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Chapter 40 Radiation Protection Procedures

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Title: Chapter 40 Radiation Protection Procedures


1
Chapter 40 Radiation Protection Procedures
  • ALARA and Occupational Exposure

2
ALARA
  • ALARA stands for As Low As Reasonably Achievable.
    It is the basic principle of radiation protection
    procedures.
  • There is much that we can do to keep exposure to
    the patient and the operator as low as possible.
  • The chiropractor is unique in the fact that you
    can perform radiography and refer your patients
    for other types of examinations.

3
Occupational Exposures
  • In radiologic technology, 95 of the occupational
    exposure comes from fluoroscopy and mobile
    radiography.
  • Neither would be used in your office so the worst
    case scenario is that you would receive 5 of the
    exposure that a technologist would receive.

4
Occupational Exposures
  • During radiography, the operator should be behind
    a protective barrier.
  • These barriers are usually considered as
    secondary barriers so protection would be from
    tube leakage and scatter from the patient. The
    tube should never be pointed toward this type
    barrier.
  • If the barrier can have the tube angled toward
    the barrier. It must be a primary barrier.
  • Staying behind the barrier effectively eliminates
    the source of occupational exposure if the
    shielding is adequate.

5
Occupational Exposures
  • Medical Imaging Exposures
  • Fluoroscopy All personnel will wear protective
    apron. If extremities get into the beam lead
    gloves can be worn.
  • The radiologist will usually be close to the
    machine during fluoroscopy so their exposure will
    be higher than that the technologist. Aprons
    between the Image intensifier and Bucky Slot
    covers reduce radiologist exposure.
  • The technologist should stand as far away from
    the table as possible during the exam and move
    closed only when necessary.
  • The radiologist will use short burst of exposure
    and keep the exposure time as short as possible.
    The 5 minute clock timer will alarm when 5
    minutes of fluoroscopy has been used.

6
Occupational Exposures
  • Medical Imaging Exposures
  • Mobile radiography
  • The technologist must wear a lead apron during
    mobile plain film or fluoroscopy examinations.
  • An apron must be assigned to each portable
    machine.
  • The exposure cord for portable radiographic
    machines must be 2 meters long to maximize
    distance from the tube during exposures.

7
Occupational Exposures
  • Radiology Ancillary Staff
  • Assuming the rooms are adequately shielded, the
    receptionist, file room and darkroom staff
    should not receive any occupational exposure.
  • Radiology ancillary staff should not be used to
    hold patients during radiography.

8
Occupational Radiation Monitoring
  • Occupational Radiation Monitoring is required if
    there is any likelihood that an individual will
    receive more than 1/10 of the recommended dose.
  • With just plain film radiography, monitoring may
    not be required as long as the operator stays in
    the control booth during all exposures.
  • There are some exams such as stress views of the
    ankle where the operator would be in the room
    with the patient. If this is done, monitoring
    would be necessary.
  • If the operator ever holds a patient monitoring
    would be necessary.

9
Occupational Radiation Monitoring
  • Occupational radiation monitoring offers no
    protection against exposure. It merely records
    the exposure received.
  • If needed, find a certified laboratory to process
    the dosimeters.
  • Types of monitors
  • Film badges
  • TLD
  • OSL

10
Film Badges
  • Film badges have been used since the 1940s and
    are still used today.
  • Exposures below 10 mR are not measured on the
    film.
  • Filters along with the window in the badge allow
    estimation of the energy of the exposure.
  • The must be worn with the proper side to the
    front.
  • They are typically worn on the collar so they
    would remain outside the lead apron.

11
Film Badges
  • Advantages
  • Inexpensive
  • Easy to handle and process
  • Reasonably accurate
  • Disadvantages
  • Can not be reused
  • Sensitive to heat and humidity
  • Must be changes monthly

12
TLD
  • TLD has several advantages over film badges.
  • Not sensitive to heat or humidity
  • Measure exposures to 5mR More sensitive and
    accurate.
  • Can be changed quarterly instead of monthly
  • Disadvantages
  • Cost but changing badges less frequently than
    monthly eliminates cost problem.

13
Optically Stimulated Luminescence
  • All of the advantages of the TLD over film badges
    plus
  • Can be re-read to confirm exposure
  • More accurate than TLD

14
Where to wear the monitor
  • The whole body badge is typically worn at collar
    level so it can be outside the lead apron.
  • Fetal monitoring badges used during pregnancy are
    worn at waist level under the apron.
  • Hand or finger TLDs are worn on the extremity.

15
Occupational Radiation Monitoring Reports
  • State and federal regulations require that the
    results of the occupational radiation monitoring
    program be recorded in a precise fashion and
    maintained for review.
  • Specific information is required to be on the
    report including current and cumulative exposure.
  • Each site of monitoring must be identified
    separately.
  • There will also be a control monitor to measure
    the background exposure during transport,
    handling and storage.

16
Occupational Radiation Monitoring Reports
  • The supplier of the badges must know the type of
    radiation for proper calibration of the
    equipment.
  • The badges are control are shipped back to the
    supplier in a timely manner.
  • For lost or damaged badges, a health physicist
    will estimate the exposure.
  • The annual exposure is discussed with each worker
    and receipt of the information is documented.
    Monthly reports may be posted but care must be
    taken with sensitive information.

17
Protective Apparel
  • Lead apron used for operator or patient
    protection must be the equivalent of 0.5mm of
    lead.
  • They must be worn when in a room during the
    exposure or during fluoroscopy.
  • Half aprons are effective means to provide gonad
    protection during radiography.
  • 0.25 mm of lead aprons should be avoided as they
    only attenuate 66 of the beam at 76 kVp.

18
Protective Apparel
  • Aprons used in interventional radiology should be
    a wrap around type. Thyroid shields may also be
    worn.
  • Lead gloves can be worn when the hands are in the
    beam.
  • Aprons must be stored on specially designed racks
    or laid flat on the floor. They are never folded.
  • Aprons are tested annually for cracks or holes in
    the lead, usually by fluoroscopy.

19
Position
  • During fluoroscopy radiologic technologist should
    stand as far as possible from the machine.
  • Standing behind the radiologist offers added
    protection.
  • If you must be in the room, position your body as
    far away from the primary beam as possible.

20
Patient holding
  • Many patients will find the x-ray examination to
    be physically demanding. Some may not be capable
    of staying in position.
  • This is a particular challenge for weight-bearing
    radiography. Mechanical supportive devices are
    limited for erect studies.
  • If you have a radiographic table, the patient may
    be examined recumbent. Sponges may be used as
    supportive devices.

21
Patient holding
  • Radiology or office staff should never hold a
    patient. Family or friends may be called upon to
    assist the patient.
  • The person assisting the patient must wear a lead
    apron and if their hands will be in the beam lead
    gloves.
  • Position the person as far away from the primary
    beam as possible.
  • Since the person holding the patient may be a
    parent, make sure they are not pregnant.

22
Reducing Unnecessary Patient Dose
  • As a doctor, you have the responsibility to
    determine if the radiography is necessary and
    justified.
  • There are more practice guidelines available
    every year to assist in determining if the
    examination will yield necessary diagnostic
    information.
  • There are many examinations that are performed
    knowing that they will yield little helpful
    information so they in no way justify the patient
    radiation dose.

23
Reducing Unnecessary Patient Dose
  • Check to see if the patient has previous
    examinations that may make the new examination
    not necessary.
  • You may be sued if you dont take films and the
    treatment plan fails because you missed something
    the films would show.
  • The yield of information must be greater than the
    risk of radiation exposure.

24
Reducing Unnecessary Patient Dose
  • Routine x-ray examinations should not be
    performed.
  • Used the most accurate tests to confirm or rule
    out your working diagnosis.
  • Consider using MR instead of CT

25
Repeat Examinations
  • One area of unnecessary patient exposure is
    repeated x-ray examinations. Past estimates of
    frequency has been as high as 10 but they should
    normally not exceed 5.
  • Most of the retakes are of the lumbar spine,
    abdomen and thoracic spine.
  • Most retake are due to the exposure factors being
    incorrect resulting in an over exposed or under
    exposed film. Proper measurement are important.

26
Repeat Examinations
  • Positioning errors account for about 25 of
    retakes. Proper training and practice is
    important to fine tune positioning skills.
  • Motion causes about 11 of retakes so proper
    patient communication during the exam is
    important.
  • But do not be afraid to retake a poor quality
    film. If you can not see a problem makes it
    likely you will miss it. Poor quality exams are
    never justified.

27
Radiographic Technique
  • Use as high kVp as possible to get adequate
    contrast and reduce patient exposure.
  • Collimate the beam to slightly smaller than film
    size or the area of interest, whichever is
    smaller.
  • Use the fastest-speed screen-film combination
    consistent with the nature of the examination.

28
Positioning
  • When taking films with the patient seated, do not
    allow the gonad to be in the primary beam.
    Position the patient lateral to the beam.
  • For female patients turn the patient PA to reduce
    breast and gonad exposures when possible.

29
Patient shielding
  • Some form of patient shielding should be used on
    all patients able to reproduce.
  • All children should have shielding.
  • Pre-menopausal women should be shielded except
    when the shield would interfere with the
    examination.
  • Men should be shielded beyond 50 years.

30
Patient shielding
  • Patient shielding includes contact shields and
    shadow shields.
  • Contact shields are placed on the patient and
    include aprons, the heart shaped filter and the
    bell.
  • Shadow shields are placed between the patient and
    the tube. Here we attach it to the tube.

31
Patient shielding
  • Shielding must be used when the gonads lie in or
    near the useful beam and when it does not
    interfere with obtaining the required diagnostic
    information.
  • Accurate placement is extremely important.
    Repeated examinations can result form improper
    placement of the shield.
  • Proper patient positioning and collimation should
    not be relaxed when gonad shields are in use.

32
Ten Commandments of ALARA
  1. Understand and apply the cardinal principles of
    radiation control time, distance and shielding.
  2. Do not allow familiarity to result in a false
    security.
  3. Never stand in the primary beam.
  4. Always wear protective apparel when not behind a
    protective barrier.
  5. Always wear a radiation monitor and position it
    outside the protective apron at collar level.

33
Ten Commandments of ALARA
  1. Never hold a patient during radiographic
    examinations. Use mechanical restraining devices
    when possible. Otherwise, use patients or friends
    to hold the patient.
  2. The person holding the patient must wear
    protective apron and if possible, gloves.
  3. Use gonadal protective on all people of
    childbearing age when it will not interfere with
    the examination.

34
Ten Commandments of ALARA
  1. Examinations of the pelvis or lower abdomen of a
    pregnant patient should be avoided whenever
    possible, especially during the first trimester.
  2. Always collimate to the smallest field size
    appropriate to the examination.

35
Chapter 31 Quality Control
  • Two areas of activity are designed to ensure the
    best possible image quality with the lowest
    possible exposure and minimum costs.
  • Quality Assurance deals with people
  • Quality Control deals with instrumentation and
    equipment.

36
Chapter 31 Quality Control
  • Two areas of activity are designed to ensure the
    best possible image quality with the lowest
    possible exposure and minimum costs.
  • Quality Assurance deals with people
  • Quality Control deals with instrumentation and
    equipment.

37
Ten Step Approach to Quality Assurance
  1. Assign responsibility
  2. Delineate scope of care
  3. Identify aspects of care
  4. Identify outcomes that effect the aspects of
    care.
  5. Establish limits of the scope of assessment.

38
Ten Step Approach to Quality Assurance
  1. Collect and organize data.
  2. Evaluate care when outcomes are reached.
  3. Take action to improve care
  4. Assess and document actions
  5. Communicate information to organization-wide QA
    Program

39
QA Projects
  • Things that QA can evaluate includes
  • Scheduling of patients
  • Instructions given to patients
  • Wait times in the office
  • Interpretation of films
  • Retake analysis
  • Record accuracy

40
QA Program
  • Quality Assurance deals with people and processes
    used to complete tasks.
  • QA involves training and record keeping.
  • As the owner of the equipment, you will be
    responsible for your radiology services.
  • The State of California Department of Radiologic
    Health established the Standards of Good Practice
    that is the foundation of QA and QC in
    radiography.

41
QA and QC Requirements
  • Degree of requirements vary by state. California
    and New York have very tight standards for
    quality control of the radiographic and
    processing equipment.
  • We are required by statue to teach QA and QC in
    the radiology program. It is covered in detail in
    9th Quarter. My textboook covers QC in detail.

42
Quality Control
  • An acceptable QC program has three steps
  • Acceptance Testing
  • Routine performance monitoring
  • Maintenance

43
Acceptance Testing
  • The x-ray machine, cassettes and film processor
    or digital system are the largest capital expense
    you may experience.
  • It makes economic sense to make sure that the
    equipment meets the performance standards.
  • It is recommended that a third party such as a
    health physicist do the testing.

44
Acceptance Testing
  • Areas that should be tested include on the x-ray
    machine
  • Shielding of Room
  • Focal spot size
  • Calibration of mA, timer or mAs
  • Calibration of kVp
  • Linearity of exposure
  • Beam alignment
  • Grid centering
  • Collimation
  • Filtration (HVL)

45
Acceptance Testing
  • Areas that should be tested on the x-ray
    cassettes
  • Screen contact
  • Screen speed
  • Light leaks
  • Light spectrum matching

46
Acceptance Testing
  • Areas that should be tested on the x-ray film
    processor
  • Developer temperature
  • Replenishment rates
  • Travel time
  • Water flow
  • Hypo retention

47
Quality Control
  • The acceptance testing ensures that the machine
    was installed and calibrated properly.
  • The performance may drift or deteriorate over
    time. Consequently, periodic testing is required
    to monitor the performance.
  • With the exception of film processing most
    testing is annual or semiannual.

48
Quality Control
  • After a major repair, the machine should be
    retested to ensure that it was repaired properly.
  • When the testing shows that the machine is not
    performing properly, service or preventive
    maintenance is required.
  • Manufactures establish recommended preventive
    service schedules. When these are followed many
    repairs become unnecessary.

49
Radiographic Quality Control
  • Areas of concern in x-ray machine
  • Focal Spot Size will impact spatial resolution
  • Filtration will impact patient exposure
  • Collimation will impact patient exposure
  • kVp calibration will impact image quality and
    exposure.
  • Exposure timer accuracy will impact image quality
    and exposure

50
Radiographic Quality Control
  • Areas of concern in x-ray machine
  • Exposure linearity will impact exposure and image
    quality
  • Exposure reproducibility will impact exposure and
    image quality.
  • Alignment of tube and image receptor will impact
    exposure and image quality.

51
Focal Spot Testing
  • When the machine is installed or the tube is
    replaced, the focal spot size should be measured.
    Then annually thereafter.
  • A pin hole camera, star test pattern or line pair
    test tool.
  • As the tube ages, the focal spot tends to grow
    and spatial resolution is lost.

52
Filtration
  • The filtration is measured but determining the
    half value layer of the beam at specific exposure
    levels. Minimum filtration is 2.5mm aluminum.
  • As a tube ages, tungsten will plate the x-ray
    port and increase filtration. This can cause
    technique problems. Inadequate filtration will
    significantly increase patient exposure.

53
Collimation
  • If the collimation is misaligned, intended
    anatomy can be missed.
  • It can be tested in many ways from using pennies
    to using test patterns.
  • Misalignment can not exceed 2 of the SID.
  • It is tested semiannually and after the
    replacement of the collimator lamp.

54
kVp Calibration
  • In diagnostic radiology, any change will impact
    patient exposure. A variation of about 3 will
    impact contrast and image density.
  • Can be tested with filtered ion chambers,
    filtered photodiodes or even a cassette with
    calibrated filters.
  • Tested annually.

55
Exposure Timer Accuracy
  • The exposure time is the responsibility of the
    operator. It will impact the density of the image
    and spatial resolution.
  • Tested with an ion chamber, multi-meter
    internally or even a spinning top.
  • Exposure time must be within 5 for exposure
    times greater than 10 ms and 20 less than 10 ms.

56
Exposure Linearity
  • Many combinations of mA and time will produce the
    same mAs value. The ability of the machine to
    produce a constant level of exposure with various
    combinations of mA and time is called exposure
    linearity.
  • Can be tested with a step wedge and densitometer
    or rate meter.
  • Should be within 10 for adjacent stations.

57
Exposure Reproducibility
  • Any exposure using the same factors should
    produce the same level of density and contrast on
    the image.
  • Sequential exposure should be reproducible to
    within 5
  • Can be tested with a rate meter or step wedge and
    densitometer.

58
Performance standards for x-ray equipment
Measurement Frequency Tolerance US Tolerance Ca
Filtration Annually 2.5 mm Al 2.7mm Al
Collimation Semiannually 2 of SID 2 of SID
Focal Spot Annual 50 50
kVp Annual 10 2 kVp between 60 100 kVp
Timer Annual 5 gt 10 ms 20 20 ms 3 phase 5 1 phase 10
Linearity Annually 10 10
Reproducibility Annual 5 5
59
Darkroom and Processing
  • The development of the image is dependent upon
    the temperature of the developer, its
    concentration and how long the film is in the
    developer.
  • The film is sensitive to variations in the
    environment and processing from the time it is
    manufactured until it is processed.
  • Darkroom and Processor QC is the key process of
    Quality Control.

60
Processing
  • Processor densitometry is performed daily before
    the first patient is exposed.
  • A sensitometer is used to produce a step wedge
    image on the film that is evaluated with a
    densitometer.
  • The densitometer reads the optical density of the
    processed image.
  • A digital thermometer is used to test the
    chemical temperatures in the processor.

61
Processing
  • Key densities on the processed film are measured
    and then graphed.
  • Base plus Fog is measured on an area of unexposed
    film to check the darkroom environment.
  • Speed is tested at the level of exposure that
    produces a density of 1.25OD
  • Contrast is tested at the level that produced a
    density of 0.40 OD and one that produced a
    density of 2.20.

62
Processing
  • By monitoring these densities, problems with film
    processing can be detected before image quality
    deteriorates.
  • In 9th Quarter we will cover how to perform
    processor QC and problem solve.

63
Waste Records
  • Since used fixer is classified as a hazardous
    waste material, it is important to maintain
    accurate records of usage and disposal.
  • The extent of records vary by city, county and
    state. You are responsible for the proper
    disposal of the waste. Some regions include
    developer as hazardous waste.

64
Silver Recovery
  • If the silver ions are removed from the fixer, it
    may be disposed of in the normal waste when
    diluted with water.
  • There are two primary types of silver recovery
    systems.
  • Metallic replacement uses steel wool and can
    recover 95 of the silver in the effluent
  • Electrolytic recovery passes direct current
    through the solution and nearly pure metallic
    silver is deposited on the cathode.

65
Silver Recovery
  • Old radiographic films and repeated films are
    retained for silver recovery. X-ray images can
    not be disposed of in normal trash.
  • They also can not be used to clean the processor
    rollers.
  • Waste recovery companies will either burn or
    chemically remove the silver from the film.

66
Performance standards for film processor and
darkroom equipment
Measurement Frequency Tolerance CA Tolerance US
Sensitometry Daily BF 0.05 MD 0.10 OD Contrast 0.10OD BF0.08 OD MD 0.15 OD Contrast 0.15 OD
Safelight Semiannual lt 0.05 OD in 2 minutes n/a
Darkroom temp Monthly 70ºF 5º n/a
Darkroom humidity Monthly 50 10 n/a
Developer temp Daily 0.5ºF 2-3º
Replenishment Daily 5
Transport Annual 3 3
67
Accessory QC
  • The cassettes and screens are the area of chief
    concern. Problems with either will result in
    artifacts on the images and increased retakes.
  • The screens need to be properly cleaned
    frequently. Mammography screens are cleaned
    daily. California recommends monthly cleaning.

68
Accessory QC
  • Dirty screens produce white artifacts on the
    image.
  • Multiple white artifacts indicate the need to
    replace the screens.
  • Screen contact is tested semiannually. A problem
    with screens contact will cause a loss of
    resolution.
  • As screens age, they loose speed so this is also
    tested.

69
Accessory QC
  • The other important accessory is the gonad
    protection devices and lead aprons.
  • Improper care of the apron can result in cracks
    and holes in the lead that reduces their
    effectiveness.
  • Aprons and shields are tested semiannually. The
    easiest was to test them is with
    video-fluoroscopy but film can be used.

70
Performance Standards for Accessories
Measurement Frequency Tolerance CA Tolerance US
Screen contact Semi annual No problems detected No problems detected
Aprons/shields Annually No holes No holes
Screen matching Annually 0.05 OD for all cassettes used
Screen cleaning Monthly Semimonthly
71
Record keeping
  • All electromechanical devices need periodic
    service.
  • There are three types of maintenance.
  • Scheduled maintenance such as processor monthly
    or weekly service. It includes observing moving
    parts and lubrication.
  • Preventive maintenance is planned service and
    replacement of parts at regular intervals before
    they fail at inopportune times.

72
Record keeping
  • Non-scheduled maintenance is the worst type of
    service because it impacts patient service. It
    may also be very expensive.
  • With proper scheduled and preventive maintenance,
    non-scheduled service can be minimized.
  • All service schedules should meet manufacture
    recommendations.
  • All service should be documented as part of the
    quality assurance program.

73
Retake Analysis
  • Required part of a QA program in California.
  • Evaluation includes
  • View repeated
  • Cause of the repeat
  • Rate of retakes should be less than 5.
  • Information can be gathered from the log that the
    state mandates for patients being exposed to
    radiation.

74
Retake Analysis
  • Done every three months using a relatively large
    sample of data to see trends in
  • Type of examination being repeated.
  • Reasons for the repeated films.
  • Determine if additional training or review is
    needed.
  • Determine if equipment service might be required.

75
Repeat Analysis
  • Your patient log can be designed to capture both
    films usage and repeated films.
  • Data is gathered from log for analysis
  • Repeated films can be put into two main
    categories
  • X-ray Personnel Errors
  • Equipment malfunctions

76
X-ray Personnel Errors
  • Failure to measure patient.
  • Use of improper technical factors (mAs, kVp or
    distance)
  • Incorrect positioning
  • Improper Collimation
  • Improper use of accessories such as cassettes,
    grids or filters

77
X-ray Personnel Errors
  • Improper handling of exposed or unexposed films.
  • Failure to clearly communicate to the patient
    breathing instructions and to remain still.
  • Failure to observe patient during exposure.

78
X-ray Equipment and Accessory Failure or
Malfunctions
  • Inaccurate calibration of kVp and mA.
  • Inaccurate timer calibration
  • Dirty or damaged cassettes
  • Improperly labeled or damaged grids
  • Malfunctioning collimator
  • Improper film storage or processor function.

79
Reasons for Retake Films
  • Over or under exposure accounts for over 50 of
    retakes nationally.
  • Errors in positioning (25)
  • Patient motion 11
  • Processing errors 6
  • Wrong view, beam alignment,cassette screen or
    grid errors and artifacts.

80
Retake Films by Region
  • Cervical Spine Exams 7
  • Thoracic Spine Exams 17
  • Lumbar and Abdominal X-rays 40
  • Skull, Chest,Lower Extremities 15
  • Majority or retake results in unnecessary
    exposure to gonads or blood forming organs of the
    body.

81
Daily Log Design
  • Most regulatory agencies will require a log of
    patients having radiation exposure.
  • Columns can be added to capture film usage,
    repeats, views repeated and reason.
  • This data can be gathered and analyzed.

82
Retake Analysis
  • In this example, most of the retakes were of the
    T-spine. Potential reasons include
  • Improper use of filters
  • Incorrect measurements
  • Faulty technique chart

83
Retake Analysis
  • The reason of each retake is recorded and
    percentages are computed to determine the
    overall rate and rate by reason.
  • Less than 5 is ideal.

84
End of Lecture
  • Return to Lecture Index
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