In scintigraphy, what is injected to trace the organ?

• A. A non-radioactive dye
• B. A radioactive pharmaceutical
• C. Water
• D. A contrast agent for CT

Answer: (B)

Scintigraphy relies on a radioactive tracer to visualize how an organ functions. A radiopharmaceutical is injected into the bloodstream, where it distributes to the target tissue or follows its normal physiological pathway. The tracer emits gamma rays, which a gamma camera detects to create an image that reflects function and flow rather than just structure. Non-radioactive dyes, plain water, or CT contrast agents wouldn’t emit the radiation needed for this technique, so they wouldn’t produce the scintigraphic image. Common tracers include technetium-99m labeled compounds that target specific organs, such as sestamibi for the heart or pertechnetate for the thyroid.