Beam And Scatter Radiation Restricting Devices

1. Beam And Scatter Radiation Restricting Devices DMI 50B Kyle Thornton

3. Factors Affecting Scatter Radiation kVp Field size Patient or part thickness

4. kVp Compton interaction increases with increasing kVp Scatter radiation increases Scatter radiation is reduced by using collimators and grids Decreasing kVp is not always desirable Increases patient dose

5. Beam Field Size As field size is increased, scatter radiation increases Restriction of field size improves image quality Even more important during fluoroscopy

6. Patient Or Part Thickness Scatter increases with patient or part thickness A chest x-ray will result in more scatter than an arm x-ray Compression devices reduce patient thickness and improve quality

7. Beam-Restricting Devices Two types of devices to reduce scatter Beam restricting devices Grids Restricted for two reasons Reduce patient dose Improve image contrast Three types of beam-restricting devices Aperture diaphragm Extension cones and cylinders Variable aperture collimator Positive beam limitation

8. Aperture Diaphragm Simplest of all beam-restricting devices Lead or lead-lined plate with an opening Used with older head units Cannot see a light

9. Extension Cones And Cylinders Modifications of aperture diaphragms Primarily used for headwork, L5-S1 Fixed openings Generally not light localizing

10. Variable-Aperture Collimator Light localizing Most commonly used A series of shutters and mirrors used Light field must coincide with x-ray beam

11. Positive Beam Limitation Devices Automatically collimates to the size of film used Does not relieve of technologist of having to collimate to anatomy

12. Collimator Filtration Some collimator housing units come with interchangeable filtration Generally, different millimeter thicknesses of aluminum is used