A grid primarily absorbs which type of radiation?

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

Answer: (C)

Grids boost image contrast by removing scatter radiation that comes from the patient. Scatter adds a fog to the image and lowers visibility of detail, so absorbing those off-angle photons improves the overall image quality. The lead strips in a grid are arranged to absorb photons traveling in directions away from the primary beam, while most of the primary photons travel straight toward the receptor and pass through the gaps between strips. That’s why the grid’s main purpose is scatter reduction rather than blocking the forward-directed primary beam. It does reduce some primary transmission, but the gain in contrast from removing scatter is the key effect. The grid isn’t designed to pre-filter low-energy photons before they reach the receptor—filtration does that, and the grid sits between patient and receptor to clean up scatter.