[Scintigraphy in the diagnosis of thyroid carcinoma]

Thyroid scans yield functional information useful in the differential diagnosis of thyroid nodules and are usually performed with TcO4-99m for its favourable physical properties, availability, low cost and good correlation with I123. Cold thyroid nodules are very frequent and generally due to benign diseases. To distinguish the minority representing carcinomas, classes of risk must be selected, according to multiple factors, including external radiation exposure, sex, age, iodine intake and thyroid morphology. These patients will undergo fine needle biopsy which can make the final diagnosis. Its accuracy is often preferred as a first line modality in the diagnostic approach to thyroid nodules. Tumour imaging agents are very useful in the staging and follow-up of thyroid carcinomas, but are rarely needed in the primary diagnosis of the disease.