Functions

• Adjusts rectangular x-ray field
  • fluoroscopic collimators may adjust circular field
• Light field indicates x-ray field coverage

Configuration

• Two sets of lead shutters
  • longitudinal
  • transverse
  • two pairs operating together with one closer to the x-ray tube.
• Lamp
• Mirror
  • directs light from lamp
• Filter (optional)

Other Information

• X-ray system may limit beam to size of receptor (positive beam limitation or PBL)
• Collimation reduces
  • field coverage
  • irradiated tissue volume
  • scatter radiation
    • improves image quality