Ultrasound, also known as sonography, is an important medical diagnostic tool that uses sound waves to create images that help physicians detect physical abnormalities and disease. The technique captures images through the use of an external transducer (a device that converts one form of energy to another), which releases high-frequency sound waves into the body and records the rebounding echo that occurs when the waves collide with an object, such as organs and soft tissue.
The transducer transmits the sound reverberations to a computer that generates real-time images. By measuring the size and shape of the waves, the performing technician or physician can conclude the distance, size, composition, and shape of the object of interest.
What Does an Ultrasound Show?
An ultrasound machine is usually operated by a sonographer, either a physician or ultrasound technician trained to understand the images it renders. Those images are examined and then used to order further tests, or to make a diagnosis and determine the appropriate form of treatment.
Through ultrasound imaging, physicians can:
- Verify the health, gender, size, age, and position of a developing fetus
- Visualize internal structures during medical procedures (such as biopsies and needle aspirations)
- Diagnose disorders affecting the kidneys, testicles, liver, gallbladder, abdomen, heart, blood vessels, bladder, uterus, ovaries, thyroid, spleen, eyes, and pancreas.
Types of Ultrasound Imaging
Ultrasound technology has advanced over the years and can offer insight about organs and soft tissues, as well as how disease and other conditions may be affecting them. There are various types of ultrasound imaging, including:
- Doppler ultrasounds, which calculate the path and speed of blood as it passes through veins and arteries. The ebb and flow of blood cells cause changes in pitch, which are processed by a computer to create images that indicate the movement of blood. The results can show blood clots and other blockages, congenital vascular malformations, and narrow vessels.
- Echocardiograms provide a visual of the chest, including the chest wall, lungs, and heart.
- 3-D and 4-D ultrasounds are rarely medically necessary and are usually done for fetal imaging. Unlike traditional ultrasound technology, the sound waves in 3-D imaging are sent from different angles so as to create a multi-dimensional image. Four-dimensional ultrasounds are similar, with the fourth dimension enabling the visualization of 3-D images in motion.
Are Ultrasounds Painful?
Since the procedure does not involve needles, incisions, or injections, it tends to be painless. The exception, however, is when a specially designed probe is directly inserted into one of the body’s openings so as to get an enhanced diagnostic image. Such cases include:
- Transrectal ultrasound: A probe inserted into the rectum can generate images of the prostate so as to detect prostate cancer and abnormalities.
- Transesophageal echocardiograms: A probe with an ultrasound transducer at its tip is inserted into the esophagus to get images of the heart. These help diagnose, examine, and observe abnormal heart valves, congenital heart disease, heart murmurs, atrial fibrillation, and more.
- Transvaginal ultrasounds: A transducer inserted into the vagina can provide a visual of a woman's ovaries and uterus so as to detect cysts, fibroid tumors, other growths, and early pregnancy.
How Safe are Ultrasounds?
Unlike X-rays and CT scans, ultrasound does not use ionizing radiation, which is a potential carcinogen. Instead, ultrasound only produces a signal about 10 percent of the time and only while it is active. The rest of the time it's inactively listening to the echoes that recoil back. Thus, a patient's exposure to ultrasound energy is extremely limited.
According to the American Urological Association, ultrasound has been in widespread clinical use for more than half a century and has no known adverse effects. (Some studies indicate that an excess of soundwaves during pregnancy, as produced by 3-D and 4-D ultrasounds, may have an impact on the developing fetus. But these are early animal studies that have not been replicated or proven in humans.)
What are the Limitations of Ultrasound?
Diagnostic ultrasound devices produce various levels of frequency, typically between 1 - 30 megahertz. The higher the frequency, the clearer the image. However, higher frequency soundwaves are more readily absorbed by skin and other tissue and cannot penetrate as deeply into the body. While lower frequencies go deeper, the image quality is reduced.
Also, while ultrasounds can be used to assess a variety of organs and soft tissues, sound waves have a difficult time traveling through thick bone and portions of the body that contain air and gas, like the bowel. Bone can only be examined on the surface, and the areas behind it cannot be reached by ultrasound energy.
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Ultrasound is a Safe, Highly Regulated Imaging Modality. (2005). American Urological Association.