Which formula represents the temperature increase when using 3 MHz ultrasound?

• A. Temp Increase = 0.6 x Intensity x Time
• B. Temp Increase = 0.8 x Intensity x Time
• C. Temp Increase = 1.2 x Intensity x Time
• D. Temp Increase = 0.4 x Intensity x Time

Answer: (A)

The main idea is that the temperature rise from therapeutic ultrasound is proportional to how long you apply it and how strong the beam is, with a frequency-specific factor that adjusts the rate of heating. For 3 MHz, energy is absorbed more readily in tissue, so the heating coefficient is higher than at lower frequencies. In clinical exam materials, the commonly used coefficient for 3 MHz is 0.6, giving the formula Temp Increase = 0.6 × Intensity × Time. This means, with intensity in W/cm^2 and time in minutes, multiply by 0.6 to estimate how many degrees Celsius the tissue temperature will rise. The other coefficients (0.8, 1.2, 0.4) would reflect different frequencies or models, not 3 MHz, so they don’t match the 3 MHz heating rate.