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
                                 14

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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.
                                  20

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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,
                                  21

-------
      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
                                  22

-------
  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 +

-------
                              REFERENCES
 1.   Minutes  of  the  Subcommittee on the Division of Training and
     Medical  Applications, Medical Radiation Advisory Committee
      (January 27-28,  1976), BRH Bulletin, !LO No. 3, Feb. 9, 1976.

 2.   Hendee,  W.R. and R.P. Rossi, "Performance Specifications for
     Diagnostic  Radiologic Equipment - A Delicate Interface Between
     Purchaser and Supplier," Proceedings of Application of Optical
     Instrumentation in Medicine IV, Atlanta, Georgia, September 25-27,
     1975, Society of Photo-Optical Instrumentation Engineers and
     Society  of  Photographic Scientists and Engineers, May 1976.

 3.   Moler, C.,  "Problems Associated with Quality Assurance in
     Diagnostic  Radiology," Bureau of Radiological Health Quality
     Assurance Seminar Series, March 26, 1975.

 4.   Robinson, A., "Quality Control Measurements on Diagnostic
     Equipment in England," Bureau of Radiological Health Quality
     Assurance Seminar Series, December 12, 1974.

 5.   Starchman,  D.,  "Field Testing and Analysis of Diagnostic X-Ray
     Units in Quality Control," Bureau of Radiological Health Quality
     Assurance Seminar Series, November 21, 1975.


 6.   Page, D.A., "An  Operational Material Certification Program,"
     Proceedings of Application of Optical Instrumentation in Medicine
     IV, Atlanta, Georgia, September 25-27, 1975, Society of Photo-
     Optical  Instrumentation Engineers and Society of Photographic
     Scientists  and Engineers, May 1976.

 7.   Thompson, T.T.,   "Quality Assurance from a Radiologist's Point of
     View," Bureau of Radiological Health Quality Assurance Seminar
     Series, March 11, 1975.

 8.   Laws, P.W.,  "How Patients View the Efficient Use of Diagnostic
     Radiation," Radiologic Technology, 47; 245-249,  No. 4,  1976.

 9.   Lundh, A.,  "Film Fogging by Radiation from Building Materials"
     Photographic Science and Engineering,  18;  517-523,  No.  5,  1974.

10.  Baiter,  S.,  "Practical Quality Control in Diagnostic Radiology,"
     Bureau of Radiological Health Quality Assurance  Seminar Series,
     August 8, 1974.

11.  "How to Protect  Patient and Physician During X-ray  Examinations
     Installment 2: Responsible Use of Diagnostic X-rays," American
     Family Physician/GP,  1:  105-120,  No.  2,  1970.


                                   33

-------
12.  international Commission on Radiological Protection,  Report of
     Committee 3,  Publication 16, Protection of the Patient in X-ray
     Diagnosis, November 1969.

13.  National Council on Radiation Protection and Measurements, Report
     No. 33, Medical X-ray and Gamma-ray Protection for Energies up to
     10 MeV, 1968.

14.  First Conference on Image Receptors "Film Screen Combinations,"
     November 13-15, 1975, FDA, in press, 1976.

15.  Buchanan, R.A., Finkelstein, S.I., and K.A. Wickerscheim, "X-ray
     Exposure Reduction Using Rare-Earth Oxysulfide Intensifying
     Screens," Radiology 105: 185-190, 1972.

16.  Evans, A., Davison, M., McLellan, J., and W. James, "Evaluation of
     a New Screen/Film Combination," British Journal of Radiology, 48.;
     858-859, 1975.

17.  Dobrin, R., Kricheff, 1.1., and R. Weathers, "Automatic Film
     Processing in Diagnostic Radiology - Problems and Solutions,"
     Proceedings of Application of Optical Instrumentation in Medicine
     IV, Atlanta, Georgia, September 25-27, 1975, Society of Photo-
     Optical Instrumentation Engineers and Society of Photographic
     Scientists and Engineers, May 1976.

18.  "Quality Assurance in Diagnostic Radiology-Why Doesn't Every
     Department Have a Complete Program?," Panel Discussion,
     Proceedings of Application of Optical Instrumentation in Medicine
     IV, Atlanta, Georgia, September 25-27, 1975, Society of Photo-
     Optical Instrumentation Engineers and Society of Photographic
     Scientists and Engineers, May 1976.

19.  Van Tuinen, R.J. and J.G. Kereiakes,  "Sensitometric Quality
     Control for Automated Film Processors in Radiology Departments,"
     Proceedings of a Symposium held in Houston, Texas, July 8, 1971
     entitled,  "Reduction of Radiation Dose in Diagnostic X-ray
     Procedures," DHEW Publication No.  (FDA) 73-8009.

20.  Winkler, N.T., "Standardization of Film Processing in a Busy
     Department," Proceedings of Application of Optical Instrumentation
     in Medicine IV, Atlanta, Georgia, September 25-27, 1975, Society
     of Photo-Optical Instrumentation Engineers and Society of
     Photographic Scientists and Engineers, May 1976.

21.  Bourne, D., "Repeats - An Aspect of Departmental Management,"
     Radiography .35; 257-261, 1969.

22.  Leggett, I.P., Jr., Schadt, W.W., and L.C. MacConnell, "X-ray Film
     Retake Rates at Selected Hospitals in 'the District of Columbia,"
     Report by the District of Columbia Department of Human Resources,


                                   34

-------
     Health Services Administration,  Bureau of Public  Health
     Engineering,  Radiological Health Division,  February 1971.

•>-\   Garner  P ,  "Oh, NoJ!  Not Again," ARK SPARKS - The Official
     Publication of ihe Arkansas Society of Radiologic Technologists,
     20 No. 3, Fall 1970.

24   Morgan, R.H.  and J.C.  Gehret,  "The Radiant Energy Received by
     Patienis in Diagnostic X-ray Practice," American  Journal Roetgenol
     Radium Ther Nucl Med 97: 793-810, 1966.

25.  Burnett, B.M., Mazzaferro, R.J., and W.W  Church, "A Study of
     Retakes in Radiology Departments of Two Large Hospitals," DHEW
     Publication  (FDA) 76-8016.

?A   Tazarus  C B  , et al., "Automation of Scheduling  and File Room
     Functions of a BTa^ostic Radiology Department,"  DHEW Publication
     No.  (FDA) 75-8020.

27   Pavne  F.W.,  "Physicians, Radiologists, and Quality Control,"
     Proceedings  of the 1972 Radiological Health Section  American
     Public Health Association, DHEW Publication No.  (FDA) 74-8002.

28   Brown  R F   and  B.M. Burnett, "Methods of Dose Reduction in
     n-iarmA«itic"x-rav Procedures," Proceedings of a Symposium held in
     Houston? Texas,  July 8, 1971 entitled  "Reduction of Radiation Dose
     in Diagnostic X-ray Procedures," DHEW Publication No. (FDA) 73-
     8009.

29.  "Diagnostic  Medical X-ray Technologists: The Issue of
     Qualifications," Bureau of Radiological Health Staff Report,
     January 1975.

30.  Webster, E.W.,  "The Physical Problem:  Possibilities and
     Limitations," Proceedings of a  Symposium held  in Houston, Texas,
     July 8,  1971 entitled  "Reduction of  Radiation Dose in Diagnostic
     X-ray Procedures,"  DHEW Publication  No.  (FDA)  73-8009.

31.  Wochos,  J.F.,  and  J.R.  Cameron,  "Patient Exposure From Diagnostic
     X-rays:  An Analysis of Two Years of  NEXT Data" 1975 AAPM Annual
     Meeting, Abstract:  Medical Physics,  2,  No.  3,  May/June  1975.

32.  Proceedings  of the Third Annual National Conference on  Radiation
     Control, DHEW Publication (FDA)  72-8021.

33.  Delineation  of Roles  and Functions of Diagnostic Radioligic
     Technology Personnel  and Development of Proficiency Tests, Bureau
     of Health  Resources Development,  Contract  No.  NIH-72-4226, 1974.

34.  Koenig, G.F., "The Role of the  Radiologic  Technologist  in Dose
     Reduction,"  Proceedings of a Symposium held in Houston,  Texas,
                                   35

-------
     July  8,  1971 entitled,  "Reduction of Radiation Dose in Diagnostic
     X-ray Procedures," DHEW Publication No.  (FDA) 73-8009.

 35.  Koch,  E.I., Statement of Congressman Koch, Co-sponsor of H.R. 559
     Hearing  before the Subcommittee on Health and the Environment of
     the Committee on Interstate and Foreign Commerce, December 18,
     1975,  Serial No. 94-54; Congressional Record, H 1998, March 16,
     1976 .

 36.  Curriculum Guide for Radiologic Technology, American Society of
     Radiologic Technologists, 1976.

 37.   Code  of Practice for the Protection of Persons against lonizina
     Radiations arising from Medical and Dental Use: Department of
     Health and Social Security; Scottish Home and Health Department-
     Ministry of Health and  Social Services, Northern Ireland- Welsh'
     Office,  London, 1972.
39
 38 *  oed^vri^L?W.DOSage Medical Radiography, Indiana State Board of
     Health and Indiana University Medical Center, 1969.
     insLX!nf?Ct^?tirt ^ P*vsician Curing X-ray Examinations,
     installment 1: Effects of Radiation," American Family
     Physician/GP, 1: 113-128, No. 1, 1970.
-40.  Braestrup  C.B  and K.j. vikterlof, Manual on Radiation Protection
     in Hospitals and General Practice: Volume 1, "Basic Protection
     Requirements," WHO, Geneva, 1974.

41.  Robinow, M. and F. Silverman, "Radiation Hazards in the Field of
     Pediatrics," Pediatrics, 20, No. 5, Part II, November 1957.

42.  "Radiologic Technology," AF Manual 160-30/TM 8-280/NAVMED P-5119
     Departments of the Air Force, the Army, and the Navy, Washington,'
     J->            JL i J.7/4.
43.  "Specific Area Gonad Shielding," Guideline for use on Patients
     during Medical Diagnostic X-ray Procedures in new  1000 50 of the
     ?nnnP^?°Sed SubPart c "Guidelines and Recommendations to Part
     II. 1975.^ ^^ 10°0)'  F6deral Register< ifi-  No- 180,
44.  Neuweg, M.E. and P.N. Brunner,  "Radiation Exposure Limits in the
     Healing Arts," Applied Radiology,  November/December 1974?
45 *  Mo^??31^0?11?^ °n Radiation Protection and Measurements,
     No. 35, Dental X-ray Protection,  1970.

46.  "A Practical Manual on the Medical and  Dental Use of X ravs With
     Control of Radiation Hazards," American College of Radiology,
                                  36

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47   "Guidelines for Dental Hygienist and Dental Assistant Training
     Programs in Dental Radiology," Oral Radiology Section of the
     American Association of Dental Schools,  Annual Meeting,  Miami
     Beach, March 20-24, 1976.

48.  American Dental Association,  Recommendations in Radiographic
     Practices,  JADA, 84; 1108,  May 1972.

49.  American Dental Association,  Council on Dental Materials and
     Devices, Guide to Dental Materials and Devices,  Sixth Edition,
     1972-73.

50.  American Academy of Oral Roentgenology,  Radiation Protection
     Committee,  "The Effective Use of X-ray Radiation in Dentistry,"
     Oral Surg., 16; 294-304, March 1963.

51   American Dental Association,  Recommendations in Radiographic
     Hygiene and Practice, JADA,  76; 363-365,  February 1968.

52   "Analysis of Suggested Amendment to the Performance Standard for
     Diagnostic X-ray Systems and Their Major Components (21  CFR
     1020.30-1020.32) to require Provision of Open-ended,  Shielded,
     Position-indicating Devices (PID)  on Dental Intraoral X-ray
     Equipment," DHEW, FDA/BRH,  DRAFT,  August 1, 1975.

53.  weissman. D.D. and F. J. Sobkowski, "Comparative Thermoluminescent
     Dosimetry of Intraoral Periapical Radiography," Oral Surg., ,29;
     376-386, No. 3, March 1970.

54.  Winkler, K.G., "Influence of Rectangular Collimation and Intraoral
     Shielding on Radiation Dose in Dental Radiography," JADA,  77; 95-
     101, 1968.

55.  Updegrave,  W.J., "Simplified and Standardized Intraoral
     Radiography with Reduced Tissue Irradiation," JADA, 85;  861-869,
     October 1972.

56.  Lilienthal, B., Rak, D., and J. Wang, "Minimizing Radiation
     Exposure in Dental Radiology," Australian Dental Journal,  .20; 1-6,
     February 1975.

57.  Webber, R., Schuette, W., and W. Whitehouse, "An Alternative
     Approach to Dose Reduction in Dental Radiography," Oral  Surg, £0;
     553-563, No. 4, October 1975.
                                    37

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