THYROID ULTRASOUND
Definition
Thyroid ultrasound is an imaging technique used for
diagnosing suspected thyroid disease. It uses harmless, high
frequency sound waves to form an image. The sound waves are
reflected by thyroid tissue to form a picture of internal
structures. It is not invasive and involves no radiation.
Purpose
The thyroid gland is an organ located in front of the neck.
It plays an important role in controlling the body's metabolism.
Most thyroid ultrasounds are performed to evaluate a small lump
(nodule) in the thyroid found during a physical examination or
found by a radionuclide study (thyroid scan). The ultrasound can
establish if the nodule is a cyst, which is an abnormal lump that
contains fluid, or a solid mass. Cysts are almost always
noncancerous (benign), although in some cases the fluid may be
taken out for additional testing.
If there are several masses or nodules, this indicates the
presence of enlargement of the thyroid gland (goiter). If there is
only one mass, it may be cancerous and needs further evaluation.
Specialized thyroid ultrasounds, 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, to further refine diagnosis.
In some cases, a needle will be inserted to remove some tissue
from the mass for evaluation in a laboratory (needle biopsy).
Ultrasound is used during this procedure to help the physician
guide the needle to the mass that needs to be evaluated.
Thyroid ultrasound can measure the size of the thyroid with
great precision. Ultrasound studies may be done periodically to
assess the response of the thyroid gland to medical therapy. An
enlarged gland or a benign nodule should decrease in size when
appropriate thyroid medication is taken.
Patients who have received therapeutic radiation to the
head or neck may be monitored at regular intervals using thyroid
ultrasound. The radiation puts these patients at higher risk for
developing thyroid cancer or other abnormalities. In the early
stages, these conditions may not cause symptoms or be apparent
during a physical examination. They can, however, be detected by
ultrasound.
Certain invasive medical procedures may be performed under
ultrasound guidance. This is because ultrasound allows the
physician to observe a needle as it enters body tissue below the
skin. This is useful to direct the removal of fluid from a cyst
(aspiration) or needle biopsy. Medications to treat recurrent
cysts may be administered directly to the area using ultrasound
guidance.
Precautions
Thyroid ultrasound is safe for people of all ages. It is
the preferred procedure to evaluate suspected disease in pregnant
women because no radiation is involved.
Description
The study may be done in an outpatient facility or in a
hospital department. The patient lies on his or her back. A pillow
or rolled towel is placed under the shoulders and upper back,
allowing the head to tilt back (hyperextend). A gel that enhances
sound transmission is spread over the thyroid area. The
technologist then gently places a transducer, an instrument about
the size of an electric shaver, against the skin. It is moved over
the thyroid area. The images from reflected sound waves appear on
a monitor screen. There is no discomfort involved with this study.
The examination takes 15-30 minutes.
Preparation
Some facilities recommend limiting food and drink for one
hour before the study to prevent discomfort. No other preparation
is needed.
Aftercare
No special restrictions or procedures are needed after a
thyroid ultrasound.
Risks
There are no risks with this procedure.
Normal results
A normal study would reveal a thyroid gland of normal size,
shape, position, and uniform texture.
Abnormal results
A thyroid ultrasound may reveal cysts, solid masses that
may or may not be cancerous, or an enlarged thyroid gland
(goiter). In many cases, the ultrasound can establish a diagnosis.
Sometimes the information revealed will need to be combined with
data from other studies to determine the problem.
