What should you limit when the thermal index exceeds 1?

What should you limit when the thermal index exceeds 1?

• A. Overall gain
• B. TGC
• C. Exposure time
• D. Scanning depth

Answer: (C)

When the thermal index is above 1, there’s a real risk of tissue heating from the ultrasound energy. The most direct way to reduce that heating is to shorten the time the tissue is exposed to the beam. Limiting exposure time lowers the total energy delivered, which lowers the thermal dose. Other adjustments like the overall gain or TGC mainly affect image brightness, not the actual energy delivered to tissue, so they don’t reliably limit heating. Scanning depth can change where you scan and how long you scan, but it’s exposure time that directly controls the potential for temperature rise.

When the thermal index is above 1, there’s a real risk of tissue heating from the ultrasound energy. The most direct way to reduce that heating is to shorten the time the tissue is exposed to the beam. Limiting exposure time lowers the total energy delivered, which lowers the thermal dose.

Other adjustments like the overall gain or TGC mainly affect image brightness, not the actual energy delivered to tissue, so they don’t reliably limit heating. Scanning depth can change where you scan and how long you scan, but it’s exposure time that directly controls the potential for temperature rise.