Receiving Ultrasound Data

As an ultrasound pulse propagates in the tissue, it interacts with organs and cellular structures. As a result of this interaction, part of the ultrasound energy is reflected back towards the transducer. This is the so-called ultrasound echo. The transducer converts this mechanical energy into an electrical signal.

The transmitted ultrasound pulse typically consists of a short duration (one or a few cycles) sinusoid. As soon as this pulse enters tissue, echos start getting back to the transducer. As the transmitted pulse travels deeper and deeper into tissue, weaker and weaker echos keep getting back to the transducer. Therefore, unlike the transmitted pulse, the echo signal is not of a short duration. As a matter of fact, the echo looks like a sinusoids whose amplitude and phase is changing over time. Because of the similarity of the temporal shape of the echo signal to the temporal shape of Radio Frequency (RF) signals used in telecommunications, the echo signal is called the RF Signal and the received ultrasound data by the transducers, the RF data in the jargon of ultrasound imaging.