What is the primary use of thyroid scanning with Tc-99m?

• A. To evaluate patients for surgery
• B. To assess kidney function
• C. To evaluate thyroid function and structure
• D. To monitor bone density

Answer: (C)

The primary use of thyroid scanning with Technetium-99m (Tc-99m) is to evaluate thyroid function and structure. This imaging technique is commonly referred to as a thyroid scan, which provides physicians with critical information about the thyroid gland's activity, including the presence of nodules, the uptake of radioactive material, and overall gland morphology.

During a thyroid scan, Tc-99m is used because of its ideal physical properties, such as a suitable half-life and gamma emission, which allow for clear imaging. The radiopharmaceutical is absorbed by the thyroid gland, which reflects the gland's functional status. Areas of increased uptake suggest hyperactivity, which may indicate conditions such as hyperthyroidism or thyroid nodules, while areas of reduced uptake can indicate hypothyroidism or other structural issues.

While evaluating patients for surgery is a potential consideration in the broader context of thyroid disease, the direct purpose of the scan itself is focused on assessing the functional and structural characteristics of the thyroid gland. This helps guide clinical decisions about further investigation, treatment, or surgical intervention based on the imaging results.