Ultrasound, or sonography, produces images of the inside of the body by generating high-frequency sound waves. As the sound waves bounce off internal organs and tissues, they create echoes. A computer then translates these echoes into images on a screen, images that can show abnormalities (disease) within the body. The process is fast, painless and completely free of radiation or harmful side effects, which is why ultrasound is often used in prenatal imaging.
Ultrasound tests sometimes use a modified technique—called Doppler—to capture moving images of the heart and large blood vessels.