Ultrasound (also called sonography or ultrasonography) is a noninvasive imaging test. An ultrasound picture is called a sonogram. Ultrasound uses high-frequency sound waves to create real-time pictures or video of internal organs or other soft tissues, such as blood vessels.
Ultrasound enables healthcare providers to “see” details of soft tissues inside your body without making any incisions (cuts). And unlike X-rays, ultrasound doesn’t use radiation.
Although most people associate ultrasound with pregnancy, healthcare providers use ultrasound for many different situations and to look at several different parts of the inside of your body.
During an ultrasound, a healthcare provider passes a device called a transducer or probe over an area of your body or inside a body opening. The provider applies a thin layer of gel to your skin so that the ultrasound waves are transmitted from the transducer through the gel and into your body.
The probe converts electrical current into high-frequency sound waves and sends the waves into your body’s tissue. You can’t hear the sound waves.
Sound waves bounce off structures inside your body and back to the probe, which converts the waves into electrical signals. A computer then converts the pattern of electrical signals into real-time images or videos, which are displayed on a computer screen nearby.
There are three main categories of ultrasound imaging, including:
Healthcare providers often use ultrasound (often called prenatal or obstetric ultrasound) to monitor you and your baby during pregnancy.
Providers use prenatal ultrasound to:
Most healthcare providers recommend an ultrasound at 20 weeks pregnant. This test tracks your unborn baby’s growth and development during pregnancy. This ultrasound may also show your baby’s biological sex. Tell your technician if you do or do not want to know the sex.
Your provider may order extra scans to get answers to any questions or concerns, such as the potential for congenital conditions.
Providers use diagnostic ultrasounds to view internal parts of your body to see if something is wrong or not working properly. They can help your provider learn more about what’s causing a wide range of symptoms, such as unexplained pain, masses (lumps) or what may be causing an abnormal blood test.
For most diagnostic ultrasound exams, the technician places the transducer (probe) on your skin. In some cases, they may need to place the probe inside your body, such as in your vagina or rectum.
The type of diagnostic ultrasound you have depends on the details of your case.
Examples of diagnostic ultrasounds include:
Providers sometimes use ultrasound to perform certain procedures precisely. A common use of ultrasound is to guide needle placement to sample fluid or tissue from:
Examples of other procedures that may require ultrasound guidance include:
For ultrasounds during pregnancy, the traditional ultrasound is a two-dimensional (2D) image of your unborn baby. 2D ultrasound produces outlines and flat-looking images, which allows your healthcare provider to see your baby's internal organs and structures.
Three-dimensional (3D) ultrasound allows the visualization of some facial features of your baby and possibly other body parts such as fingers and toes. Four-dimensional (4D) ultrasound is 3D ultrasound in motion. Providers rarely use 3D or 4D fetal ultrasound imaging for medical purposes, though it can be useful in diagnosing a facial or skeletal issue. They do, however, use 3D ultrasound for other medical purposes, such as evaluating uterine polyps and fibroids.
While ultrasound is generally considered to be safe with very low risks, the risks may increase with unnecessary prolonged exposure to ultrasound energy or when untrained users operate an ultrasound machine. Because of this, the U.S. Food and Drug Administration (FDA) advises against getting a 3D ultrasound for non-medical reasons such as for “keepsake” moments or entertainment.
A doctor or a healthcare provider called an ultrasound technician or sonographer performs ultrasounds. They’re specially trained to operate an ultrasound machine properly and safely.
It’s important to always have your ultrasound performed by a medical professional and in a medical facility.