What is done to check for back scatter radiation?

• A. A letter "B" 12 mm (1/2 in) is placed on the back of the film.
• B. A lead shield is placed around the film during exposure.
• C. The film is exposed at a higher energy for comparison.
• D. A calibrated standard is used to measure scatter.

Answer: (A)

Backscatter can fog a film by adding exposure from photons that bounce off the object or surroundings and strike the film from the back. A practical way to detect this effect is to place a small marker on the back of the film before exposure. A letter such as "B" serves as a backscatter indicator: after development, if backscatter is present, the area around the marker will reveal the extra exposure, alerting you that backscatter contributed to the image. This single, simple check directly shows whether backscatter is influencing the film density.

Adding a lead shield around the film wouldn’t specifically diagnose backscatter; it would just alter shielding and exposure. Exposing the film at a higher energy for comparison changes the primary beam characteristics and isn’t a targeted check for backscatter. Using a calibrated standard to measure scatter involves separate dosimetry equipment and procedures beyond this quick in-film indicator.