Which X-ray accessory is used to shape the size and geometry of the x-ray beam?

• A. Filtration
• B. X-ray tube
• C. Cassettes
• D. Collimator

Answer: (D)

Shaping the primary x-ray beam is accomplished by the collimator, which uses adjustable lead shutters to control the field size and geometry of the beam. By narrowing or expanding the exposed area, the collimator directs the radiation to the region of interest, reduces patient dose, and minimizes scatter that can degrade image quality. Modern collimators also provide reproducible field size and alignment with the central ray, helping ensure consistent imaging. Filtration softens the beam by removing low-energy photons but does not alter the field size or shape. The x-ray tube is the source of the radiation, and the cassette is simply the image receptor. Thus, the accessory responsible for shaping the beam’s size and geometry is the collimator.