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What is an ultrasound?

An ultrasound scan uses high frequency sound waves to look inside the body and produce live images on a computer display.

Ultrasound is also known as a sonogram and is commonly used to look at the functions of the beating heart and to check on the growth of a baby during pregnancy.

Pregnant couple getting ultrasound

How ultrasound imaging works

A hand-held a transducer emits the high-frequency sound, too high for the human ears to hear and then records the echoes as the sound waves bounce back to determine the size, shape and consistency of soft tissues and organs.

Ultrasound technicians, or sonographers, have special training in how to interpret ultrasound images and can work with your doctor to help diagnose and treat certain conditions using this technology.

An ultrasound scan usually takes between 15 and 45 minutes. These tests are not painful.

Sonographers may be able to say what they've seen during the scan, or may need to save images for later and consult further with a doctor before the results are given.

Uses of ultrasound tests

Ultrasound imaging has many uses in medicine, from confirming and dating a pregnancy to diagnosing certain conditions and guiding doctors through precise medical procedures.

  • Pregnancy. Ultrasound images have many uses during pregnancy. Early on, they may be used to determine due dates, reveal the presence of twins or other multiples and rule out ectopic pregnancies. They also are valuable screening tools in detecting potential problems, including birth defects, placental issues, breech positioning and others. Many expectant parents look forward to learning the sex of their babies via ultrasound midway through a pregnancy. And later in pregnancy, doctors can even use ultrasounds to estimate how large a baby is just before delivery.
  • Diagnostics. Doctors use ultrasound imaging in diagnosing a wide variety of conditions affecting the organs and soft tissues of the body, including the heart and blood vessels, liver, gallbladder, spleen, pancreas, kidneys, bladder, uterus, ovaries, eyes, thyroid and testicles. Ultrasounds do have some diagnostic limitations, however, as sound waves do not transmit well through dense bone or parts of the body that may hold air or gas, such as the bowel.
  • Use during medical procedures. Ultrasound imaging can help doctors during procedures such as needle biopsies, which require the doctor to remove tissue from a very precise area inside the body for testing in a lab.
  • Therapeutic applications. Ultrasounds sometimes are used to detect and treat soft-tissue injuries.


Types of ultrasound

Most ultrasounds are done using a transducer on the surface of the skin. Sometimes, however, doctors and technicians can get a better diagnostic image by inserting a special transducer into one of the body's natural openings:

  • In a transvaginal ultrasound, a transducer wand is placed in a woman’s vagina to get images of her uterus and ovaries.
  • A transrectal ultrasound is sometimes used in the diagnosis of prostate conditions.
  • A transoesophageal echocardiogram uses the transducer probe in the oesophagus so that the sonographer can obtain clearer images of the heart.

WebMD Medical Reference

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