Norm of Thyroid Ultrasonography (Thyroid Echogram, Thyroid Ultrasonogram)
Proper size, shape, and position of the thyroid gland. Negative for cyst or tumor. Thyroid tissue demonstrates an even mixture of medium-level echoes. Suspicious for malignancy: hypoechogenicity, poorly defined irregular margins, and microcalcifications.
Usage of Thyroid Ultrasonography (Thyroid Echogram, Thyroid Ultrasonogram)
Differentiation between cyst and tumor not distinguishable by other studies; guidance for aspiration of thyroid cyst or suspected thyroid tumor; monitoring of thyroid nodules during pregnancy; ongoing monitoring of size and density of thyroid during radioactive therapy; provides information about vascular flow and velocity when used with color-flow Doppler.
Description of Thyroid Ultrasonography (Thyroid Echogram, Thyroid Ultrasonogram)
High-frequency B-mode sonography and color-power Doppler are used to evaluate the thyroid gland size, shape, and positions. Ultrasound creates an oscilloscopic picture from the echoes of high-frequency sound waves passing over the neck area (acoustic imaging). The time required for the ultrasonic beam to be reflected back to the transducer from differing densities of tissue is converted by a computer to an electrical impulse displayed on an oscilloscopic screen to create a three-dimensional picture of the thyroid gland. The differing tissue densities of cysts and tumors enable the ultrasonogram to be helpful in determining which is present. Cysts are clearly demarcated by smooth borders and do not demonstrate internal echoes. Adenoma appearances vary but usually demonstrate halo. Multinodular goiter may also demonstrate a halo. In thyroiditis, the gland appears enlarged, with a greater than normal amount of low-level echoes. Ultrasound is a cost-effective procedure for screening for thyroid cancer because thyroid tissue has a high echogenicity. Thyroid cancer is usually poorly defined, with low-level echoes and without a halo. Advantages of this test are that it is safe for use during pregnancy because it does not use radiation, it can visualize the entire area of the anterior neck, it can detect smaller nodules (2 mm) than a nuclear scan, it can differentiate cysts from solid nodules (which a nuclear scan cannot), and it can improve the sensitivity of fine-needle aspiration biopsy.
Professional Considerations of Thyroid Ultrasonography (Thyroid Echogram, Thyroid Ultrasonogram)
Consent form NOT required.
- Remove any metallic objects or jewelry from the head and neck area.
- Obtain ultrasonic gel.
- The client is positioned supine, with a towel roll, pillow, or sponge beneath the shoulder blades, and the neck hyperextended, with the head turned away from the side of the thyroid gland being scanned. This permits better transducer access to the area because the mandible is moved out of the scanning area.
- The neck area is covered with ultrasonic gel, and a lubricated transducer is passed slowly and firmly over the thyroid gland and neck at specific intervals. Each lobe of the thyroid gland is examined separately and completely, beginning with transverse scanning followed by longitudinal scanning. Finally the isthmus is scanned transversely.
- Photographs are taken of the oscilloscopic display.
- The procedure takes less than 20 minutes.
- Remove ultrasonic gel from the skin.
- If thyroid cyst aspiration is performed under ultrasonogram guidance, see separate test listing: Needle aspiration.
Client and Family Teaching
- The procedure is painless.
Factors That Affect Results
- Thyroid volume is larger in males than in females, and varies with body surface area.
- Ultrasound alone should not be relied on for diagnosis of malignant thyroid nodules. Aspiration biopsy cytologic examination is necessary to confirm or add to the diagnosis.