The terms sonogram and ultrasound are used interchangeably. Ultrasound is a test that uses reflected sound waves to produce an image of organs and other structures in the body. It does not use X-rays or other types of possibly harmful radiation.
For ultrasound testing, gel or oil 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 high-pitched sound waves (above the range of human hearing) that are reflected back to the transducer. A computer analyzes the sound waves and converts them into a picture that is displayed on a TV screen. The picture produced by ultrasound is called a sonogram, echogram, or ultrasound scan. Pictures or videos of the ultrasound images may be made for a permanent record.
Ultrasound is most useful for looking at organs and structures that are either uniform and solid (like the liver) or fluid-filled (like the gallbladder).