Which device is used to physically restrict the size and shape of the x-ray beam?

• A. Filtration
• B. Grid
• C. Collimator
• D. Anode

Answer: (C)

The device that physically restricts the size and shape of the x-ray beam is the collimator. It uses adjustable lead shutters in the x-ray tube housing to confine the primary beam to the selected field, shaping it to match the area of interest. This minimizes patient dose and reduces scatter, while helping produce a more consistent image.

Filtration sits in the beam path to remove low-energy photons, improving image quality but not changing the beam’s geometry. A grid reduces scatter after the patient but does not define the beam’s shape. The anode is part of the x-ray tube that generates the beam; it does not determine field size or shape.