Final answer:
The purpose of applying acoustic gel to the transducer in ultrasound is to reduce the impedance mismatch between the transducer and the skin, thus enhancing the transmission of ultrasonic waves into the tissue and improving imaging quality.
Step-by-step explanation:
The purpose of applying acoustic gel to the face of the transducer is to reduce the difference in impedance between the matching layer and the skin. This gel facilitates the transmission of the ultrasound between the transducer and the patient's body. The presence of air would cause a large mismatch in acoustic impedance, leading to an almost total reflection at the skin-air interface, hence very little transmission into the body. However, the acoustic impedance of the gel is similar to that of water, and therefore to that of human tissues, resulting in a much lower intensity reflection coefficient and enhanced transmission of ultrasonic waves into the tissue.
When the impedance of two materials at a boundary is similar, there is an efficient coupling of sound energy from one medium to another, which is necessary for creating the image in ultrasound imaging. The acoustic gel assists in impedance matching, thereby maximizing the transmitted sound energy for improved imaging.