Download presentation
Presentation is loading. Please wait.
1
Resident Physics Lectures
Christensen, Chapter 7 X-Ray Beam Restrictors George David Associate Professor Department of Radiology Medical College of Georgia
2
Restrictors Types Aperture Diaphragms Cones and Cylinders Collimators
3
Aperture Diaphragms Lead sheet with hole in center simple
large penumbra (shadow) Lead close to focal spot Focal Spot Penumbra Film
4
Cones & Cylinders Focal Spot Focal Spot Film Film
With cone angle as above, this functions as an aperture Reduced Penumbra
5
Collimators Advantages Configuration
Provides adjustable rectangular field fluoro may also have circular field light beam indicates x-ray field Configuration two sets of shutters longitudinal transverse sets may actually have two pairs of shutters operating together One set; two pairs
6
Collimators Generally include filter & light Focal Spot Filter Lamp
Mirror Filter Focal Spot Shutters (only 1 set shown)
7
Collimator Features Numerical field size indicators
Field size is SID dependent 40”
8
Collimator Features Field center indicator (crosshairs)
plastic sheet attached to bottom of collimator two black lines drawn on it light projects field center on patient Shutters Crosshairs Bottom of Collimator
9
Positive Beam Limitation (PBL or Automatic Collimation)
senses film size, orientation, & SID source - image distance limits x-ray field to size of film No longer required PBL does not insure tube & bucky are aligned! Cassette
10
Collimator Checks X-Ray / Light Field alignment
Alignment of x-ray field to bucky Field Size Indicator accuracy PBL accuracy
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.