Sonography, also known colloquially as ultrasound, is the use of ultrasound as an imaging procedure for the examination of organic tissue (organs and neighbouring structures) in medicine. A significant advantage of sonography over X-rays, which are also frequently used in medicine, is the harmlessness of the sound waves used. Due to the absolute harmlessness of ultrasound waves, this procedure is also used as the method of choice in prenatal care.

Ultrasound has been used in nature for thousands of years, since animals - the most popular example being the bat - have learnt to orientate themselves in space using ultrasound. The Austrian neurologist K. Th. Dussik was the first physician to utilise ultrasound for diagnostic purposes in 1938. However, it was not until the early 1980s that ultrasound devices as we know them today were introduced into clinical routine on a larger scale. The performance in visualising difficult findings has improved dramatically since then.