Resident Physics Series

1
Resident Physics Series

• ACR Mammography Protocols

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Mammography QC Manual
Revised Edition, 1999
Sections

• Radiologist
• Clinical Image Quality
• Radiologic Technologist
• Medical Physicist

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Quality Assurance (QA)
QA should ensure

• Every imaging procedure is necessary
  appropriate to clinical problem at hand
• images contain information critical to solution
  of that problem

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Quality Assurance (QA)

• recorded information is
• correctly interpreted
• made available to patients physician in a timely
  fashion
• consistent with image quality objectives,
  examination results in lowest possible
• radiation exposure
• cost
• inconvenience to the patient

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Quality Control (QC)
QC is integral part of QA

• Acceptance Testing
• detection of defects in equipment that is newly
  installed or has undergone major repair
• Baselines
• Establishment of baseline equipment performance
• quantitative data when system operating properly

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Quality Control (QC)

• Diagnosis
• Diagnosis of changes in equipment performance
  before they become radiologically apparent
• Verification
• Verification of correction of causes of
  deterioration in equipment performance

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Facility Responsibility

• Designate One Lead Interpreting Physician

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Lead Physicians Responsibilities

• Ensure technologists have adequate
• orientation
• based on procedure manual
• training
• continuing education
• Ensure effective QC program

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Radiologists Responsibilities

• Designate one technologist responsible for QC
• QC tech can delegate responsibilities to others

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Radiologists Responsibilities

• Ensure availability of appropriate test
  equipment
• Arrange staffing / scheduling to allow time for QC

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Radiologists Responsibilities

• provide frequent consistent positive negative
  feedback to technologists about film quality QC
• Review technologists test results
• no less than every 3 months
• more often if inconsistentresults

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Radiologists Responsibilities

• Select a medical physicist
• administers QC program
• performs physicists tests
• Review physicists test results

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Radiologists Responsibilities

• Oversee or designate qualified individual to
  oversee radiation protection program for
• employees
• patients
• individuals in surrounding area

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Radiologists Responsibilities

• Ensure proper maintenance of records in QC
  procedures manual
• employee qualifications
• mammography technique / procedures
• quality control / safety / protection
• infection control

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Radiologists Responsibilities

• The radiologist is ultimately responsible for
  the quality of films produced under his or her
  direction and bears ultimate responsibility for
  both proper QC testing and QA procedures in
  mammography.

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Physicists Responsibilities

• Note All physicists tests are to be done
  annually or after tube replacement or major
  service

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Physicists Responsibilities Mammography Unit
Assembly Evaluation

• mechanical stability / identification of sharp
  edges
• receptor stability
• locks / motions / detents
• operator shielding
• thickness scale accuracy
• indicator lights working
• technique chart posted (see next slide)

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Technique Chart

• Even though most mammo is phototimed, still need
  technique chart
• For given breast size, density, view specify
  machine set-up
• Phototimer mode (auto standard, contrast, dose,
  )
• Density (-2, -1, 0, )

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Technique Chart

• Wrong
• Display kVp, mAs, target, filter calculated by
  machine for given image
• Correct
• Display machine settings selectable by
  technologist for this breast and view
• Should provide enough guidance to allow a
  technologist who has not worked in this room or
  facility to properly set up a study

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Physicists Responsibilities Mammography Unit
Assembly Evaluation

• Cassettes slide smoothly into/out of holder
• Override available for auto-decompression
• display must indicate when auto-decompression
  turned off
• Manual release of compression if power lost

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Collimation Assessment

• x-ray light field alignment
• beam does not exceed receptor by gt 2 SID
• compression paddle / receptor alignment at chest
  wall within 1 SID
• paddle not visible on image
• Image should fill film
• Many units by design will not do this

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Physicists Responsibilities

• Focal Spot Performance
• limiting resolution pattern
• kVp accuracy / reproducibility
• Beam quality (HVL)
• minimum maximum
• minimum patient dose
• maximum image contrast

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Automatic Exposure Control (AEC / Phototiming)

• kVp tracking
• Thickness tracking
• image mode tracking (cassette sizes, w w/o grid)
• automatic mode tracking
• unit selects kVp, target, filter
• density control
• even steps of 15-20

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Physicists Responsibilities

• Screen Uniformity
• compare O.D. of each cassette using phototimer
• AEC Reproducibility

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Physicists Responsibilities

• Breast Entrance Exposure, Average Glandular Dose,
  
• RMI-156 accreditation phantom used for entrance
  exposure / average glandular dose

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Breast Average Glandular Dose Limits

• 0.3 rad (300 mrads, 3 mGy) maximum per view for
  screen-film receptors using a grid
• 0.1 rad (100 mrads, 1 mGy) maximum per view for
  non-grid screen-film receptors
• Radiation output rate gt 800 mR/sec

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Image Quality Evaluation

• use RMI-156 accreditation phantom
• record
• fibers
• speck groups
• masses
• optical densities
• technique

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A Poor Phantom Image
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Artifact Identification

• Artifact evaluation / description
• determination of artifact source
• processor
• other equipment
• Done with phantomfilm

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Physicists Responsibilities

• Viewing conditions
• ambient light
• viewbox brightness
• My experience
• Ambient lighting often ignored

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Technologists Responsibilities
All QC must not only be performed but must be
documented!

• Daily
• darkroom cleanliness
• processor quality control
• sensitometric data
• Weekly
• screen cleanliness
• viewboxes and viewing conditions
• Phantom images

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Technologists ResponsibilitiesMonthly Visual
Checklist

• visual checklist
• SID indicator
• angle indicator
• locks
• field light
• smooth motions

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Technologists ResponsibilitiesMonthly Visual
Checklist

• cassette lock
• Is cassette held firmed in place when tubestand
  tilted
• Compression device firm compression
• Smooth edges
• Holds pressure
• hand switch placement
• visibility
• switches/ lights/ meters
• cones/ collimators

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Technologists ResponsibilitiesQuarterly

• Fixer retention analysis
• Fixer affects archivability of films
• Repeat analysis
• breakdown by cause
• motion
• positioning
• technique
• static
• etc.

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Semi-Annual Technologists Responsibilities
Darkroom Fog

• must use sensitized film
• partially cover previously exposed phantom film
  in darkroom for 2 minutes
• up to .05 O.D. increase acceptable

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Semi-annual Technologists Responsibilities

• Screen Film Contact
• 40 lines/inch Copper mesh
• subjective results
• poor contact can result if time (15 minutes) not
  provided for air to bleed out of cassette after
  closing
• NOTE 15 minutes between cassette loading
  exposure must be provided for all clinical films
  to insure good contact

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Semi-annual Technologists Responsibilities

• Screen Film Contact

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Semi-Annual Technologists Responsibilities

• Compression
• can use bathroom scale covered with towel
• 25 - 40 pounds for automatic systems
• at least 25 pounds for manual compression

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The End

• Questions?