Which statement about collimation is NOT true?

• A. It decreases patient dose
• B. It improves image contrast
• C. It reduces the area exposed to the primary beam
• D. It increases scatter

Answer: (D)

Collimation confines the X-ray beam to the region of interest, shrinking the volume of tissue that can interact with photons. This directly lowers the dose to the patient because less tissue is irradiated. It also reduces the area exposed to the primary beam, and because there’s less tissue and a smaller field for photons to scatter from, the amount of scatter that reaches the image receptor decreases, which improves image contrast. The statement that collimation increases scatter isn’t true; in fact, collimation reduces scatter reaching the detector.