Define thermal index (TI) and its clinical purpose.

• A. TI estimates potential tissue heating during the exam to help assess safety
• B. TI estimates peak temperature rise in tissue
• C. TI measures mechanical tissue disruption risk
• D. TI indicates image brightness scaling

Answer: (A)

Thermal Index is a safety metric that estimates the potential for ultrasound energy to heat tissue during an exam. It isn’t a direct temperature reading; instead, it combines factors like acoustic power, pulse duration, frequency, and tissue attenuation to predict how much the tissue might rise in temperature under worst‑case conditions. Clinically, it helps clinicians gauge safety and guide exposure settings—if TI indicates a higher risk, they can reduce power, shorten exposure, or adjust focus to minimize heating.

The other ideas don’t fit because TI does not measure actual peak temperature, nor does it relate to mechanical disruption risk (that’s the Mechanical Index) or to image brightness scaling.