In thyroid imaging, what does it mean if a lesion is described as 'cold'?

In thyroid imaging, what does it mean if a lesion is described as 'cold'?

• A. Nonfunctioning
• B. Hyperfunctioning
• C. Functioning
• D. Noncontrast

Answer: (A)

In thyroid nuclear medicine imaging, nodules are described by how much radiotracer they take up compared with the rest of the gland. A cold lesion does not take up the radiotracer, so it is nonfunctioning relative to the surrounding thyroid tissue. On the scan it appears darker than the normal thyroid, indicating reduced or absent function in that area. This is in contrast to hyperfunctioning (hot) nodules, which concentrate more tracer and appear brighter due to autonomous hormone production. The term noncontrast isn’t part of this functional assessment. Cold nodules can be benign (like cysts or colloid nodules) or malignant, so evaluation is guided by risk factors and further testing as appropriate.

In thyroid nuclear medicine imaging, nodules are described by how much radiotracer they take up compared with the rest of the gland. A cold lesion does not take up the radiotracer, so it is nonfunctioning relative to the surrounding thyroid tissue. On the scan it appears darker than the normal thyroid, indicating reduced or absent function in that area. This is in contrast to hyperfunctioning (hot) nodules, which concentrate more tracer and appear brighter due to autonomous hormone production. The term noncontrast isn’t part of this functional assessment. Cold nodules can be benign (like cysts or colloid nodules) or malignant, so evaluation is guided by risk factors and further testing as appropriate.