Ultrasound is a method of looking inside a person’s body to examine tissue-based and liquid-based organs and systems without physically entering the body. Ultrasound systems direct high-frequency sound (usually between 5 and 7 megahertz) into particular regions of the body, and measure the time it takes for the sound wave to reflect back to the machine. By analyzing the pattern of reflections received, a computer can create a visual representation of the interior of the body.

Ultrasound is sometimes used instead of X rays because it does not use ionizing radiation and thus is safer for the person being examined. Obstetricians use ultrasound to examine the progress and/or problems that a fetus might be experiencing. Ultrasound is also used to observe different fluid-like organs and systems in the body such as the nervous, circulatory, urinary, and reproductive systems.

Ultrasound can also be used to pulverize kidney “stones.” In this application very intense, tightly focused beams of high-frequency sound are directed at the stone. The stones are shattered and the small pieces can be passed through the urinary track with little or no pain.