What is the meaning of cold, cool, warm or hot nodules on an isotope thyroid scan? Because of the thyroid’s specific absorption of radioactive iodine (131I) or technetium (99mTc), it is commonly used clinically to show the location, shape, and size of the thyroid. Because different lesions of the thyroid gland absorb different amounts of isotope, isotope can be used to show the location, extent, and functional status of thyroid lesions. The report of a thyroid scan is divided into: ① Hot nodules: suggest that the nodules are taking up more iodine than the normal thyroid gland. The chance of thyroid cancer is extremely low. (2) Warm nodules: suggest that the iodine uptake function of the nodules is close to that of the normal gland, which is usually seen in benign thyroid adenoma and nodular goiter. ③Cold nodules: The distribution of radioactivity at the nodule site is lower than that of the surrounding normal tissue, indicating low iodine uptake. ④Cold nodules: The distribution of radioactivity at the nodule is significantly lower than that of the normal gland, which is close to no iodine uptake.