Thyroid ultrasound

Definition

A thyroid ultrasound is a diagnostic imaging test that uses sound waves to create a picture of the thyroid.

Purpose

A thyroid ultrasound is performed to help diagnose abnormalities of the thyroid. It may be performed when a lump or enlargement is felt during a physical examination of the neck to help provide additional information about the problem. A thyroid ultrasound is also often performed to help guide other procedures. When a biopsy is performed on the thyroid, an ultrasound image can be used to help guide the needle. An ultrasound can also be used to help guide catheter placement when drainage is required.

Thyroid ultrasound can also be performed to help monitor the progress of a disease or treatment. When an element of the thyroid has occurred, thyroid ultrasound can be used to help monitor the success of the treatment being used in shrinking the thyroid to a more normal size. It can also be used to help monitor suspicious growths to determine if they are increasing in size or changing shape, which could indicate intervention or additional diagnostic procedures are required.

Precautions

Thyroid ultrasound does not involve the use of any radiation or radioactive material, unlike x-ray imaging tests and those thyroid function tests that use radioactive markers. This means that a thyroid ultrasound is completely safe, even for women who are pregnant or breastfeeding.

Description

The thyroid is a small gland in the neck that weighs less than one ounce. It is butterfly shaped and is located slightly above the collar bone. The thyroid uses iodine to produce two hormones thyroxine (T4) and triiodothyronine (T3). The thyroid hormones are required for regulation of body temperature, metabolism, heartbeat, digestion, and a variety of other necessary body functions.

A thyroid ultrasound is performed with an ultrasound machine. An ultrasound machine consists of a handheld device, called a transducer, and a computer. The transducer is placed in direct contact with the skin and gives of high-frequency sound waves. These sound waves are above the frequency range that can be heard by humans. The sound waves bounce off of body tissues and return to the transducer. The transducer sends information about the angle of the returning waves and how long it took them to return to the computer. The computer then takes this information and uses it to create a visual image of the tissues and organs as the transducer passes over them.

During a thyroid ultrasound the patient is asked to remove any jewelry from the head and heck. He or she may be asked to remove his or her shirt and replace it with a gown. The patient then lies on a table with the neck extended. A gel is often rubbed onto the skin in the area of interest. This gel helps to ensure that there is good contact between the transducer and the skin, allowing for a clear image. The ultrasound technician or radiologist then slowly moves the transducer back and forth across the area of interest.

The procedure usually takes about 30 minutes. The ultrasound technician or radiologist may reposition the patient or turn the head to get a better image or to take images of the thyroid from different angles. After the procedure the gel is wiped off and the patient can return to normal activities.

Preparation

No special Preparation is required for a thyroid ultrasound.

Aftercare

No special Aftercare is required for a thyroid ultrasound.

QUESTIONS TO ASK YOUR DOCTOR

• Are there any other imaging or diagnostic tests that would help to diagnose my disease or condition?
• If the ultrasound shows abnormal Results, what is the next step?
• If the ultrasound shows no abnormal Results, what is the next step?

Complications

No complications are expected from a thyroid ultrasound.

Results

A thyroid ultrasound produces images of the thyroid that are interpreted by a radiologist. A normal thyroid will be of a normal size and shape, be in a normal position within the neck, and have no apparent lumps, growths, or nodules.

A thyroid ultrasound could return abnormal Results in a variety of situations. The thyroid may appear to have a lump on it. The ultrasound can help determine if the lump is a cyst (a fluid filled sac) or a tumor. In most cases it is not possible to tell if the tumor is cancerous or not using only the ultrasound images. In such cases a biopsy of the tumor is usually taken, which may be guided by an additional thyroid ultrasound procedure. About 90% of nodules of the thyroid are found to be benign (non-cancerous). The thyroid may also appear abnormal if it is enlarged. The ultrasound may also appear abnormal because of enlarged thyroid (goiter).

Thyroid ultrasound can only produce Results relating to the image of the thyroid produced by the procedure. These images allow the radiologist to see what the thyroid looks like. They do not, however, provide any information about thyroid function. When a thyroid ultrasound shows an abnormal result other tests, called thyroid function tests, may be performed to help determine if there are any problems with the thyroid's functioning. A nuclear medicine test, called a thyroid scan, can also be used to help determine if the thyroid is absorbing iodine normally. Tests of the thyroid's function can help doctors make a diagnosis when the Results of the thyroid ultrasound are not clear.

Caregiver concerns

A doctor determines the need for a thyroid ultrasound based on the patient's symptoms, a physical examination, healthy history, and previous diagnostic tests. The doctor, a nurse, or a member of the radiology team explains the procedure to the patient and answers any questions about the ultrasound and why it is needed. The ultrasound itself is performed by a radiologist or an ultrasound technician. The pictures produced by the procedure are interpreted by a radiologist. The Results of the ultrasound, in addition to copies of the images in many cases, are sent to the doctor who ordered the test. The doctor, a member of the doctor's staff, or a member of the radiology team communicates the Results to the patient. The doctor then decides which, if any, treatment or additional diagnostic procedures, are indicated.

Resources

BOOKS

Fischbach, Frances Talaska, and Marshall Barnet Dunnin III. A Manual of Laboratory and Diagnostic Tests. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2009.

Milton, Carl A., ed. Trends in Thyroid Cancer Research. New York: Nova Biomedical Books, 2007.

Rone, James K. The Thyroid Paradox: How to Get the Best Care for Hypothyroidism. Languna Beach, CA: Basic Health Publications, 2007.

PERIODICALS

Bunevicius, Robertas, et al. “Mood and Thyroid Immunity Assessed by Ultrasonographic Imaging in Primary Health Care.” Journal of Affective Disorders 97.1-3 (January 2007): 85–91.

Stacul, F., et al. “The Radiologist and the Cytologist in Diagnosing Thyroid Nodules: Results of Cooperation.” La Radiologia Medica 112.4 (June 2007): 597–603.

ORGANIZATIONS

American Institute of Ultrasound in Medicine, 14750 Sweitzer Lane, Suite 100, Laurel, MD, 20707-5906, (301) 498-4100, (800) 638-5352, (310) 498-4450, www.aium.org.

Robert Bockstiegel