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Resident Physics Lectures

Christensen, Chapter 7 X-Ray Beam Restrictors. Resident Physics Lectures. George David Associate Professor Department of Radiology Medical College of Georgia. Aperture Diaphragms Cones and Cylinders Collimators. Restrictors Types. Lead sheet with hole in center simple

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Resident Physics Lectures

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  1. Christensen, Chapter 7 X-Ray Beam Restrictors Resident Physics Lectures George David Associate Professor Department of Radiology Medical College of Georgia

  2. Aperture Diaphragms • Cones and Cylinders • Collimators Restrictors Types

  3. Lead sheet with hole in center • simple • large penumbra (partial shadow) • Lead close to focal spot Focal Spot Aperture Diaphragms Penumbra Receptor

  4. Focal Spot Focal Spot Film Film Cones & Cylinders With cone angle as above, this functions as an aperture Reduced Penumbra

  5. Advantages • Adjustable rectangular field • fluoro may have circular field • Light beam indicates x-ray field • Two sets of shutters • longitudinal • transverse • Each set may have 2 pairs of shutters operating together Collimators One set; two pairs

  6. Focal Spot Filter Lamp Mirror Shutters (only 1 set shown) • Generally include filter & light Radiographic Collimators

  7. Numerical field size indicators • Field size dependent on source-image distance • SID • Focal spot to image receptor 8 10 12 14 17 40” 8 10 12 14 17 Collimator Features

  8. Senses cassette size, orientation, & SID • source - image distance • limits x-ray field to size of receptor • PBL does not insure tube & bucky aligned Positive Beam Limitation(PBL or Automatic Collimation) Cassette

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