Final answer:
The constants during trial exposures are type of cassette, focal-film distance, and x-ray film type. Proper shielding and use of fast films can minimize radiation exposure during imaging.
Step-by-step explanation:
The constants during trial exposures in radiographic imaging are A. type of cassette, B. focal-film distance, and C. x-ray film type. These parameters are kept the same to ensure consistency across exposures for comparison and accurate measurements. Work that is likely to cause an increase in radiation exposure includes tasks in close proximity to x-ray sources without proper shielding, prolonged exposure times, and repeated imaging without protective measures. It's important to reduce this exposure by using fast films, lead aprons, and shielding around the x-ray tubes as seen in Figure 32.7. Technicians reduce their occupational exposure by standing behind lead-lined doors during imaging. The film's darkening relates to exposure levels but also depends on the radiation type, which is why absorbers may be used to obtain specific information.