Thyroid Ultrasound: Nodules, TIRADS, and Preparation
Thyroid Ultrasound: Nodules, TIRADS System and How to Prepare
Everything you need to know about thyroid ultrasound: what it evaluates, how a nodule is classified with TIRADS and when the endocrinologist requests a biopsy.
Reviewed by diagnostic imaging specialists · GSMED Imaging ColombiaThyroid ultrasound —also called thyroid ultrasound or thyroid sonography— is the first-line imaging study to evaluate the thyroid gland and the lymph nodes of the neck. It is the most sensitive method to detect thyroid nodules, determine their characteristics and guide clinical decision-making: observe, biopsy or refer to surgery.
In Colombia, the prevalence of thyroid nodules detectable by ultrasound exceeds 50% in adults over 50 years old. The vast majority are benign, but ultrasound —and especially the TIRADS classification system— allows the doctor to identify which ones warrant a biopsy and which ones only require follow-up.
What does thyroid ultrasound evaluate?
The thyroid is a superficial gland located in the anterior part of the neck, which makes it ideal for ultrasound. The high-frequency probe allows for highly detailed images without radiation. The parameters that are systematically evaluated are:
Gland size and volume
The three axes of each lobe and the isthmus are measured. The normal total volume is 8–18 ml in adults. Higher values indicate goiter.
Parenchymal echostructure
Homogeneous or heterogeneous. Diffuse reduced echogenicity suggests autoimmune thyroiditis (Hashimoto). Nodular pattern in multinodular goiter.
Nodule characterization
Composition (solid/cystic/mixed), echogenicity, shape, margins, calcifications and size. These are the criteria of the TIRADS system.
Vascularization (Doppler)
Intranodular and perinodular flow. "Thyroid hell" (diffuse hypervascularization) is typical of Graves' disease. Hypervascularized nodules may require additional attention.
Cervical lymph nodes
Evaluation of lymph node chains to detect metastasis in cases of suspicious nodules or known thyroid carcinoma.
How to prepare for thyroid ultrasound
Preparation is minimal. The thyroid gland is superficial and its image does not depend on the digestive state or the bladder. Even so, there are some practical points that improve the quality of the exam:
You can eat and drink normally before the exam.
Necklaces, chains and long earrings should be removed to facilitate probe access.
Avoid turtlenecks or closed shirts. Loose clothing facilitates positioning.
If there are previous ultrasounds, bring them to compare the size and evolution of the nodules.
Levothyroxine, propylthiouracil or other drugs that may modify the ultrasound image.
The exam is fast, painless and without side effects. The conductive gel may be cold.
💡 Tip: The patient is positioned in supine decubitus with the neck in slight hyperextension (pillow under the shoulders). This position better exposes the gland and facilitates the exploration of the lower poles.
TIRADS System: thyroid nodule classification
ACR-TIRADS (Thyroid Imaging Reporting and Data System) was developed by the American College of Radiology to standardize the description of thyroid nodules and guide the biopsy decision. It assigns points according to five ultrasound characteristics:
Cystic=0 · Spongiform=0 · Mixed=1 · Solid=2
Anechoic=0 · Hyperechoic=1 · Isoechoic=2 · Hypoechoic=3
Wider than tall=0 · Taller than wide=3
Regular=0 · Indefinite=0 · Lobulated=2 · Spiculated=3
None=0 · Coarse=1 · Peripheral=2 · Punctate=3
The sum of points defines the TIRADS category from 1 to 5:
| TIRADS | Points | Description | Malignancy risk | Recommended management |
|---|---|---|---|---|
| TR1 | 0 | Normal thyroid, no nodules | ~0% | No specific follow-up |
| TR2 | 0 | Benign nodule (simple cyst, spongiform) | <2% | No biopsy. Optional follow-up |
| TR3 | 3 | Slightly suspicious | ~5% | Biopsy if ≥2.5 cm · Follow-up if ≥1.5 cm |
| TR4 | 4–6 | Moderately suspicious | 5–20% | Biopsy if ≥1.5 cm · Follow-up if ≥1 cm |
| TR5 | ≥7 | Highly suspicious of malignancy | >20% | Biopsy if ≥1 cm · Follow-up if ≥0.5 cm |
* ACR-TIRADS 2017 criteria. The final management is determined by the endocrinologist or thyroid surgeon based on the complete clinical context.
When is a biopsy requested (ultrasound-guided FNA)?
Ultrasound-guided fine-needle aspiration (FNA) is the standard procedure for obtaining cells from a suspicious nodule and analyzing them under a microscope. Real-time ultrasound guidance increases diagnostic accuracy and reduces unsatisfactory samples.
Indications for FNA according to ACR-TIRADS
- TR5TIRADS 5: Biopsy if the nodule measures ≥ 1 cm. Follow-up if it measures 0.5–0.9 cm.
- TR4TIRADS 4: Biopsy if the nodule measures ≥ 1.5 cm. Follow-up if it measures 1–1.4 cm.
- TR3TIRADS 3: Biopsy if the nodule measures ≥ 2.5 cm. Follow-up if it measures 1.5–2.4 cm.
The procedure is outpatient and performed under local anesthesia. With real-time ultrasound guidance, the radiologist directs a fine needle directly into the nodule, aspirates cells, and sends them to a pathologist for cytological analysis (Bethesda system). The result is usually available in 3–7 business days.
💡 Important: A TIRADS 3 or 4 result does not mean cancer. The vast majority of these nodules turn out to be benign on biopsy. The goal of TIRADS is precisely to avoid unnecessary biopsies of low-risk nodules.
Common findings on thyroid ultrasound
🔵 Simple or multinodular goiter
Diffuse or nodular enlargement of the gland. Multinodular goiter is very common in Colombia due to historical iodine deficiency in some regions. Ultrasound measures the volume and maps the nodules.
🟣 Hashimoto's thyroiditis
Diffusely heterogeneous and hypoechoic echostructure, with a "mottled" appearance. It is the most frequent cause of hypothyroidism in Colombia. Ultrasound supports the diagnosis along with anti-TPO antibodies.
🟡 Benign colloid nodule
The most frequent type. Spongiform appearance or with "comet tail" artifacts. TIRADS 2: no biopsy required. Follow-up only if it grows significantly (>20% in two dimensions).
🟢 Graves' disease (hyperthyroidism)
Intense diffuse hypervascularization ("thyroid inferno") on color Doppler, with an enlarged gland and hypoechoic parenchyma. It correlates with suppressed TSH and TSH-R antibodies.
🔴 Nodule suspicious of malignancy
Hypoechoic solid, taller than wide, spiculated margins, punctate calcifications (microcalcifications). Features associated with papillary thyroid carcinoma, the most frequent.
🔵 Simple thyroid cyst
Completely anechoic lesion, with thin walls, without a solid component. TIRADS 2: benign by definition. Only treated if they cause compressive symptoms.
Ultrasound equipment for thyroid
The key to a quality thyroid ultrasound is the high-frequency linear probe. Unlike other regions that require low-frequency convex probes for greater penetration, the thyroid is superficial and benefits from high frequencies that offer greater spatial resolution.
Linear 7.5–12 MHz
Suitable for most thyroid studies. Good resolution to characterize medium-large nodules and evaluate the glandular parenchyma.
Linear 12–15 MHz
Recommended for microcalcification detection (1–2 mm), nodules smaller than 5 mm, and cervical lymph node evaluation. Standard in specialized endocrinology centers.
Mindray TE/Resona series
Mindray equipment with L12-4 and L14-6N linear probes offers high-sensitivity color Doppler, ideal for characterizing intra- and perinodular vascularization and guiding FNA procedures.
Do you need equipment with high-frequency probes for thyroid?
At GSMED Imaging, we are authorized Mindray distributors in Colombia. We advise on the selection of equipment and probes according to the specialty: endocrinology, radiology, and internal medicine.
Request advice →Frequently Asked Questions about Thyroid Ultrasound
The most common questions from patients and professionals.
