Ultrasound imaging uses a transducer or probe to generate sound waves and produce pictures of the body's internal structures. It does not use ionizing radiation, has no known harmful effects, and provides a clear picture of soft tissues that don't show up well on x-ray images.
Ultrasound is often used to help diagnose unexplained pain, swelling and infection. It may also be used to provide imaging guidance to needle biopsies or to see and evaluate conditions related to blood flow. It's also the preferred imaging method for monitoring a pregnant woman and her unborn child.