Which statement best describes the collimator?

Which statement best describes the collimator?

• A. A lead restricting device that limits the beam to 2.75 inches diameter
• B. A detector in the image receptor
• C. A device that increases beam energy
• D. A device that triggers exposure

Answer: (A)

Collimation controls radiation safety by restricting the x-ray beam to the size needed for the image. The collimator is a lead device at the end of the X-ray assembly that defines a specific aperture, shaping the primary beam so it matches the receptor area. Because lead blocks most x‑ray photons outside this opening, limiting the beam reduces patient dose and decreases scatter, which helps improve image contrast. It doesn’t change the beam’s energy—that’s determined by kVp—and it doesn’t trigger the exposure or serve as the detector. So the best description is a lead restricting device that limits the beam to the necessary size.

Collimation controls radiation safety by restricting the x-ray beam to the size needed for the image. The collimator is a lead device at the end of the X-ray assembly that defines a specific aperture, shaping the primary beam so it matches the receptor area. Because lead blocks most x‑ray photons outside this opening, limiting the beam reduces patient dose and decreases scatter, which helps improve image contrast. It doesn’t change the beam’s energy—that’s determined by kVp—and it doesn’t trigger the exposure or serve as the detector. So the best description is a lead restricting device that limits the beam to the necessary size.