Why is proper collimation important for patient dose and image quality?

• A. Reduces unnecessary radiation, minimizes scatter, and improves image contrast by limiting the field.
• B. Increases scatter and lowers image quality.
• C. Has no impact on patient dose.
• D. Requires more intense exposure to achieve acceptable image brightness.

Answer: (A)

Proper collimation narrows the x-ray beam to the size and shape of the anatomy being imaged. This means fewer tissues are irradiated, so the patient’s overall dose is reduced. With less tissue interaction, less scattered radiation is produced and less scatter reaches the image receptor, which decreases fog and improves image contrast and sharpness. By limiting exposure to only the area of interest, image quality becomes more reliable while keeping the dose as low as reasonably achievable. The idea that collimation increases scatter, has no effect on dose, or requires more exposure to look bright does not fit the reality of how collimation controls radiation and image quality.