What is the duty cycle of a pulsed wave ultrasound with a 2 msec on time and 8 msec off time?

To determine the duty cycle of a pulsed wave ultrasound, you calculate the total duration of one complete cycle (which includes both the "on" and "off" times) and then find out what fraction of that cycle is spent in the "on" state.

In this scenario, the ultrasound is "on" for 2 milliseconds and "off" for 8 milliseconds. To find the total cycle time, you add the on time and off time together:

Total cycle time = On time + Off time = 2 msec + 8 msec = 10 msec.

Next, the duty cycle is calculated by taking the ratio of the on time to the total cycle time. This is expressed as a percentage:

Duty Cycle = (On time / Total cycle time) × 100

= (2 msec / 10 msec) × 100

= 20%.

Thus, the duty cycle of the pulsed wave ultrasound is 20%, which correlates to the selected answer. This percentage indicates that the ultrasound is active for 20% of the entire cycle duration, which is significant in clinical contexts for understanding the effects on tissue heating and repair processes during treatment.