Ultrasonography (US) is the most common and most useful way to imagine the thyroid gland and the surrounding tissues of the neck to the level of clavicles, especially when information concerning blood flow is added to the signal by employing the Doppler effect. It facilitates the diagnosis of clinically apparent and a multitude of clinically imperceptible abnormalities, especially nodules most of which are benign, and is completely safe using high frequency sound waves in the megahertz range (ultrasound). During examination, which takes only several minutes, the patient remains comfortable, does not require discontinuation of any medication, or preparation. The procedure is usually done with the patient reclining and with the neck hyperextended. Any necklases and other accessories should be removed from the neck before the test is started. Some gel or liquid must be applied between the probe and the skin.
Ultrasonography of the thyroid is used to:
describe the anatomy of the neck in the thyroid region
assess the comparative size of palpable and non-palpable nodules, lymph nodes, or goiters in patients who are under observation or therapy
give clues about the likelihood of malignancy and thyroiditis
facilitate fine needle aspiration biopsy
evaluate for recurrence of a thyroid mass after surgery
monitor thyroid cancer patients.
It is important to bear in mind that performance and interpretation of thyroid sonograms are quite subjective and reflect probabilities, not certainty. Especially in large goiters and nodules there may be considerable differences between sonologist in estimating their size.