Which factor is associated with less scatter in CT imaging according to the material?

• A. Lower patient motion
• B. Tight collimation
• C. Increased detector size
• D. Higher kilovoltage

Answer: (B)

Scatter in CT comes from photons that interact inside the patient and get deflected toward the detector. Tight collimation narrows the X-ray beam, dramatically reducing the volume of tissue irradiated. With less tissue to scatter from, fewer photons are deflected into directions that reach the detectors, so the amount of scatter reaching the image is minimized. The result is better image contrast and less fog from scattered radiation.

Lower patient motion mainly affects motion blur rather than scatter. A larger detector area tends to collect more scattered photons, which can worsen image quality. Higher kilovoltage increases beam penetration and tends to raise scatter and reduce contrast, not reduce scatter.