A thyroid ultrasound is a non-invasive medical imaging procedure utilizing sound waves to create detailed images of the thyroid gland. This technique allows healthcare professionals to visualize the gland’s structure and identify any abnormalities. A small transducer placed on the neck emits high-frequency sound waves that bounce off internal structures. These echoes are converted into real-time images displayed on a monitor, providing diagnostic information without radiation.
Why a Thyroid Ultrasound is Performed
A thyroid ultrasound is performed to investigate various thyroid-related concerns. One common reason is the detection or evaluation of thyroid nodules, which are lumps or growths within the gland. It also helps in assessing an enlarged thyroid gland, a condition known as goiter, to determine its size and characteristics. The procedure can further identify signs of inflammation, such as in cases of thyroiditis. A thyroid ultrasound is also used for monitoring known thyroid conditions over time, tracking changes in existing nodules or assessing the effectiveness of treatments.
Visualizing the Thyroid: Normal Anatomy
On an ultrasound, a normal thyroid gland appears as a homogeneous structure with a medium-level echogenicity, meaning it has a consistent texture and brightness. The gland consists of two main lobes, the right and left, situated on either side of the trachea in the lower neck. These lobes are connected by a narrow band of thyroid tissue called the isthmus, which crosses in front of the trachea.
Several other anatomical structures are visible surrounding the thyroid gland. The carotid arteries and jugular veins are often seen adjacent to the thyroid lobes, appearing as dark, anechoic (fluid-filled) tubular structures. Muscles like the strap muscles (sternohyoid, sternothyroid, omohyoid) are situated anterior to the gland and appear as hypoechoic (darker) bands of tissue.
Identifying Common Findings
When examining the thyroid with ultrasound, various common findings can be identified and characterized. Thyroid nodules are described based on their internal composition: solid, cystic (fluid-filled), or mixed (containing both solid and fluid components). A solid nodule might appear as a well-defined mass within the gland, while a cystic nodule would show an anechoic center with posterior acoustic enhancement. Mixed nodules display a combination of these characteristics.
Calcifications within nodules are another finding, categorized as macrocalcifications (larger, brighter echoes with shadowing) or microcalcifications (tiny, punctate bright echoes without shadowing). Microcalcifications can prompt further investigation. Signs of inflammation, such as in thyroiditis, may present as diffuse hypoechogenicity, meaning the entire gland appears darker than normal, often with increased blood flow on Doppler imaging. Examples of descriptions include “hypoechoic solid nodule with microcalcifications” or “diffusely enlarged hypoechoic gland.”
Understanding Your Ultrasound Report
Your thyroid ultrasound report provides a detailed description of the sonographic findings. The report includes information on the size, location, and specific characteristics of any identified nodules, such as their shape, margins (smooth or irregular), internal composition (solid, cystic, mixed), and echogenicity. For instance, a report might note a “2.5 cm hypoechoic nodule in the right lobe with irregular margins and microcalcifications.”
A standardized system used in these reports is the Thyroid Imaging Reporting and Data System (TI-RADS), which categorizes the risk of malignancy for thyroid nodules based on their ultrasound features. TI-RADS scores range from TR1 (benign, no follow-up needed) to TR5 (highly suspicious for malignancy, biopsy recommended). A TR3 nodule, for example, has a low suspicion of malignancy, while a TR4 nodule has a moderate suspicion. The report’s conclusion, often including the TI-RADS score, guides the next steps, from routine monitoring to a recommendation for fine-needle aspiration biopsy.