An ultrasound test uses reflected sound waves to produce an image of organs
and other structures in the body. It does not use X-rays. For ultrasound
testing, gel is applied to the skin to help transmit the sound waves.
A small, handheld instrument called a transducer is passed back and forth
over the area of the body being examined. The transducer sends out sound
waves and converts them into an image that is displayed on a monitor.
Ultrasound is most useful for obstetrics—meaning pregnancy—and
gynecology. It is also used for looking at organs and structures that
are either uniform and solid, such as the liver, or fluid-filled, such
as the gallbladder. Mineralized structures such as bones or air-filled
organs such as the lungs do not show up well on a sonogram.