Which principle is NOT used to manage radiation exposure to patients and healthcare personnel?

The principle that is not used to manage radiation exposure to patients and healthcare personnel is concentration. In radiation safety, the focus is typically on minimizing exposure through three key principles often referred to as the "ALARA" principle: Duration, Distance, and Shielding (or Protection).

Duration involves reducing the amount of time spent near a radiation source, as exposure is directly related to the time of exposure. Distance refers to maximizing the distance from the radiation source, since intensity decreases with increased distance. Protection includes the use of barriers and shielding materials to absorb or deflect radiation, thereby reducing exposure.

Concentration, however, is not a recognized principle in the context of radiation management. It does not directly relate to limiting exposure or protecting individuals from radiation, which is why this option is the one that stands out as incorrect in this context. Understanding and applying these principles is crucial for ensuring safety in environments where radiation is present.