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Ultrasound imaging — Overview describes what it is, how it works and when it's used.

Ultrasound examination, also called diagnostic medical sonography or sonography, is an imaging method that uses high-frequency sound waves to produce precise images of structures within your body. These images often provide information that's valuable in diagnosing and treating a variety of diseases and conditions.

Who is an ultrasound for?

You may need to undergo an ultrasound for a variety of reasons. Ultrasound may be used, among other things, to:

  • Evaluate a fetus
  • Diagnose gallbladder disease
  • Evaluate flow in blood vessels
  • Guide a needle biopsy
  • Guide the biopsy and treatment of a tumor
  • Check your thyroid gland
  • Study your heart
  • Diagnose some forms of infection
  • Diagnose some forms of cancer
  • Reveal abnormalities in the scrotum and prostate

How is an ultrasound done?

Ultrasound is based on the same principles as sonar — a technology used to detect underwater objects. During an ultrasound, a technician trained in ultrasound imaging (sonographer) presses a small hand-held device (transducer), about the size of a bar of soap, against your skin. The transducer generates and receives high-frequency sound waves that can't be heard by the human ear.

As the sonographer places the transducer on your skin, crystals inside the transducer emit pulses of sound waves that travel into your body. Your tissues, bones and body fluids reflect the sound waves and bounce them back to the transducer. The transducer then sends this information to a computer, which composes detailed images based on the patterns created by the sound waves.

Though the majority of ultrasound exams are performed with a transducer on your skin, some ultrasounds are done inside your body (invasive ultrasounds). For these exams, the transducer is attached to a probe that's inserted into a natural opening in your body. Examples of these exams include:

  • Transesophageal echocardiogram. The transducer is inserted into your esophagus to obtain images of the nearby heart.
  • Transrectal ultrasound. The transducer is inserted into a man's rectum to view his prostate.
  • Transvaginal ultrasound. The transducer is inserted into a woman's vagina to view her uterus and ovaries.

Breast cyst

Ultrasound image of a breast cyst

This ultrasound shows a breast cyst.

Liver tumor

Ultrasound image of a liver tumor

This ultrasound shows a liver tumor.


Ultrasound image of gallstones

This ultrasound shows gallstones.

Ultrasound depiction of a needle entering a tumor

Ultrasound image of a needle entering a tumor

These ultrasound images help guide a needle into a tumor (left), where material is injected (right) to help destroy tumor cells.

Results of an ultrasound

When your exam is complete, the sonographer and a radiologist generally view the ultrasound images on film or on a computer monitor. The radiologist analyzes the images and sends a report of the findings to your doctor.

Last Updated: 12/29/2007
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