The energy that is reflected from the interface is known as the echo and it is received by the transducer in order to build the image. The pulse-echo principle is the core principle of Ultrasound imaging. The strength of the echo mainly depends on the difference between the acoustic impedance values of the objects that it interacts with. The energy reflected from the air interface is approximately 500 times weaker than that of water. This means that the efficiency of any diagnostic imaging technique is enhanced up to five hundred times when using gel. This shows how massive the difference is and how much of a significant role the gel plays in the Ultrasound scanning.