Beam And Scatter Radiation Restricting Devices DMI 50B Kyle Thornton

Scatter Radiation Compton interaction Higher kVp energies in diagnostic range As scatter increases, radiographs lose contrast Radiographs will look dull, blurred, and fogged

Factors Affecting Scatter Radiation kVp Field size Patient or part thickness

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

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

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

Compression Used to Decrease Effects of Scatter Radiation

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

Different Types of Beam Limitation Devices

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

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

Cones and Cylinders

Comparison of Sinuses W/W- Out Use of Cones

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

Variable Aperture Device

Schematic Drawing of the Variable Aperture Device

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