Ultrasound, which is sometimes called ultrasonography or sonogram, uses high-frequency sound waves to create images of organs, blood vessels and tissues. The sound waves are too high for the human ear to hear, but they produce an image that allows physicians to view internal organs and to assess blood flow through various vessels. Ultrasound is often performed by a technician and then analyzed by a physician.

Inspired by sonar technology, which uses sound waves to detect objects underwater, ultrasound can help diagnose a wide range of diseases and conditions. It can be used alone or with other diagnostic procedures. Sonography is the medical term for the testing and recording of the ultrasound. Sound waves are sent by a transducer into the body. Some sound waves pass through tissue, and others bounce back. The returning sound waves are picked up by sensors connected to a computer, which measures the distance by using the elapsed time from transmission to reception.

Because ultrasound does not expose the patient to any radiation, it may be used as a substitute for x-ray imaging when diagnosing certain populations. These include pregnant women and infants, who may be more vulnerable to the negative effects of radiation.

Ultrasound can also help a physician detect, diagnose or monitor various obstetric and gynecological conditions. Because it uses low-energy sound waves, it is an invaluable tool to confirm and monitor a woman’s pregnancy. In the early stages of pregnancy, ultrasound, in combination with the date of the last menstrual period, can help reveal the fetus’ gestational age and due date. It also can:

• Reveal the gender of the fetus (not usually possible until the second trimester)
  
  
• Reveal the number of fetuses a woman is carrying
  
  
• Provide important details about growth rate and organ development in the fetus
  
  
• Record fetal heartbeat and breathing movements
  
  
• Provide important insights about the fetus’ overall health and reveal signs of potential health problems, such as possible birth defects
  
  
• Provide information about the location of the placenta (organ that connects the fetus to the uterus to provide oxygen and nutrients and to remove waste products)

Women who have an ultrasound early in pregnancy should not expect to view a recognizable form of a baby in the image that is produced. In the first ultrasound of the pregnancy (often performed at six to seven weeks), the most obvious image is usually that of the fetus’ pumping heart. A physician or other healthcare professional trained in analysis will interpret the image.

In addition to pregnancy, ultrasound can provide vital information on diseases, including the following:

• Dysfunctional uterine bleeding (DUB). Occurs when the menstrual period is not regular, when bleeding lasts longer than normal, is heavier than normal, or when bleeding patterns change.
  
  
• Polycystic ovarian syndrome (PCOS). Hormone imbalance that can cause irregular periods, unwanted hair growth and acne. Ultrasound imaging of the uterus is helpful in diagnosing this disorder.
  
  
• Uterine fibroids. Noncancerous tumors that grow slowly and usually require no treatment. Ultrasound can be used to help confirm the presence of fibroids initially detected during a pelvic examination.
  
  
• Cancer and other disorders. The test is especially effective when a tumor is located in soft tissue and it is unclear whether an abnormality is a cyst (sac of fluid) or a solid mass. Cancers that can be detected with ultrasound include those of the ovaries, endometrium, cervix, vagina and breast. However, further testing (e.g., biopsy) is necessary to confirm diagnosis of cancer.

• Urinary system disorders. These are disorders – including infections – of the kidneys, ureters, bladder or urethra.

Ultrasound can also be used to examine the internal structures of the abdomen (liver, spleen, pancreas, etc.), as well as detect gallstones and kidney stones. Other common uses for ultrasound include the detection of fluid, cysts, tumors or abscesses in the abdomen or liver, reduced blood flow due to clots or arteriosclerosis in the legs, aneurysms of the aorta and the structure of the thyroid gland in the neck.

Ultrasound may be used for therapeutic reasons in physical and occupational therapy. The thermal effects have been found to be helpful for treatment of musculoskeletal injuries, breaking down scar tissue and helping to stretch tendons.

Finally, ultrasound can be used to guide needle biopsies and other procedures. In some cases, ultrasound is used to help a physician guide a needle or other instrument to a location under the skin surface. For example, a physician may use the image from an ultrasound to help guide a needle to the site of a tumor to extract cells from a tumor for analysis in a laboratory. Additionally, ultrasound is used to guide a needle into the uterine cavity during an amniocentesis.