Which concept is most directly used to limit the x-ray field to the size of the receptor?

• A. Fixed filtration
• B. Positive beam limitation
• C. Diagnostic filtration
• D. Adjustable collimation

Answer: (D)

Collimation shapes the x-ray beam and is controlled by the collimator. The visible light field from the collimator guides how you frame the anatomy and sets the actual exposure area. When you adjust the collimator, you directly change the field size to match the size of the receptor being used for that exam. This hands-on adjustment is what confines the emitted beam to the receptor boundaries, reducing unnecessary exposure and limiting scatter. While automatic features like positive beam limitation help ensure the beam isn’t larger than the receptor, the most direct way you actively control and ensure the field matches the receptor is through adjustable collimation.