Ultrasonography is a technique that offers diagnostic images by using ultrasounds that are produced by specific probes.
When ultrasounds pass through a tissue they are reflected by tissue boundaries and are received back by the probe. Based on sound speed in tissues, the computer can calculate the distance between the reflection boundaries and the probe. In this way an image with different shades of grey is created. In addition, the Doppler technique, combined with standard ultrasonography, allows studies of blood flow.