What is the effect of proper collimation on patient dose?

• A. Reduces dose
• B. Increases dose
• C. No effect
• D. Reduces image resolution

Answer: (B)

Proper collimation confines the X-ray beam to the area of interest, so a smaller tissue volume is irradiated. Since dose is tied to how much tissue is exposed, reducing the exposed field lowers the patient dose. Collimation also cuts down on scatter produced within the patient, which decreases the amount of stray radiation reaching the detector and improves image contrast. So, the main effect of proper collimation is a reduction in patient dose, and it does not reduce image resolution—in fact, by lowering scatter it can improve overall image quality.