Thyroid Ultrasound

Thyroid ultrasound is the primary modality for evaluating the thyroid gland and characterizing nodules using high-resolution grayscale and Doppler imaging. It stratifies malignancy risk and guides selection of nodules for fine-needle aspiration through the ACR TI-RADS system. It also assesses the cervical lymph nodes for metastatic involvement and evaluates diffuse thyroid disease.

Indications

Palpable thyroid nodule or gland enlargement (goiter)
Incidental thyroid nodule detected on CT, MRI, PET, or carotid ultrasound
Evaluation of a neck mass or cervical lymphadenopathy
Assessment of diffuse thyroid disease in hyper- or hypothyroidism
Guidance for fine-needle aspiration biopsy
Surveillance of known nodules and post-thyroidectomy neck for recurrence
Screening in patients at risk, such as prior neck radiation or familial thyroid cancer

Contraindications & Cautions

No contraindications; safe, radiation-free, and repeatable
Not a functional study; correlate with thyroid function tests and, for hyperfunctioning nodules, scintigraphy
Large substernal goiters extend beyond the sonographic window and may require CT or MRI
Follow ALARA for Doppler settings

Patient Preparation

No fasting or special preparation required
Supine positioning with the neck hyperextended over a pillow or bolster
No consent needed for diagnostic scanning; consent obtained separately for FNA
Remove neck jewelry and high collars
Document relevant history including thyroid function status and prior surgery or radiation

Technique & Parameters

High-frequency linear transducer (7-15 MHz)
Both lobes and isthmus scanned in transverse and longitudinal planes
Gland dimensions and lobe measurements recorded; isthmus thickness noted
Each significant nodule measured in three dimensions and assessed for composition, echogenicity, shape, margins, and echogenic foci
Color and spectral Doppler to assess nodule and gland vascularity
Systematic survey of cervical lymph node levels II-VI
Apply ACR TI-RADS to assign points and determine FNA thresholds
Cine clips and representative static images documented

Systematic Review

Gland size, symmetry, and overall echotexture
Nodule composition: cystic, spongiform, mixed, or solid
Nodule echogenicity: anechoic, hyperechoic, isoechoic, hypoechoic, or very hypoechoic
Shape: wider-than-tall versus taller-than-wide
Margins: smooth, ill-defined, lobulated, irregular, or extrathyroidal extension
Echogenic foci: comet-tail artifact, macrocalcification, rim calcification, punctate echogenic foci
Vascularity on Doppler
Cervical lymph nodes for size, shape, hilum, calcification, and cystic change

Key Findings & Significance

Solid hypoechoic nodule, taller-than-wide, with irregular margins and punctate echogenic foci is highly suspicious (TR5)
Spongiform or purely cystic nodule is benign (TR1-TR2)
Macrocalcifications and rim calcification are intermediate features
Diffusely heterogeneous hypoechoic gland with hypervascularity suggests Graves disease
Heterogeneous gland with pseudonodules and increased vascularity suggests Hashimoto thyroiditis
Round lymph node with loss of fatty hilum, microcalcifications, or cystic change suggests metastasis
Extrathyroidal extension and abnormal nodes indicate advanced disease

Differential Considerations

Solitary solid nodule: benign follicular nodule, adenoma, papillary or follicular carcinoma
Multiple nodules: multinodular goiter, still requiring individual TI-RADS assessment of the dominant or suspicious nodules
Cystic nodule: colloid cyst, hemorrhagic degeneration, cystic papillary carcinoma
Diffuse gland change: Graves disease, Hashimoto thyroiditis, subacute (de Quervain) thyroiditis
Hyperechoic solid nodule: benign hyperplastic nodule, follicular adenoma
Abnormal node: reactive versus metastatic papillary or medullary carcinoma versus lymphoma

Pearls & Pitfalls

TI-RADS determines whether and at what size to biopsy; not every nodule requires FNA
Punctate echogenic foci (microcalcifications) are the most specific feature for papillary carcinoma but comet-tail artifact in cystic components is benign
Taller-than-wide shape is assessed on the transverse image and is a suspicious feature
Do not overlook posterior nodules and the retrosternal extension of a goiter
Coexisting Hashimoto thyroiditis increases lymphoma risk and complicates nodule assessment
Cystic lymph nodes in the lateral neck are metastatic papillary carcinoma until proven otherwise
Correlate a hyperfunctioning nodule with scintigraphy before biopsy, as autonomous nodules are rarely malignant

Structured Report

Report gland size and echotexture and any diffuse disease
Describe each significant nodule with three measurements, location, and TI-RADS descriptors and score
State FNA recommendation based on TI-RADS points and nodule size
Report cervical lymph nodes and any suspicious features
Compare with prior studies for interval change
Impression: enumerate nodules with TI-RADS categories and clear management recommendation (FNA, follow-up interval, or no further imaging)

References

Tessler FN et al. ACR Thyroid Imaging Reporting and Data System (TI-RADS), 2017
American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer
ACR-AIUM-SRU Practice Parameter for the Performance of Thyroid and Parathyroid Ultrasound
Bethesda System for Reporting Thyroid Cytopathology

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.

Thyroid Ultrasound

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References