Thyroid nodule or suspected thyroid cancer
ACR TI-RADS 2017; ACR Manual on Contrast MediaUltrasound is the whole of the initial answer: it characterises the nodule, stratifies risk against a structured system, and directs fine-needle aspiration. Cross-sectional imaging has two narrow roles, and iodinated contrast in a patient heading for radioiodine is a sequencing decision the vetter owns.
Palpable thyroid nodule, thyroid nodule found incidentally on another study, or clinical features raising suspicion of thyroid malignancy.
Referenced decision support — confirm against your local protocol.
Decision support, not a directive. Protocols and timings shown are typical published ones — your local protocol takes precedence, and the vetting radiologist decides.
- The features that predict malignancy — marked hypoechogenicity, taller-than-wide shape, irregular or extrathyroidal margin, punctate echogenic foci — are resolvable only at the spatial resolution of high-frequency ultrasound, and none of them is visible on CT. The same examination surveys the cervical nodal levels, which is where the finding that actually changes surgical planning is made, and it guides the needle when aspiration is indicated. No ionising radiation and no contrast, so nothing about it prejudices later radioiodine.
Nothing needs resolving before this goes ahead. Routine checks below are owned downstream.
How was this decided?
- pathwaystandard — Adults — thyroid nodule assessment
Decision support only. Local protocol takes precedence.
Pathways
Big forks are separate pathways; the first whose conditions match is the one used.
Adults — thyroid nodule assessment
Matches your inputsDefault| Role | Study & protocol | Why this answers the question |
|---|---|---|
| First line | Ultrasound neck / thyroid Ultrasound neck and thyroid usually appropriate | The features that predict malignancy — marked hypoechogenicity, taller-than-wide shape, irregular or extrathyroidal margin, punctate echogenic foci — are resolvable only at the spatial resolution of high-frequency ultrasound, and none of them is visible on CT. The same examination surveys the cervical nodal levels, which is where the finding that actually changes surgical planning is made, and it guides the needle when aspiration is indicated. No ionising radiation and no contrast, so nothing about it prejudices later radioiodine. |
| Problem solving | CT Neck (Soft Tissues) CT Neck — Contrast-Enhanced Soft Tissue | Two narrow indications, both anatomical rather than diagnostic: retrosternal extension that ultrasound cannot follow below the thoracic inlet, and locally advanced disease where airway, oesophageal or vascular invasion must be mapped before surgery. If the patient is a candidate for radioiodine, the iodinated contrast load is a genuine cost and the sequence must be settled before the scan is booked. |
Pitfalls
- Accepting a CT neck to characterise a thyroid nodule. It cannot apply the risk features, adds radiation, and may block radioiodine.
- Aspirating on size alone. A structured risk category combined with size is what the systems require, and biopsying every nodule over a centimetre generates indeterminate cytology and unnecessary surgery.
- Overlooking the nodes. An abnormal cervical node changes the operation, and the nodal survey is part of the thyroid ultrasound rather than an optional extra.
- Failing to mention retrosternal extension in a patient with compressive symptoms, where ultrasound is simply blind below the inlet.
- Treating a history of hyperthyroidism as a contraindication to contrast. A treated or biochemically controlled patient needs no restriction and no routine thyroid function testing; the genuine cautions are untreated overt hyperthyroidism, where an iodine load can precipitate thyrotoxicosis, and planned radioiodine imaging or therapy, where the load blocks uptake for weeks. Neither is the patient who once had a thyroidectomy.
Priors — what to pull first
- Compare with any previous thyroid ultrasound: documented stability over years lowers the index of suspicion and may end the pathway.
- Where the nodule was found on PET, note the pattern — focal uptake in a thyroid nodule carries a materially higher malignancy risk than diffuse uptake, which is usually thyroiditis.
What makes a good request
- Risk stratification systems score composition, echogenicity, shape, margin and echogenic foci, and combine that score with maximum diameter to decide between aspiration, ultrasound follow-up and no action. Size alone is a poor discriminator and a large benign-appearing nodule may need nothing.
- An incidental thyroid nodule seen on CT or PET should be characterised by ultrasound, not by repeating or extending the cross-sectional study.
- Where radioiodine imaging or therapy is planned, iodinated contrast saturates the thyroid iodine pool and blocks uptake for weeks. The order of investigations is the decision, and only the vetting radiologist can reorder it.
Scoring this once it is done
The classification and risk tools this question ends in.
How these studies are acquired
Contrast, phases and timing for every study on the pathways above.
Confirm locally
- Timings, contrast volumes and rates above are typical published values. Your department's protocol, scanner and patient population decide the actual numbers.
- Safety thresholds and premedication policy follow local policy where it differs from the cited guidance.
References
- ACR Thyroid Imaging, Reporting and Data System (TI-RADS) white paper · Other
- ACR Manual on Contrast Media — thyroid effects of iodinated contrast · ACR Contrast Manual
- ACR TI-RADS resource page · Other
Implemented from the cited published sources. Educational and workflow support only; confirm against current guidelines and local policy before clinical use.