Medical ultrasound (also known as diagnostic sonography or ultrasonography) is a diagnostic imaging technique based on the application of soundwaves. It is used to see internal body structures such as tendons, muscles, joints, blood vessels, and internal organs. Its aim is often to find a source of a disease or to exclude any pathology such as injuries (you may also be familiar with its use for pregnancy scans). Ultrasound is sound waves with frequencies that are higher than those audible to humans. Ultrasonic images, also known as sonograms, are made by sending pulses of ultrasound into tissue using a probe that glides over applied gel. The sound echoes off the tissue; with different tissues reflecting varying degrees of sound. These echoes are recorded and displayed as an image to the operator. Many different types of images can be formed using sonographic instruments.
Compared to other prominent methods of medical imaging, ultrasound has several advantages. It provides images in real-time and can be portable. It is usually substantially lower in cost, to operate and therefore lower in cost to clients. It also does not use radiation.
Drawbacks include various limits to its field of view, difficulty imaging structures behind bone and air. A skilled Sonographer can adapt to these restrictions quite often.