EPA 520/4-76-019
FEDERAL GUIDANCE REPORT NO. 9
RADIATION PROTECTION GUIDANCE
FOR
DIAGNOSTIC X RAYS
ENVIRONMENTAL PROTECTION AGENCY
-, • ' MTERAGENCY WORKING GROUP ON MEDICAL RADIATION
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FEDERAL GUIDANCE REPORT NO. 9
RADIATION PROTECTION GUIDANCE FOR DIAGNOSTIC X RAYS
Interagency Working Group on Medical Radiation
U.S. Environmental Protection Agency
Washington, D.C. 20460
October 1976
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PREFACE
The authority of the Federal Radiation Council to provide radiation protection
guidance was transferred to the Environmental Protection Agency on December 2,1970,
by Reorganization Plan No. 3. Prior to this transfer, the Federal Radiation Council
developed reports which provided the basis for guidance recommended to the President
for use by Federal agencies in developing standards for a wide range of radiation
exposure circumstances. This report, which was prepared in cooperation with an
Interagency Working Group on Medical Radiation formed on July 5, 1974, constitutes a
similar objective to provide the basis for recommendations to reduce unnecessary
radiation exposure due to medical uses of diagnostic x rays.
The Interagency Working Group developed its recommendations with the help of
two subcommittees. The Subcommittee on Prescription of Exposure to X rays examined
factors to eliminate clinically unproductive examinations and the Subcommittee on
Technic of Exposure Prevention examined factors to assure the use of optimal technic in
performing x-ray examinations. Both subcommittees also considered the importance of
appropriate and properly functioning equipment in producing radiographs of the required
diagnostic quality with minimal exposure. Reports by these subcommittees were made
available for public comment. The recommendations of the Working Group, the results of
public participation, and other considerations form the basis for guidance recommended
to the President for use by Federal agencies.
The recommendations contained in this report represent consensus judgment of
the Interagency Working Group for the practice of diagnostic radiology by Federal
agencies. Since the body of knowledge on both the radiation exposure and efficacy of x-
ray examinations is rapidly changing, comments and suggestions on the areas addressed
by this report will assist the Agency to conduct periodic review and to make appropriate
revisions.
Russell E. Train
Administrator
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CONTENTS
PAGE
PREFACE i
MEMBERS iii
INTRODUCTION 1
PROBLEM SCOPE 3
PRESCRIPTION OF X-RAY STUDIES 5
Qualifications to Prescribe X rays
Screening and Administrative Programs
Self-referral Examinations
Procedure and Review
EQUIPMENT 13
General Radiographic Equipment
Fluoroscopic Equipment
TECHNIC 15
Quality Assurance
Equipment Operator Performance
Patient Exposure Considerations
DENTAL RADIOGRAPHY 23
Prescription of Dental X rays
Dental Operator Qualifications
Dental Technic
SUMMARY AND RECOMMENDATIONS 26
REFERENCES 29
II
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INTERAGENCY WORKING GROUP ON MEDICAL RADIATION
Department of the Army
COL Vandy Miller, MSC
Office of the Surgeon General
LTC Robert Quillin, MSC
Walter Reed Army Medical Center
Department of the Navy
CAPT Charles Ochs, MC
National Naval Medical Center
CAPT William Bottomley, DC
National Naval Medical Center
LCDR William Beckner, MSC
Bureau of Medicine & Surgery
LCDR Robert Devine, MSC
Bureau of Medicine & Surgery
Department of the Air Force
LTC Johan Bayer, BSC
Office of the Surgeon General
Veterans Administration
Leonard Bisaccia. M.D.
Radiology Service
Donald Knoeppel, D.D.S.
Dental Service
James Smith, M.D.
Nuclear Medicine Service
Environmental Protection Agency
James Martin, Ph.D., CHAIRMAN
DeVaughn Nelson, Ph.D.
Harry Pettengill, Ph.D.
SUBCOMMITTEE ON PRESCRIPTION
OF EXPOSURE TO X RAYS
SUBCOMMITTEE ON TECHNIC
OF EXPOSURE PREVENTION
Department of the Air Force
COL John Campbell, MC
COL Charles Mahon, MC
Department of the Army
LTC Robert Quillin, MSC
Department of the Navy
CAPT Charles Ochs, MC, CHAIRMAN
CAPT James Dowling. MSC
CAPT William Bottomley, DC
CDR James Spahn, MSC
CDR Peter Kirchner, MC
Veterans Administration
Leonard Bisaccia. M.D.. VICE CHAIRMAN
Donald Knoeppel, D.D.S.
James Smith, M.D.
Department of the Air Force
LTC Johan Bayer, BSC
Department of the Army
COL Vandy Miller, MSC
LTC Robert Quillin, MSC
Department of the Navy
CAPT William Bottomley, DC
LCDR William Beckner, MSC
LCDR Robert Devine, MSC
HMC Felton Pugh
Environmental Protection Agency
James Martin, Ph.D., CHAIRMAN
DeVaughn Nelson, Ph.D.
Harry Pettengill, Ph.D.
SUBCOMMITTEE CONSULTANTS
William S. Cole, M.D.
U.S. Food and Drug Administration
William Properzio, Ph.D.
U.S. Food and Drug Administration
John Doppman, M.D.
National Institutes of Health
Otha Linton, M.S.J.
American College of Radiology
S. David Rockoff, M.D.
George Washington Univ. Medical Cent
III
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INTRODUCTION
One of the most significant factors in good medical care is the use of x rays to
diagnose and define the extent of disease or physical injury. Because of its diagnostic
value, the per capita use of x rays in medicine and dentistry has expanded rapidly in the
United States. This expanded use is also due to wider availability of services, new
equipment, and an increase in sophisticated diagnostic examinations. Although many
procedures now require less exposure per film, the increased number of procedures and
use has resulted in an increase in the per capita exposure as well as that to the
population. A number of medical and scientific groups generally agree that there is
unproductive radiation exposure from x-ray uses that could, and should, be reduced.
Because of these factors and trends, the Environmental Protection Agency
undertook a program in 1974 to develop, in cooperation with Federal agencies, guidance
for reducing unproductive exposures to medical radiation in Federal facilities while
maintaining high standards of health care. This guidance was developed pursuant to 42
U.S.C. 2021 (h) wherein "...[t]he Administrator shall advise the President with respect to
radiation matters, directly or indirectly affecting health, including guidance for all Federal
agencies in the formulation of radiation standards and in the establishment and execution
of programs of cooperation with States."
The first memorandum from the Federal Radiation Council was approved by the
President on May 13, 1960, as guidance for Federal agencies. The first two
recommendations in the memorandum develop the basic radiation protection guidance
for Federal agencies: 1) that there should not be any man-made radiation exposure
without the expectation of benefit resulting from such exposure, and 2) that every effort
should be made to maintain radiation doses as low as practicable. The memorandum also
includes recommended numerical radiation protection guides for radiation workers and
individuals in the population. The first two recommendations apply to all radiation
exposure, including those in medicine and dentistry; the numerical guides do not apply,
however, to the purposeful exposure of patients by practitioners of the healing arts.
Subsequent reports (2 through 8) and memoranda to the President applied these two
basic principles to several types of radiation exposure. The purpose of this report is to
apply these same principles to the use of diagnostic x rays and to develop
recommendations which would be implemented by Federal agencies.
The guidance on use of diagnostic x rays in Federal activities was developed by an
Interagency Working Group on Medical Radiation. The basic approach taken by the
Working Group for reducing exposure from diagnostic uses of x rays in Federal facilities
involved three principal considerations: 1) eliminating clinically unproductive
examinations, 2) assuring the use of optimal technic when examinations are performed,
and 3) requiring appropriate equipment to be used. A Subcommittee on Prescription of
Exposure to X rays (SPEX), was established to examine the first; the Subcommittee on
Technic of Exposure Prevention (STEP) considered the second. Both Subcommittees
examined the third subject area from the standpoint of assuring that Federal equipment is
as consistent as practicable with the performance standards issued by the U.S. Food and
Drug Administration prior to required conformity.
The Interagency Working Group recognized that the most important factor in
reducing radiation exposure is to eliminate clinically unproductive examinations.
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Appropriate prescription of x-ray studies involves two considerations: 1) the clinical
decision to order a particular examination, and 2) the minimization of the number of
radiographic views required in an examination. The qualifications of those who order
examinations, the elimination of unproductive screening programs, and appropriate clinic
procedures were viewed by SPEX as being especially important to eliminating
unproductive exposure.
Although the largest reductions in radiation exposure may be to preclude the
prescription of an unproductive x-ray examination, patient exposure can also be reduced
by assuring that good radiographic technic is practiced. In order to promote principles of
good radiography in Federal activities, the Subcommittee on Technic of Exposure
Prevention developed recommendations on quality assurance, radiographic technic,
operator qualifications, and exposure guides for selected standard examinations.
Both Subcommittee reports were published and were announced in the Federal
Register inviting public comment on the various considerations for appropriate x-ray
prescription, technic, and equipment. These reports and the comments received were
considered by the Interagency Working Group. This report presents the various subject
areas addressed by the two Subcommittees which have been adjusted, where
appropriate, to be responsive to comments and information received. The report includes
discussions on the scope of the problem, prescription of x-ray studies, equipment,
technic, dental radiography, and recommendations that are appropriate for guidance to
Federal agencies.
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PROBLEM SCOPE
Over 50 percent of the population receives at least one radiographic examination
annually (1). Although the attendant benefits from the use of x rays in medicine are well
recognized, the extent of use and the rate of increase in radiographic procedures in
medical practice raise the question of whether there may be unnecessary risks to public
health. It is well recognized that any amount of exposure to ionizing radiation represents
incremental risk to the person being exposed and, under some exposure conditions, to
any subsequent progeny.
Early in 1970, the former Federal Radiation Council initiated a comprehensive
review and evaluation of the relevant scientific information on radiation protection that
had become available in the previous decade, including exposure of the population to
radiation from consumer products. The major part of this review was undertaken by the
Committee on the Biological Effects of Ionizing Radiation (BEIR Committee) of the
National Academy of Sciences - National Research Council.
Two of the major conclusions in the BEIR Committee's report (issued in 1972) were
that "...medical diagnostic radiology accounts for at least 90% of the total man-made
radiation dose to which the U.S. population is exposed..." and "...that it appears
reasonable that as much as a 50% reduction in the genetically significant dose from
medical radiology might be possible through improved technical and educational
methods" (1). The United Nations Scientific Committee on the Effects of Atomic
Radiation reached a similar conclusion in its 1972 report in stating its awareness that
"...protection of the patient is probably the greatest factor in the control of population
exposure." The findings of the BEIR and UNSCEAR committees are corroborated by
numerous other professional and scientific groups and others who are carrying out
research on the efficacy of diagnostic radiologic procedures. In 1959 and again in 1966,
the National Advisory Committee on Radiation apprised the Surgeon General of the
Public Health Service of the apparent overuse of diagnostic x-ray examinations (2).
Although there appears to be significant potential for reducing x-ray exposures to
the population, such activities must be mindful of the large benefits of improved medical
care afforded to society by appropriate use of diagnostic x rays. Thus, insofar as requisite
quality radiographs may be obtained with lesser exposure, the expected net benefits
would be enhanced. This consideration is emphasized by the National Council on
Radiation Protection and Measurements, the International Commission on Radiation
Protection, The American Academy of Family Physicians, the American College of
Radiology, and other organizations concerned with elimination of unnecessary and
unproductive radiation exposure (3,4,5,6). According to the BEIR Committee, "...the aim
is not only to reduce the radiation exposure to the individual, but also to have procedures
carried out with maximum efficiency so that there can be a continuing increase in medical
benefits accompanied by a minimum of radiation exposure." Fortunately, good
radiologic procedures result in both improved diagnosis and minimal patient exposure.
The problem of unnecessary risks associated with unwarranted x-ray examinations
is compounded by the marked increase in the number of diagnostic x-ray examinations
performed in the United States over the last decade. This increase is estimated to range
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from one to four percent per capita annually (7). Surveys of x-ray exposures in diagnostic
radiology practice in 1964 and 1970 indicate the following significant changes (8):
1. There was a 20 percent increase in the number of persons receiving one or more
x-ray procedures from 108 million in 1964 to 130 million in 1970. The population increased
only 7 percent during this period.
2. There was a 22 percent increase in the number of x-ray examinations performed
from 174 million in 1964 to 212 million in 1970.
3. There was a 30 percent increase in the number of films exposed from 506 million
in 1964 to 661 million in 1970.
4. The average number of films per radiographic examination increased from 2.2 in
1964 to 2.4 in 1970.
These trends have probably continued since 1970, especially insofar as increased
film usage is concerned.
In 1971 the National Conference of Radiation Control Program Directors initiated
the Nationwide Evaluation of X-ray Trends (NEXT) to assess patient exposure from
specific routine radiographic examinations. Analysis of data from this program indicates
that the weighted mean exposure for 9 of the 12 radiographic projections surveyed
increased between 1973 and 1975.
The use of diagnostic dental and medical x-ray units is widespread. It is estimated
that there are approximately 143,000 dental units and 135,000 general purpose medical
units in the United States; of the diagnostic medical units 31 percent are used in hospitals,
34 percent in doctors' offices, 9 percent in chiropractors' offices, 6 percent in clinics, and
4 percent in podiatrists' offices while the remainder (about 8,000) are used for veterinary,
educational, and research purposes (9). Approximately 5,000 dental and medical units
are being used for diagnostic purposes in the Federal health care sector. Although the
exact numbers and classifications of these units are not known, it is estimated that 40
percent are dental units. The Veterans Administration, which handles the purchases of
the majority of x-ray units for Federal facilities, currently estimates the useful life of a unit
at 10 years. This would suggest that nearly 500 new units are purchased annually for use
in Federal facilities.
In summary, the problem to be addressed with respect to uses of diagnostic x rays
involves the following factors: 1) radiographic procedures provide over 90% of all man-
made exposure, 2) past trends indicate that the rate of use of radiology procedures is
increasing faster than the growth in the population, thus placing a larger segment of the
population at risk, 3) the number of films per patient is increasing, and 4) most scientific
groups have concluded that a significant proportion of radiologic procedures may be
unwarranted and the exposure for a needed examination is often higher than necessary.
The task addressed by the Interagency Working Group on Medical Radiation was not one
of examining whether the overall risks outweigh the benefits to the population, but rather
the prescription of unproductive examinations or the use of less than optimum equipment
or technic.
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PRESCRIPTION OF X-RAY STUDIES
The most important factor in reducing radiation exposure is to eliminate clinically
unproductive procedures by appropriate prescription of x-ray studies. The factors
involved in appropriate prescription of x-ray studies were examined by the Subcommittee
on Prescription of Exposure to X rays. The Subcommittee's report was published ar.J
made available for public comment on March 12, 1976 (10). The following discussion
broadly summarizes the Subcommittee's report and takes into account information and
comments received.
The ideal basis for prescription of a diagnostic x-ray examination is for a physician
or dentist to have determined that sufficient clinical symptoms or history necessitate the
examination. Many x-ray examinations are prescribed, however, that do not necessarily
satisfy such clinical/historical prerequisites (66,82). The Subcommittee on Prescription of
Exposure to X rays concluded that some of the major factors involved in ordering
unnecessary x-ray examinations are:
Administrative Control or Convenience
Criticism and Legal
Intellectual Curiosity
Inexperience
Public Health Screening
Appropriate prescription of x-ray examinations involves two major considerations:
the clinical decision to order a given examination, and the choice of the number and type
of views required to conduct it within the principles of good radiological practice.
Establishment of routine examinations either for administrative non-medical reasons or
efficiency of clinic operation tends to be counterproductive to minimizing exposure. No x-
ray examination should ever be routine, but should be based on clinical evaluation of the
patient to determine its medical necessity.
Qualifications to Prescribe X rays
The level of qualifications of medical personnel authorized to prescribe diagnostic
x-ray examinations is the most important factor in limiting the prescription of unproductive
examinations. Clinicians who prescribe an x-ray examination have a dual responsibility to
assure that requisite diagnostic information is obtained and that the radiation
administered is done so only with commensurate benefit. Requests for x-ray
examinations in general radiography or fluoroscopy in Federal health care facilities should
be made only by Doctors of Medicine or Osteopathy who are eligible for licensure in the
United States or one of its territories or possessions. Properly trained and physician-
supervised individuals such as physician assistants, nurse practitioners, and persons in
postgraduate medical training status do not have to meet the above requirements, but
they should be under the supervision of a licensable physician.
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In addition to the privileges for which broad qualifications are needed, there are a
number of specialties which require only limited types of x-ray examinations. For example,
Doctors of Dental Surgery or Dental Medicine may request appropriate examinations of
the head, neck, and chest, although such requests are normally confined to the oral
region. Podiatrists who have been granted clinical privileges may request x-ray
examinations appropriate to their specialty.
It is recognized that medical students, interns, residents, and some physician
assistants may not have developed medical judgment as to which test would be most
efficacious. Such lack of experience is remedied by work under conditions where there is
sufficient expert supervision to monitor the prescription of examinations and to provide
appropriate medical assistance.
Variances to the above qualification requirements should occur only for emergency
or life-threatening situations. Non-peacetime operations in the field and aboard ship could
require such variances. Equipment designed for field use might need to be operated by
those personnel available to assist in the performance of necessary medical services.
Any requests in specialized radiography and fluoroscopy, such as angiography,
pneumoencephalography, computerized axial tomography, or other complex studies
requiring many exposures should be made by persons having special training or expertise
to evaluate the indications of the examinations. In recognition of this consideration,
privileges to request such specialized examinations should be restricted to physicians
and dentists meeting recommendations of Federal facility committees established to
credential those who may prescribe general radiographic procedures and who have had
advanced training in the medical specialty involved.
Screening and Administrative Programs
Many x-ray examinations are the result of screening programs or administrative
decisions, the reasons for which may no longer be justifiable. In general, such
examinations are not preceded by clinical evaluation by a physician to determine their
need. All screening programs should be under the auspices of an appropriate medical
staff committee which annually reviews and affirms the need to continue the program.
This annual review should eliminate all routine or screening examinations which are not
clinically justified. Other routine or screening x-ray examinations which should be carefully
evaluated are pre-employment lower back studies and routine physical examinations
which involve routine upper Gl, barium enema, gall bladder, and IVP examinations (11).
Examinations required by legislation for certain high risk populations in order to establish
worker disability compensation should be evaluated carefully to determine their
continuing necessity.
Chest X rays
Chest x-ray examinations to screen for tuberculosis in the general population are
not justified except for certain high risk population groups (12,13). The U.S. Public Health
Service, the National Tuberculosis and Respiratory Disease Association (now the
American Lung Association), the American College of Chest Physicians, and the
American College of Radiology have publicly opposed such screening programs. A
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review board should establish that the expected incidence of tuberculosis is sufficiently
high in a population before a screening program is started. The radiation exposure and
economic considerations suggest that the primary screening examination for tuberculosis
should be a tine or tuberculin test even in populations exhibiting a higher than average
incidence of the disease (14); radiological examinations should be used only to follow-up
clinical indications derived from such methods.
Where chest x-ray screening has involved large numbers of persons, it has been
common practice to employ a photofluorographic technic to save time and expense. This
technic uses a fluoroscope to produce an image of the chest which is then photographed
on 70 mm film. Whereas the procedure is relatively fast and adaptable to examining
patients quickly at mobile stations, the exposure per examination is often considerably
higher than an x-ray examination performed on general purpose equipment which uses
standard-sized films and screens. Also, the size and quality of the 70 mm film is such that
only gross abnormalities can be diagnosed. Although the technic was perhaps justified a
few decades ago when there was a high incidence of tuberculosis in the United States,
the relatively higher exposure and lower diagnostic yield of this technic make its use
generally impracticable even when chest x-ray screening may be justified. Whenever
avoidable, Federal agencies should not use photofluorographic equipment to perform
chest x-ray examinations.
A routine chest examination for hospital admission is not suggested nor presently
required by the guidelines of the Joint Commission on Accreditation of Hospitals. A chest
examination is currently not justified as a routine requirement for hospital admission due
to the low yield of abnormalities diagnosed. A recent study of routine screening in a
hospital population indicated that routine chest examinations, obtained solely because of
hospital admission or scheduled surgery, are not warranted in patients under the age of
20 and the lateral projection can generally be eliminated in patients under age 40 (15).
Careful evaluations should be made of the need for existing admission x-ray examinations
and, of course, should precede the institution of new ones.
X-ray Examination of Pregnant Women
X-ray examinations which result in exposure of a fetus should be avoided whenever
possible (16). In prescribing x-ray examinations for women who are or may be pregnant,
clinicians should determine if a patient is or may be pregnant and whether the diagnostic
information sought outweighs the potential risk to the fetus. This finding should be
communicated to the x-ray facility so that it may conduct the examination in a way that the
information is obtained at minimum risk to the fetus. Examples of exposures which may
not be justified include routine prenatal chest and routine pelvimetry examinations for
pregnant women who have otherwise received adequate prenatal care.
Mammography
Breast cancer in women is recognized as one of the significant causes of cancer
death in the United States. Because of the importance of early detection in control and
survival, an increased emphasis on the use of mammography has occurred. This technic
has improved considerably, especially with respect to lowering exposure per examination
with the development of low-dose mammography and xeroradiography; however, even at
the current state of the art, these techniques often result in a dose of several rads to each
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8
breast for a typical examination. Whereas the procedure is justified to examine
symptomatic women at any age, the use of mammography to screen asymptomatic
women is still being seriously examined by several groups, in particular, the National
Cancer Institute and the American Cancer Society. A committee of the American College
of Radiology has evaluated mammography data accumulated from the Health Insurance
Plan (HIP) in New York and the National Cancer Institute. On the basis of this evaluation,
the Committee recently presented interim recommendations on mammography
screening to the U.S. Food and Drug Administration's Medical Radiation Advisory
Committee (17).
Almost all groups which have issued recommendations about mammography
agree that it should not be used routinely to screen asymptomatic women under the age
of 35 for breast cancer. Likewise, most groups generally agree that above age 50 routine
screening appears to be indicated. Data on the effectiveness of mammography screening
of asymptomatic women between the ages of 35 and 50 has been uncertain for
establishing firmly whether such screening was justified as part of routine programs to
detect breast cancer. There has been no controversy over its recommended use as part
of the evaluation of women of any age who have symptoms of the disease.
Asymptomatic women are defined as those without complaint, without history,
without physical findings, and without a strong family history of breast cancer.
Symptomatic women are those who exhibit clinical findings, including cysts or lumps,
repeated pain, enlargement of the lymph nodes, fluid discharges or other abnormalities of
the nipples or any change in the shape of the breast. Other risk factors include previous
breast cancer, a family history of breast disease, an unusually early menopause and first
pregnancies after the age of 30.
The American Cancer Society and the National Cancer Institute undertook a joint
demonstration project in 1972 to evaluate the efficacy of routine mammographic
examinations for 270,000 women in various age groups above age 35. Even though the
efficacy of mammographic screening of women under age 50 was questionable at the
time the project was started, it was believed that newer x-ray technic would result in lower
radiation exposures such that younger women could be expected to derive an overall
benefit from annual screening examinations which included mammography. Recent
studies have questioned the efficacy of mammography as part of a screening program for
early detection of breast cancer for women under age 50 (79). Because of recent
controversy over mammography screening of asymptomatic women, the National Cancer
Institute established three committees to evaluate all relevant data on risks and benefits.
The first committee, which reevaluated the HIP data, has reported that mammography
does not appear to be efficacious for asymptomatic women under the age of 50. The
second committee reviewed radiation risk data and concluded that even with lower dose
mammography the risk for each film appeared to provide an additional one percent to the
current lifetime risk of breast cancer; thus, the benefit to screening large groups of women
under age 50 would be questionable. The third committee, which is reviewing the
pathological tissue of women in the HIP study, has not yet reported its findings. On the
basis of these committee evaluations, the National Cancer Institute recently informed the
directors of the 27 breast cancer detection centers that routine mammography should not
be performed on asymptomatic women under age 50 (80). This communique also
emphasized the need to continue providing mammography to women under age 50 who
exhibit clinical symptoms or a strong family history as determined by their physicians and
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recommended continued screening of asymptomatic women above age 50. This policy is
also recommended for Federal agencies; however, because of the continuing
development of new information on mammography, Federal agencies should periodically
evaluate available data in order to reaffirm screening policies for asymptomatic women.
Any change in this policy should be based on current data on yield, radiation risks, and
economic and social factors. It is also recommended that mammographic procedures
continue to be evaluated to develop technic that represents an appropriate balancing
between low exposures and diagnostic accuracy.
Cancer Patient Evaluations
In many health care facilities it is common practice for cancer patients to receive
extensive x-ray studies as part of their treatment planning and follow-up. Bagley, et al.,
have reported the effectiveness of several studies in managing the treatment of cancer
patients admitted to the National Institutes of Health (18). Their findings indicate that once
the primary diagnosis was made and confirmed for some cancers, the results of routine x-
ray studies, such as a barium enema and an upper Gl series, were found to have little
influence in the treatment of the patient. These findings also suggest that the yield of
certain x-ray examinations is too low to justify their use as a general screening tool for
cancer evaluation. Although any study that would assist in the control of cancer in a
patient can be justified, such examinations should be generally productive in the care and
follow-up of a patient. For this reason, Federal facilities should periodically evaluate
existing protocol studies to establish those that are appropriate for the initial evaluation of
patients with carcinomas and any required follow-up care. It is particularly important to
establish the appropriate studies for evaluating the various types of malignancy and its
metastatic spread. In this respect, the American College of Surgeons recently
recommended that tumor committees be established to periodically review cancer
evaluations and management (19). Such requirements have also been established by the
Joint Commission on Accreditation of Hospitals.
Self-referral Examinations
A 1970 study indicates that approximately 30% of the medical x-ray examinations
in the U.S. were performed by non-radiologic clinicians (7). Some examinations
performed by non-radiologists may occur because of the convenience of having the x-ray
unit and the patient in the same location, or, in the case of civilian contract services, need
to justify the equipment purchased or maintenance costs. Self-referral examinations are
frequently performed by equipment operators lacking adequate training and having
supervision by clinicians with inadequate radiologic experience.
Unnecessary radiation exposure caused by self-referral practices generally need
not occur in Federal health care installations where facilities staffed by radiologists are
normally provided. Exceptions could be small operational units, such as ships, field units,
or isolated stations where the normal workload does not justify a staff radiologist. Thus,
the conduct of self-referral x-ray examinations should be permitted only for a physician
whose qualifications to supervise, perform, and interpret diagnostic radiologic procedures
have been demonstrated to the appropriate authorities.
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It is recognized that limited self-referral type examinations are performed in Federal
medical centers in certain clinical specialties. The use of such self-referral x-ray
examinations should, however, be limited to studies unique to and required by the
specialty of the physician performing them and be consistent with a peer review policy.
Self-referral practices in contract civilian facilities should be prohibited. It has been
shown that self-referral practices have led to overutilization (21). Exception may be made
in remote areas where no practicable alternative exists.
Procedure and Review
Although the largest reduction in radiation exposure is to prevent the ordering of an
unproductive x-ray examination, patient exposure can also be reduced by the
diagnostician by careful consideration of the numbers and types of radiographs to be
taken during the examination (22). These considerations can also be classified as
prescription decisions. In conducting x-ray examinations, therefore, the diagnostician
should be capable of making the best diagnosis possible and be aware of the quantity and
potential risk of the radiation he is administering.
Each x-ray examination should be as objective-related as possible to accomplish
the diagnosis with the minimum amount of exposure. Most x-ray facilities establish a set of
standard examination procedures which specify the number and types of radiographic
views to be taken when the procedure is performed. A periodic review of all standard
examination procedures should be performed to determine if the established routine is
achieving the objectives and whether modifications are warranted. Continuation of a
standardized examination procedure should be predicated on satisfying the following
criteria: a) the efficacy of the examination is sufficiently high to assure that the diagnosis
could not have been made with less risk by other non-radiological means or a lower
number of views, b) consideration of previous similar examinations performed with
multiple views established that in a significant number of the cases all views were
necessary for the diagnoses rendered, and c) the yield of the examinations offsets the
radiation exposure delivered.
A periodic review of standard operating procedures should be made at least
annually by the appropriate medical or dental staff committee with the advice of referring
physicians. Such reviews should consider the consensus and advice of professional
societies concerning the efficacy of radiologic examinations.
Minimum Number of Examinations and Views
A written outline containing the minimum number of views to be obtained for each
requested examination should be made available to each clinician and equipment
operator in every radiology facility. Beyond the specified minimum views, the examination
should be individualized according to a patient's needs.
All examinations should be tailored to the individual department taking into account
the equipment available. In some instances, certain examinations should be done only on
certain types of equipment.
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The outline of procedures should indicate who may authorize deviations from the
standard set of views for any examination. Every effort should be made to reduce to a
minimum the number of standard views for any examination. The necessity of additional
views, such as comparison views, should be determined by the radiological diagnostician.
In order to effect this important procedural aspect of the prescription of x-ray studies, it is
recommended that the standard views for defined examinations be provided in a current
document and that the number, sequence, and types of standard views for an
examination be problem-oriented and kept to a minimum.
Follow-up for examinations are commonly done so that significant changes in
clinical information are obtained for making proper decisions on continuation or alteration
of the management of the patient. Such examinations may result in unnecessary patient
exposure if repeated before significant changes in clinical information occur; therefore, it
is recommended that they be done only at time intervals long enough to make proper
decisions concerning continuation or alteration of treatment.
Patient History and Physical Condition
Important considerations in providing optimal diagnostic information at minimum
patient exposure, are the role of radiologic diagnosticians and the information provided.
Requests for x-ray examinations should be considered as medical consultations between
the clinician and the diagnostician and should state the diagnostic objective of the
examination and detail relevant medical history including results of previous diagnostic x-
ray examinations and other relevant tests.
Whenever possible a radiologist should review all examination requests requiring
fluoroscopy or multiple film studies, especially those associated with tomography or
scanning techniques, before the examination is given and preferably before it is
scheduled (23). For this reason, it is important that a thorough and accurate patient
history be included with each examination request. Based upon a review of the history and
previously documented studies, the radiologic diagnostician should direct the
examination to obtain the diagnostic objective stated by the referring clinician through the
addition, substitution or deletion of views. It is preferable that changes in the examination
be done in consultation with the requesting clinician.
Patients are sometimes referred to another health care facility for medical care and
previous x-ray examinations conducted at the first facility will be repeated. Only the
studies needed for proper referral should be performed in the first facility. When
examinations have been conducted prior to referral, these x-ray films should accompany
the patient to minimize the need for additional diagnostic x-ray examinations and the
added patient exposure (20). Films from such studies should also be put in the patients
record or given to the patient for transfer to further reduce this kind of unnecessary
exposure.
Another means by which the radiologic diagnostician may reduce patient exposure
is to avoid any repeat examinations due to improper patient preparation for contrast
media studies. Miller has reported that poor bowel preparation is a frequent cause of
marginal or repeated contrast media studies of the lower Gl tract (24). The radiology
department can minimize the number of marginal studies of the lower Gl tract by
instituting pre-examination procedures to assure that patients have had the necessary
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laxatives and enemas (20). It may also be advantageous to place bedridden, elderly, or
constipation-prone patients on low-residue diets several days before scheduling the
studies. Determination that a patient has had previous surgery before Gl tract
examinations could also help minimize the number of marginal studies. Similarly, the prior
determination that a patient had taken any prescribed oral contrast media would prevent
unnecessary retakes of such studies.
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EQUIPMENT
Once the physician or dentist determines that the prescription of an x-ray
examination is warranted for diagnostic purposes, other factors become important in
limiting patient exposure. One of the more important factors is the design of x-ray
equipment to be used in performing the examination. Minimization of patient exposure
may not be accomplished even with well designed equipment unless appropriate quality
assurance programs exist to keep it functioning properly and those who operate it are
properly qualified to use the features ot the equipment. These latter considerations
discussed in the chapter on Technic.
General Radiographic Equipment
The Nationwide Evaluation of X-ray Trends survey has demonstrated that the same
technique factors used with different x-ray generators may produce widely varying patient
exposures. Thus, the performance of x-ray equipment utilized for diagnostic x-ray
procedures is an important factor in limiting patient and operator exposure. The Federal
Diagnostic X-Ray Equipment Performance Standard (21 CFR Subchapter J) requires that
x-ray equipment manufactured after August 1, 1974, be certified by manufacturers to
comply with performance standards issued by the U.S. Department of Health, Education,
and Welfare pursuant to the Radiation Control for Health and Safety Act of 1968 (PL
90-602). All Federal health care facilities which perform diagnostic x-ray examinations
should meet this standard sooner than required if practicable. Although it is possible to
obtain variances for special medical and dental x-ray equipment purchased after August
1,1974, Federal use of this variance should be minimized.
All existing, non-certified equipment being used is not necessarily substandard. In
order to preclude substantial economic costs involved with large-scale replacement or
retrofit of all non-certified equipment, while still providing for the elimination of equipment
which is determined to be sub-standard with reference to currently accepted radiation
safety standards, it is recommended that all non-certified medical and dental x-ray
equipment meet the criteria in parts F.4, F.5, F.6, and F.7 of "Suggested State
Regulations for Control of Radiation" (25). Whereas the above criteria do not meet the
rigid requirements for certification according to the Federal performance standard, they
provide adequate conformance with those parameters which affect radiation protection of
the patient and operator. Assurance that the x-ray generator meets the "Suggested State
Regulations for Control of Radiation" can be demonstrated with test equipment
considerably less complex than that required to demonstrate compliance with the
equipment performance standards for x-ray equipment required by 21 CFR Subchapter J.
Certain sections of the x-ray equipment performance standard provide for planned
obsolescence, such as the provision which permits the use of non-certified components
as replacement items in equipment manufactured before August 1, 1974. Although such
use of non-certified replacement components is permitted until August 1,1979, their use
should be justified. Stockpiling of either x-ray equipment or components should also be
minimized, since the technological advances in x-ray equipment tends to preclude its use.
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To insure that x-ray equipment used is justifiably representative of present day
technological advances, authorities should develop and periodically review a planned
replacement schedule for all types of diagnostic x-ray equipment used in their programs.
Fluoroscopic Equipment
Although the aggregate population dose is larger from the use of general purpose
diagnostic equipment, the highest exposures to individuals are generally associated with
fluoroscopic examinations. Fluoroscopic examinations require large exposure rates for
periods of time long enough to observe dynamic changes; thus, it is of utmost importance
that Federal health care facilities give particular attention to minimization of fluoroscopic
examinations. X-ray equipment should not exceed the medical mission of the facilities,
i.e., fluoroscopy should not be available in facilities where qualified medical personnel are
not assigned.
Because the reduction of patient exposure is considerable and the additional cost
of image-intensified units is justifiable, fluoroscopic units which do not contain image-
intensification systems should not be used. The retention of older non-image intensified
units for the reason that they may not be used with great frequency should not be
permitted because the patient exposure rates are an order of magnitude greater than
intensified units. If the medical mission requires fluoroscopy, only image-intensified units
operated by those with demonstrated competence should be permitted.
Specialized procedures (hip replacements, transphenoid hypophysectomy, biopsy
and cannulizations via fibro optic scopes) may require fluoroscopic assistance. In order to
provide fluoroscopic assistance for such special procedures and to minimize patient
exposure, non-radiological specialists such as orthopedists, neurosurgeons,
gastroenterologists, cardiologists, chest surgeons, etc. should where practicable only use
equipment with electronic image holding features such as pulsed video-hold or equipment
with similar low-exposure features. The advantage of such units is that the radiation
exposure is about one-twentieth of that from continuous fluoroscopy and yet the image is
adequate.
Non-radiologists who operate a special fluoroscopic unit should take a course of
instruction in radiation safety which meets guidelines established by responsible authority
and demonstrate competence in the use of this equipment. Such courses of instruction
should be considered as a standard part of the training program for physicians who may
have occasion to use such equipment in their practice. Use of pulsed video-hold or similar
dose-saving special equipment should be approved by a senior radiologist in order to
prevent use of such units for studies other than those for which they were designed. This
consideration should be generally given to all special purpose equipment such as
computer assisted tomography.
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TECHNIC
The fundamental objective in performing an x-ray examination is to obtain optimum
diagnostic information with minimum patient exposure. Achievement of this objective
requires: 1) assurance that 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 considered each of these
areas in developing recommendations to assure that good technic is employed in Federal
health care facilities. Recommendations were made by the Subcommittee on quality
assurance, radiographic technic, operator qualifications, and exposure guidance in the
form of broad principles to be achieved by qualified professionals (81). The discussion
that follows broadly summarizes the areas addressed in the Subcommittee's report,
which was made available to the public on July 8, 1976, and takes into account
appropriate comments and information received.
Quality Assurance
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. 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 (26).
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 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
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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
responsible 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 (27) 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 maintenance (27,28,29).
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, equipment quality assurance programs should be established. These
programs should contain equipment specifications, equipment calibration requirements,
materials and equipment performance requirements, and preventive maintenance
schedules. For equipment manufactured after August 1, 1974, the manufacturer is
required by the Federal Equipment Performance Standard (21 CFR Subchapter J) to
provide recommended preventive maintenance schedules which should be followed.
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
examinations also suggests the need for a program to ensure adequate evaluation and
handling of films (30,31,32). All films should be handled and stored under carefully
controlled light, temperature, humidity, and background radiation conditions so that
fogging can be minimized (27,33,34). Use of "safe lights" to minimize film fogging
requires the selection of proper filters for the particular wave length sensitivities of the
films. Dark rooms should be 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 reduces patient
exposure (3,4,5). On the other hand, cursory acceptance of 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 (35). 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/high-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
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in quality of the image (36,37). 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. When their use is
consistent with image quality requirements, the highest-speed film and film-screen
combinations 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.
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 (31,38,39). 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 (27,40,41). In addition to these considerations, 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 assuring that high quality
radiographs are produced with minimized patient exposure. A procedural quality
assurance program for the performance of x-ray examinations is important to this goal.
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 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 (42,43,44,45,46). Some variation in
retake rates is reflective of the medical specialty and whether the x-ray facility is in a clinic,
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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, which has shown a reduction in the number of duplicate
examinations (47).
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 (22). 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.
Equipment Operator Performance
It is possible to obtain a range of radiographs considered diagnostically acceptable
and have entrance skin exposure vary by a factor of six to ten because of the choice of the
various technic factors (48,49,50). Operators should be cognizant of those technic
interrelationships which accomplish minimized exposure. Federal agencies should assure
that equipment operators involved in Federal health care delivery: 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
Responsible use of medical and dental x-ray equipment involves restricting its
operation to properly qualified and supervised individuals. Such a policy should be
established for each x-ray facility by the responsible authority upon the recommendations
of medical and dental staff. Medical personnel eligible for utilization of x-ray equipment
are physicians and radiologic technologists. Eligible physicians include radiologists and
other physicians granted privileges in radiology on the basis of the needs of patients
served by the facility. Such privileges might include the use of x-ray equipment by
cardiologists for cardiac catheterizations and by dentists or podiatrists as part of their
practice. Before physicians and dentists are granted radiology privileges they should have
received adequate training in equipment use and radiation protection. However, specific
protocols establishing the limit of radiology privileges to specified types of physicians or
dentists should be part of the written policy statement.
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 (49,51). 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-
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ray Trends (NEXT) program (52) data and recent proficiency test results indicate that
inadequately trained operators are likely to expose patients and themselves
unnecessarily (49,53). Personnel responsible for patient preparation and positioning,
selection of technic factors, radiation protection 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 (3,48,54,55).
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 (56). Continuing competence and professional growth should be encouraged
with specific opportunities to further the person's knowledge and skills through
attendance at workshops or by other means of training.
Other medical personnel such as nurses and laboratory technologists should not
be eligible to operate x-ray equipment. Their use of such equipment could be warranted
only in a life-saving or life-threatening situation during which qualified personnel as
specified above are not available to perform the examination.
The above considerations for operators of x-ray equipment should be implemented
by the responsibile authority in a protocol 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 continuing education
and demonstration of proficiency. This policy should be reviewed periodically and revised
as appropriate.
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. It is especially important to confine the useful beam to
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the clinical area of interest (4,5,57,58). The beam size should be generally limited to the
image receptor size or smaller. The operator has a responsibility to properly collimate the
x-ray beam and to use shielding where appropriate and practicable to further limit the
exposure of body tissues (3,22,48,59,60). Special effort should be made to protect the
blood forming organs of children (58,61,62).
Particular care should be exercised when a fetus may be irradiated. It is important,
therefore, that facility protocol concerning x-ray examinations of pregnant or possibly
pregnant patients verifies that medical consideration has been given to possible fetal
exposure 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.
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 cooperation with its Medical Radiation Advisory Committee and the
American College of Radiology, has developed a voluntary 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 (63). 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 (4,5,57,58,61).
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 considered extensively by the Subcommittee on Technic of
Exposure Prevention for this purpose (81). The NEXT data probably provide a
representative profile of the practice of diagnostic radiology in the United States at the
present time because they reflect the myriad of combinations of x-ray generator types,
films and screens, film processing technic, contrast requirements, and a range of skills of
equipment operators. Therefore, regardless of the specific details or combinations of all
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these factors, the frequency distributions of entrance skin exposures (ESE) derived from
the NEXT data were assumed to be sufficiently representative of the complex system of
diagnostician preference, operator technic, and x-ray equipment performance for each of
the selected standard examinations.
The distributions of ESE from the NEXT data are widely varying and generally
cannot be described in terms of conventional distributions. However, for each distribution,
there is a point above which the exposure is likely to be unnecessary 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. The measured ESE values for selected standard
examinations above which it was determined that practicable measures should be taken
to evaluate and reduce exposures are as follows:
Examination (Projection) ESEG (milliroentgens)*
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 or Periapical) 700
'Entrance skin exposure determined by the NEXT program for a patient
with the following body part/thickness: head/15 cm, neck/13 cm,
thorax/23 cm, abdomen/23 cm, and foot/8 cm.
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 the third quartile
can be considered as overexposures to patients" (49). 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 (64).
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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 the diagnostic information justifies the additional exposure.
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 diagnostician's preference for image
receptor combinations and radiographic technic.
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DENTAL RADIOGRAPHY
One of the most common radiographic procedures an individual is likely to receive
as a part of health care is a dental x ray. A large portion of the U.S. population visits a
dentist one or more times each year for routine checkups and associated dental care. The
1970 study of population exposure to x rays estimated that 661 million radiographic films
were produced in 1970 and of this number 279 million were dental films (7).
A dental patient has a good chance of receiving a dental x ray even though he may
have no immediate dental problems. A study of dental radiography in Nashville,
Tennessee indicated that 57 percent of the facilities surveyed routinely do interproximal
examinations each year on regular patients and 21 percent do a full-mouth series every
one to three years; on new patients 58 percent routinely do interproximal examinations
and 64 percent selectively do a full-mouth series (65). The mean exposure per film in the
Nashville study was 542 mR in 1972; after an educational program the mean dropped to
340 mR per film, indicating the value of carefully controlled procedures in reducing patient
exposure due to dental radiography. Because of the increased use of dental radiography
in the United States, it appears reasonable to optimize the exposure per film and the
number of films per examination.
Prescription of Dental X rays
The proper decision to use x-ray studies in dental examinations should be based on
a requirement for proper diagnosis or definition of disease and the number of radiographs
should be the minimum necessary to obtain the essential diagnostic information (6). It is
recommended that dental radiographs be taken only after a dentist has examined the
patient and established by clinical indication the need for the x-ray examination; neither a
full mouth series nor a bitewing series is justified as part of periodic preventive dental
care. This recommendation is consistent with those of the American Dental Association
which also decidely disagrees with any requirement to provide post-operative radiographs
as proof of services rendered (67). A full mouth radiograph of the teeth and jaw structure
may be justified for forensic purposes for military personnel.
As in general medical radiology, the qualifications of those who order dental x rays
are important to eliminating unproductive radiation exposure in dentistry; thus, privileges
to request dental x-ray examinations should be limited to Doctors of Dental Surgery or
Dental Medicine who are eligible for licensure in the United States or one of its territories
or commonwealths. Exception may be granted only for persons in post graduate training
status under the supervision of a person meeting such requirements.
Dental Operator Qualification
Dental equipment operators should receive 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. Such proficiency can be met by satisfying the Guidelines for Dental Hygienist
and Dental Assistants Training Programs in Dental Radiography adopted by the Oral
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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;
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; and
4. Produce films with density, definition, contrast and other attributes of sufficient
diagnostic value to the dentist" (68).
Dental Technic
Important factors in 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 and a number of voluntary standard-setting organizations have
recommended their use (54,69,70,71). In 1968, the Council on Dental Research of the
American Dental Association (ADA) developed a set of recommendations which includes
the use of shielded open-ended cylinders (72). The Department of Health, Education and
Welfare has also concluded that dental practitioners should be encouraged through
increased educational and training activities to adopt the paralleling, long-cylinder
(source-to-cylinder tip distance greater than 30 cm) technic which uses the long open-
ended shielded position indicating device in order to obtain the optimum balance between
film quality and minimized exposure (73). 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.
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 ADA Council on Dental
Research recommended that dental clinics "...use the fastest speed film available" and
that they "...request film of ANSI group rating of "D" or faster" (72,73). Because patient
exposure can be reduced with adequate film quality, it is recommended that such films be
used for intra-oral radiography when they are 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 receptor has been accomplished only recently, for example, by rectangular
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collimation (74,75,76,77). Another approach which involves placing a new focused
radiation source within the mouth to redlice patient exposure is currently being
investigated at the National Institute of Dental Research (78). Therefore,
recommendations for dental radiography will, of necessity, need periodic review and
appropriate revision.
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SUMMARY AND RECOMMENDATIONS
This report has examined the elements of good radiography, the fundamental
objective of which is to obtain optimal diagnostic information with minimum patient
exposure. Achievement of this objective requires elimination of clinically unproductive
examinations, the use of appropriate and properly functioning equipment, and the use of
optimal technic by qualified operators. Satisfactory accomplishment of each of these
requirements depends on sound judgment applied to a wide range of individual situations;
thus, the recommendations developed for Federal agencies are directed towards the
achievement of broad principles by qualified professionals. The programs of various
Federal agencies should continue to develop basic information and optimal procedures
for meeting these broad principles.
Recommendations for guidance to Federal agencies for prescribing and
performing medical and dental radiographic procedures in order to minimize unnecessary
exposure without loss of requisite diagnostic benefits are as follows:
1. General radiographic or fluoroscopic examinations should be prescribed only by
licensable Doctors of Medicine or Osteopathy; specialized studies should be prescribed
only by those physicians with advanced training in the particular specialty. Exception for
certain limited procedures may be made for dentists and podiatrists or properly-trained
physician assistants, nurse practitioners, and physicians in postgraduate training status.
2. Prescription of an x-ray study should be a medical consultation between the
clinician and the x-ray diagnostician, be based on clinical evaluation of the patient, and
should state the diagnostic objective and detail relevant medical history.
3. Routine or screening examinations in which no clinical evaluation is made should
not be performed; exception may be made for high risk groups on the basis of careful
consideration of diagnostic yield, radiation risk, and economic and social factors.
Examinations which should not be routinely performed are:
a) chest and lower back x-ray examinations in routine physical
examinations or as a Federal requirement for employment,
b) tuberculosis screening by chest radiography,
c) chest x rays for hospital admission of patients under the age of 40
unless a clinical indication of chest disease exists,
d) chest radiography in routine prenatal care,
e) mammography examinations for women under the age of 50 who do
not exhibit symptoms or have a strong family history of disease.
4. Prescription of x-ray examinations of pregnant or possibly pregnant patients
should assure that medical consideration has been given to possible fetal exposure and
appropriate protective measures are applied.
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5. The number, sequence, and types of standard views for an examination should
be problem-oriented and kept to a minimum. Diagnosticians should closely monitor the
performance of x-ray examinations, and, where practicable, direct examinations to obtain
diagnostic objectives stated by clinicians by appropriate addition, substitution, or deletion
of prescribed views. Technic protocols for performing medical and dental x-ray
examinations should detail the operational procedures for all standard radiographic
projections, patient preparation requirements, use of technic charts, and image receptor
specifications.
6. X-ray equipment used in Federal programs should meet, where practicable,
Federal performance standards (21 CFR Subchapter J) sooner than required, or in the
interim, the 1974 "Suggested State Regulations for Control of Radiation." General
purpose fluoroscopy units should provide image-intensification; fluoroscopy units for non-
radiology specialty use should, when practicable, have electronic image-holding features.
Photofluorographic x-ray equipment should not be used for chest radiography.
7. X-ray facilities should have quality assurance programs designed to produce
radiographs that satisfy diagnostic requirements with minimal patient exposure; such
programs should contain materials and equipment specifications, equipment calibration
and preventive maintenance requirements, quality control of image processing, and
operational procedures to reduce retake and duplicate examinations.
8. Operation of medical or dental x-ray equipment should be by individuals who
have demonstrated proficiency to produce diagnostic quality radiographs with the
minimum of exposure required; these individuals should be qualified by didactic training
and practical experience identical to or equivalent to those programs approved by the
Council on Medical Education of the American Medical Association or the American
Registry of Clinical Radiography Technologists for medical x-ray equipment operators, or
for dental equipment operators, the guidelines of the Oral Radiology Section of the
American Association of Dental Schools.
9. Proper collimation should be used to restrict the x-ray beam as much as
practicable to the clinical area of interest and within the dimensions of the image receptor;
shielding should be used to further limit the exposure of the fetus and the gonads when
such exclusion does not interfere with the examination being conducted.
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10. Technic appropriate to the equipment and materials available should be used to
maintain exposures as low as is reasonably achievable without loss of requisite diagnostic
information; measures should be undertaken to evaluate and reduce, where practicable,
exposures for non-specialty examinations which exceed the following Entrance Skin
Exposure Guides (ESEG):
Examination (Projection) ESEG (milliroentgens)*
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 or Periapical) 700
'Entrance skin exposure determined by the NEXT program for a patient
with the following body part/thickness: head/15 cm, neck/13 cm,
thorax/23 cm, abdomen/23 cm, and foot/8 cm.
11. Dental x-ray examinations should be prescribed only by licensable Doctors of
Dental Surgery or Dental Medicine or properly supervised postgraduate dentists on the
basis of clinical evaluation or pertinent history; neither a full-mouth series nor bitewing
radiographs should be part of routine preventive dental care. Exceptions may be made for
certain forensic purposes.
12. Intra-oral radiography should be performed with open-ended, shielded, position
indicating devices having a source-to-cylinder tip distance greater than 30 cm and dental
film which meets the requirements of ANSI speed group rating "D" or faster; the x-ray
beam should be as near the size of the image receptor as practicable.
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29
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