Which adjustment is necessary when increasing the focal-film distance while maintaining image density?

When increasing the focal-film distance (FFD), more X-ray photons diverge before reaching the film or the detector, which can lead to a decrease in image density. To compensate for this loss of density while still obtaining a proper image, it is necessary to increase the milliampere-seconds (mAs).

Increasing the mAs means increasing the number of X-ray photons produced, which enhances exposure to the film/detector. This adjustment counters the effect of the increased distance, allowing for consistent image density. Maintaining proper image density is crucial for effective diagnostic imaging, as it ensures that the contrast and detail in the images are retained even with adjustments in distance.

In contrast, altering the kilovolt peak (kVp) impacts the penetrating power of the X-rays rather than directly increasing the quantity of photons, hence it isn't the most effective adjustment in this scenario. Therefore, increasing mAs is the appropriate response to maintain image density when focal-film distance is increased.