Thryoid Ultrasound Health Article

Definition

A thyroid ultrasound, or sonogram, is a diagnostic imaging technique used to evaluate the structure of the thyroid gland. The thyroid is an endocrine gland, which means that it releases its secretions directly into the bloodstream or lymph. It consists of two lobes located in the front of the neck that are connected by a thin band of tissue called the isthmus, which lies in front of the trachea (windpipe). Ultrasound procedures utilize high frequency sound waves to obtain images of various anatomical structures. Ultrasonography is the most common imaging technique used to evaluate the thyroid because it is not invasive, does not expose patients to radioactive materials, is less expensive than CT scans or MRI, and is more effective in detecting small lesions on the thyroid.

Purpose

An ultrasound of the thyroid is performed to evaluate thyroid nodules discovered during a physical examination or revealed by a radionuclide study (thyroid scan). A sonogram is most useful when the physician must distinguish between cystic lesions and solid ones, or evaluate any mass in the neck. In many cases the ultrasound examination identifies additional nodules in the thyroid that are too small for the doctor to feel during the external physical examination.

Most thyroid cysts are benign; however, ultrasound imaging cannot be used to differentiate between benign cysts or nodules and cancer. Specialized thyroid sonograms, such as color Doppler flow studies, can add valuable information. By showing an image of the blood circulation in the gland, this study can assess some ambiguous masses in greater detail. The shade and intensity of the color indicate the direction and the velocity of the flow. The physician may insert a needle in order to remove some tissue for laboratory evaluation (needle biopsy or fine needle aspiration). Ultrasound is used during this procedure to help the physician guide the needle into the mass under evaluation. The use of color Doppler flow helps the physician to avoid puncturing a blood vessel while collecting the tissue sample.

Thyroid ultrasound can measure the size of the gland with great precision, and may be done periodically to assess the results of treatment. An enlarged thyroid gland or a benign nodule should decrease in size with appropriate medication. In addition, patients who have had radiotherapy of the head or neck may be monitored at regular intervals using thyroid ultrasound. Patients who had radiation treatment in these areas in childhood or adolescence have a 30% risk of developing thyroid cancer or other glandular abnormalities in adult life. In the early stages, these conditions may not cause symptoms or be discovered during a physical examination. They may, however, be detected by ultrasound.