EPA 520/4-76-012
BACKGROUND REPORT
RECOMMENDATIONS ON GUIDANCE
FOR TECHNIC TO REDUCE
UNNECESSARY EXPOSURE FROM
X-RAY STUDIES IN
FEDERAL HEALTH CARE FACILITIES
ENVIRONMENTAL PROTECTION AGENCY
INTERAGENCY WORKING GROUP ON MEDICAL RADIATION
SUBCOMMITTEE ON TECHNIC OF EXPOSURE PREVENTION
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RECOMMENDATIONS ON GUIDANCE FOR TECHNIC TO REDUCE UNNECESSARY EXPOSURE
FROM X-RAY STUDIES IN FEDERAL HEALTH CARE FACILITIES
Report of
Subcommittee on Technic of Exposure Prevention
Interagency Working Group on Medical Radiation
U.S. Environmental Protection Agency
Washington, D.C. 20460
June 1976
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PREFACE
The Administrator of the Environmental Protection Agency formed an
Interagency Working Group on July 5, 1974, to develop guidance to
reduce unnecessary radiation exposures from the use of x rays in the
healing arts in Federal health care facilities. The consensus of this
group was that it is desirable and possible in Federal facilities to
reduce exposure from diagnostic uses of x rays by: 1) eliminating
clinically unproductive examinations, 2) assuring the use of optimal
technic when examinations are performed, and 3) requiring appropriate
equipment to be used. As a result of this consensus a Subcommittee on
Technic of Exposure Prevention was formed to examine the use of
equipment and technic to perform medical and dental x-ray examinations
and to make recommendations for guidance to assure that diagnostic
quality radiographs are produced with minimal patient exposure. The
recommendations made herein are believed to be basic to assuring that
these considerations are met in Federal health care facilities.
A Subcommittee on Prescription of Exposure to X rays has examined
considerations for eliminating clinically unproductive examinations.
Its report, which was published in March 1976, and this report will
form the basis for recommended Federal radiation guidance for the use
of x rays in Federal health care facilities. This Subcommittee
recognizes that the body of knowledge on both radiation exposure and
technic for performing x-ray examinations is rapidly changing and the
recommendations will, of necessity, need periodic review and
appropriate revision.
Fames E. Martin, Ph.D.
Chairman, Subcommittee on
Technic of Exposure Prevention
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CONTENTS
PAGE
PREFACE ii
MEMBERS iv
INTRODUCTION AND RECOMMENDATIONS 1
QUALITY ASSURANCE PROGRAMS 5
Equipment and Materials
Operational Procedures
EQUIPMENT OPERATOR PERFORMANCE 12
Operator Qualification
Operator Responsibility
PATIENT EXPOSURE CONSIDERATIONS 17
DENTAL CONSIDERATIONS 21
Operator Qualification
Technic
APPENDIX A 25
REFERENCES 33
iii
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MEMBERS
Department of the Air Force
Lt. Col. Johan Bayer, USAF, BSC
Department of the Army
Col. Vandy Miller, MSC, USA
Lt. Col. Robert Quillin, MSC, USA
Department of the Naw
Captain William Bottomley, DC, USN
Lt. Comdr. William Beckner, MSC, USN
Lt. Comdr. Robert Devine, MSC, USN
Chief Felton Pugh, MSC, USN
Environmental Protection Agency
James E. Martin, Ph.D., CHAIRMAN
DeVaughn Nelson, Ph.D.
Harry Pettengill, Ph.D.
Consultants
Otha Linton, M.S.J.
Director of Governmental Relations
American College of Radiology
William Properzio, Ph.D.
Bureau of Radiological Health
U.S. Food and Drug Administration
IV
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INTRODUCTION AND RECOMMENDATIONS
The fundamental objective of an x-ray examination is to obtain
optimum diagnostic information with minimum patient exposure. The
achievement of optimum diagnostic information with minimum exposure
requires: 1) assurance that all equipment is functioning properly and
calibrated as required; 2) operation of equipment is only by competent
personnel; 3) the patient is appropriately prepared; and 4) technic
factors which will minimize exposure are selected.
The Subcommittee on Technic of Exposure Prevention has considered
each of the above areas to assure that good technic is employed in
Federal health care facilities. The recommendations of this report
address quality assurance, radiographic technic, operator
qualifications, and exposure guidance. Because many details of good
radiographic procedures depend on good judgment by qualified
professionals, the recommended guidance is stated in the form of broad
principles. Programs of the various Federal agencies continue to
develop information and procedures that are expected to lead to optimal
mechanisms of meeting these broad principles.
Within this framework, the following recommendations are made for
guidance on technic for performing medical and dental radiographic
procedures in fixed Federal and government owned contractor-operated
health care facilities:
1. An equipment quality assurance program containing equipment
specifications, equipment calibration requirements, materials and
equipment performance requirements, and preventive maintenance
schedules should be established in all Federal health care facilities.
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2. The highest-speed film and film-screen combinations, which are
consistent with image quality requirements, should be used.
3. Radiographic films should be stored, handled, and processed in
appropriately equipped rooms. Periodic quality control inspections
should be made for each aspect of film storage, handling, and
processing that may affect radiographic quality or patient exposure.
4. The performance of diagnostic x-ray examinations should be in
accordance with a procedural program which details patient preparation,
use of technic charts, and quality control checks of finished
radiographs to minimize retakes.
5. Operation of diagnostic medical x-ray equipment should be by
individuals having adequate knowledge of radiation principles. These
individuals should be qualified by a combination of didactic training
and experience identical to or equivalent to the requirements of
programs approved by either the council on Medical Education of the
American Medical Association or the American Registry of Clinical
Radiography Technologists.
6. Individuals performing radiographic examinations should select
optimal technic and provide patients optimal preparation, instruction,
and positioning; proper collimation and shielding should be used to
restrict the x-ray beam as much as practicable to the clinical area of
interest.
7. Facility protocol concerning examinations of pregnant or
potentially pregnant patients should assure that medical consideration
has been given to possible fetal exposure and appropriate protective
measures are applied.
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8. Appropriate area shielding should be used to limit gonadal
exposure where such protection does not interfere with the objectives
of the examination.
9. Exposures from routine diagnostic x-ray examinations should be
periodically determined, the technic evaluated, and practicable
measures undertaken to reduce exposures for those examinations which
exceed the following Entrance Skin Exposure Guides (ESEG):
Examination (Projection) ESEG (milliroentaensT*
Chest (P/A) 30
Skull (Lateral) 300
Abdomen (A/P) 750
Cervical Spine (A/P) 250
Thoracic Spine (A/P) 900
Full Spine (A/P) 300
Lumbo-Sacral Spine (A/P) 1000
Retrograde Pyelogram (A/P) 900
Feet (D/P) 270
Dental (Bitewing and Periapical) 700
*Entrance skin exposure for a reference patient selected by
the NEXT program to have the following body part/thickness:
head/15 cm, neck/13 cm, thorax/23 cm, abdomen/23 cm, and
foot/8' cm.
10. Operation of diagnostic dental x-ray equipment should be by
individuals having adequate knowledge of radiation protection
principles. These individuals should be qualified by didactic training
and experience programs consistent with the Guidelines for Dental
Hygienist and Dental Assistant Training Programs in Dental Radiology
adopted by the Oral Radiology Section of the American Association of
Dental Schools.
11. Intra-oral radiography should be performed with open-ended,
shielded, position-indicating devices with the x-ray beam as near the
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size of the image receptor as practicable; other body tissues should be
shielded from the direct beam and stray radiation.
12. The highest-speed film or image receptor of ANSI speed group
rating of "D" or faster should be used for intra-oral radiography
consistent with image quality requirements.
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QUALITY ASSURANCE PROGRAMS
The production of consistent and high quality radiographs
concurrent with minimal patient exposure depends on two important
factors: quality performance of equipment and materials and optimal
performance of the operator. Because of the complex interrelationship
of equipment, technic, and procedural factors, each of which could
affect radiographic quality and exposure, a functional quality
assurance program to monitor the significant elements is desirable.
Such a program is important to provide the diagnostician with
consistent quality radiographs regardless of which operator or x-ray
generator is involved in performing the examinations. At the same time
such a program could minimize patient exposure and the number of retake
examinations with an anticipated reduction in material, equipment, and
personnel costs.
There is considerable recognition of the need for quality
assurance programs in diagnostic radiology. A Subcommittee of the Food
and Drug Administration's Medical Radiation Advisory Committee views
the existing lack of quality assurance programs in hospitals and
outpatient facilities as a major source of unnecessary patient exposure
and radiographs of poor diagnostic quality (1).
The benefits of consistently high quality radiographs and
increased production efficiency would in themselves seem to provide
compelling support for implementation of quality assurance programs in
Federal health care facilities. In addition, it appears that a
substantial portion of costs associated with a quality assurance
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program could be justified by savings of resources such as film,
processing chemicals, and labor. Meeting the objectives of quality
assurance requires periodic monitoring of equipment performance and
standards of procedure. The design and scope of quality assurance
programs are expected to vary. The program should be consistent with
the clinical specialty and available resources.
Equipment and Materials
The quality performance of equipment and materials is determined
by such factors as: 1) initial verification of equipment performance
per specifications, 2) ongoing testing and calibrations of equipment,
3) periodic cleaning, adjustment, and preventive maintenance for
equipment, and 4) verification of material performance. The level of
emphasis of each will vary according to the needs of each Federal
health care facility. Therefore, the details for implementing each of
these factors should be established by the appropriate authority.
Quality assurance of equipment begins with assuring that upon
completion of installation and calibration of newly purchased
equipment, and prior to its clinical use, that it meets Federal
regulations (3) and any additional performance requirements. Once
equipment has been placed into service, periodic performance and
preventive maintenance surveys should be conducted to provide prompt
remedial action and continuing assurance of desired operation. It is
important to monitor such parameters as x-ray tube potential, tube
current, timer, beam quality, filtration, and focal spot size,
especially when equipment is calibrated or receives preventive
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maintenance (3,4,5). Another factor which often affects the optimum
use of x-ray equipment is the beam alignment and beam-limiting device.
Because of the importance of equipment and materials in producing
high quality radiographs, it is recommended that:
An equipment quality assurance program containing
equipment specifications, equipment calibration
requirements, materials, and equipment performance
requirements, and preventive maintenance schedules
should be established in all Federal health care
facilities.
The quality of the finished radiograph depends upon the condition
of the film prior to its use; thus, it is desirable to evaluate
periodically the quality of unused film. Considerations of time, cost,
and traumatized patients associated with repeat exams also suggests the
need for a program to ensure adequate evaluation and handling of films
(6,7,8). All films should be handled and stored under carefully
controlled light, temperature, humidity, and background radiation
conditions so that fogging can be minimized (3,9,10). Use of "safe
lights" to minimize film fogging requires the selection of appropriate
filters for the particular wave length sensitivities of the films.
Dark rooms should be appropriately designed and operated to eliminate
light leaks.
A periodic review of film and film-screen combinations used and
their performance is suggested to assure optimal high quality
radiography with minimum patient exposure. Image receptors should be
as sensitive as is practicable consistent with the requirements of
examinations since the use of faster speed receptors generally reduce
patient exposure (11,12,13). On the other hand, cursory acceptance of
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advanced speed films or screens should not occur at the expense of
compromising necessary diagnostic information.
It is apparent that patient exposures can vary significantly just
on the basis of film/screen considerations. Image receptor
combinations recommended in the summary report of the First Image
Receptor Conference on Film-Screen Combinations can be used as a
current guide in this regard (14). The image receptor combinations
discussed in this report represent a recent consensus of an assembled
group of radiology experts. For most cases, the typically preferred
receptors ranged from par-speed film/par-speed screen to par-speed
film/hi-speed screen combinations. Recent studies have shown that some
of the newer film/screen combinations can achieve a reduction in
exposure for the majority of diagnostic x-ray examinations by factors
of two to four without a reduction in quality of the image (15,16).
Reductions in exposure can be achieved with certain technic factors by
the use of rare earth intensifying screens together with suitable films
which match the light emission characteristics of the screens. On this
basis, it is recommended that:
The highest-speed film and film-screen
combinations, which are consistent with image
quality requirements, should be used.
The concurrent objectives of consistently high quality radiographs
and minimized patient exposure also require quality film processing.
Whether processing is accomplished manually or by machine, the quality
of the equipment, materials, calibrations, housekeeping, and preventive
maintenance are important.
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Automatic processing machines can, with proper maintenance and
monitoring, be used to obtain consistent high quality processing.
Selection of processors should assure that the processing achieved
provides an image commensurate with the level of resolution and
consistency of the other components of the radiology system (7,17,18).
A preventive maintenance protocol for automatic processors is
particularly important because of the many moving parts susceptible to
failure. The scheduled cleaning and maintenance recommendations of the
equipment manufacturers or an equivalent should be followed.
The concentration and replenishment of chemical solutions, proper
functioning of temperature, process speed, and other controllers are
significant considerations of film processing equipment. One method of
assuring quality of film processing is to use control films
periodically, especially upon the introduction of new preparations of
processing chemicals. Sensitometric strip techniques have been shown
to be of value in monitoring the quality of film processing (3,19,20).
On the basis of these considerations, it is recommended that:
Radiographic films should be stored, handled, and
processed in appropriately equipped rooms;
periodic quality control inspections should be
made for each aspect of film storage, handling,
and processing that may affect radiographic
quality or patient exposure.
Operational Procedures
Monitoring of operator performance is important to ensuring that
high quality radiographs are produced with minimized patient exposure.
Upon receipt of an examination request, the x-ray equipment operator
determines a patient's measurements and, in accordance with facility
protocol, selects the film-screen-grid combination, the kV, and the
mAs. Some facilities have both single and three-phase x-ray generators
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and use several film-screen-grid combinations. In such situations, an
up-to-date technic chart which gives optimum values for each generator
is especially important. The chart can be particularly important for
unusual situations and when the usual operator is not available.
Reduction of the number of radiographic retakes is generally
agreed to be important in eliminating unnecessary exposure. Common
causes for retakes are patient motion, errors in exposure, collimation,
or positioning. Values of reported retake rates have ranged from
approximately two to ten percent (21,22,23,24,25). Some variation in
retake rates is reflective of the medical specialty and whether the x--
ray facility is in a clinic, hospital, or teaching facility. Every
reasonable effort should be made to eliminate retake examinations.
Unnecessary duplicate examinations result in costs and patient
exposure that should be eliminated. Use of examinations on file is
basic to this concern. This consideration has been addressed in a
large-scale pilot project to automate scheduling and file room
functions (26) .
Monitoring by qualified technologists of the final processed
radiograph for diagnostic quality before the diagnostician views it
appears to be of value in identifying problem areas. Prompt monitoring
provides for timely repeat examinations with minimum inconvenience and
anxiety to the patient and provides notice of poor performance of
equipment or operators (27). The recording of information related to
retakes (e.g., the examination, projection, reason, technologist, x-ray
generator, etc.) can assist in determining patterns of retakes and in
decreasing their frequency.
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It is recommended that:
The performance of diagnostic x-ray examinations
should be in accordance with a procedural program
which details patient preparation, use of technic
charts, and quality control checks of finished
radiographs to minimize retakes.
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EQUIPMENT OPERATOR PERFORMANCE
It is possible to obtain a range of radiographs considered
diagnostically acceptable by most radiologists and have entrance skin
exposure vary by a factor of six to ten because of the choice of the
various technic factors (28,29,30). Because of the importance of
operators in minimizing exposure they ought to be cognizant of those
technic interrelationships which accomplish minimized exposure. Each
patient should have confidence that equipment operators: 1) are
adequately trained to produce a diagnostic quality radiograph, 2) know
how to produce the prescribed radiograph with the lowest possible
exposure, and 3) periodically demonstrate continuing occupational
competence.
Operator Qualification
Available evidence indicates that x-ray technologists who are
trained and credentialed (registered, licensed, or certified by a State
or voluntary credentialing organization) more often produce radiographs
with lower average patient exposures than nontrained or noncredentialed
operators (29,31). Such results should not be unexpected since many
noncredentialed operators have little or no formal training in anatomy,
patient positioning, or radiation protection practices. The analyses
of Nationwide Evaluation of X-ray Trends (NEXT) program (32) data and
recent proficiency test results indicate that inadequately trained
operators are likely to expose patients and themselves unnecessarily
(29,33). Personnel responsible for patient preparation and
positioning, selection of technic factors, radiation protection
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measures, and film processing should be trained to produce quality
radiographs. They should also be able to optimize various technic
factors of the x-ray equipment to produce the radiograph at the lowest
practicable patient exposure and to use optimal procedures in working
with patients and ancillary equipment to reduce to a minimum the number
of repeat examinations (11,28,34,35). Performance of x-ray
examinations by untrained personnel does not appear justified except
for unusual circumstances.
Operator competence is normally achieved through the successful
completion of a professionally approved training program which provides
both a didactic base and sufficient practical experience. Such
competence should be developed in accordance with training programs
identical to or equivalent to those approved by the Council on Medical
Education of the American Medical Association or the American Registry
of Clinical Radiography Technologists.
Even though both didactic and practical training are necessary,
the primary criterion is for each operator to accomplish and maintain a
capability to perform optimal examinations. The American Society of
Radiologic Technologists has advocated such a criterion (36).
Continuing competence and professional growth should be encouraged with
specific opportunities to further the person's knowledge and skills
through attendance at workshops and institutes.
A policy should be established by the responsibile authority which
details: 1) who may operate diagnostic x-ray equipment and the
supervision required, 2) the education-training and/or proficiency
requirements for x-ray equipment operators, and 3) requirements for
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continuing education and demonstration of proficiency. This policy
should be reviewed periodically and revised as appropriate. It is
recommended that:
Operation of diagnostic medical x-ray equipment
should be by individuals having adequate knowledge
of radiation protection principles. These
individuals should be qualified by a combination
of didactic training and experience identical to
or equivalent to the requirements of programs
approved by either the Council on Medical
Education of the American Medical Association or
the American Registry of Clinical Radiography
Technologists.
Operator Responsibility
The responsibility of operators in performing x-ray examinations
should be discharged through adherence to prescribed protocol. The
operator should not perform any examination which has not been
prescribed by an authorized person. In performing an examination, he
should prepare the patient on the basis of the requesting prescription
and facility protocol. Patients should be attired suitably with all
objects removed that might cause artifacts and be positioned properly.
They should also be instructed when to hold their breath and on the
position required in each view to prevent blurring of the radiograph
due to motion.
Collimation of the x-ray beam and shielding of body areas not
being examined minimizes unnecessary exposure. Regardless of all other
technic considerations, the useful beam should be confined to the
clinical area of interest (12,13,37,38). The beam size should be
generally limited to the image receptor size or smaller. The operator
has a responsibility to use shielding where appropriate and practicable
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to further limit the exposure of body tissues (11,27,28,39,40).
Therefore, it is recommended that:
Individuals performing radiographic examinations
should select optimal technic and provide patients
optimal preparation, instruction, and positioning;
proper collimation and shielding should be used to
restrict the x-ray beam as much as practicable to
the clinical area of interest.
Special effort should be made to protect the blood forming organs
of children (38,41,42). Particular care should be exercised when a
fetus may be irradiated. The determination of whether a female patient
may be pregnant should be considered by the referring clinician when
the x-ray examination is prescribed. In addition, the procedure
followed by an x-ray facility should ascertain that such a
consideration has been made prior to exposing the patient so that
additional precautions may be taken. Such a procedure would provide a
mechanism for the diagnostician to consult the referring clinician
before conducting the examination or to alter the examination, if the
examination could result in exposure of the fetus, operators have a
responsibility to use shielding to minimize such exposure. Therefore,
it is recommended that:
Facility protocol concerning x-ray examinations of
pregnant or potentially pregnant patients should
assure that medical consideration has been given
to possible fetal exposure and appropriate
protective measures are applied.
Minimization of the Genetically Significant Dose (GSD) has been a
major goal of radiological protection for many years in order to
provide protection for future generations. In an effort to reduce the
GSD to the population, the U.S. Food and Drug Administration, in
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cooperation with its Medical Radiation Advisory Committee and the
American College of Radiology, has developed a proposed guideline (21
CFR 1000, Subpart C) which recommends the use of gonadal protection for
those procedures in which the gonads lie within or are in close
proximity to the x-ray field and where their exclusion would not
compromise the clinical objectives of the examination (43) . Specially
designed shields for males were field tested during the course of
developing the proposed guidelines and were found to be a desirable
action for minimizing the GSD. This consideration is particularly
important for those examinations which result in gonadal exposure of
persons of reproductive potential due to the increasing use of x-rays
in medical care (12,13,37,38,41). On this basis, it is recommended
that:
Appropriate area shielding should be used to limit
gonadal exposure where such protection does not
interfere with the objectives of the examination.
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PATIENT EXPOSURE CONSIDERATIONS
Production of a radiograph results in two determinants: the
qualitative evaluation by the diagnostician of the required diagnostic
quality of the radiograph and the amount of radiation exposure required
to produce it. Each radiograph is evaluated for acceptable quality by
a technologist or the diagnostician. An explicit evaluation of
exposure is not usually made for each radiograph, although a change in
radiographic quality generally provides an indication of exposure
variation. A periodic evaluation of exposures in accordance with
appropriate guidelines for routine examinations would appear to provide
a mechanism to indicate levels above which good technic was probably
not used and appropriate actions are warranted to reduce such
exposures.
The development of exposure guides necessitates consideration of
those technic factors which most affect the exposure. Data from the
Nationwide Evaluation of X-ray Trends (NEXT) were used for this purpose
as detailed in Appendix A. The NEXT data probably provide a
representative profile of the practice of diagnostic radiology in the
United States at the present time. These data reflect the myriad of
combinations of x-ray generator types; high, medium, and slow films and
screens; film processing technic; high, medium, and low contrast
requirements of the diagnostician; and a range of skills of equipment
operators. Therefore, regardless of the specific details or
combinations of all these factors, the frequency distributions of
entrance skin exposures (ESE) derived from the NEXT data are assumed to
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be sufficiently representative of the complex system of diagnostician
preference, operator technic, and x-ray equipment performance for the
selected routine examinations.
The distributions of ESE from the NEXT data (Appendix A, Figures
1-12) are generally skewed to the high exposure side and at some point
they begin to represent unnecessary exposure due to poor equipment or
less than optimal technic factors. The choice of the point in the
distribution where exposures become unnecessarily high is difficult
since it is necessary to allow for a normal range of diagnostician
preference and state-of-the-art variations in x-ray generating
equipment, ancillary equipment, and technic factors. Careful
consideration of these factors and the ESE data from the NEXT program
suggests that exposures above the third quartile (i.e., those in the
fourth quartile) probably represent unnecessary exposure. In order to
determine whether exposures in the fourth quartile were unnecessary,
the military services reviewed such surveys to determine whether
adjustments in equipment and technic factors could be made to reduce
the ESE below the fourth quartile without significantly affecting image
quality. For these surveys, it was found that minor adjustments in
technic could reasonably be made to reduce values of ESE below the
fourth quartile.
There are several examples for the use of the third quartile as
the level above which patient exposures could be considered excessive.
In the consideration of the range of exposures utilized for chest
examinations as represented by NEXT survey data, a Bureau of
Radiological Health staff report noted that "exposures falling above
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the third quartile can be considered as overexposures to patients"
(29). The Illinois Division of Radiological Health, Department of
Public Health, reasoned that if 75* of the existing facilities could
obtain a clinically acceptable radiograph by exposing patients below
that level, then the other 25% of facilities should be able to alter
their technic to reduce unnecessarily high radiation exposure (44).
The decision that exposure guides should be at the third quartile
of the NEXT data accommodates these considerations. It is important,
however, to emphasize that good technic can be selected which will
generally produce practicable levels of exposure well below these
guides. For each type of x-ray examination there exists, within
available technology, an optimal combination of type of x-ray
generator, technic factors and ancillary equipment to produce a
diagnostic radiograph at optimal exposure. Hence, it is important to
evaluate each system to determine what exposure is as low as reasonably
achievable and to establish procedures that routinely assure that
exposures are consistently near that exposure level. Such
determinations require an evaluation of the diagnostic requirements,
generators, films, screens, technic factors, etc. of each facility. In
certain instances, it may be reasonable to exceed the exposure guide
for the purpose of specified diagnostic information. The decision to
exceed a guide should be based on an evaluation that the need for
additional diagnostic information justifies the exception.
It is emphasized that these proposed guides apply to exposures for
routine or non-specialty examinations and their implementation could be
done with a reasonable expenditure of resources without restricting the
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diagnostician's preference for image receptor combinations and
radiographic technic. On the basis of these considerations it is
recommended that:
Exposures from routine diagnostic x-ray
examinations should be periodically determined,
the technic evaluated, and practicable measures
undertaken to reduce exposures for those
examinations which exceed the following Entrance
Skin Exposure Guides (ESEG):
Examination (Prolection) ESEG (milliroentaens) *
Chest (P/A) 30
Skull (Lateral) 300
Abdomen (A/P) 750
Cervical Spine (A/P) 250
Thoracic Spine (A/P) 900
Full Spine (A/P) 300
Lumbo-Sacral Spine (A/P) 1000
Retrograde Pyelogram (A/P) 900
Feet (D/P) 270
Dental (Bitewing and Periapical) 700
*Entrance skin exposure for a reference patient selected by
the NEXT program to have the following body part/thickness:
head/15 cm, neck/13 cm, thorax/23 cm, abdomen/23 cm, and
foot/8 cm.
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DENTAL CONSIDERATIONS
The basic objective of the use of radiation in dentistry is to
obtain the optimal diagnostic yield with the minimum of exposure to the
patient, dental personnel and the public (45,46). Therefore, the
previous considerations of quality assurance, operator competence, and
minimized patient exposure have the same applicability to diagnostic
dental radiology. The significant use of radiographic procedures in
dentistry warrants addressing elements of recommended practice
specifically related to this profession.
Equipment Operator Qualification
The operator should receive the appropriate education and training
in the areas of anatomy, physics, technic principles of radiographic
exposure, radiation protection, radiographic positioning, and film
processing that are relevant to dental radiography.
All training programs designed to qualify a person to perform
radiographic procedures in dentistry should satisfy the Guidelines for
Dental Hygienist and Dental Assistants Training Programs in Dental
Radiography adopted by the Oral Radiology Section of the American
Association of Dental Schools. These guidelines were developed to
assure the protection of the public and improve -the diagnostic yield of
dental radiographs. Primary objectives of the guidelines are that
"...upon completion of a dental radiology training program the dental
hygienist and dental assistant should be able to;
1. Express and practice radiological health measures that are
required by legal and/or ethical considerations,
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2. Describe and demonstrate competency in theoretical
considerations underlying radiation hygiene and radiological practice,
3. Expose, process, evaluate for quality, mount and file
radiographic projections usually involved in dental practice,
4. Produce films with density, definition, contrast and other
attributes of sufficient diagnostic value to the dentist" (47).
Therefore, it is recommended that:
Operation of diagnostic dental x-ray equipment
should be by individuals having adequate
knowledge of radiation protection principles.
These individuals should be qualified by didactic
training and experience programs consistent with
the Guidelines for Dental Hygienist and Dental
Assistant Training Programs in Dental Radiology
adopted by the Oral Radiology Section of the
American Association of Dental Schools.
Technic
Technic is as important for producing quality dental radiographs
as it is in general medical diagnostic radiology. Important aspects of
dental technic for reducing patient exposure are the accurate
positioning and the use of the smallest practicable x-ray beam to the
clinical area of interest. Collimation for dental x-ray systems to
limit the beam should be in accordance with the beam diameter at skin
entrance requirement of the Federal Diagnostic X-ray Equipment
Performance Standards [21 CFR 1020.31(f)]. Significant advances in
exposure reduction have been shown by the use of open-ended, shielded,
position-indicating devices (PID) and a number of voluntary standard-
setting organizations have recommended their use (45,48,49,50). In
1968, the Council on Dental Research of the American Dental Association
(ADA) developed a set of recommendations which includes the use of
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open-ended shielded cones (51). The Department of Health, Education
and Welfare has also recommended that dental practitioners should be
encouraged through increased educational and training activities to
adopt the paralleling, long-cone technic which uses the long open-ended
shielded PID (52). Regardless of other technic considerations, the
useful beam should be limited insofar as practicable to the clinical
area of interest through the use of definitive beam collimation and
body shields. Therefore, it is recommended that:
Intra-oral radiography should be performed with
open-ended, shielded, position-indicating devices
with the x-ray beam as near the size of the image
receptor as practicable; other body tissues should
be shielded from the direct beam and stray
radiation.
In addition to the essential considerations of collimation, the
general recommendation to use the fastest speed image receptor
consistent with diagnostic requirements is again most important and
appropriate. In 1968 the Council on Dental Research (ADA) recommended
that dental clinics "...use the fastest speed film available" and that
they "...request film of ANSI group rating of "D" or faster" (51,52).
On the basis of this finding and the resultant patient exposure
reduction with adequate film quality, it is recommended that:
The highest-speed film or image receptor of ANSI
speed group rating of "D" or faster should be used
for intra-oral radiography consistent with image
quality requirements.
It is recognized that the technic and technology of dental
radiography are continually evolving and that new methodologies will be
refined to provide practicable alternatives to current ones. The
desirability of limiting the x-ray beam size to that of the image
23
-------
receptor has been accomplished only recently, for example, by
rectangular collimation technic (53,54,55,56). Another approach which
involves placing a new focused radiation source within the mouth to
reduce patient exposure is being investigated at the National Institute
of Dental Research (57). Therefore, recommendations for dental
radiography will, of necessity, need periodic review and appropriate
revision.
24
-------
APPENDIX A
The purpose of this Appendix is to present the data considered in
developing exposure guidelines. The exposure data were obtained from
the Nationwide Evaluation of X-ray Trends (NEXT), a program of the
Conference of Radiation Control Program Directors (32).
The NEXT surveys provide the most recent data on radiation
exposures and the corresponding technic factors used for selected
radiographic examinations. Table 1 contains a list of the radiographic
projections currently being surveyed in the NEXT program and the number
of surveys conducted by the 37 participating States (labeled "all
states") for the period July 1, 1973 through June 30, 1975 and the
military services (labeled "Federal") from July 1973 through December
1975. The number of "Federal" surveys is quite limited when compared
to "all-states" surveys, but both groups of surveys exhibit similar
technic factors and exposure value summary statistics as shown in
Tables 2, 3, and 4. For this reason, the larger statistical base
provided by the "all-states" survey data were used as representative of
patient exposure from x-ray examinations in Federal facilities.
The summary data in Tables 2, 3, and 4 do not demonstrate a
consistent statistically-firm pattern for these factors. The frequency
distributions of entrance skin exposures (ESE) derived from the "all-
states" NEXT data for each examination/projection are shown in Figures
1 through 12. The distributions of these data are generally skewed to
the high exposure side probably because of the use of either faulty x--
ray generators or less than optimal technic.
25
-------
Table 1
Type and Number of Nationwide Evaluation of X-ray Trends (NEXT)
Radiographic Examination Surveys for "All-States"
(July 1, 1973 to June 30, 1975) and "Federal"
(July 1, 1973 to December 31, 1975)
Examination (Projection)
Chest (P/A)
Skull (Lat)
Abdomen (A/P)
Retrograde Pyelogram (A/P)
Thoracic Spine (A/P)
Cervical Spine (A/P)
Lumbo-Sacral Spine (A/P)
Full Spine (A/P)
Feet (D/P)
Bi tewing Dental
Periapical Dental
Cephalometric Dental
No. of Surveys
"All-States"
1670
136
564
122
51
223
695
47
66
1752
1055
35
No. of Surveys
"Federal"
281
49
135
20
13
18
97
3
13
138
115
0
26
-------
TABLE 2. SUMMARY OF kVp FACTORS FOR NEXT SURVEYS
Type of Examination
Chest (P/A)
Skull (Lateral)
Abdomen (A/F)
Retrograde Pyelogram
Thoracic Spine (A/P)
Cervical Spine (A/P)
Lumbo-Sacral Spine (A/P)
Full Spine (A/P)
Feet (D/P)
Dental (Bitewing)
Dental (Periapical)
Dental (Cephalometric)
"All-States" Surveys
No. of
Surveys
1667*
136
564
122
51
223
695
47
59*
1759*
1054*
35
kVp VALUES
Mean Low High
80
72
78
77
75
69
77
79
61
71
71
81
40
48
45
55
57
40
55
64
45
40
40
60
150
94
125
106
90
100
106
96
90
110
110
98
"Federal" Surveys
No. of
Surveys
281
49
135
20
13
18
97
3
13
138
115
0
kVp VALUES
Mean Low High
83
73
83
72
80
71
79
76
58
84
83
0
40
58
58
58
68
60
62
72
50
60
43
0
140
92
110
82
92
80
100
80
72
100
100
0
to
-J
*The number of surveys differs from number of surveys given in Table 1, due to omission of kVp entry in
survey data.
-------
TABLE 3. SUMMARY OF mAs FACTORS FOR NEXT SURVEYS
Type of Examination
Chest (P/A)
Skull (Lateral)
Abdomen (A/F)
Retrograde Pyelograms
Thoracic Spine (A/P)
Cervical Spine (A/P)
Lumbo-Sacral Spine (A/P)
Full Spine (A/P)
Feet (D/P)
Dental (Bitewing)
Dental (Periapical)
Dental (Cephalometric)
"All-States" Surveys
No. of
Surveys
1670
136
564
122
51
223
695
47
66
1752
1055
35
mAs VALUES
Mean Low High
12
50
85
91
82
48
112
173
18
7
7
18
2
5
2
6
12
2
15
20
1
1
1
3
100
150
300
300
200
200
450
400
80
54
75
60
No. of
Surveys
281
49
135
20
13
18
97
3
13
138
115
0
"Federal" Surveys
mAs VALUES
Mean Low High
12
60
87
122
91
33
100
97
66
6
7
0
1
25
2
20
30
20
25
90
2
1
1
0
100
150
200
240
160
60
200
100
150
30
105
0
to
00
-------
TABLE 4. SUMMARY OF ESE FACTORS FOR NEXT SURVEYS
Type of Examination
Chest (P/A)
Skull (Lateral)
Abdomen (A/F)
Retrograde Pyelogram
Thoracic Spine (A/P)
Cervical Spine (A/P)
Lumbo-Sacral Spine (A/P)
Full Spine (A/P)
Feet (D/P)
Dental (Bitewing)
Dental (Per lap leal)
Dental (Cephalometric)
"All-States" Surveys
No. of
Surveys
1670
136
564
122
51
223
695
46
66
1752
1055
35
ESE VALUES1
Mean Low
24
291
601
673
646
206
787
275
275
579
588
44
2
28
22
78
60
13
41
70
28
62
51
7
High
266
2730
2222
2200
1737
1099
5372
1417
2676
6771
7559
138
"Federal" Surveys
No. of
Surveys
281
49
135
20
13
18
97
3
13
138
115
0
ESE VALUES1
Mean Low High
33
337
659
558
746
144
777
495
128
354
330
0
3
39
4
62
67
32
40
331
2
15
15
0
369
2821
2471
1131
1572
319
5544
653
470
2258
2345
0
to
VO
1Entrance Skin Exposure (ESE) in milliroentgens.
-------
FIGURE 1 CHEST (P/A) 1670 SURVEYS
FIGURE 3 ABDOMEN (A/P) 564 SURVEYS
C*3
30
25
20
151
10
5
0
—
_
16
-
2
5 10
23
15
19
20
EXPOSURE
FIGURE 2
30
25
20
15
10
5
-
_
15
-
1
1
0 "
1
12
25
7
I 5
30 35
4 1
— — 1 z
40 45 50
7
50 +
SKIN ENTRANCE IN mR
SKULL (LAT.) 136
i i
I
i_15
'
12
1 10
SURVEYS
4 3
9
JU
25
5
5 20
E._
15
z
| 10
»
0
—
15 15
MMIM..^
.„ . " 1 11 i-^-l
10 1 ^H 9
L... _
6 R
1 1
1
100 200300400500600700800900 1000 1000 +
EXPOSURE SKIN ENTRANCE IN mR
FIGURE 4 RETROGRADE PYELOGRAM
122 SURVEYS
30
25
&
3 20
a
£ 15
s
5 10
a.
5
n
-
19
1 1B
1 14
11
9
7 | ' 7 77
-^-1 1
inn inn onn xnn cm an IIHl RHfl Mm IflDn IflflflH
50 100150200250300 350400450 500500 +
EXPOSURE SKIN ENTRANCE IN mR
EXPOSURE SKIN ENTRANCE IN mR
-------
FIGURE 5 THORACIC SPINE (A/P) 51 SURVEYS
FIGURE 7 LUMBO-SACRAL SPINE (A/P) 695 SURVEYS
30
25
15
to
0
2
100
8 8
200 300
17
400
11
1 •
500 600
13
700
EXPOSURE SKIN ENTRANCE IN
FIGURE 6 CERVICAL SPINE
30
25
20
15
10
5
0
r-
_
7
19 19
13
13 13
0
BOO
mR
10
4
30
25
5
19 5 20
900
1000
1000 +
i
£ 15
0
gg 10
a.
5
0
21 21
16
lj
10
5
bMMM^^^K ^
3 ' 1 2 2
1
200 400 600 800 1000 1200 1400 1600 1800 2000 2000 +
EXPOSURE SKIN ENTRANCE IN mR
(A/P) 223 SURVEYS FIGURE 8 FULL SPINE (A/P) 47 SURVEYS
2
2
4
1
1 2
30
25
S
g 20
15
a 10
6 °"
5
0
-
19
I/
15 j [ 15
- 9 9
6
| 4 4
^1 ^ ^^^^^™
i — >
Ql 1M 150 200250300350400 500500 +
50 100 150 200250300350400 450 500500 +
EXPOSURE SKIN ENTRANCE IN mR
EXPOSURE SKIN ENTRANCE IN mR
-------
FIGURE 9 FOOT WEIGHT BEARING (D/P) 66 SURVEYS
FIGURE 11 DENTAL PERIAPICAL 1055 SURVEYS
ro
30
25
Z in
gc
t
i •
5
g
r a
17
-
11
50 100 150
6
200
11
250
0
300
5 8
30
25
1
3
E 15
12 £
2 2
350 400
EXPOSURE SKIN ENTRANCE IN mR
FIGURE 10
DENTAL BITEWING POSTERIOR 1752
30
25
B 9fl
£ IE
5 10
£•
5
0
i-
20
15
-
1
15
12
7
i
6
~^~\ 4
E 10
5
n
—
20
15 15 15
10
^-L_6
1 4 * 3
1 '
450 500 500+ 100 200 300 400500 600 700 800 900 1000 1000 +
EXPOSURE SKIN ENTRANCE IN mR
FIGURE 12
SURVEYS DENTAL CEPHALOMETRIC (LAT.) 35 SURVEYS
30
25
59(1
20
3
3
11 rr ic
4
I—LJ
~~ 13
j= 1"
5.
5
0
r-
20
| 17
44
11
~R 991 „
V O
61 — ft c
100 200300400500600700800900 1000 1000 +
EXPOSURE SKIN ENTRANCE IN mR
1020304050607080
EXPOSURE SKIN ENTRANCE IN mR
90 100 100 +
-------
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37
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