Through a transducer, sound waves are emitted above the audible range of humans. These sound waves are reflected differently by different tissues and received again by the same transducer (echo sounder principle). The modified received sound waves can be analysed and converted into an image via computer technology.
As air is a strong absorber of sound waves, a contact gel must be applied between the transducer and the body. Nowadays, almost every tissue except for bone can be examined via ultrasound.
In urology, ultrasound examination plays an important role.