What Is an Ultrasound?

Many people who hear the term "ultrasound" likely picture a pregnant woman in her doctor's office getting a sneak peek of the baby growing inside her womb -- perhaps even finding out whether she should paint the nursery pink or blue. But while fetal imaging is one of the most common uses of ultrasounds, this diagnostic tool actually has many applications.

How Ultrasound Imaging Works

Ultrasound, also called sonography, uses sound waves to develop ultrasound images of what's going on inside the body. An instrument called a transducer emits high-frequency sound, inaudible to human ears, and then records the echoes as the sound waves bounce back to determine the size, shape, and consistency of soft tissues and organs.

This information is relayed in real time to produce images on a computer screen. Ultrasound technicians, or sonographers, have special training in how to perform the test. Then a radiologist or your doctor will interpret the ultrasound images. This technology can help diagnose and treat certain conditions.

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 helping to detect 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 employ 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; 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.