In Nuclear Medicine, a tracer is introduced into the body by which routes?

• A. TRACER
• B. Radiopharmaceutical
• C. Contrast agent
• D. Dye

Answer: (A)

In Nuclear Medicine, the key idea is that the substance used to visualize physiology is a tracer, a radiopharmaceutical designed for imaging. This tracer is the agent that is administered to the patient to trace a biological process, and it can be given by various routes such as intravenous injection, oral intake, or inhalation, depending on the study area. The question is asking what gets introduced into the body, and the best fit among the terms is the tracer, because it is the actual imaging agent delivered to the patient. The other terms describe broader categories or unrelated types of substances—radiopharmaceuticals are the class of compounds used as tracers, while contrast agents and dyes are used in other imaging modalities and contexts. So, the tracer is the substance introduced for the purpose of imaging in nuclear medicine.