Which radiopharmaceutical is commonly used for thyroid imaging when evaluating thyroid structure and function?

The most appropriate radiopharmaceutical for thyroid imaging when evaluating both thyroid structure and function is I-123, or iodine-123. Iodine is an essential element for the synthesis of thyroid hormones, and using I-123 allows for a functional assessment of the gland. This isotope emits gamma radiation, providing clear images of the thyroid and allowing for assessment of the thyroid's ability to uptake iodine, which is vital for hormone production.

Thyroid imaging typically aims to evaluate conditions such as hyperthyroidism, hypothyroidism, and thyroid nodules. I-123 is preferred over other options because it has favorable imaging properties, including a half-life that allows for sufficient imaging time and optimal energy emissions for gamma detection in nuclear medicine.

Other radiopharmaceuticals, such as Tc99m pertechnetate, can also visualize the thyroid but primarily assess its anatomy rather than directly providing functional information related to iodine uptake. Similarly, Tc99m MDP is utilized for bone imaging, and I-125, while used in some diagnostic applications, is less common than I-123 for thyroid studies due to its physical properties and radiation safety considerations.