Final answer:
A used needle should always be treated as if it is contaminated and potentially hazardous in the diagnostic imaging department to prevent the transmission of infections.
Step-by-step explanation:
A used needle should always be treated as if it is contaminated and potentially hazardous when working in the diagnostic imaging department. This is because needles used in medical procedures have the potential to come into contact with blood or bodily fluids that may contain disease-causing organisms, making them a biohazard. It is important to handle and dispose of used needles properly to prevent the transmission of infections.