What is the relationship between duty factor and imaging depth?

The relationship between duty factor and imaging depth is inversely proportional. Duty factor is defined as the ratio of the time that the ultrasound beam is on (the transmitting time) to the total time of the pulse cycle (which includes both the transmitting and receiving times). As imaging depth increases, the time it takes for the ultrasound wave to travel to the deeper structures and back increases, leading to a longer receiving time during which the system cannot transmit.

This extended receiving time results in a lower duty factor because the pulse duration (time spent transmitting) remains relatively constant, while the total time of the pulse cycle increases. Essentially, the deeper the imaging, the less time is available for the ultrasound system to actively transmit, thus reducing the duty factor. Therefore, as imaging depth increases, duty factor decreases, demonstrating an inverse relationship. This concept is essential in understanding how ultrasound systems manage their operation at varying depths during imaging procedures.