The function of a ______ is to reduce the scattered radiation produced in the patient before it reaches the X-ray film.

• A. Grid
• B. Filter
• C. Collimator
• D. Kevlar cassette

Answer: (A)

Reducing scatter that reaches the film is achieved by a grid placed between the patient and the receptor. A grid has lead strips with interspace material; scattered photons come from many angles and are more likely to be absorbed by those lead strips, while the primary photons traveling straight toward the film pass through the gaps. This selective absorption cuts down the fog on the image, improving contrast.

Beam filtration and collimation play related roles but in different ways. Filtration removes low-energy photons to harden the beam, not primarily to clean up scatter at the film. Collimation limits the exposed area and therefore reduces scatter production by irradiating less tissue, but the device best suited for removing scatter before it reaches the film is the grid. Kevlar cassette isn’t a standard component for this purpose.