What term refers to the lead diaphragm technique used to restrict beam size?

• A. Collimation
• B. Filtration
• C. Shielding
• D. Focusing

Answer: (A)

Collimation is about shaping the x‑ray beam by using a lead diaphragm or collimator to define the size and shape of the field. By restricting the beam to the area of interest, collimation minimizes patient exposure because fewer photons are produced and interact outside the target area. It also reduces scatter and fog, which helps improve image contrast and sharpness.

Filtration, on the other hand, changes the beam quality by removing low-energy photons, but it doesn’t change the geometric size of the beam. Shielding provides protection to areas outside the field but isn’t used to mold the beam itself. Focusing relates to aligning the beam and focal spot to improve sharpness, not to restricting the field size.