What is the function of the grid?

• A. Absorb primary radiation
• B. Absorb remnant radiation
• C. Absorb scattered radiation
• D. Absorb low energy radiation before it reaches the patient

Answer: (C)

Grids are used to boost image contrast by absorbing scatter radiation before it reaches the image receptor. When X-rays pass through the patient, some photons are scattered in many directions; these scattered photons reach the receptor and create a hazy, low-contrast image. The grid sits between the patient and the detector and is made of lead strips with radiolucent interspaces. The lead strips absorb a large portion of scatter, especially photons traveling at angles away from the primary beam, while the spaces allow the majority of the primary, useful photons to pass through. The result is a sharper image with improved contrast. Higher grid ratios absorb more scatter but require higher exposure to maintain receptor signal, and grids don’t filter low-energy photons before they reach the patient; that function is filtration.