Final answer:
Piezoelectric ultrasonic units emit a directional and adjustable ultrasonic beam that is used to create images based on the constructive interference of multiple sources and reflections from within the body.
Step-by-step explanation:
Piezoelectric ultrasonic units, commonly used in medical imaging, generate a directional beam that is swept across the area of interest to produce an image. This is possible due to multiple ultrasound sources in the probe's head, which are phased to interfere constructively in an adjustable direction. The reflection of ultrasonic waves from tissues and organs provides detailed information on their shape and density, forming an image thanks to the time delay and intensity loss detected by the system.
With piezoelectric ultrasonic technology, the emitted ultrasonic waves act upon tissue contact, and the reflected waves are similarly detected by the transducer, functioning as both sender and receiver. These reflections give crucial information about the internal structures of the body.