Question: how does ultra sound work?

Emma Ross answered on 20 Jun 2013:

Ultrasound is a high-frequency sound that you cannot hear, but it can be sent out and also detected by special machines. Ultrasound travels freely through fluid and soft tissues. However, ultrasound bounces back as ‘echoes’ when it hits a more solid or dense surface. For example, the ultrasound will travel freely through blood in
a heart chamber. But, when it hits a solid valve, a lot of the ultrasound echoes back. So, as ultrasound ‘hits’ different structures of different density in the body, it sends back echoes of varying strength. The echoes are detected by the probe and are sent down the wire to the ultrasound machine. They are displayed as a picture on the monitor. The picture is constantly updated so the scan can show movement as well as structure. For example, the valves of a heart opening and closing during a scan of the heart. The operator moves the probe around over the surface of the skin to get views from different angles.