Overview
Ultrasound imaging sends high-frequency sound waves into the body and builds a picture from the echoes returning from tissue boundaries. This topic covers the properties of ultrasound, the piezoelectric transducer, the principle of echography, the A, B and M modes and Doppler sonography.
Properties of ultrasound and the piezoelectric effect
- Ultrasound technology leverages high-frequency sound waves (above 20,000 Hz) for various medical applications, including diagnostics and treatment. The piezoelectric effect is central to ultrasound generation and detection, involving the conversion between mechanical stress and electric charge in certain materials. Echography and sonography use ultrasound waves to visualize internal body structures by detecting reflections from tissue boundaries with differing acoustic impedances. The Doppler effect and its application in Doppler sonography are crucial for assessing blood flow, detecting shifts in frequency caused by the movement of blood cells relative to the ultrasound probe. These technologies facilitate numerous medical applications, from 2D imaging in prenatal care to therapeutic uses like breaking up kidney stones.
- Ultrasound Properties:
- Frequencies above 20,000 Hz, inaudible to humans.
- Mechanically waves absorbed by tissues, useful for cell and microorganism disruption.
- High-intensity ultrasound can induce cavitation and luminescence.
- Utilized in echography, where ultrasound is reflected at boundaries between media of different acoustic impedances.
- Piezoelectric Effect:
- Direct Piezoelectric Effect: Generation of an electric charge in response to mechanical stress.
- Inverse Piezoelectric Effect: Material deformation resulting from an applied electric field.
- Fundamental to ultrasound device functionality, converting electrical signals into ultrasonic waves and vice versa.