What radiopharmaceutical is used for evaluating conditions such as cancer, nodules, and thyroid dysfunction?

The use of I-123 is particularly relevant for evaluating thyroid function and detecting abnormalities in the thyroid gland. I-123 is a radioiodine that is absorbed by thyroid tissue, making it an excellent choice for imaging the thyroid and assessing conditions such as thyroid nodules, hyperthyroidism, or cancer. This radiopharmaceutical provides functional information about the thyroid's activity, allowing clinicians to distinguish between normal and abnormal tissue.

F-18 FDG, while highly effective for detecting cancer in various tissues due to its uptake in metabolically active cells, is not specific to thyroid evaluations. Tc99m-MDP is typically used for bone imaging rather than thyroid assessments. I-131, although also used for thyroid imaging and treatment, has a longer biological half-life and is primarily used in therapeutic settings rather than diagnostic evaluations in many cases.

Therefore, I-123 is the most suitable choice for specifically examining thyroid conditions, making it the correct answer for this question.