What is the duration of an ultrasound pulse from start to end?

• A. Pulse duration
• B. PRP
• C. PRF
• D. Duty cycle

Answer: (A)

The duration of an ultrasound pulse is the time from when the transducer begins emitting the pulse to when it stops—this is the pulse duration. It depends on how many cycles are packed into the pulse and the period of each cycle. If the center frequency is f, the period is T = 1/f, and if the pulse contains N cycles, the pulse duration equals N × T. For example, a 5 MHz transducer with 2 cycles has a period of 0.2 microseconds, so the pulse lasts about 0.4 microseconds. In practice, pulses are very short, often only a fraction of a microsecond to a few microseconds.

This is distinct from the time between pulses, which is the pulse repetition period, and from how often pulses occur per second, which is the pulse repetition frequency. Duty cycle is the fraction of time the system is emitting within one repetition period, calculated as pulse duration divided by the repetition period. The correct term specifically describes the length of the emitted burst itself, not the spacing or rate of bursts.