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 that is 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
reflected 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 (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. eMedicineHealth
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