Diagnostic ultrasound, also called sonography or diagnostic medical sonography, is an imaging method that uses sound waves to produce images of structures within your body. The images can provide valuable information for diagnosing and directing treatment for a variety of diseases and conditions.

Most ultrasound examinations are done using an ultrasound device outside your body, though some involve placing a small device inside 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. .