What is a major difference between the RAIU test and a thyroid ultrasonography scan?

• A. The RAIU test measures the amount of radioisotope absorbed, while the scan gives an image of the structure.
• B. Both are done to assess the function and structure of the thyroid gland. 
• C. The thyroid scan uses radioactive iodine, while the RAIU test does not.
• D. Unlike a thyroid scan, the RAIU test is used in the treatment of thyroid cancer.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the purpose of the RAIU test (Radioactive Iodine Uptake test). It is primarily used to measure how much radioactive iodine the thyroid gland absorbs, which reflects the gland's functional activity.
2. Step 2: Understand the purpose of thyroid ultrasonography (thyroid scan). This imaging technique uses sound waves to create a visual image of the thyroid gland's structure, helping to identify physical abnormalities such as nodules or enlargement.
3. Step 3: Recognize that the RAIU test provides quantitative data about thyroid function by measuring radioisotope uptake, whereas the thyroid ultrasonography provides qualitative data by showing the anatomical structure.
4. Step 4: Note that the RAIU test involves administering a small amount of radioactive iodine and measuring its absorption, while thyroid ultrasonography does not involve radioactivity but uses sound waves instead.
5. Step 5: Summarize the major difference: the RAIU test assesses thyroid function through radioisotope absorption, whereas the thyroid ultrasonography scan assesses thyroid structure through imaging.