How does increasing collimation affect the amount of Compton scatter reaching the image receptor?

How does increasing collimation affect the amount of Compton scatter reaching the image receptor?

• A. Increasing collimation increases the scatter striking the receptor
• B. Increasing collimation decreases the scatter striking the receptor
• C. Increasing collimation has no effect on the scatter striking the receptor
• D. Collimation redirects scatter away from the receptor

Answer: (B)

Increasing collimation narrows the X-ray field, so fewer tissues are irradiated. Compton scatter comes from interactions within that irradiated volume, and scattered photons travel in many directions. With a smaller field, there are fewer opportunities for photons to scatter toward the image receptor, and the collimator itself also blocks many off-axis photons. So the amount of Compton scatter that reaches the receptor decreases, which improves image contrast and reduces patient dose. Collimation doesn’t redirect scatter; it mainly reduces its production and absorbs scatter before it can reach the receptor.

Increasing collimation narrows the X-ray field, so fewer tissues are irradiated. Compton scatter comes from interactions within that irradiated volume, and scattered photons travel in many directions. With a smaller field, there are fewer opportunities for photons to scatter toward the image receptor, and the collimator itself also blocks many off-axis photons. So the amount of Compton scatter that reaches the receptor decreases, which improves image contrast and reduces patient dose. Collimation doesn’t redirect scatter; it mainly reduces its production and absorbs scatter before it can reach the receptor.