Pulse Echo Principles

• Pulse:

  • A pulse is a group of ultrasound waves that travel together. Each ultrasound pulse has a beginning and an end and has certain characteristics.
  • In pulsed ultrasound the same piezoelectric crystal is used to send the ultrasound pulse and receive the returning echoes.

• Components of a pulse:

  • The transmit time which is also called the on time. During this time the ultrasound machine is on and short bursts of ultrasound pulses are produced and transmitted.
  • The receive time which is also called the off time. During this time the returning echo signals are received by the transducer. No sound pulses are produced during this time.

• Spatial Pulse Length: the distance from the start of a pulse to the end of that pulse.

  • The spatial pulse length is determined by both the source and the medium through which it travels
  • Spatial pulse length determines the longitudinal resolution which determines the image quality. Shorter pulses create the higher quality images.

• Pulse Duration: the amount of time it takes from the start of a pulse to the end of that pulse. It is the time when the ultrasound system is on and transmitting the ultrasound pulse.