At 1 meter from the patient, scatter radiation is approximately what percent of the useful beam?

At 1 meter from the patient, scatter radiation is approximately what percent of the useful beam?

• A. 10%
• B. 1%
• C. 0.1%
• D. 0.01%

Answer: (C)

The amount of scatter radiation at a given distance from the patient is a small fraction of the useful (primary) beam, and it drops off quickly with distance because of the inverse square law and the way scatter is produced inside the patient. Most scatter comes from Compton interactions in the body, and only a tiny portion escapes toward the operator at distance. At about one meter from the patient, the scatter is roughly one tenth of one percent of the primary beam. In other words, about 0.1% of the useful beam is scattered to that distance. This small fraction reflects why increasing distance dramatically reduces exposure to staff. If you move farther away, the scatter falls even more—about a quarter as much at two meters, roughly 0.025%—illustrating the strong distance effect.

The amount of scatter radiation at a given distance from the patient is a small fraction of the useful (primary) beam, and it drops off quickly with distance because of the inverse square law and the way scatter is produced inside the patient. Most scatter comes from Compton interactions in the body, and only a tiny portion escapes toward the operator at distance.

At about one meter from the patient, the scatter is roughly one tenth of one percent of the primary beam. In other words, about 0.1% of the useful beam is scattered to that distance. This small fraction reflects why increasing distance dramatically reduces exposure to staff. If you move farther away, the scatter falls even more—about a quarter as much at two meters, roughly 0.025%—illustrating the strong distance effect.