Grids

• Grids objective is to minimize the amount of scattered radiation coming from the patient before it reaches the IR
• • When used correctly, grids improve radiographic contrast by reducing the amount of scattered radiation reaching the IR
  • By improving contrast, detail is no longer obscured
• The grid is placed between the patient and the IR
• As the primary beam passes through the patient, many photons are scattered in many different directions
• A grid is compiled of many fine thin lead strips
• • A grid allows the straighter photons (remnant radiation carrying the aerial image) to reach the IR
  • While photons not carrying useful information (scatter) are absorbed
• Grids

  • Body parts greater than 10 cm (ex: knee, shoulder, neck, skull)
  • Lead strips run parallel to centerline
  • Absorbs scatter radiation which improves visibility of detail
• strips run the length of the grid
• • While scatter radiation increases density, using a grid will decrease it
  • Therefore, higher technical factors must be increased to compensate for that loss of density
  • In doing so, patient exposure is increased
• Grid advantage: decrease scatter, decrease density, increasing contrast, increasing resolution
• Grids are used for body parts greater than 10cm (skull, abdomen, spine, pelvis, femur, sternum, ribs)
• When was the grid invented and by who?

  1913 by Gustave Bucky
• Grid is constructed with extremely thin, closely spaced lead strips (placed vertically or slanted) separated by radiolucent material

  • plastic, aluminum, fibrous material
• True or False: There is a front and back side to a grid?

  True
• What is the positive aspect of using grids?

  Increase contrast by reducing scatter radiation reaching the IR
• What is the negative aspect of using Grids?

  • Grid Lines
  • Increased patient dose