To measure the ultrasound beam intensity, use a

• A. Calibrated Hydrophone
• B. Lateral Oscilloscope
• C. Water Filled Phantom
• D. Tissue Equivalent Phantom

Answer: (A)

Measuring ultrasound beam intensity requires sensing the acoustic pressure in a medium with a calibrated device. A calibrated hydrophone is designed for this purpose: it acts as a tiny microphone that responds to the pressure fluctuations of the acoustic field and, because it comes with a traceable calibration, its electrical output can be converted into actual acoustic pressure values at the frequencies used. Once you have the pressure waveform in a known medium (typically water), you can compute intensity from the pressure, such as I = p_rms^2/(ρc), giving a quantitative map of the beam’s strength.

A water-filled phantom can help position the sensor and simulate how the beam propagates, but by itself it does not provide an absolute measurement of intensity. A tissue-equivalent phantom serves similarly for imaging contrast and beam interaction studies, not for direct intensity measurement. A lateral oscilloscope can display voltage versus time, showing the waveform shape, but without a calibrated transducer to translate that signal into pressure units, it cannot give true intensity values.