What type of transport mechanism is primarily involved in the thyroid localization of Tc-99m during imaging procedures?

• A. Passive transport
• B. Facilitated diffusion
• C. Active transport
• D. Sodium exchange

Answer: (C)

The correct choice highlights that active transport is the primary mechanism involved in the localization of Tc-99m in the thyroid during imaging procedures. In the context of radiopharmaceuticals, Tc-99m is taken up by the thyroid gland due to its chemical similarity to iodine, which is actively transported into the thyroid cells.

Active transport requires energy and often involves the movement of ions or molecules against their concentration gradient. In the case of Tc-99m, the thyroid gland has specific uptake mechanisms that utilize this energy-driven process to concentrate the radiopharmaceutical, thereby allowing for effective imaging of the gland. This process involves sodium-iodide symporter (NIS) proteins, which actively transport iodide into the thyroid cells. Since Tc-99m mimics iodide, it follows a similar pathway.

Understanding this transport mechanism is crucial for optimizing imaging techniques and interpreting results accurately in thyroid studies. Therefore, recognizing the role of active transport in the localization of Tc-99m aids in grasping the broader concepts of radiopharmaceutical behavior and their interactions with physiological systems.