22.1 Radiographic Quality Control Variables in Radiographic Equipment

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22.1 Radiographic Quality ControlVariables in
Radiographic Equipment

• kVp Calibration
• mA Calibration
• Timer accuracy
• Collimator accuracy
• Beam Alignment
• Grid Centering
• Focal Spot

• Impacts technique
• Impacts technique
• Impacts Technique
• Impacts Collimation
• Impacts Grid Cut off
• Impacts Grid Cut Off
• Impacts Resolution

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Radiographic Quality Assurance

• Begins with the Acceptance Tests to set baseline
  values and assure proper operation.
• Periodic monitoring to assure continued
  compliance. Annual or Semiannual
• After major component repair or replacement

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Radiographic Performance Standards

• kVp Accuracy
• mA, Timer, mAs
• Collimator
• Beam Alignment
• Grid Centering
• Exposure Reproducibility

• 5 2 between 60 and 100 kVp
• 5
• 2 of SID
• 2º
• 2º
• 5

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22.2 Collimator Accuracy and Beam Alignment

• Tools needed
• 9 pennies or
• Collimator alignment tool
• Beam perpendicularity test tool
• Standard Must be within 2 of SID or 0.8 at 40
  SID

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Collimator Accuracy and Beam Alignment

• Procedure
• Set SID _at_ 40 to Bucky
• Place 8X10 Cassette in Bucky
• Center beam to film center
• Collimate to 5 square
• Mark borders with pennies taped to Bucky
• Make exposure and process film.

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Collimator Accuracy and Beam Alignment

• Procedure
• mark center and horizontal and vertical axis of
  beam
• The exposure should be to the outer edges of the
  pennies.
• Must be within the diameter of the pennies to
  pass the test.

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Collimator Accuracy and Beam Alignment

• Procedure
• mark center and horizontal and vertical axis of
  beam
• The exposure should be to the outer edges of the
  pennies.
• Must be within the diameter of the pennies to
  pass the test.

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Collimator Accuracy and Beam Alignment

• Frequency semiannual or after replacement of
  collimator light bulb or tube replacement.
• You should hold the x-ray machine supplier to a
  much higher standard.
• The beam and light fields should match!

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Collimator Accuracy and Beam Alignment

• Procedure with beam alignment test tool
• Set SID to 40 to Bucky
• Center 8 x 10 film to Beam
• Tape collimator test tool to Bucky centered to
  light field.
• Collimate to marked borders on tool (5 x 7)

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Collimator Accuracy and Beam Alignment

• Procedure with beam alignment test tool
• Tape the beam perpendicularity test tool to the
  collimation tool with the metal ball centered to
  center of tool.
• Make exposure and process the film

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Collimator Accuracy and Beam Alignment

• Viewing of test film
• The both small balls must be within the first
  circle to be in proper alignment.
• Collimation should match borders of test tool.
• Frequency semiannual or after tube or Bucky
  replacement or repair

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22.3 Grid Cut Off and Perpendicularity Testing

• If the tube is not perpendicular to the Bucky,
  Grid Cut-Off will result.
• If the grid focus is not correct, grid cut off
  will also result.
• The left knee is under exposed compared to the
  right. This is grid cut off.

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Grid Cut Off and Perpendicularity Testing

• Tools Needed
• A homogenous phantom that will produce some
  density on the film. This cane be A lead apron
  or piece of Lucite 14x17x2
• Densitometer
• 14 x 17 Cassette

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Grid Cut Off and Perpendicularity Testing

• Procedure
• Set the SID at 40 Bucky
• Drape Apron over Bucky or
• Place Lucite in stool in front of Bucky
• Place cassette in Bucky Tray and center tube to
  film.

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Grid Cut Off and Perpendicularity Testing

• Procedure
• Collimate to film size and make exposure.
• Process film
• Repeat test at 72 SID.
• Process Film

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Grid Cut Off and Perpendicularity Testing

• Standard There should be not more than 0.10 OD
  change from center of image to sides of image.
• If 40 or 72 test passes and the other fails,
  the focal range of the grid may be wrong.
• If both fail, the grid is misaligned.

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Grid Cut Off and Perpendicularity Testing

• Grid misalignment can be common with new
  installations.
• If the Bucky crashes to the floor, the grid can
  be knocked out of alignment.
• Frequency of test Semiannual

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22.4 Linearity Of Exposure

• The same mAs should produce the same exposure
  each time.
• This will be true if the mA and Timer are
  accurately calibrated.
• The kVp must be the same.

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Linearity Of Exposure

• Tools needed
• Aluminum Step wedge
• Lead Blockers
• 14 x17 Cassette
• Densitometer
• Standard Exposure should be within 5 across
  the mA, Time and mAs settings

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22.4 Linearity Of Exposure

• Procedure
• Set SID to 40 table top
• Place cassette on table
• Step wedge is placed on cassette.
• Collimation set to size of step wedge.
• Lead blockers cover the area around exposure.

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Linearity Of Exposure

• Procedure
• Set a baseline technique and initiate first
  exposure
• Cover exposed section of film and prepare for
  second exposure.
• Change control setting and the put back to
  original setting.
• Make exposure.

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Linearity Of Exposure

• Procedure
• Continue process with changes in power level or
  mA setting, Focal Spot settings and time
  settings.
• Make sure that the exposed areas of the cassette
  are covered by the lead blockers.
• Process the film.

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Linearity Of Exposure

• This is an example of poor calibration of the
  x-ray generator.
• The small and large focal spot mA setting are not
  calibrated.
• This was a new unit that the service engineer
  failed to calibrate.

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Linearity Of Exposure

• This is an example of proper calibration of the
  machine.
• Each exposure is virtually identical. If you need
  to adjust a technique on this machine, you can do
  it reliably.

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22.5 Focal Spot Testing

• Test Tools
• RMI Focal Spot Test Tool or
• Pin Hole Camera or
• NEMA Star Pattern Test Tool
• Extremity Cassette
• Lead Blocker

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Focal Spot Testing

• Procedure
• Place Extremity Cassette or Card Board Film
  Holder on Table.
• Cover half of cassette with Lead Blocker
• Set SID to 40 Table Top
• Place test tool on cassette with rivets aligned
  with the anode and cathode.

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Focal Spot Testing

• Procedure
• Collimate to size of test tool.
• Set technique and make exposure on small focal
  spot.
• Cover exposed section of cassette.
• Set tool on unexposed section of cassette.

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Focal Spot Testing

• Procedure
• Place L on film and make exposure with large
  focal spot.
• Process the film.

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Focal Spot Testing

• Interpretation of film
• Compare vertical and horizontal three bars.
• 1.0mm Focal spot will resolve 11 line pairs/mm.
• 2.0mm focal spot will resolve 5 to 6 line
  pairs/mm.
• If you cannot see this far, the tube may be bad.

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Focal Spot Test Film Passed
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Focal Spot Testing

• While the focal spot passes the test, the
  exposure is different between the large and small
  focal spots.
• This was the first clue that the calibration of
  the machine was wrong.

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Focal Spot Test Film

• Both exposures are at the same mAs and kVp
• Resolution Passed
• Exposure Fail

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Accessory Testing

• Accessories include the cassettes, grids outside
  the Bucky, Lead Aprons and gonadal protection.
• The cassettes and screens are the primary
  concern.
• Screens should be cleaned monthly with screen
  cleaner. Keeping the darkroom clean is also
  important for screen cleanliness.

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23.4 Screen Contact Testing

• Procedure
• Clean screens and let them dry. Use screen
  cleaner design for the screen used.
• With a felt tip pen, write an identification
  number on the screen next to the I.D. and on the
  back of the cassette.
• Load cassettes.

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Screen Contact Testing

• Procedure
• Set SID to 40 Table Top
• Place cassette on table.
• Place wire mesh tool on cassette.
• Set collimation to film size.
• Make exposure and process film.

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Screen Contact Testing

• Procedure
• Hang film on view box.
• Step back 72 from view box and view film.
• Areas of increased density or loss of resolution
  indicates poor contact or stained screens.

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Screen Contact Testing

• Procedure
• The I.D. will help you find a cassette that
  needs to be cleaned or taken from service.
• Frequency of tests semiannual

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Poor Screen Contact

• There is a loss of detail in the thoracic and
  lumbar spine due to poor screen contact.
• This was a new cassette.

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Poor Screen Contact

• Note the blurry image in the spine but sharp
  image of the ribs.
• The screens were not in proper contact in the
  middle of the cassette due to a bow in the
  cassette back.

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Screen Cleaning

• Materials needed
• Screen Cleaner designed for type of screens used.
• 4 x 4 gauze or cotton balls
• Tape Pen

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Screen Cleaning

• Procedure
• Unload cassette if contact is not being tested.
• Apply cleaner with gauze.
• Wipe excess off with dry gauze.

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Screen Cleaning

• Leave open to air dry.
• Make sure cassette is still legible.
• After dry, reload cassette.

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Screen Cleaning

• Record date on tape and place on back of
  cassette.
• By having each cassette identified, selected
  cassette can be cleaned as needed.

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Screen Cleaning

• California Department of Radiologic Health
  recommends cleaning screens monthly.
• Should definitely be done quarterly and sooner as
  needed when artifacts are identified on films.
• Never use alcohol or detergents not designed for
  cleaning screens.

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Cassette Care

• Methods to get the maximum life from cassettes
• Avoid dropping the cassettes
• Open only far enough the change films
• Keep outside of cassette clean and dry.
• Keep screens clean
• Store on end.

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Dirty or Damaged Screens

• Dirty or damaged screen will cause white spots on
  the image.

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Dirty Damaged Screens

• The white spots on this film are the result of
  damaged or worn out screens.
• Never use alcohol or detergents to clean screens.

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Speed Matching

• After looking for screen contact problems
• Measure speed of cassettes by reading density
  with the Densitometer. The density of the exposed
  area should not vary more than 0.05 OD.
• As screen age, they loose speed.
• Always make sure the light spectrum of the
  screens and film are matched.

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23.5 Apron and Gonad Shield Testing

• Lead aprons and shields should be tested
  semiannually for defects
• Aprons with defective lead provide little
  protection for the patient.

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Apron and Gonad Shield Testing

• Tools needed
• 14 x 17 cassette
• View Box
• Coat Apron Procedure
• Drape apron over Bucky
• Place cassette in Bucky make exposures in upper
  and lower Bucky slots.

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Apron and Gonad Shield Testing

• Coat Apron Procedure
• Note that this is the same test as used for grid
  alignment.
• Process films
• View films on view box

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Apron and Gonad Shield Testing

• Half Apron and Small Shield Procedure
• Place cassette on table
• Set SID at 40
• Place apron or shields on cassette.
• Make exposure and process the film.

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Apron and Gonad Shield Testing

• Viewing the test films
• Note creases in the lead.
• Full holes will produce a black area on the film.
• If cracks or defects are in the area that should
  cover the gonads, replace apron.

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Care of Aprons

• Never fold aprons
• Store flat or hung on apron rack
• Use only aprons with the lead equivalency of
  0.5mm for patient and staff protection.
• Do not use as lead blockers for extremity films.
• Protect from heat and direct sun light.

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Grid Uniformity Testing

• Procedure is the same as testing the Bucky Grid.
• Place homogenous phantom or lead apron over grid
  that is taped to the top of the cassette.
• Make exposure and look for density changes and
  grid damage.

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