Which device shapes the primary X-ray beam?

• A. Grid
• B. Filter
• C. Collimator
• D. Cassette

Answer: (C)

Shaping the primary X-ray beam is done by the collimator. It sits at the tube head and uses adjustable shutters to define the field size and shape, aligning the beam with the area of interest on the patient and receptor. This geometry control reduces patient dose and minimizes unnecessary exposure, while also helping to limit scatter produced in the patient. A light localizing field on the collimator lets you visualize the actual imaging area before exposure. The filter changes the energy of the beam by absorbing low-energy photons, improving image quality and reducing dose, but it doesn’t change the beam’s shape. A grid reduces scattered radiation after the patient, and the cassette is simply the receptor that records the image.