An ultrasound scanner uses high frequency sound waves to create an image of the internal of the body. It is one of the safest types of scan as it can be used on pregnant women. During the scan, a small transducer is moved over the skin. This sensor is able to project and detect its own sound waves, which bounce off from different parts of the body. A computer then organises the reflected waves into a dynamic picture in which the radiologist uses to help make a diagnosis. The scan is usually done by a sonographer, but some doctors are trained to be able to do the scan too.