What serves as the source of emitted energy in an ultrasound procedure?

In an ultrasound procedure, the transducer serves as the source of emitted energy. It is a critical component that converts electrical energy into sound waves. The transducer contains piezoelectric crystals that vibrate when electricity is applied, generating high-frequency sound waves that travel through the body's tissues. These sound waves then reflect back to the transducer when they encounter different densities in the tissues, and the ultrasound machine processes these echoes to create images.

The other options do not generate the ultrasound waves. The ultrasound gel aids in transmission of sound waves by reducing air gaps between the transducer and the skin, thereby enhancing the quality of the images. The patient is the subject being examined, providing structures that the sound waves interact with, but does not emit ultrasound energy. The imaging software processes the data received from the transducer to display images, but it does not generate sound waves itself. The transducer is thus the key source of energy in ultrasound imaging.