When assessing ultrasound parameters for increasing tissue temperature, the most critical factor is:

In the context of using ultrasound for therapeutic purposes, the duty cycle is indeed a critical factor when assessing parameters for increasing tissue temperature. The duty cycle refers to the proportion of time that the ultrasound is on during a treatment session compared to the total time of the cycle.

When using continuous ultrasound, the ultrasound energy is applied continuously, allowing for a more significant and sustained increase in temperature within the tissue. This is essential for achieving the therapeutic effects sought, such as increased blood flow, decreased pain, and improved tissue healing.

In cases where pulsed ultrasound is used, the duty cycle significantly affects temperature increase because the intensity of the ultrasound is only applied during the "on" periods and not during the "off" periods. Therefore, a lower duty cycle would generally result in less temperature increase compared to a higher duty cycle.

While intensity, time, and frequency also play roles in the effectiveness of ultrasound, the duty cycle more directly influences how much thermal energy is delivered to the tissue during treatment. This makes it a vital parameter to consider for achieving desired temperature increases in therapeutic ultrasound applications.