quality assurance

• Quality Assurance and Quality Control


  • Managing Patient Care and Image Quality
• Quality Control


  • Equipment quality control measures
  • Acceptance testing
  • Performance monitoring
  • Maintenance (including preventive maintenance)
• QC measures are also tied to accreditation and reimbursement
• Most states have legislation that requires QC measures to be performed and documented
• Radiographic Quality Control


  • Filtration
  • Collimated field/x-ray field congruence
  • SID indicator
  • Light beam centering device
  • Focal-spot size
  • kVp accuracy
  • Timer accuracy
  • Linearity
  • Reproducibility
• Inherent + added filtration

  >2.5 mm Al for tubes operated over 70 kVp
• Collimated field/x-ray field congruence

  +/- 2% of the SID
• SID indicator


  +/- 2% of the SID
• Light beam centering device


  +/- 1% of SID
• Focal-spot size


  <150% of nominal size
• kVp accuracy


  +/- 10% of indicated kVp
• Timer accuracy


  +/- 5% over 10 msec

  +/- 20% <10 msec
• Linearity


  +/- 10% for adjacent mA stations
• Reproducibility


  +/- 5% for sequential exposures
• The machine does not meet reproducibility requirements
• The machine passes the linearity test
• Aprons, gloves and shields are examined under fluoroscopy or radiographed annually for cracks, holes or defects
• Defective lead apparel is replaced
• Digital Imaging


  • Detector/CR cassette performance
  • Software performance
  • Monitor display
  • DICOM and GSDF
• Fluoroscopic Quality Control


  • Exposure rate (ESE) not to exceed 10 R/min

  High dose fluoroscopy for interventional or cardiac may not exceed 20 R/min

  ABC systems (AERC) must be calibrated for II and FPD
• Mammography as a Model for QC

  • Annual QC evaluations

  Elements of a mammographic QC program
• Exposure Technique Charts


  Purpose is to allow for consistent quality image production

  Decreases repeat rate

  Lowers patient dose
• Manufacturers often provide technique charts with equipment
• These charts are guidelines and should not be used without modification
• Technique charts may vary between different radiographic rooms in the same department
• Types of Technique Charts

  • Variable kVp chart

  Fixed kVp chart

  High kVp chart

  AEC chart
• Variable kVp Technique Chart

  Uses a fixed mAs and varies the kVp according to the thickness of the part

  Advantage: the use of a lower kVp results in a shorter scale of contrast

  Disadvantages: may result in higher patient dose and less exposure latitude
• Variable kVp Technique Chart formula


  Beginning kVp (high frequency generator) = 2 x thickness of part (cm) + 23

  For single phase add 30 and for three phase add 25

  The kVp increases by 2 kVp/cm

  Make test exposures of a phantom with three different mAs values and pick the one with optimum exposure
• Fixed kVp Technique Chart

  Select an optimum kVp for penetration of part

  Vary mAs based on size of part/patient

  Patients are sorted into small, medium and large categories

  Advantage: may allow for lower patient dose and more exposure latitude due to inherently higher kVp

  mAs changes must be between 30-50%
• High kVp Technique Chart

  Used for barium studies and chest radiography

  kVp is over 100

  Lower patient dose and increased exposure latitude
• AEC Technique Chart


  Positioning is critical

  May be APR system of variable kVp system, or both

  kVp must be specified or programmed

  Density control buttons specified

  Collimation specified

  Detector cells specified