Which factors increase ultrasound bioeffects?

• A. Increasing exposure time and acoustic intensity
• B. Increasing TGC gain
• C. Reducing beam power
• D. Using shorter exposure time

Answer: (A)

Bioeffects scale with the total energy deposited into the tissue during exposure. That energy depends on how strong the beam is (acoustic intensity or power) and how long the tissue is exposed (exposure duration, including duty cycle for pulsed modes). When you increase either exposure time or acoustic intensity, more energy accumulates in the tissue, raising the potential for heating and mechanical effects like cavitation, which heightens bioeffects risk.

TGC gain is a receiver setting that changes image brightness by amplifying echoes, not the energy delivered to tissue, so it doesn’t increase bioeffects. Reducing beam power or shortening exposure time lowers the energy reaching tissue, thus reducing bioeffects.