The operator (sonographer) sets and changes the frequency and duration of the ultrasound pulses, as well as the scan mode of the machine with the transducer pulse control. The commands from the operator are translated into changing electric currents that are applied to the piezoelectric crystals in the transducer probe.

See also Blanking Distance.

A piezoelectric crystal changes the physical dimensions when subjected to an electric field. When deformed by external pressure, an electric field is created across the crystal. Piezoelectric ceramic and crystals are used in ultrasound transducers to transmit and receive ultrasound waves.
The piezoelectric crystal in ultrasound transducers has electrodes attached to its front and back for the application and detection of electrical charges. The crystal consists of numerous dipoles, and in the normal state, the individual dipoles have an oblique orientation with no net surface charge.
In ultrasound physics, an electric field applied across the crystal will realign the dipoles and results in compression or expansion of the crystal, depending on the direction of the electric field. For the transmission of a short ultrasound pulse, a voltage spike of very short duration is applied, causing the crystal to initially contract and then vibrate for a short time with its resonant frequency.

See also Composite Array, Transducer Pulse Control, and Temporal Peak Intensity.

Ultrasound machines, widely used in medical imaging, are essential tools in the field of diagnostic ultrasound. These devices utilize high-frequency sound waves to create real-time images of internal body structures. Ultrasound machines consist of several key components that work together to generate diagnostic images. These include:
B-mode machines represent the vast majority of machines used in echocardiology, obstetrical scans, abdominal scans, gynecological scans, etc. B-mode ultrasound machines usually produce the sector (or pie segment-shaped) scans. These ultrasound scans require either a mechanical scanner transducer (the transducer moves to produce the sector scan), or a linear array transducer operated as a phased array.


Ultrasound machines come in different types, each catering to specific clinical needs. The two primary types are stationary and portable ultrasound machines:


See also Handheld Ultrasound, Ultrasound System Performance, Equipment Preparation, Coaxial Cable, and Microbubble Scanner Modification, Environmental Protection and Ultrasound Accessories and Supplies.

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(DAC) Part of the interface that converts digital numbers from the computer into analog (ordinary) voltages or currents. In ultrasound systems e.g., the high voltage transmit amplifiers that drive the transducers might be controlled by digital to analog converters (DACs) to shape the transmit pulses for better energy delivery to the transducer elements.