All fluorescent screens exhibit some persistence or afterglow. This is a function of the phosphor and activator used and
−5
to this extent may be somewhat controlled by the manufacturer. It is usually of the order of 10 s for calcium tungstate (CaWO )
−2 3 3 3+ 3+
screens and 10 for zinc sulfide (ZnS). Rare earth screens with terbium (Tb ) and europium (Eu ) activators have about the
−2 3+ −6 −9
same persistence (10 s), but other activators such as Ce can produce characteristic decay times as short as 10 to 10 s. The
relationship between brightness and resolution is clearly shown in Table 4.
10.6.1.5 These screens are commercially available and the choice of screen will be governed by the requirements of the user,
who must make a compromise choice between brightness, resolution, keV range, and apparent color of the image. The apparent
color of the fluorescent image is important both in the directly viewed and electronically scanned systems. Matching of spectral
content to the response of the human eye or that of a detector such as a television camera is significant in low-light-level systems,
E1000 − 16
A
TABLE 4 Properties of Some Common Fluorescent Screens
B
Relative Brightness With Attenuation
C
1 1 Resolution Color
⁄4-in. ⁄4-in.
Aluminum Aluminum
No. Formula Name Aluminum Steel
50 100 150 100 150 100 150 150 lp/in. nm
keVcp keVcp keVcp keVcp keVcp keVcp keVcp keVcp (mm)
1 CaWO calcium 6 13 2 8 1 2 0.5 30 (1.2) violet ;420
tungstate
2 ZnCdS zinc cadmium 3.5 46 120 22 65 7 25 3 50 (2.0) green ;540
sulfide
3 ZnCdS zinc cadmium 8 122 320 50 160 16 60 5 20 (0.8) green ;540
sulfide
4 Gd O S gadolinium 5 89 250 43 150 16 65 12 40 (1.6) yellow-green
2 2 j
oxysulfide ;550
5 Gd O S gadolinium 3.5 61 175 30 105 11 50 5 60 (2.4) yellow-green
2 2 j
oxysulfide ;550
6 LaOBr lanthanum 1 19 50 8 29 3.5 13 2 30 (1.2) blue ;460
oxybromide
A
TABLE 4 Properties of Some Common Fluorescent Screens
B
Relative Brightness With Attenuation
C
Resolution Color
Soft Medium Hard Hardest
Harder Spectrum
No. Formula Name Spectrum Spectrum Spectrum
50 100 150 100 150 100 150 150 lp/mm nm
keVp keVp keVp keVp keVp keVp keVp keVp
...