ARDMS Ultrasound Physics & Instrumentation Practice Exam

What does the duty factor describe in ultrasound systems?

1. The total energy output

2. The percentage of time ultrasound pulses are produced

3. The time the machine is idle

4. The frequency of the sound wave

The correct answer is: The percentage of time ultrasound pulses are produced

The duty factor is a key concept in ultrasound systems that specifically describes the percentage of time that the ultrasound machine is actively producing pulses of sound during a given cycle. It is a dimensionless ratio typically expressed as a percentage, quantifying how much of the overall time is occupied by the "on" state (when pulses are being emitted) compared to the "off" state (when the machine is not sending out ultrasound waves). For instance, if an ultrasound system has a duty factor of 20%, it means that during the total time considered, 20% is spent transmitting ultrasound pulses while 80% is spent in the idle state. This aspect of ultrasound operation is crucial because it influences the thermal effects on tissue and the quality of the imaging produced. A lower duty factor indicates longer periods of listening for echoes, which can enhance the quality of the received signals and ultimately result in better imaging quality. In contrast, the other choices relate to different aspects of ultrasound systems. The total energy output involves the amplitude and duration of pulses but does not directly define duty factor. Time the machine is idle refers to the period when no pulses are produced but does not encompass the overall understanding of duty factor. The frequency of the sound wave pertains to how many cycles