Thyroid Ultrasound in the Clinic: Technique, TI-RADS and Referral
Thyroid nodules are common and most are benign. Ultrasound decides which ones need a needle. The probe and settings, a systematic scan, ACR TI-RADS scoring and size thresholds, and what to look for in a machine.
Probe and settings
High-frequency linear probe
Thyroid scanning uses a linear probe, usually around 10–14 MHz or higher. A lower-frequency linear or convex probe helps with a large goitre or a nodule that extends below the collarbone.
Probe types and frequenciesThyroid or small-parts preset
Loads a shallow depth, fine near-field focus and the thyroid measurement package. Set the depth so the whole lobe and the carotid artery fit on screen.
Colour and power Doppler
Shows vascularity in the gland, separates solid tissue from debris inside a nodule, and helps judge lymph nodes. Sensitivity to slow flow matters more than headline colour speed.
Colour and power DopplerElastography (optional)
Strain or shear-wave elastography adds stiffness information on higher-end systems. It is an adjunct and is not part of ACR TI-RADS scoring.
Elastography explainedA systematic scan
- Patient lying flat with a pillow under the shoulders and the neck gently extended.
- Scan each lobe in transverse from top to bottom, then in longitudinal, and the isthmus in both planes.
- Measure each lobe and note the overall echotexture and vascularity — diffuse changes suggest thyroiditis or Graves’ disease.
- Measure each nodule in three dimensions and label its location: right, left or isthmus; upper, mid or lower.
- Scan the lymph nodes of the lateral neck on both sides — ACR calls this a vital part of every thyroid exam.
- Save clips as well as stills, so the next scan can be compared.
ACR TI-RADS in brief
The American College of Radiology’s Thyroid Imaging Reporting and Data System (ACR TI-RADS), published in 2017, scores five grey-scale features of a nodule. Choose one option in each of the first four rows, add every echogenic focus that applies, and total the points.
| Feature | Points |
|---|---|
| Composition | Cystic or almost completely cystic 0 · spongiform 0 · mixed cystic and solid 1 · solid or almost completely solid 2 |
| Echogenicity | Anechoic 0 · hyperechoic or isoechoic 1 · hypoechoic 2 · very hypoechoic (darker than the strap muscles) 3 |
| Shape | Wider-than-tall 0 · taller-than-wide on a transverse image 3 |
| Margin | Smooth or ill-defined 0 · lobulated or irregular 2 · extension beyond the thyroid 3 |
| Echogenic foci | None or large comet-tail artefacts 0 · macrocalcifications 1 · peripheral (rim) calcifications 2 · punctate echogenic foci 3 |
TI-RADS levels and size thresholds
| Points | Level | FNA if | Follow-up scans if |
|---|---|---|---|
| 0 | TR1 Benign | No FNA | Not needed |
| 2 | TR2 Not suspicious | No FNA | Not needed |
| 3 | TR3 Mildly suspicious | 2.5 cm or more | 1.5 cm or more; scans at 1, 3 and 5 years |
| 4–6 | TR4 Moderately suspicious | 1.5 cm or more | 1.0 cm or more; scans at 1, 2, 3 and 5 years |
| 7 or more | TR5 Highly suspicious | 1.0 cm or more | 0.5 cm or more; scans every year for up to 5 years |
Biopsy, growth and follow-up rules
- Biopsy no more than two nodules — those with the highest points, not simply the largest.
- Significant growth means a 20% increase in at least two dimensions with at least 2 mm, or a 50% increase in volume.
- Follow-up can stop at 5 years if the size is unchanged. If a nodule moves up a level, rescan in a year.
- Suspicious lymph nodes — round, without a fatty hilum, with peripheral flow, cystic change or tiny calcifications — should be sampled as well.
When a clinic should refer
Ultrasound-guided fine-needle aspiration (FNA) is usually done by a radiologist, surgeon or endocrinologist, and the cytology is reported using the Bethesda System for Reporting Thyroid Cytopathology. Refer when there is:
- A nodule that meets the FNA threshold for its TI-RADS level.
- A suspicious lymph node in the neck.
- Rapid growth, a hard fixed lump, a hoarse voice, or difficulty swallowing or breathing.
- A nodule together with abnormal thyroid function, for endocrine assessment.
- Any scan the operator is unsure of — a second opinion costs little compared with a missed cancer.
Read next Ultrasound for GP clinics
What to look for in a machine
- A linear probe that shows small nodules, calcifications and the thyroid capsule clearly at 1–3 cm depth — test it on real patients, not only a phantom.
- Doppler that fills small vessels without colour spilling outside them.
- A thyroid package with nodule measurement and labelling, and a TI-RADS worksheet or report template if offered.
- Clip storage and DICOM export, for comparison with earlier scans and for referral.
- Needle visualisation, if you plan to do guided FNA yourself.
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