Thyroid ultrasound is the main imaging test for the thyroid. It is painless, uses no radiation and provides detailed information about the gland’s structure and any nodules.
What the scan shows
Ultrasound shows:
- The size of each lobe and the isthmus
- The texture (echogenicity) of the gland
- Any nodules, cysts or calcification
- Blood flow within the gland
- Nearby lymph nodes
It is particularly useful for evaluating a neck lump, monitoring known nodules and guiding biopsy.
How nodules are described
When a nodule is found, the report describes several features:
- Size — measured in three dimensions
- Composition — solid, cystic or mixed
- Echogenicity — how bright or dark it appears compared with normal tissue
- Shape — including whether it is taller than wide
- Margins — smooth, irregular or ill-defined
- Calcification — including microcalcifications
- Vascularity — blood flow within the nodule
These features are combined to estimate the risk that a nodule is cancerous.
What TIRADS means
TIRADS (Thyroid Imaging Reporting and Data System) is a scoring system that categorises nodules from benign-appearing to highly suspicious. Higher categories are associated with a greater chance of malignancy and often prompt biopsy.
A TIRADS score is a risk estimate, not a diagnosis. Many nodules in higher categories are still benign.
When is a biopsy needed?
Biopsy (FNAC) is generally recommended for nodules with suspicious features above a certain size, or for growing nodules. Small, low-risk nodules are often monitored with repeat ultrasound instead.
Preparing for the scan
No special preparation is needed. You can eat and take medications normally. The scan takes about 15–30 minutes and is performed with a gel and probe on the neck.
What happens after
The report is interpreted alongside your thyroid function tests and examination. Your clinician will explain whether monitoring, biopsy or another step is recommended.
The bottom line
Thyroid ultrasound is a safe and detailed way to assess the thyroid. Understanding the report’s structure — size, features and risk category — helps you have a more useful conversation with your clinician.